Colonization and diversification: towards a phylogeographic synthesis for the Canary Islands

Diversity of Ladybird Beetles (Coleoptera: Coccinellidae) in Tenerife and La Gomera (Canary Islands): The Role of Size and Other Island Characteristics

This paper provides new data on the ladybird beetles (Coccinellidae) from two islands in the Canary archipelago: Tenerife, the largest island, and La Gomera, the second smallest. As they clearly differ in size but are similar in location and geological age, they are a suitable model for testing the species-area relationship. Our study shows that, in line with this main assumption of the theory of island biogeography, clearly more species occur on a large island (Tenerife) than on a small one (La Gomera). The field surveys documented the occurrence of 35 ladybird species on Tenerife (including 5 not previously reported from this island) and of 20 species on La Gomera (2 species new to the island). Coelopterus sp. collected on Tenerife (a single female that could not be identified to species) is the first record of this genus for the whole Canary Islands. Taking our data and previously published records into account, 47 species of Coccinellidae are known to occur on Tenerife and 26 species on La Gomera. Tenerife has by far the richest ladybird fauna of all the Canary Islands (the next in line, Gran Canaria, has 41 recorded species), but it also has the highest number of non-native ladybird species. All of the ten non-native species recorded in the Canary Islands are found on Tenerife, and for most of them, Tenerife was the island of their first appearance in the archipelago. This island, much more distant from the mainland than the other relatively large islands (Fuerteventura, Lanzarote), appears to be the main recipient of ladybirds immigrating to the Canary Islands. Tenerife can play this role probably because of its great habitat diversity and altitude variation, as well as intensive tourism and trade-related transport.

Genomics of ecological adaptation in Canary Island Descurainia (Brassicaceae) and comparisons with other Brassicaceae

Oceanic archipelagos provide striking examples of lineages that have radiated over pronounced ecological gradients. Accompanying this diversification, lineages have evolved adaptations allowing survival in extreme environments. Here, we investigate the genomic basis of ecological adaptation in Canary Island Descurainia (Brassicaceae), an island relative of Arabidopsis. The seven endemic species have diversified in situ along an elevational and ecological gradient, from low-elevation scrub to high-elevation sub-alpine desert. We first generated a reference genome for Descurainia millefolia, phylogenetic analysis of which placed it as sister to D. sophioides. Ninety-six gene families were found to be specific to D. millefolia and a further 1087 and 1469 gene families have expanded or contracted in size, respectively, along the D. millefolia branch. We then employed genome re-sequencing to sample 14 genomes across the seven species of Canary Island Descurainia and an outgroup. Phylogenomic analyses were consistent with previous reconstructions of Canary Island Descurainia in resolving low- and high-elevation clades. Using the branch-site dN/dS method, we detected positive selection for 275 genes on the branch separating the low- and high-elevation species and these positively selected genes (PSGs) were significantly enriched for functions related to reproduction and stress tolerance. Comparing PSGs to those in analyses of adaptation to elevation and/or latitude in other Brassicaceae, we found little evidence of widespread convergence and gene reuse, except for two examples, one of which was a significant overlap between Descurainia and Draba nivalis, a species restricted to high latitudes. The study of Canary Island Descurainia suggests that the transition to high-elevation environments such as that found in the high mountains of the Canary Islands involves selection on genes related to reproduction and stress tolerance but that repeated evolution across different lineages that have evolved into similar habitats is limited, indicating substantially different molecular trajectories to adaptation.

Speciation happens in company - not in isolation

Oceanic islands are considered the classic arenas for allopatric speciation and adaptive radiation. Established concepts of speciation and endemism are strongly focused on spatial and temporal scales. However, biotic interactions and ecological drivers, although widely recognized as playing a role, still need to be integrated into our understanding of these processes. Here, I highlight ecosystems as the evolutionary arena within islands. Ecosystem functioning, such as the regulation of abiotic fluxes of energy and matter, has been intensely studied in the context of climate change and biodiversity loss. Biogeography, on the other hand, when it focuses on speciation and endemism, often lacks a functional understanding of the ecosystem beyond species lists. This contribution aims to stimulate a stronger integration of ecological processes, assembly rules, and vegetation structures into future biogeographical and macroecological studies.

Molecular analyses of the Kalotermes dispar-complex (Blattodea: Kalotermitidae) from the Canary Islands reveal cryptic intraspecific divergence and a connection to a lone Nearctic congener

The Canary Islands is a Macaronesian volcanic archipelago with a depauperate community of three species of Kalotermitidae, including Kalotermes dispar. A total of 54 Kalotermes colonies were collected from Gran Canaria, Tenerife, La Gomera, La Palma, and El Hierro islands. Soldiers and imagos were morphologically examined and sequenced for four mitochondrial markers. Although morphological differences could not be detected, phylogenetic analysis of both cox1/tRNA/cox2 and rrnL markers revealed two distinct clades of K. dispar, suggesting cryptic diversity. The diversification within the Canary Kalotermes lineage most likely occurred around 7.5 Mya, while the divergence within the two clades was reconstructed at about 3.6 Mya and 1.9 Mya. Kalotermes approximatus from the southeastern Nearctic constitutes a sister to the Canary Kalotermes, while the Palearctic K. flavicollis, K. italicus, and K. phoenicae form a separate clade. It is hypothesized that a faunal exchange of Kalotermes from the Nearctic to the Canary Islands occurred via transoceanic rafting during the mid-Miocene.

Origins of the central Macaronesian psyllid lineages (Hemiptera; Psylloidea) with characterization of a new island radiation on endemic Convolvulus floridus (Convolvulaceae) in the Canary Islands

A molecular survey of native and adventive psyllids in the central Macaronesian islands provides the first comprehensive phylogenetic assessment of the origins of the psyllid fauna of the Canary and Madeira archipelagos. We employ a maximum likelihood backbone constraint analysis to place the central Macaronesian taxa within the Psylloidea mitogenome phylogeny. The native psyllid fauna in these central Macaronesian islands results from an estimated 26 independent colonization events. Island host plants are predicted by host plants of continental relatives in nearly all cases and six plant genera have been colonized multiple times (Chamaecytisus, Convolvulus, Olea, Pistacia, Rhamnus, and Spartocytisus) from the continent. Post-colonization diversification varies from no further cladogenesis (18 events, represented by a single native taxon) to modest in situ diversification resulting in two to four native taxa and, surprisingly, given the diverse range of islands and habitats, only one substantial species radiation with more than four native species. Specificity to ancestral host plant genera or family is typically maintained during in situ diversification both within and among islands. Characterization of a recently discovered island radiation consisting of four species on Convolvulus floridus in the Canary Islands shows patterns and rates of diversification that reflect island topographic complexity and geological dynamism. Although modest in species diversity, this radiation is atypical in diversification on a single host plant species, but typical in the primary role of allopatry in the diversification process.

