Miocene diversification of an open‐habitat predatorial passerine radiation, the shrikes (Aves: Passeriformes: Laniidae)

Songbirds of the Americas show uniform morphological evolution despite heterogeneous diversification

Studying the relationship between diversification and functional trait evolution among broadly co-occurring clades can shed light on interactions between ecology and evolutionary history. However, evidence from many studies is compromised because of their focus on overly broad geographic or narrow phylogenetic scales. We addressed these limitations by studying 46 independent, biogeographically delimited clades of songbirds that dispersed from the Eastern Hemisphere into the Americas and assessed (1) whether diversification has varied through time and/or among clades within this assemblage, (2) the extent of heterogeneity in clade-specific morphological trait disparity and (3) whether morphological disparity among these clades is consistent with a uniform diversification model. We found equivalent support for constant rates birth-death and density-dependent speciation processes, with notable outliers having significantly fewer or more species than expected given their age. We also found substantial variation in morphological disparity among these clades, but that variation was broadly consistent with uniform evolutionary rates, despite the existence of diversification outliers. These findings indicate relatively continuous, ongoing morphological diversification, arguing against conceptual models of adaptive radiation in these continental clades. Additionally, they suggest surprisingly consistent diversification among the majority of these clades, despite tremendous variance in colonization history, habitat valences and trophic specializations that exist among continental clades of birds.

Wallacean and Melanesian Islands Promote Higher Rates of Diversification within the Global Passerine radiation Corvides

The complex island archipelagoes of Wallacea and Melanesia have provided empirical data behind integral theories in evolutionary biology, including allopatric speciation and island biogeography. Yet, questions regarding the relative impact of the layered biogeographic barriers, such as deep-water trenches and isolated island systems, on faunal diversification remain underexplored. One such barrier is Wallace's Line, a significant biogeographic boundary that largely separates Australian and Asian biodiversity. To assess the relative roles of biogeographic barriers-specifically isolated island systems and Wallace's Line-we investigated the tempo and mode of diversification in a diverse avian radiation, Corvides (Crows and Jays, Birds-of-paradise, Vangas, and allies). We combined a genus-level dataset of thousands of ultraconserved elements (UCEs) and a species-level, 12-gene Sanger sequence matrix to produce a well-resolved supermatrix tree that we leveraged to explore the group's historical biogeography and effects of biogeographic barriers on their macroevolutionary dynamics. The tree is well-resolved and differs substantially from what has been used extensively for past comparative analyses within this group. We confirmed that Corvides, and its major constituent clades, arose in Australia and that a burst of dispersals west across Wallace's Line occurred after the uplift of Wallacea during the mid-Miocene. We found that dispersal across this biogeographic barrier were generally rare, though westward dispersals were two times more frequent than eastward dispersals. Wallacea's central position between Sundaland and Sahul no doubt acted as a bridge for island-hopping dispersal out of Australia, across Wallace's Line, to colonize the rest of Earth. In addition, we found that the complex island archipelagoes east of Wallace's Line harbor the highest rates of net diversification and are a substantial source of colonists to continental systems on both sides of this biogeographic barrier. Our results support emerging evidence that island systems, particularly the geologically complex archipelagoes of the Indo-pacific, are drivers of species diversification.

Migration-tracking integrated phylogeography supports long-distance dispersal-driven divergence for a migratory bird species in the Japanese archipelago

Long-distance dispersal (LDD) outside a species' breeding range contributes to genetic divergence. Previous phylogeographic studies of migratory bird species have not discriminated LDD from vicariant speciation in their diversification process. We conducted an integrative phylogeographic approach to test the LDD hypothesis, which predicts that a Japanese migratory bird subspecies diverged from a population in the coastal region of the East China Sea (CRECS) via LDD over the East China Sea (ECS). Haplotype networks of both mitochondrial and nuclear genes of its three subspecies were reconstructed to examine whether the Japanese subspecies of the Brown Shrike (Lanius cristatus superciliosus) diverged from an ancestral CRECS population. A species distribution model (SDM) for the Japanese subspecies was constructed using bioclimatic variables under the maximum entropy algorithm. It was projected backwards to the climate of the last glacial maximum (LGM) to infer the candidate source area of colonization. A migratory route of L. c. superciliosus, which possibly reflects a candidate past colonization route, was tracked by light-level geolocators. Molecular phylogenetic networks suggest that the Japanese subspecies diverged from a population in the CRECS and maintained anciently diverged haplotypes. The SDM inferred that the emerged continental shelf of the ECS and the present CRECS were suitable breeding areas for the Japanese subspecies during the LGM. A major migratory route for L. c. superciliosus was inferred between the CRECS and the Japanese archipelago across the ECS. Our integrative approach supported the LDD hypothesis for divergence of the Japanese subspecies of the Brown Shrike. Shrinkage of the ECS may have been responsible for successful population establishment, due to a sufficient number of migrants overshooting to the Japanese archipelago from the CRECS. Our framework provides a new phylogeographic scenario for this region. Discriminating LDD and vicariance models helps improve our understanding of the phylogeographic histories of migratory species.

