Genomic signatures of isolation, hybridization, and selection during speciation of island finches

Sister species occurring sympatrically on islands are rare and offer unique opportunities to understand how speciation can proceed in the face of gene flow. The São Tomé grosbeak is a massive-billed, 'giant' finch endemic to the island of São Tomé in the Gulf of Guinea, where it has diverged from its co-occurring sister species the Príncipe seedeater, an average-sized finch that also inhabits two neighbouring islands. Here, we show that the grosbeak carries a large number of unique alleles different from all three Príncipe seedeater populations, but also shares many alleles with the sympatric São Tomé population of the seedeater, a genomic signature signifying divergence in isolation as well as subsequent introgressive hybridization. Furthermore, genomic segments that remain unique to the grosbeak are situated close to genes, including genes that determine bill morphology, suggesting the preservation of adaptive variation through natural selection during divergence with gene flow. This study reveals a complex speciation process whereby genetic drift, introgression, and selection during periods of isolation and secondary contact all have shaped the diverging genomes of these sympatric island endemic finches.

Selection-driven adaptation to the extreme Antarctic environment in the Emperor penguin

The eco-evolutionary history of penguins is profoundly influenced by their shift from temperate to cold environments. Breeding only in Antarctica during the winter, the Emperor penguin appears as an extreme outcome of this process, with unique features related to insulation, heat production and energy management. However, whether this species actually diverged from a less cold-adapted ancestor, thus more similar in ecology to its sister species, the King penguin, is still an open question. As the Antarctic niche shift likely resulted in vast changes in selective pressure experienced by the Emperor penguin, the identification and relative quantification of the genomic signatures of selection, unique to each of these sister species, could answer this question. Applying a suite of phylogeny-based methods on 7,651 orthologous gene alignments of seven penguins and 13 other birds, we identified a set of candidate genes showing significantly different selection regimes either in the Emperor or in the King penguin lineage. Our comparative approach unveils a more pervasive selection shift in the Emperor penguin, supporting the hypothesis that its extreme cold adaptation is a derived state from a more King penguin-like ecology. Among the candidate genes under selection in the Emperor penguin, four genes (TRPM8, LEPR, CRB1, and SFI1) were identified before in other cold adapted vertebrates, while, on the other hand, 161 genes can be assigned to functional pathways relevant to cold adaptation (e.g., cardiovascular system, lipid, fatty acid and glucose metabolism, insulation, etc.). Our results show that extreme cold adaptation in the Emperor penguin largely involved unique genetic options which, however, affect metabolic and physiological traits common to other cold-adapted homeotherms.

Surveys of Afrotemperate forests yields two new freshwater crabs (Decapoda: Potamonautidae: Potamonautes MacLeay, 1838) from South Africa

Sampling of remote inland aquatic habitats in South Africa has constantly been yielding novel endemic freshwater crab species (Potamonautes MacLeay,1838). During the present study, we report on the discovery and description of two new freshwater crab species (Potamonautes baziya sp. nov., and P. mariepskoppie sp. nov.) from Afrotemperate forested mountain regions in the Eastern Cape and Mpumalanga provinces of South Africa, respectively. Phylogenetic evidence derived from DNA sequence data of three partial mitochondrial loci (12S rRNA, 16S rRNA and cytochrome oxidase subunit one, COI) corroborates the evolutionary distinction of the two novel species. In addition, morphological and ecological data for the two new species further delineate their evolutionary distinction from congeneric sister species. A comparison of the taxonomically important gonopods 1 and 2 and carapace features among the sister species and other known freshwater crabs of South Africa was further used to provide evidence for the distinction of the two novel species. The discovery of two new species suggest that remote mountainous areas or unsampled regions in South Africa likely harbor several novel species, reiterating a call to document aquatic inland biodiversity in forested and mountainous regions of the country.