Towards a Canary Islands barcode database for soil biodiversity: revealing cryptic and unrecorded mite species diversity within insular soils

Soil arthropod diversity contributes to a high proportion of the total biodiversity on Earth. However, most soil arthropods are still undescribed, hindering our understanding of soil functioning and global biodiversity estimations. Inventorying soil arthropods using conventional taxonomical approaches is particularly difficult and costly due to the great species richness, abundance and local-scale heterogeneity of mesofauna communities and the poor taxonomic background knowledge of most lineages. To alleviate this situation, we have designed and implemented a molecular barcoding framework adapted to soil fauna. This pipeline includes different steps, starting with a morphology-based selection of specimens which are imaged. Then, DNA is extracted non-destructively. Both images and voucher specimens are used to assign a taxonomic identification, based on morphology that is further checked for consistency with molecular information. Using this procedure, we studied 239 specimens of mites from the Canary Islands including representatives of Mesostigmata, Sarcoptiformes and Trombidiformes, of which we recovered barcode sequences for 168 specimens that were morphologically identified to 49 species, with nine specimens that could only be identified at the genus or family levels. Multiple species delimitation analyses were run to compare molecular delimitations with morphological identifications, including ASAP, mlPTP, BINs and 3% and 8% genetic distance thresholds. Additionally, a species-level search was carried out at the Biodiversity Databank of the Canary Islands (BIOTA) to evaluate the number of species in our dataset that were not previously recorded in the archipelago. In parallel, a sequence-level search of our sequences was performed against BOLD Systems. Our results reveal that multiple morphologically identified species correspond to different molecular lineages, which points to significant levels of unknown cryptic diversity within the archipelago. In addition, we evidenced that multiple species in our dataset constituted new records for the Canary Islands fauna and that the information for these lineages within online genetic repositories is very incomplete. Our study represents the first systematic effort to catalogue the soil arthropod mesofauna of the Canary Islands and establishes the basis for the Canary Islands Soil Biodiversity barcode database. This resource will constitute a step forward in the knowledge of these arthropods in a region of special interest.

Ecological network structure in response to community assembly processes over evolutionary time

The dynamic structure of ecological communities results from interactions among taxa that change with shifts in species composition in space and time. However, our ability to study the interplay of ecological and evolutionary processes on community assembly remains relatively unexplored due to the difficulty of measuring community structure over long temporal scales. Here, we made use of a geological chronosequence across the Hawaiian Islands, representing 50 years to 4.15 million years of ecosystem development, to sample 11 communities of arthropods and their associated plant taxa using semiquantitative DNA metabarcoding. We then examined how ecological communities changed with community age by calculating quantitative network statistics for bipartite networks of arthropod-plant associations. The average number of interactions per species (linkage density), ratio of plant to arthropod species (vulnerability) and uniformity of energy flow (interaction evenness) increased significantly in concert with community age. The index of specializationH 2 ' has a curvilinear relationship with community age. Our analyses suggest that younger communities are characterized by fewer but stronger interactions, while biotic associations become more even and diverse as communities mature. These shifts in structure became especially prominent on East Maui (~0.5 million years old) and older volcanos, after enough time had elapsed for adaptation and specialization to act on populations in situ. Such natural progression of specialization during community assembly is probably impeded by the rapid infiltration of non-native species, with special risk to younger or more recently disturbed communities that are composed of fewer specialized relationships.

Habitat-associated Genomic Variation in a Wall Lizard from an Oceanic Island

The lizard Teira dugesii exhibits morphological divergence between beach and inland habitats in the face of gene flow, within the volcanic island of Madeira, Portugal. Here, we analyzed genomic data obtained by genotyping-by-sequencing, which provided 16,378 single nucleotide polymorphisms (SNPs) from 94 individuals sampled from 15 sites across Madeira. Ancient within-island divergence in allopatry appears to have mediated divergence in similar species within other Atlantic islands, but this hypothesis was not supported for T. dugesii. Across all samples, a total of 168 SNPs were classified as statistical outliers using pcadapt and OutFLANK. Redundancy analysis (RDA) revealed that 17 of these outliers were associated with beach/inland habitats. The SNPs were located within 16 sequence tags and 15 of these were homologous with sequences in a 31 Mb region on chromosome 3 of a reference wall lizard genome (the remaining tag could not be associated with any chromosome). We further investigated outliers through contingency analyses of allele frequencies at each of four pairs of adjacent beach-inland sites. The majority of the outliers detected by the RDA were confirmed at two pairs of these matched sites. These analyses also suggested some parallel divergence at different localities. Six other outliers were associated with site elevation, four of which were located on chromosome 5 of the reference genome. Our study lends support to a previous hypothesis that divergent selection between gray shingle beaches and inland regions overcomes gene flow and leads to the observed morphological divergence between populations in these adjacent habitats.

Phylogeography of the true freshwater crab, Geothelphusa dehaani: Detected dual dispersal routes via land and sea

Dispersal is an important factor that determines the potential for colonization to pioneer sites. Although most decapods employ seaward migration for reproduction with a planktonic larval phase, true freshwater crabs spend their entire life cycle in freshwater. Therefore, it is expected that genetic regionality can be easily detected. In this study, we focused on true freshwater crabs, Geothelphusa Stimpson, 1858. Herein, we reveal the evolutionary history and dispersal patterns of freshwater crustaceans. We collected and genetically analyzed 283 specimens at 138 localities across the Japanese Islands. Phylogenetic analyses were conducted on the combined dataset (mtDNA COI, 16S, and nDNA ITS1, histone H3 regions) and the data set based on the mtDNA COI region. The phylogenetic relationships detected 10 clades that were highly monophyletic. The highlights of this study were the discovery of several cryptic species or undescribed species, and the completely different heterogeneous dual dispersal pathways within a single species; i.e., both land and ocean routes. Although it was concluded that Japanese crabs are basically genetically divided by straits, strong evidence for dispersion via ocean currents was also detected (i.e., a "sweepstake"). It was also confirmed that Geothelphusa dehaani (White, 1847) could survive in seawater.

What Darwin could not see: island formation and historical sea levels shape genetic divergence and island biogeography in a coastal marine species

Oceanic islands play a central role in the study of evolution and island biogeography. The Galapagos Islands are one of the most studied oceanic archipelagos but research has almost exclusively focused on terrestrial organisms compared to marine species. Here we used the Galapagos bullhead shark (Heterodontus quoyi) and single nucleotide polymorphisms (SNPs) to examine evolutionary processes and their consequences for genetic divergence and island biogeography in a shallow-water marine species without larval dispersal. The sequential separation of individual islands from a central island cluster gradually established different ocean depths between islands that pose barriers to dispersal in H. quoyi. Isolation by resistance analysis suggested that ocean bathymetry and historical sea level fluctuations modified genetic connectivity. These processes resulted in at least three genetic clusters that exhibit low genetic diversity and effective population sizes that scale with island size and the level of geographic isolation. Our results exemplify that island formation and climatic cycles shape genetic divergence and biogeography of coastal marine organisms with limited dispersal comparable to terrestrial taxa. Because similar scenarios exist in oceanic islands around the globe our research provides a new perspective on marine evolution and biogeography with implications for the conservation of island biodiversity.