Contrasting Trends of Population Size Change for Two Eurasian Owlet Species—Athene brama and Glaucidium radiatum From South Asia Over the Late Quaternary

Climatic oscillations over the Quaternary have had a lasting impact on species’ distribution, evolutionary history, and genetic composition. Many species show dramatic population size changes coinciding with the last glacial period. However, the extent and direction of change vary across biogeographic regions, species-habitat associations, and species traits. Here we use genomic data to assess population size changes over the late Quaternary using the Pairwise Sequential Markovian Coalescent (PSMC) approach in two Eurasian Owlet species—the Spotted Owlet, Athene brama, and the Jungle Owlet, Glaucidium radiatum. While Spotted Owlets are typically associated with open habitats, Jungle Owlets are found in deciduous forests and scrublands. We find that the effective population size for the Spotted Owlet increased after the Interglacial period till the Last Glacial Maxima and subsequently declined toward the Mid-Holocene. On the other hand, effective population size estimates for the Jungle Owlet increased gradually throughout this period. These observations are in line with climatic niche model-based predictions for range size change for both species from a previous study and suggest that habitat associations at the local scale are important in determining responses to past climatic and vegetational changes. The Spotted Owlet result also aligns well with the expectation of open habitat expansion during the arid Glacial Maxima, whereas for the Jungle Owlet the contrasting expectation does not hold. Therefore, assessing the impacts of glacial history on population trajectories of multiple species with different habitat associations is necessary to understand the impacts of past climate on South Asian taxa.

Molecular Species Delimitation of Larks (Aves: Alaudidae), and Integrative Taxonomy of the Genus Calandrella, with the Description of a Range-Restricted African Relic Taxon

Larks constitute an avian family of exceptional cryptic diversity and striking examples of convergent evolution. Therefore, traditional morphology-based taxonomy has recurrently failed to reflect evolutionary relationships. While taxonomy ideally should integrate morphology, vocalizations, behaviour, ecology, and genetics, this can be challenging for groups that span several continents including areas that are difficult to access. Here, we combine morphometrics and mitochondrial DNA to evaluate the taxonomy of Calandrella larks, with particular focus on the African C. cinerea and the Asian C. acutirostris complexes. We describe a new range-restricted West African taxon, Calandrella cinerea rufipecta ssp. nov. (type locality: Jos, Plateau State, Nigeria), with an isolated relic population 3000 km from its closest relative in the Rift Valley. We performed molecular species delimitation, employing coalescence-based multi-rate Poisson Tree Processes (mPTP) on cytochrome b sequences across 52 currently recognized lark species, including multiple taxa currently treated as subspecies. Three species-level splits were inferred within the genus Calandrella and another 13 across other genera, primarily among fragmented sub-Saharan taxa and taxa distributed from Northwest Africa to Arabia or East Africa. Previously unknown divergences date back as far as to the Miocene, indicating the presence of currently unrecognized species. However, we stress that taxonomic decisions should not be based on single datasets, such as mitochondrial DNA, although analyses of mitochondrial DNA can be a good indicator of taxa in need of further integrative taxonomic assessment.

Seasonal environments drive convergent evolution of a faster pace-of-life in tropical butterflies

New ecological niches that may arise due to climate change can trigger diversification, but their colonisation often requires adaptations in a suite of life-history traits. We test this hypothesis in species-rich Mycalesina butterflies that have undergone parallel radiations in Africa, Asia, and Madagascar. First, our ancestral state reconstruction of habitat preference, using c. 85% of extant species, revealed that early forest-linked lineages began to invade seasonal savannahs during the late Miocene-Pliocene. Second, rearing replicate pairs of forest and savannah species from the African and Malagasy radiation in a common garden experiment, and utilising published data from the Asian radiation, demonstrated that savannah species consistently develop faster, have smaller bodies, higher fecundity with an earlier investment in reproduction, and reduced longevity, compared to forest species across all three radiations. We argue that time-constraints for reproduction favoured the evolution of a faster pace-of-life in savannah species that facilitated their persistence in seasonal habitats.

Foraging behaviour and diet in two sympatric shrike species during autumn migration across the Arabian Peninsula

In situations of restricted food supply, the trophic niches of closely-related species of animals should be separate. For sit-and-wait hunters, such as shrikes, this is associated with competition for food and hunting sites. In the present study, the foraging behaviour of two shrike species - Red-tailed Shrike Lanius phoenicuroides and Red-backed Shrike Lanius collurio - was studied in a desert habitat in Oman. The fieldwork was carried out in September 2019, during the peak migration of these birds. Their behaviour was recorded in detail during 30-minute observation bouts. A General Linear Mixed Model with logit link function and binomial error variance was used to compare their behaviour. The type of perch and its height did not differ between them, but there were significant differences in their use of look-out posts only in the mean duration of a single perching event, which was more than twice as long in Red-backed Shrike. No differences in prey size were found between the species and hunting success (the ratio of successful attacks to all attacks) was similar in both (RtS-RbS: 46 vs. 61%). Dietary diversity was twice as great in Red-tailed Shrike as in Red-backed Shrike, but in general, their diets did not differ very much. Dietary overlap between the species at this level of prey identification was 92%. This absence of differences in some aspects of behaviour and diet may be due to the similarity of the two species, above all their same body size, and even the possibility of hybridization. If the species compared are so similar due to body size, behaviour and evolutionary relationship their food niches may overlap.