Hidden tribe: A new species of Stream Toad of the genus Ansonia Stoliczka, 1870 (Anura: Bufonidae) from the poorly explored mountainous borderlands of western Thailand

The integrated results of morphological and molecular phylogenetic analyses confirmed the new species status of a recently discovered population of Ansonia from Suan Phueng District, Ratchaburi Province, Thailand. Ansonia karensp. nov. is separated from all other species of Ansonia by a unique combination of mensural, discrete morphological, and color pattern characteristics and is the sister species of A. thinthinae from Tanintharyi Division, Myanmar. This discovery fills a geographic hiatus of 350 km between it and A. kraensis from Ranong Province, Thailand. Ansonia karensp. nov. is the newest member of a long list of range-restricted endemics having been recently discovered in the northern Tenasserim Mountain region of western Thailand and continues to underscore the unexplored nature of this region and its need for conservation.

A new cryptic arboreal species of the Cyrtodactylus brevipalmatus group (Squamata: Gekkonidae) from the uplands of western Thailand

The first integrative taxonomic analysis of the Cyrtodactylus brevipalmatus group of Southeast Asia recovered two newly discovered populations from the Tenasserim Mountains in Suan Phueng District, Ratchaburi Province, Thailand as a new species described here as C. rukhadeva sp. nov. Based on 1397 base pairs of the mitochondrial gene NADH dehydrogenase subunit 2 (ND2), C. rukhadeva sp. nov. is the well-supported sister species to a clade containing three undescribed species, C. ngati, and C. cf. interdigitalis with a large uncorrected pairwise sequence divergence from other species in the brevipalmatus group ranging from 15.4–22.1%. Cyrtodactylus elok and C. brevipalmatus are recovered as poorly supported sister species and the well-supported sister lineage to the remainder of the brevipalmatus group. Cyrtodactylus rukhadeva sp. nov. is putatively diagnosable on the basis of a number of meristic characters and easily separated from the remaining species of the brevipalmatus group by a number of discrete morphological characters as well as its statistically significant wide separation in multivariate morphospace. The discovery of C. rukhadeva sp. nov. continues to underscore the unrealized herpetological diversity in the upland forests of the Tenasserim Mountains and that additional field work will undoubtedly result in the discovery of additional new species.

Integrative taxonomy of two thrush complexes (Aves: Turdidae) reveals introgression across sister species

The classification of some Turdus species, such as the Naumann’s and dusky thrush complexes and the red-throated and black-throated thrush complexes, is controversial. Herein, we used molecular data (mitochondrial genes and microsatellite loci) and morphological characters to review the taxonomy of these thrush complexes and analyze the genetic differentiation between them. Our phylogenetic analysis based on mitochondrial genes indicated that all haplotypes could be divided into two reciprocally monophyletic sister clades corresponding to these two thrush complexes. The same results were revealed by coalescence-based species delimitation. Therefore, these two thrush complexes should be divided into two separate species (T. naumanni and T. ruficollis) and include two subspecies per species according to combined characters from morphological analyses and multilocus approaches. The above classifications were also supported by an analysis of genetic differentiation between T. naumanni and T. ruficollis and within each species. Moreover, there was significant mixing between these two thrush species in the neighbor-joining (NJ) tree and the cluster analysis of microsatellite loci. This led to a pattern of nuclear-mitochondrial discordance between the two species. This could be the result of extensive nuclear introgression between these two sister species. We also provide a potential explanation for the mechanism of gene introgression and nuclear-mitochondrial discordance between the two bird species.

Contributions to the taxonomy and biogeography of the genus Dichagyris (subg. Dichagyris) Lederer, 1867 (Lepidoptera, Noctuidae, Noctuinae)

The taxonomically important characters and subgeneric subdivision of Dichagyris are presented with several historical and nomenclatural considerations. Subdivision of D. vallesiaca is revised based on the type material of the known subspecies. The D. psammochroa group is revised, with description of a new species, D. kurbatskyi from Kazakhstan, and one new subspecies, D. psammochroa kopetdaghimena from the Kopet-Dagh massif. The D. taftana group is revised, with the description of a new species (D. guentereberti from Afghanistan) and two new subspecies (D. taftana elborsasta and D. taftana safavida, from different areas of Iran). The eastern sister species of D. humilis, D. hypotacta from Afghanistan and Pakistan, is described. Major phylogenetic clades of Dichagyris s. str. are associated to western Palaearctic and/or Central Asiatic mountainous regions. Core areas of allopatric speciation of Dichagyris s. str. are discussed with taxonomic considerations and outlook on the subgenera Yigoga and Albocosta, as well.