A review of the jumping plant-lice (Hemiptera: Psylloidea) of the Canary Islands, with descriptions of two new genera and sixteen new species

The psyllid fauna of the Canary Islands is reviewed on the basis of recent field work on Tenerife, La Gomera, La Palma Gran Canaria and Lanzarote, as well as the examination of material deposited in several collections. Two new genera and 16 new species are described: Drepanoza Bastin, Burckhardt & Ouvrard gen. nov., Percyella Bastin, Burckhardt & Ouvrard gen. nov., Agonoscena atlantica Bastin, Burckhardt & Ouvrard sp. nov., A. sinuata Bastin, Burckhardt & Ouvrard sp. nov., Arytaina meridionalis Bastin, Burckhardt & Ouvrard sp. nov., Cacopsylla crenulatae Bastin, Burckhardt & Ouvrard sp. nov., C. falcicauda Bastin, Burckhardt & Ouvrard sp. nov., Diaphorina gonzalezi Bastin, Burckhardt & Ouvrard sp. nov., Drepanoza canariensis Bastin, Burckhardt & Ouvrard sp. nov., D. fruticulosi Bastin, Burckhardt & Ouvrard sp. nov., D. molinai Bastin, Burckhardt & Ouvrard sp. nov., Euphyllura confusa Bastin, Burckhardt & Ouvrard sp. nov., Percyella benahorita Bastin, Burckhardt & Ouvrard sp. nov., P. canari Bastin, Burckhardt & Ouvrard sp. nov., P. gomerita Bastin, Burckhardt & Ouvrard sp. nov., P. guanche Bastin, Burckhardt & Ouvrard sp. nov., Strophingia canariensis Bastin, Burckhardt & Ouvrard sp. nov. and S. paligera Bastin, Burckhardt & Ouvrard sp. nov. Arytaina insularis Loginova, 1976, stat. nov. is elevated from a subspecies of A. devia Loginova, 1976 to species rank. Five new combinations are proposed: Drepanoza fernandesi (Aguiar, 2001) comb. nov., D. lienhardi (Burckhardt, 1981) comb. nov., D. montanetana (Aguiar, 2001) comb. nov., D. pittospori (Aguiar, 2001) comb. nov. and Lauritrioza laurisilvae (Hodkinson, 1990) comb. nov., all transferred from Trioza. The hitherto unknown last-instar immatures are described for Megadicrania tecticeps Loginova, 1976, Cacopsylla atlantica (Loginova, 1976) and Lauritrioza laurisilvae (Hodkinson, 1990). We also report Agonoscena targionii (Lichtenstein, 1874) for the first time from the Canary Islands. Our review increases the number of known psyllid taxa from the Canary Islands to 24 genera and 62 species (one of which remains undescribed). Endemism, host plant relationships and biogeographic patterns are discussed. Keys for the identification of adults and immatures are provided, as well as information on host plants, distribution and predators.

Ocean crossers: a tale of disjunctions and speciation in the dwarf-fruticose Lichina (lichenized Ascomycota)

Lichens thrive in rocky coastal areas in temperate and cold regions of both hemispheres. Species of the genus Lichina, which form characteristic black fruiting thalli associated with cyanobacteria, often create distinguishable bands in the intertidal and supralittoral zones. The present study uses a comprehensive specimen dataset and four gene loci to (1) delineate and discuss species boundaries in this genus, (2) assess evolutionary relationships among species, and (3) infer the most likely causes of their current geographic distribution in the Northern and Southern hemispheres. A dated phylogeny describes the time frame in which extant disjunctions of species and populations were established. The results showed that the genus is integrated by four species, with Lichina pygmaea, L. confinis and the newly described L. canariensis from rocky seashores in the Canary Islands, occurring in the Northern Hemisphere, whereas L. intermedia is restricted to the Southern Hemisphere. Lichina intermedia hosted a much higher intraspecific genetic diversity than the other species, with subclades interpreted as species-level lineages by the different species delimitation approaches. However, a conservative taxonomic approach was adopted. This species showed a striking disjunct distribution between Australasia and southern South America. The timing for the observed interspecific and intraspecific divergences and population disjunctions postdated continental plate movements, suggesting that long-distance dispersal across body waters in the two hemispheres played a major role in shaping the current species distributions. Such ocean crossings were, as in L. canariensis, followed by speciation. New substitution rates for the nrITS of the genus Lichina were inferred using a tree spanning the major Ascomycota lineages calibrated using fossils. In conclusion, this work lays the foundation for a better understanding of the evolution through time and space of maritime lichens.

The role of geography, ecology, and hybridization in the evolutionary history of Canary Island Descurainia

PREMISE

Oceanic islands offer the opportunity to understand evolutionary processes underlying rapid diversification. Along with geographic isolation and ecological shifts, a growing body of genomic evidence has suggested that hybridization can play an important role in island evolution. Here we use genotyping-by-sequencing (GBS) to understand the roles of hybridization, ecology, and geographic isolation in the radiation of Canary Island Descurainia (Brassicaceae).

METHODS

We carried out GBS for multiple individuals of all Canary Island species and two outgroups. Phylogenetic analyses of the GBS data were performed using both supermatrix and gene tree approaches and hybridization events were examined using D-statistics and Approximate Bayesian Computation. Climatic data were analyzed to examine the relationship between ecology and diversification.

RESULTS

Analysis of the supermatrix data set resulted in a fully resolved phylogeny. Species networks suggest a hybridization event has occurred for D. gilva, with these results being supported by Approximate Bayesian Computation analysis. Strong phylogenetic signals for temperature and precipitation indicate one major ecological shift within Canary Island Descurainia.

CONCLUSIONS

Inter-island dispersal played a significant role in the diversification of Descurainia, with evidence of only one major shift in climate preferences. Despite weak reproductive barriers and the occurrence of hybrids, hybridization appears to have played only a limited role in the diversification of the group with a single instance detected. The results highlight the need to use phylogenetic network approaches that can simultaneously accommodate incomplete lineage sorting and gene flow when studying groups prone to hybridization; patterns that might otherwise be obscured in species trees.

The evolutionary history of rice azaleas (Rhododendron tschonoskii alliance) involved niche evolution to a montane environment

PREMISE

The formation of isolated montane geography on islands promotes evolution, speciation, and then radiation if there are ecological changes. Thus, investigating evolutionary histories of montane species and associated ecological changes may help efforts to understand how endemism formed in islands' montane floras. To explore this process, we investigated the evolutionary history of the Rhododendron tschonoskii alliance, which grows in montane environments of the Japanese archipelago and the Korean Peninsula.

METHODS

We studied the five species in the R. tschonoskii alliance and 30 outgroup species, using genome-wide single-nucleotide polymorphisms and cpDNA sequences, in association with environmental analyses.

RESULTS

The monophyletic R. tschonoskii alliance diverged since the late Miocene. Species in the alliance currently inhabit a cold climatic niche that is largely different from that of the outgroup species. We observed clear genetic and niche differentiations between the taxa of the alliance.

