Phylogeography and evolutionary lineage diversity in the small-eared greater galago, Otolemur garnettii (Primates: Galagidae)

Assessing the true lineage diversity in elusive nocturnal organisms is particularly challenging due to their subtle phenotypic variation in diagnostic traits. The cryptic small-eared greater galago (Otolemur garnettii) offers a great opportunity to test if currently recognized subspecies, suggested by discontinuities in coat colour pattern and geographic barriers, represent distinct evolutionary lineages. To answer this question, we conducted the first population-level phylogeographic study of the species, sampling wild specimens from across almost its entire latitudinal range, including the Zanzibar Archipelago. We applied five species-delimitation algorithms to investigate the genetic diversity and distribution pattern of mitochondrial DNA across the geographic range of three out of four subspecies. Our results suggest that far-northern populations of O. g. lasiotis potentially represent an independently evolving lineage, but populations assigned to O. g. garnettii from Zanzibar Island and of O. g panganiensis from mainland Tanzania do not constitute two independent lineages. A dated phylogeny suggests that this northern clade diverged from all remaining samples approximately 4 Mya. Such old divergence age is in line with the split between many galagid species. This northern lineage could potentially represent an incipient species; however, there is not yet enough evidence to support a new taxonomic status for this unique mitochondrial group.

Geographic variation in the skulls of the horseshoe bats, Rhinolophus simulator and R. cf. simulator: Determining the relative contributions of adaptation and drift using geometric morphometrics

The relative contributions of adaptation and genetic drift to morphological diversification of the skulls of echolocating mammals were investigated using two horseshoe bat species, Rhinolophus simulator and R. cf. simulator, as test cases. We used 3D geometric morphometrics to compare the shapes of skulls of the two lineages collected at various localities in southern Africa. Size and shape variation was predominantly attributed to selective forces; the between-population variance (B) was not proportional to the within-population variance (W). Modularity was evident in the crania of R. simulator but absent in the crania of R. cf. simulator and the mandibles of both species. The skulls of the two lineages thus appeared to be under different selection pressures, despite the overlap in their distributions. Difference in the crania of R. cf. simulator was centered largely on the nasal dome region of R. cf. simulator but on the cranium and mandibles of R. simulator. It is likely that the size and shape of the nasal dome, which acts as a frequency-dependent acoustic horn, is more crucial in R. cf. simulator than in R. simulator because of the higher echolocation frequencies used by R. cf. simulator. A larger nasal dome in R. cf. simulator would allow the emission of higher intensity pulses, resulting in comparable detection distances to that of R. simulator. In contrast, selection pressure is probably more pronounced on the mandibles and cranium of R. simulator to compensate for the loss in bite force because of its elongated rostrum. The predominance of selection probably reflects the stringent association between environment and the optimal functioning of phenotypic characters associated with echolocation and feeding in bats.

A phylogeny for African Pipistrellus species with the description of a new species from West Africa (Mammalia: Chiroptera)

Pipistrelloid bats are among the most poorly known bats in Africa, a status no doubt exacerbated by their small size, drab brown fur and general similarity in external morphology. The systematic relationships of these bats have been a matter of debate for decades, and despite some recent molecular studies, much confusion remains. Adding to the confusion has been the recent discovery of numerous new species. Using two mitochondrial genes, we present a phylogeny for this group that supports the existence of three main clades in Africa: Pipistrellus, Neoromicia and the recently described Parahypsugo. However, the basal branches of the tree are poorly supported. Using an integrative taxonomic approach, we describe a new species of Pipistrellus sp. nov. from West Africa, which has been cited as Pipistrellus cf. grandidieri in the literature. We demonstrate that it is not closely related to Pipistrellus grandidieri from East Africa, but instead is sister to Pipistrellus hesperidus. Furthermore, the species Pi. grandidieri appears to be embedded in the newly described genus Parahypsugo, and is therefore better placed in that genus than in Pipistrellus. This has important taxonomic implications, because a new subgenus (Afropipistrellus) described for Pi. grandidieri predates Parahypsugo and should therefore be used for the entire “Parahypsugo” clade. The Upper Guinea rainforest zone, and particularly the upland areas in the south-eastern Guinea—northern Liberia border region may represent a global hotspot for pipistrelloid bats and should receive increased conservation focus as a result.

