Why are there so many species of mining bees (Hymenoptera,Andrenidae)? The possible roles of phenology and Wolbachia incompatibility in maintaining species boundaries in the Andrena proxima-complex

The factors leading to the extraordinary diversity of the bees of the genus Andrena Fabricius, the second most speciose genus among bees, remain largely unknown. To examine the pattern of diversification in this genus, we investigate species boundaries within the controversial Andrena proxima-complex using a dataset of ultra-conserved elements and various species delimitation analyses (admixture analyses, BPP, DAPC). Our results confirm the presence of three separate species in this species group (Andrena proxima (Kirby), A. ampla Warncke and A. alutacea Stöckhert) and suggest very low levels of interspecific gene flow. Andrena proxima and A. alutacea are regularly found in sympatry, suggesting an advanced stage of speciation. By contrast, A. ampla shows a parapatric distribution with both other species. Andrena alutacea harbours a unique strain of Wolbachia Hertig, absent in the other two species, which are infected by the two same strains of Wolbachia. In addition, the three species have distinct phenologies, with A. proxima flying earlier in the season and A. alutacea significantly later; the phenology of A. ampla is intermediate. Our results suggest that Wolbachia-induced incompatibilities and phenological differences maintain species boundaries in this group. The most advanced stage of speciation is observed in the two species showing putatively incompatible strains of Wolbachia and strongly distinct phenologies, A. alutacea and A. proxima. We propose that the smaller differences in phenological differentiation between A. ampla and both other species may explain the observed pattern of parapatric distribution. We discuss how these factors may underlie the high diversification rate observed in other groups of Andrena, a genus characterized by particularly variable and short flying periods.     

Replicated divergence in cichlid radiations mirrors a major vertebrate innovation

Decoupling of the upper jaw bones—jaw kinesis—is a distinctive feature of the ray-finned fishes, but it is not clear how the innovation is related to the extraordinary diversity of feeding behaviours and feeding ecology in this group. We address this issue in a lineage of ray-finned fishes that is well known for its ecological and functional diversity—African rift lake cichlids. We sequenced ultraconserved elements to generate a phylogenomic tree of the Lake Tanganyika and Lake Malawi cichlid radiations. We filmed a diverse array of over 50 cichlid species capturing live prey and quantified the extent of jaw kinesis in the premaxillary and maxillary bones. Our combination of phylogenomic and kinematic data reveals a strong association between biting modes of feeding and reduced jaw kinesis, suggesting that the contrasting demands of biting and suction feeding have strongly influenced cranial evolution in both cichlid radiations.     

More than 1000 ultraconserved elements provide evidence that turtles are the sister group of archosaurs

We present the first genomic-scale analysis addressing the phylogenetic position of turtles, using over 1000 loci from representatives of all major reptile lineages including tuatara. Previously, studies of morphological traits positioned turtles either at the base of the reptile tree or with lizards, snakes and tuatara (lepidosaurs), whereas molecular analyses typically allied turtles with crocodiles and birds (archosaurs). A recent analysis of shared microRNA families found that turtles are more closely related to lepidosaurs. To test this hypothesis with data from many single-copy nuclear loci dispersed throughout the genome, we used sequence capture, high-throughput sequencing and published genomes to obtain sequences from 1145 ultraconserved elements (UCEs) and their variable flanking DNA. The resulting phylogeny provides overwhelming support for the hypothesis that turtles evolved from a common ancestor of birds and crocodilians, rejecting the hypothesized relationship between turtles and lepidosaurs.     

The evolution of peafowl and other taxa with ocelli (eyespots): a phylogenomic approach

The most striking feature of peafowl (Pavo) is the males'' elaborate train, which exhibits ocelli (ornamental eyespots) that are under sexual selection. Two additional genera within the Phasianidae (Polyplectron and Argusianus) exhibit ocelli, but the appearance and location of these ornamental eyespots exhibit substantial variation among these genera, raising the question of whether ocelli are homologous. Within Polyplectron, ocelli are ancestral, suggesting ocelli may have evolved even earlier, prior to the divergence among genera. However, it remains unclear whether Pavo, Polyplectron and Argusianus form a monophyletic clade in which ocelli evolved once. We estimated the phylogeny of the ocellated species using sequences from 1966 ultraconserved elements (UCEs) and three mitochondrial regions. The three ocellated genera did form a strongly supported clade, but each ocellated genus was sister to at least one genus without ocelli. Indeed, Polyplectron and Galloperdix, a genus not previously suggested to be related to any ocellated taxon, were sister genera. The close relationship between taxa with and without ocelli suggests multiple gains or losses. Independent gains, possibly reflecting a pre-existing bias for eye-like structures among females and/or the existence of a simple mutational pathway for the origin of ocelli, appears to be the most likely explanation.