CONCLUSIONS

The association of the alliance's evolution with the formation of cooler climates on mountains indicates that it was driven by global cooling since the mid-Miocene and by rapid uplift of mountains since the Pliocene. The combination of geographic and climatic isolation promoted high genetic differentiation between taxa, which has been maintained by climatic oscillations since the Quaternary.

Life on a beach leads to phenotypic divergence despite gene flow for an island lizard

Limited spatial separation within small islands suggests that observed population divergence may occur due to habitat differences without interruption to gene flow but strong evidence of this is scarce. The wall lizard Teira dugesii lives in starkly contrasting shingle beach and inland habitats on the island of Madeira. We used a matched pairs sampling design to examine morphological and genomic divergence between four beach and adjacent (<1 km) inland areas. Beach populations are significantly darker than corresponding inland populations. Geometric morphometric analyses reveal divergence in head morphology: beach lizards have generally wider snouts. Genotyping-by-sequencing allows the rejection of the hypothesis that beach populations form a distinct lineage. Bayesian analyses provide strong support for models that incorporate gene flow, relative to those that do not, replicated at all pairs of matched sites. Madeiran lizards show morphological divergence between habitats in the face of gene flow, revealing how divergence may originate within small islands.

Multiple introductions, polyploidy and mixed reproductive strategies are linked to genetic diversity and structure in the most widespread invasive plant across Southern Ocean archipelagos

Biological invasions in remote areas that experience low human activity provide unique opportunities to elucidate processes responsible for invasion success. Here we study the most widespread invasive plant species across the isolated islands of the Southern Ocean, the annual bluegrass, Poa annua. To analyse geographical variation in genome size, genetic diversity and reproductive strategies, we sampled all major sub-Antarctic archipelagos in this region and generated microsatellite data for 470 individual plants representing 31 populations. We also estimated genome sizes for a subset of individuals using flow cytometry. Occasional events of island colonization are expected to result in high genetic structure among islands, overall low genetic diversity and increased self-fertilization, but we show that this is not the case for P. annua. Microsatellite data indicated low population genetic structure and lack of isolation by distance among the sub-Antarctic archipelagos we sampled, but high population structure within each archipelago. We identified high levels of genetic diversity, low clonality and low selfing rates in sub-Antarctic P. annua populations (contrary to rates typical of continental populations). In turn, estimates of selfing declined in populations as genetic diversity increased. Additionally, we found that most P. annua individuals are probably tetraploid and that only slight variation exists in genome size across the Southern Ocean. Our findings suggest multiple independent introductions of P. annua into the sub-Antarctic, which promoted the establishment of genetically diverse populations. Despite multiple introductions, the adoption of convergent reproductive strategies (outcrossing) happened independently in each major archipelago. The combination of polyploidy and a mixed reproductive strategy probably benefited P. annua in the Southern Ocean by increasing genetic diversity and its ability to cope with the novel environmental conditions.

Living on the edge – An overview of invertebrates from groundwater habitats prone to extreme environmental conditions

Groundwater ecosystems from cold polar and circumpolar regions, hot springs, as well as those developed in salt, gypsum or in volcanic rocks are one of the environments considered to exhibit extreme environmental conditions such as low (below 0°C) or high (over 45°C) temperatures, hypersaline waters, or with elevated content of toxic gases like hydrogen sulfide or methane. They represent the “unseen ecosystem beneath our feet” and are inhabited by a large diversity of organisms, persisting and flourishing under severe environmental conditions that are usually hostile to the majority of organisms. These types of groundwater ecosystems are remarkable “evolutionary hotspots” that witnessed the adaptive radiation of morphologically and ecologically diverse species, whereas the organisms living here are good models to understand the evolutionary processes and historical factors involved in speciation and adaptation to severe environmental conditions. Here, we provide an overview of the groundwater invertebrates living in continental groundwater habitats prone to extreme environmental conditions in one or more physico-chemical parameters. Invertebrates are represented by a wide variety of taxonomic groups, however dominated by crustaceans that show specific adaptations mostly metabolic, physiologic, and behavioral. Symbiotic associations among bacteria and invertebrates are also discussed enlightening this biological interaction as a potential adaptation of different groundwater invertebrates to cope with severe environmental conditions. Given the high pressures that anthropogenic activities pose on groundwater habitats worldwide, we predict that several of these highly specialized organisms will be prone to extinction in the near future. Finally, we highlight the knowledge gaps and future research approaches in these particular groundwater ecosystems by using integrative-omic studies besides the molecular approach to shed light on genetic variation and phenotypic plasticity at species and populational levels.

GRAPHICAL ABSTRACT

Genomic basis of insularity and ecological divergence in barn owls (Tyto alba) of the Canary Islands

Islands, and the particular organisms that populate them, have long fascinated biologists. Due to their isolation, islands offer unique opportunities to study the effect of neutral and adaptive mechanisms in determining genomic and phenotypical divergence. In the Canary Islands, an archipelago rich in endemics, the barn owl (Tyto alba), present in all the islands, is thought to have diverged into a subspecies (T. a. gracilirostris) on the eastern ones, Fuerteventura and Lanzarote. Taking advantage of 40 whole-genomes and modern population genomics tools, we provide the first look at the origin and genetic makeup of barn owls of this archipelago. We show that the Canaries hold diverse, long-standing and monophyletic populations with a neat distinction of gene pools from the different islands. Using a new method, less sensitive to structure than classical F_ST, to detect regions involved in local adaptation to insular environments, we identified a haplotype-like region likely under selection in all Canaries individuals and genes in this region suggest morphological adaptations to insularity. In the eastern islands, where the subspecies is present, genomic traces of selection pinpoint signs of adapted body proportions and blood pressure, consistent with the smaller size of this population living in a hot arid climate. In turn, genomic regions under selection in the western barn owls from Tenerife showed an enrichment in genes linked to hypoxia, a potential response to inhabiting a small island with a marked altitudinal gradient. Our results illustrate the interplay of neutral and adaptive forces in shaping divergence and early onset speciation.

Assessment of Toxic Metals (Al, Cd, Pb) and Trace Elements (B, Ba, Co, Cr, Cu, Fe, Mn, Mo, Li, Zn, Ni, Sr, V) in the Common Kestrel (Falco tinnunculus) from the Canary Islands (Spain)

The monitoring of trace elements and toxic metals in apical predators of the trophic chain provides data on the degree of contamination in ecosystems. The common kestrel is one of the most interesting raptors in this respect in the Canary Islands; therefore, the study of the levels of trace elements and toxic metals in this species is of much scientific value. The content of trace elements and toxic metals (B, Ba, Co, Cr, Cu, Fe, Mn, Mo, Li, Zn, Ni, Sr, V, Al, Cd, Pb) was determined in the liver, muscle, and feathers of 200 specimens of common kestrel carcasses (Falco tinnunculus canariensis) from Tenerife. Cr (0.82 ± 2.62 mg/kg), Cu (11.82 ± 7.77 mg/kg), and Zn (198.47 ± 520.80 mg/kg) are the trace elements that stand out in the feather samples; this may be due to their affinity for the pigments that give them their coloring. Li was noteworthy in the liver samples (8.470 ± 5.702 mg/kg). Pb stood out in the feathers (4.353 ± 20.645 mg/kg) > muscle (0.148 ± 0.095 mg/kg) > liver (0.187 ± 0.133 mg/kg). The presence of metals in feathers correlates with recent exposure and reflects environmental contamination. When using raptor feathers as indicators of metal contamination, it is important to know what the levels of each metal signify. The analysis of the different tissues and organs of raptors, such as the common kestrel, provides valuable information on the degree of environmental contamination of the ecosystem in which it lives. Gender was not an influencing factor in this study.