Demographic responses of forest-utilizing bats to past climate change in South Africa

Historical forest contractions may have restricted the distributions of forest-utilizing fauna while providing opportunities for range expansions for open-habitat species. We aimed to test if habitat associations have played an important role in determining population genetic structure and demographic responses of six bats to oscillations in forest extent since the Last Glacial Maximum (LGM). We hypothesized that forest-associated species would display high levels of population structure and past population contractions as their distribution is dependent on fragmented forests. By contrast, habitat generalists would demonstrate low geographical structuring and historical population stability as suitable habitats are widely available. We used mitochondrial DNA to generate genetic diversity and population structure metrics of three forest-associated species and three habitat generalists in South Africa. Neutrality tests and Bayesian skyline plots were used to investigate demographic histories. A forest habitat association did not inform the population genetics of the study species. Rather, species-specific traits of roosting requirements, philopatry to the natal range and dispersal ability informed the observed structure. All species demonstrated population expansions during the Pleistocene, with no apparent decline during the LGM. It appears that the lower climate change footprint and refuge-status of eastern South Africa prevented population declines of insectivorous bats during the LGM.

Molecular phylogenetics of the African horseshoe bats (Chiroptera: Rhinolophidae): expanded geographic and taxonomic sampling of the Afrotropics

Background

The Old World insectivorous bat genus Rhinolophus is highly speciose. Over the last 15 years, the number of its recognized species has grown from 77 to 106, but knowledge of their interrelationships has not kept pace. Species limits and phylogenetic relationships of this morphologically conservative group remain problematic due both to poor sampling across the Afrotropics and to repeated instances of mitochondrial-nuclear discordance. Recent intensive surveys in East Africa and neighboring regions, coupled with parallel studies by others in West Africa and in Southern Africa, offer a new basis for understanding its evolutionary history.

Results

We investigated phylogenetic relationships and intraspecific genetic variation in the Afro-Palearctic clade of Rhinolophidae using broad sampling. We sequenced mitochondrial cytochrome-b (1140 bp) and four independent and informative nuclear introns (2611 bp) for 213 individuals and incorporated sequence data from 210 additional individuals on GenBank that together represent 24 of the 33 currently recognized Afrotropical Rhinolophus species. We addressed the widespread occurrence of mito-nuclear discordance in Rhinolophus by inferring concatenated and species tree phylogenies using only the nuclear data. Well resolved mitochondrial, concatenated nuclear, and species trees revealed phylogenetic relationships and population structure of the Afrotropical species and species groups.

Conclusions

Multiple well-supported and deeply divergent lineages were resolved in each of the six African Rhinolophus species groups analyzed, suggesting as many as 12 undescribed cryptic species; these include several instances of sympatry among close relatives. Coalescent lineage delimitation offered support for new undescribed lineages in four of the six African groups in this study. On the other hand, two to five currently recognized species may be invalid based on combined mitochondrial and/or nuclear phylogenetic analyses. Validation of these cryptic lineages as species and formal relegation of current names to synonymy will require integrative taxonomic assessments involving morphology, ecology, acoustics, distribution, and behavior. The resulting phylogenetic framework offers a powerful basis for addressing questions regarding their ecology and evolution.

Electronic supplementary material

The online version of this article (10.1186/s12862-019-1485-1) contains supplementary material, which is available to authorized users.

Morphology and stable isotope analysis demonstrate different structuring of bat communities in rainforest and savannah habitats

Bats play important ecological roles in tropical systems, yet how these communities are structured is still poorly understood. Our study explores the structure of African bat communities using morphological characters to define the morphospace occupied by these bats and stable isotope analysis to define their dietary niche breadth. We compared two communities, one in rainforest (Liberia) and one in savannah (South Africa), and asked whether the greater richness in the rainforest was due to more species 'packing' into the same morphospace and trophic space than bats from the savannah, or some other arrangement. In the rainforest, bats occupied a larger area in morphospace and species packing was higher than in the savannah; although this difference disappeared when comparing insectivorous bats only. There were also differences in morphospace occupied by different foraging groups (aerial, edge, clutter and fruitbat). Stable isotope analysis revealed that the range of δ ¹³C values was almost double in rainforest than in savannah indicating a greater range of utilization of basal C₃ and C₄ resources in the former site, covering primary productivity from both these sources. The ranges in δ ¹⁵N, however, were similar between the two habitats suggesting a similar number of trophic levels. Niche breadth, as defined by either standard ellipse area or convex hull, was greater for the bat community in rainforest than in savannah, with all four foraging groups having larger niche breadths in the former than the latter. The higher inter-species morphospace and niche breadth in forest bats suggest that species packing is not necessarily competitive. By employing morphometrics and stable isotope analysis, we have shown that the rainforest bat community packs more species in morphospace and uses a larger niche breadth than the one in savannah.