Dispersal ability and its consequences for population genetic differentiation and diversification

Dispersal ability is known to influence geographical structuring of genetic variation within species, with a direct relationship between low vagility and population genetic structure, which can potentially give rise to allopatric speciation. However, our general understanding of the relationship between dispersal ability, population differentiation and lineage diversification is limited. To address this issue, we sampled mitochondrial DNA variation within lineages of beetles and spiders across the Canary Islands to explore the relationships between dispersal ability, differentiation within lineages and diversification. We found positive relationships between population genetic structure and diversification for both beetles and spiders. Comparisons between dispersive and non-dispersive lineages revealed significant differences for both lineage differentiation and diversification. For both taxa, non-dispersive lineages had stronger population genetic structure. Genus-level endemic species richness and proxies for diversification rate within genera were higher in non-dispersive taxa for both beetles and spiders. Comparisons of average and maximum node divergences within genera suggest that species turnover may be higher in non-dispersive genera. Our results reveal a model where dispersal limitation may shape the diversity of lineages across evolutionary timescales by positively influencing intraspecific and species diversity, moderated by higher extinction rates compared to more dispersive lineages.

Endemism, invasion, and overseas dispersal: the phylogeographic history of the Lesser Antillean frog, Eleutherodactylus johnstonei

Cryptogenic species are those whose native and introduced ranges are unknown. The extent and long history of human migration rendered numerous species cryptogenic. Incomplete knowledge regarding the origin and native habitat of a species poses problems for conservation management and may confound ecological and evolutionary studies. The Lesser Antilles pose a particular challenge with regard to cryptogenic species because these islands have been anthropogenically connected since before recorded history. Here, we use population genetic and phylogeographic tools in an attempt to determine the origin of Eleutherodactylus johnstonei, a frog species with a potentially widespread introduced range and whose native range within the Lesser Antilles is unknown. Based on elevated estimates of genetic diversity and within-island geographic structure not present elsewhere in the range, we identify Montserrat as the native island of E. johnstonei. We also document two major clades within E. johnstonei, only one of which is the primary source of introduced populations throughout the Americas. Our results demonstrate the utility of genetic tools for resolving cryptogenic species problems and highlight E. johnstonei as a potential system for understanding differences in invasive potential among sister lineages.

Genetic data from the extinct giant rat from Tenerife (Canary Islands) points to a recent divergence from mainland relatives

Evolution of vertebrate endemics in oceanic islands follows a predictable pattern, known as the island rule, according to which gigantism arises in originally small-sized species and dwarfism in large ones. Species of extinct insular giant rodents are known from all over the world. In the Canary Islands, two examples of giant rats, †Canariomys bravoi and †Canariomys tamarani, endemic to Tenerife and Gran Canaria, respectively, disappeared soon after human settlement. The highly derived morphological features of these insular endemic rodents hamper the reconstruction of their evolutionary histories. We have retrieved partial nuclear and mitochondrial data from †C. bravoi and used this information to explore its evolutionary affinities. The resulting dated phylogeny confidently places †C. bravoi within the African grass rat clade (Arvicanthis niloticus). The estimated divergence time, 650 000 years ago (95% higher posterior densities: 373 000–944 000), points toward an island colonization during the Günz–Mindel interglacial stage. †Canariomys bravoi ancestors would have reached the island via passive rafting and then underwent a yearly increase of mean body mass calculated between 0.0015 g and 0.0023 g; this corresponds to fast evolutionary rates (in darwins (d), ranging from 7.09 d to 2.78 d) that are well above those observed for non-insular mammals.

Morphological and genetic data suggest a complex pattern of inter-island colonisation and differentiation for mining bees (Hymenoptera: Anthophila: Andrena) on the Macaronesian Islands

Oceanic islands have long been considered engines of differentiation and speciation for terrestrial organisms. Here we investigated colonisation and radiation processes in the Madeira Archipelago and the Canary Islands of the Andrena wollastoni group of bees (subgenus Micrandrena), which comprises six endemic species and five endemic subspecies on the islands. Mitochondrial COI sequences support the monophyly of the four species of the Canary Islands and the two species of the Madeira Archipelago and suggest a relatively young age for all taxa. The data do not support a simple stepping-stone model (eastern-western colonisation from the mainland, with splitting into new taxa), but suggest Andrena gomerensis (extant on La Gomera and La Palma) or its ancestor as the basal lineage from which all other taxa evolved. Andrena lineolata (Tene-rife) or its putative ancestor (A. gomerensis) is sister to A. dourada (Porto Santo), A. catula (Gran Canaria), and A. acuta (also Tenerife). Andrena dourada (Porto Santo) and A. wollastoni (Madeira Island) are sister species. Morphologically and morphometrically defined subspecies were not distinguishable with COI DNA sequences. Colonisation likely led from the Canary Islands to the Madeira Archipelago and not from the mainland directly to the latter.

Description of larval morphology and phylogenetic relationships of Heterotemna tenuicornis (Silphidae)

Providing clear and detailed morphological descriptions of endemic species in limited areas enables new knowledge of their biology and ecology to be obtained through citizen science. This information can be further used for their protection. Our study presents the first morphological description of the larvae of all three instars of Heterotemna tenuicornis (Brullé, 1836), an endemic species of the Canary Islands that, together with H. britoi García & Pérez, 1996 and H. figurata (Brullé, 1839), belongs to the peculiar genus Heterotemna Wollaston, 1864. Furthermore, we present the first sequences of two mitochondrial genes (COI, 16S) obtained from larval specimens, and cross reference them with sequences from an adult specimen. Phylogenetic analysis of molecular data placed the genus Heterotemna within the genus Silpha Linnaeus, 1758, suggesting paraphyly of Silpha. In our study, we underline the importance of using a combination of morphological description and molecular data, that can be used for barcoding developmental stages which could not otherwise be definitely associated.

Sequential colonization of oceanic archipelagos led to a species-level radiation in the common chaffinch complex (Aves: Fringilla coelebs)

Oceanic archipelagos are excellent systems for studying speciation, yet inference of evolutionary process requires that the colonization history of island organisms be known with accuracy. Here, we used phylogenomics and patterns of genetic diversity to infer the sequence and timing of colonization of Macaronesia by mainland common chaffinches (Fringilla coelebs), and assessed whether colonization of the different archipelagos has resulted in a species-level radiation. To reconstruct the evolutionary history of the complex we generated a molecular phylogeny based on genome-wide SNP loci obtained from genotyping-by-sequencing, we ran ancestral range biogeographic analyses, and assessed fine-scale genetic structure between and within archipelagos using admixture analysis. To test for a species-level radiation, we applied a probabilistic tree-based species delimitation method (mPTP) and an integrative taxonomy approach including phenotypic differences. Results revealed a circuitous colonization pathway in Macaronesia, from the mainland to the Azores, followed by Madeira, and finally the Canary Islands. The Azores showed surprisingly high genetic diversity, similar to that found on the mainland, and the other archipelagos showed the expected sequential loss of genetic diversity. Species delimitation methods supported the existence of several species within the complex. We conclude that the common chaffinch underwent a rapid radiation across Macaronesia that was driven by the sequential colonization of the different archipelagos, resulting in phenotypically and genetically distinct, independent evolutionary lineages. We recommend a taxonomic revision of the complex that takes into account its genetic and phenotypic diversity.

Archipelago-Wide Patterns of Colonization and Speciation Among an Endemic Radiation of Galápagos Land Snails

Newly arrived species on young or remote islands are likely to encounter less predation and competition than source populations on continental landmasses. The associated ecological release might facilitate divergence and speciation as colonizing lineages fill previously unoccupied niche space. Characterizing the sequence and timing of colonization on islands represents the first step in determining the relative contributions of geographical isolation and ecological factors in lineage diversification. Herein, we use genome-scale data to estimate timing of colonization in Naesiotus snails to the Galápagos islands from mainland South America. We test inter-island patterns of colonization and within-island radiations to understand their contribution to community assembly. Partly contradicting previously published topologies, phylogenetic reconstructions suggest that most Naesiotus species form island-specific clades, with within-island speciation dominating cladogenesis. Galápagos Naesiotus also adhere to the island progression rule, with colonization proceeding from old to young islands and within-island diversification occurring earlier on older islands. Our work provides a framework for evaluating the contribution of colonization and in situ speciation to the diversity of other Galápagos lineages.

Speciation and secondary contact in a fossorial island endemic, the São Tomé caecilian

A period of isolation in allopatry typically precedes local adaptation and subsequent divergence among lineages. Alternatively, locally adapted phenotypes may arise and persist in the face of gene flow, resulting in strong correlations between ecologically-relevant phenotypic variation and corresponding environmental gradients. Quantifying genetic, ecological, and phenotypic divergence in such lineages can provide insights into the abiotic and biotic mechanisms that structure populations and drive the accumulation of phenotypic and taxonomic diversity. Low-vagility organisms whose distributions span ephemeral geographic barriers present the ideal evolutionary context within which to address these questions. Here, we combine genetic (mtDNA and genome-wide SNPs) and phenotypic data to investigate the divergence history of caecilians (Amphibia: Gymnophiona) endemic to the oceanic island of São Tomé in the Gulf of Guinea archipelago. Consistent with a previous mtDNA study, we find two phenotypically and genetically distinct lineages that occur along a north-to-south axis with extensive admixture in the centre of the island. Demographic modelling supports divergence in allopatry (~300 kya) followed by secondary contact (~95 kya). Consequently, in contrast to a morphological study that interpreted latitudinal phenotypic variation in these caecilians as a cline within a single widespread species, our analyses suggest a history of allopatric lineage divergence and subsequent hybridization that may have blurred species boundaries. We propose that late Pleistocene volcanic activity favoured allopatric divergence between these lineages with local adaptation to climate maintaining a stable hybrid zone in the centre of São Tomé Island. Our study joins a growing number of systems demonstrating lineage divergence on volcanic islands with stark environmental transitions across small geographic distances.

Evolutionary effects of geographic and climatic isolation between Rhododendron tsusiophyllum populations on the Izu Islands and mainland Honshu of Japan

Geographic and environmental isolations of islands and the mainland offer excellent opportunity to investigate colonization and survival dynamics of island populations. We inferred and compared evolutionary processes and the demographic history of Rhododendron tsusiophyllum, in the Izu Islands and the much larger island Honshu, treated here as the mainland, using thousands of nuclear SNPs obtained by ddRAD-seq from eight populations of R. tsusiophyllum and three populations of R. tschonoskii as an outgroup. Phylogenetic relationships and their habitats suggest that R. tsusiophyllum had evolved and migrated from cold north to warm south regions. We detected clear genetic divergence among populations in three regions of Honshu and the Izu Islands, suggesting restricted migration between them due to isolated habitats on mountains even in the mainland. The three regions have different changes in effective population size, especially, genetic diversity and population size of the Izu Islands are small compared to the others. Further, habitats of populations in the Izu Islands are warmer than those in Honshu, suggesting that they have undergone adaptive evolution. Our study provides evidences of montane rather than insular isolation on genetic divergence, survival of populations and significance of adaptive evolution for island populations with small population size and low genetic diversity, despite close proximity to mainland populations.

The Asian plethodontid salamander preserves historical genetic imprints of recent northern expansion

The Korean Peninsula, located at the southern tip of Northeast Asia, has never been covered by ice sheets and was a temperate refugium during the Pleistocene. Karsenia koreana, the sole Asian plethodontid salamander species, occurs only on the southern half of the Korean Peninsula and is thought to have found various climatic refugia. Despite its phylogenetic and biogeographic importance, no population-level genetic analysis has been performed on this species. Here we study the population genetic structure of K. koreana using mitochondrial and microsatellite loci to understand the recent historical dispersion process that shaped its current distribution. Overall, the genetic distance between populations correlated well with the spatial distance, and the genetic structure among populations showed signs of a unilateral northward expansion from a southernmost refugium population. Given the distinct genetic structure formed among the populations, the level of historical gene flow among populations appears to have been very low. As the estimated effective population size of K. koreana was also small, these results suggest that the small, restricted populations of K. koreana are extremely vulnerable to environmental changes that may require high levels of genetic diversity to cope with. Thus, special management strategies are needed to preserve these remnant populations.

Reconstruction of the spatio-temporal diversification and ecological niche evolution of Helianthemum (Cistaceae) in the Canary Islands using genotyping-by-sequencing data

BACKGROUND AND AIMS

Several biogeographical models have been proposed to explain the colonization and diversification patterns of Macaronesian lineages. In this study, we calculated the diversification rates and explored what model best explains the current distribution of the 15 species endemic to the Canary Islands belonging to Helianthemum sect. Helianthemum (Cistaceae).

METHODS

We performed robust phylogenetic reconstructions based on genotyping-by-sequencing data and analysed the timing, biogeographical history and ecological niche conservatism of this endemic Canarian clade.

KEY RESULTS

Our phylogenetic analyses provided strong support for the monophyly of this clade, and retrieved five lineages not currently restricted to a single island. The pristine colonization event took place in the Pleistocene (~1.82 Ma) via dispersal to Tenerife by a Mediterranean ancestor.

CONCLUSIONS

The rapid and abundant diversification (0.75-1.85 species per million years) undergone by this Canarian clade seems the result of complex inter-island dispersal events followed by allopatric speciation driven mostly by niche conservatism, i.e. inter-island dispersal towards niches featuring similar environmental conditions. Nevertheless, significant instances of ecological niche shifts have also been observed in some lineages, making an important contribution to the overall diversification history of this clade.

Diversification of Aeonium Species Across Macaronesian Archipelagos: Correlations Between Genome-Size Variation and Their Conservation Status

The rich endemic flora of the Macaronesian Islands places these oceanic archipelagos among the top biodiversity hotspots worldwide. The radiations that have determined the evolution of many of these insular lineages resulted in a wealth of endemic species, many of which occur in a wide range of ecological niches, but show small distribution areas in each of them. Aeonium (Crassulaceae) is the most speciose lineage in the Canary Islands (ca. 40 taxa), and as such can be considered a good model system to understand the diversification dynamics of oceanic endemic floras. The present study aims to assess the genome size variation within Aeonium distribution, i.e., the Macaronesian archipelagos of Madeira, Canaries and Cabo Verde, and analyse it together with information on distribution (i.e., geography and conservation status), taxonomy (i.e., sections), morphological traits (i.e., growth-form), geological data (i.e., island's geological age), and environmental variables (i.e., altitude, annual mean temperature, and precipitation). Based on extensive fieldwork, a cytogeographic screening of 24 Aeonium species was performed. The conservation status of these species was assessed based on IUCN criteria. 61% of the taxa were found to be threatened (4% Endangered and 57% Vulnerable). For the first time, the genome size of a comprehensive sample of Aeonium across the Macaronesian archipelagos was estimated, and considerable differences in Cx-values were found, ranging from 0.984 pg (A. dodrantale) to 2.768 pg (A. gorgoneum). An overall positive correlation between genome size and conservation status was found, with the more endangered species having the larger genomes on average. However, only slight relationships were found between genome size, morphological traits, and environmental variables. These results underscore the importance of characterizing the cytogenomic diversity and conservation status of endemic plants found in Macaronesian Islands, providing, therefore, new data to establish conservation priorities.

Endemics Versus Newcomers: The Ladybird Beetle (Coleoptera: Coccinellidae) Fauna of Gran Canaria

Simple Summary

Many plants and animals that live in the Canary Islands belong to the so-called endemic species, i.e., they do not occur outside of this particular region. Several other species have a slightly wider geographical distribution, apart from the Canaries, which also includes some islands of the nearby archipelagos, such as Madeira or the Azores, or the northwestern periphery of Africa. Here, we call such species subendemics. However, the Canary Islands have recently been colonized by a substantial number of immigrants from more or less remote areas. In this paper, based on our field survey and previously published data, we analyzed the fauna of the ladybird beetles (Coccinellidae) of Gran Canaria, one of the central islands of the archipelago. Among 42 ladybird beetle species so far recorded on this island, 17 (40%) are endemics and subendemics, and 21 (50%) probably arrived in Gran Canaria relatively recently, i.e., in the 20th and 21st century. Of those newcomers, there are Australian, American, African, and European species. The nonnative ladybird species may pose a threat to the unique ladybird communities from Gran Canaria and other islands of the archipelago.

Abstract

Research on the fauna of beetles (Coleoptera) of the Canary Islands has a long tradition, which enables tracking changes in their species composition and arrival of new species. In this paper, we provide new faunistic data on the ladybird beetles (Coccinellidae) recorded on Gran Canaria, one of the central islands of the archipelago, and then analyze available information on the Gran Canarian ladybird fauna from geographical and historical points of view. The field survey resulted in recording 1402 ladybird individuals belonging to 30 species. Ten of these species were new to Gran Canaria and three of them, Chilocorus bipustulatus (Linnaeus), Nephus bisignatus (Boheman), and Nephus ulbrichi Fürsch, had not previously been reported to be on any of the islands of the Canarian archipelago. Tetrabrachys tinerfensis (Hodgson) is synonymized with T. deserticola (Wollaston). Our survey and literature reports allowed us to recognize 42 species of Coccinellidae so far recorded on Gran Canaria. Seventeen of them (40%) belonged to the Canarian endemic and subendemic species, and 21 (50%) were newcomers and presumed newcomers. Colonization of Gran Canaria and other islands of the archipelago by ladybird species of various origins seems to be a frequent phenomenon that may pose a threat to the unique communities of the native Canarian species.

Spatiotemporal patterns of avian host-parasite interactions in the face of biogeographical range expansions

Exploration of interactions between hosts and parasitic symbionts is important for our understanding of the temporal and spatial distribution of organisms. For example, host colonization of new geographical regions may alter levels of infections and parasite specificity, and even allow hosts to escape from co-evolved parasites, consequently shaping spatial distributions and community structure of both host and parasite. Here we investigate the effect of host colonization of new regions and the elevational distribution of host-parasite associations between birds and their vector-transmitted haemosporidian blood parasites in two geological and geographical settings: mountains of New Guinea and the Canary Islands. Our results demonstrate that bird communities in younger regions have significantly lower levels of parasitism compared to those of older regions. Furthermore, host-parasite network analyses demonstrate that blood parasites may respond differently after arriving to a new region, through adaptations that allow for either expanding (Canary Islands) or retaining (New Guinea) their host niches. The spatial prevalence patterns along elevational gradients differed in the two regions, suggesting that region-specific biotic (e.g., host community) and abiotic factors (e.g., temperature) govern prevalence patterns. Our findings suggest that the spatiotemporal range dynamics in host-parasite systems are driven by multiple factors, but that host and parasite community compositions and colonization histories are of particular importance.

Analysis of the genetic diversity of the coastal and island endangered plant species Elaeagnus macrophylla via conserved DNA-derived polymorphism marker

The genetic diversity and genetic structure of five natural populations of the island and coastal endangered plant species Elaeagnus macrophylla were analyzed via conserved DNA-derived polymorphism molecular markers. A total of 289 discernible loci were obtained from 102 individuals via fifteen primers, and 100% of the loci were polymorphic. The observed number of alleles was 1.9654, and the effective number of alleles was 1.2604. Nei’s genetic diversity index was 0.1724 on average, and Shannon’s information index was 0.2869, indicating that Elaeagnus macrophylla had lower levels of genetic diversity than those reported for its continental relatives and other continental species. The average percentage of polymorphic loci was 42.1%, and the maximum and minimum were 80.97% and 14.88%, respectively, which were associated with the Nanji Island and Liugong Island populations, respectively. The populations of Elaeagnus macrophylla were highly differentiated. Cluster analysis revealed that the similarity between the tested samples was related to their geographical location, that the samples from the same island tended to cluster together, and that there was no cross-clustering between samples. The Nanji Island and Da Rushan populations differentiated into two subpopulations. Last, we detected no correlation between genetic distance and geographic distance between populations (Pearson’s correlation coefficient r = 0.256579, p-value = 0.8309).

First nearly complete skull of Gallotia auaritae (lower-middle Pleistocene, Squamata, Gallotiinae) and a morphological phylogenetic analysis of the genus Gallotia

The Canary Islands are an Atlantic archipelago known for its high number of endemic species. Among the most known endemic vertebrate species are the giant lizards of the genus Gallotia. We describe the cranial osteology of the first almost complete and articulated fossil skull of the taxon Gallotia auaritae, recovered from the lower-middle Pleistocene of the La Palma island. In this work, X-ray computed microtomography images were used to perform an exhaustive phylogenetic analysis where most of the extant and fossil species of the genus Gallotia were included for first time. This analysis recovered a monophyletic Gallotia clade with similar topology to that of molecular analyses. The newly described specimen shares some characters with the group formed by G. bravoana, G. intermedia and G. simonyi, G. auaritae, and its position is compatible with a referral to the latter. Our study adds new important data to the poorly known cranial morphology of G. auaritae, and the phylogenetic analysis reveals an unexpected power of resolution to obtain a morphology-based phylogeny for the genus Gallotia, for inferring the phylogenetic position of extinct species and for helping in the identification of fossil specimens.

Phylogenetic divergence of island biotas: Molecular dates, extinction, and "relict" lineages

Island formation is a key driver of biological evolution, and several studies have used geological ages of islands to calibrate rates of DNA change. However, many islands are home to "relict" lineages whose divergence apparently pre-dates island age. The geologically dynamic New Zealand (NZ) archipelago sits upon the ancient, largely submerged continent Zealandia, and the origin and age of its distinctive biota have long been contentious. While some researchers have interpreted NZ's biota as equivalent to that of a post-Oligocene island, a recent review of genetic studies identified a sizeable proportion of pre-Oligocene "relict" lineages, concluding that much of the biota survived an incomplete drowning event. Here, we assemble comparable genetic divergence data sets for two recently formed South Pacific archipelagos (Lord Howe; Chatham Islands) and demonstrate similarly substantial proportions of relict lineages. Similar to the NZ biota, our island reviews provide surprisingly little evidence for major genetic divergence "pulses" associated with island emergence. The dominance of Quaternary divergence estimates in all three biotas may highlight the importance of rapid biological turnover and new arrivals in response to recent climatic and/or geological disturbance and change. We provide a schematic model to help account for discrepancies between expected versus observed divergence-date distributions for island biotas, incorporating the effects of both molecular dating error and lineage extinction. We conclude that oceanic islands can represent both evolutionary "cradles" and "museums" and that the presence of apparently archaic island lineages does not preclude dispersal origins.

A paradise for parasites? Seven new haemogregarine species infecting lizards from the Canary Islands

Oceanic islands are hotspots of biodiversity due to their high levels of endemism, with the Canary Islands being a notable example. A previous molecular study on the biogeography and host associations of haemogregarines (Apicomplexa: Adeleorina) infecting lizards from this archipelago detected seven parasite haplogroups. These haplogroups exhibited high host-specificity and geographical structure, suggesting that they might correspond to distinct biological identities. In this study, along with sequencing a longer fragment of the 18S rRNA, we further explore the distinctiveness of these parasites by analysing their morphology, effects on host erythrocytes and parasitaemia levels. These lines of evidence together with their genetics, host associations, frequency of occurrence and geographical distribution support them as different biological entities. As such, we describe seven new species: Karyolysus canariensis sp. nov., Karyolysus galloti sp. nov., Karyolysus stehlini sp. nov., Karyolysus gomerensis sp. nov., Karyolysus atlanticus sp. nov., Karyolysus tinerfensis sp. nov. and Karyolysus makariogeckonis sp. nov. These new taxa are further examples of endemic diversity in the Canarian archipelago. They also contribute to clarify the taxonomy within the Apicomplexa, a phylum estimated to have one of the lowest percentages of described species.

A novel dendroecological method finds a non-linear relationship between elevation and seasonal growth continuity on an island with trade wind-influenced water availability

Climatic seasonality drives ecosystem processes (e.g. productivity) and influences plant species distribution. However, it is poorly understood how different aspects of seasonality (especially regarding temperature and precipitation) affect growth continuity of trees in climates with low seasonality because seasonality is often only crudely measured. On islands, exceptionally wide elevational species distribution ranges allow the use of tree rings to identify how growth continuity and climate-growth relationships change with elevation. Here, we present a novel dendroecological method to measure stem growth continuity based on annual density fluctuations (ADFs) in tree rings of Pinus canariensis to indicate low climatic seasonality. The species ranges from 300 to >2000 m a.s.l. on the trade wind-influenced island of La Palma (Canary Islands), where we measured three decades of tree-ring data of 100 individuals distributed over 10 sites along the entire elevational range. The successfully implemented ADF approach revealed a major shift of stem growth continuity across the elevational gradient. In a remarkably clear pattern, stem growth continuity (percentage of ADFs) showed a hump-shaped relationship with elevation reaching a maximum at around 1000 m a.s.l. Low- to mid-elevation tree growth was positively correlated with the Palmer Drought Severity Index (PDSI; indicating aridity) and sea surface temperature (indicating trade wind-influenced moderation of water supply), while high-elevation tree growth was positively correlated with winter temperature (indicating a cold-induced dormancy period). We conclude that ADFs are a useful method to measure stem growth continuity in low-seasonality climates. Growth of P. canariensis on the Canary Islands is more frequently interrupted by winter cold at high elevations and by summer drought at low elevations than in the trade wind-influenced mid elevations, where growth sometimes continues throughout the year. Climate change-associated alterations in trade wind cloud formation might cause non-analogue growth limitations for many unique island species.

A tale of two forests: ongoing aridification drives population decline and genetic diversity loss at continental scale in Afro-Macaronesian evergreen-forest archipelago endemics

BACKGROUND AND AIMS

Various studies and conservationist reports have warned about the contraction of the last subtropical Afro-Macaronesian forests. These relict vegetation zones have been restricted to a few oceanic and continental islands around the edges of Africa, due to aridification. Previous studies on relict species have generally focused on glacial effects on narrow endemics; however, little is known about the effects of aridification on the fates of previously widespread subtropical lineages.

METHODS

Nuclear microsatellites and ecological niche modelling were used to understand observed patterns of genetic diversity in two emblematic species, widely distributed in these ecosystems: Canarina eminii (a palaeoendemic of the eastern Afromontane forests) and Canarina canariensis (a palaeoendemic of the Canarian laurel forests). The software DIYABC was used to test alternative demographic scenarios and an ensemble method was employed to model potential distributions of the selected plants from the end of the deglaciation to the present.

KEY RESULTS

All the populations assessed experienced a strong and recent population decline, revealing that locally widespread endemisms may also be alarmingly threatened.

CONCLUSIONS

The detected extinction debt, as well as the extinction spiral to which these populations are subjected, demands urgent conservation measures for the unique, biodiversity-rich ecosystems that they inhabit.