Scott L. Travers

Tectonic collision and uplift of Wallacea triggered the global songbird radiation

Songbirds (oscine passerines) are the most species-rich and cosmopolitan bird group, comprising almost half of global avian diversity. Songbirds originated in Australia, but the evolutionary trajectory from a single species in an isolated continent to worldwide proliferation is poorly understood. Here, we combine the first comprehensive genome-scale DNA sequence data set for songbirds, fossil-based time calibrations, and geologically informed biogeographic reconstructions to provide a well-supported evolutionary hypothesis for the group. We show that songbird diversification began in the Oligocene, but accelerated in the early Miocene, at approximately half the age of most previous estimates. This burst of diversification occurred coincident with extensive island formation in Wallacea, which provided the first dispersal corridor out of Australia, and resulted in independent waves of songbird expansion through Asia to the rest of the globe. Our results reconcile songbird evolution with Earth history and link a major radiation of terrestrial biodiversity to early diversification within an isolated Australian continent.

The Eurasian invasion: phylogenomic data reveal multiple Southeast Asian origins for Indian Dragon Lizards

BackgroundThe Indian Tectonic Plate split from Gondwanaland approximately 120 MYA and set the Indian subcontinent on a ~ 100 million year collision course with Eurasia. Many phylogenetic studies have demonstrated the Indian subcontinent brought with it an array of endemic faunas that evolved in situ during its journey, suggesting this isolated subcontinent served as a source of biodiversity subsequent to its collision with Eurasia. However, recent molecular studies suggest that Eurasia may have served as the faunal source for some of India’s biodiversity, colonizing the subcontinent through land bridges between India and Eurasia during the early to middle Eocene (~35–40 MYA). In this study we investigate whether the Draconinae subfamily of the lizard family Agamidae is of Eurasian or Indian origin, using a multi locus Sanger dataset and a novel dataset of 4536 ultraconserved nuclear element loci.ResultsResults from our phylogenetic and biogeographic analyses revealed support for two independent colonizations of India from Eurasian ancestors during the early to late Eocene prior to the subcontinent’s hard collision with Eurasia.ConclusionThese results are consistent with other faunal groups and new geologic models that suggest ephemeral Eocene land bridges may have allowed for dispersal and exchange of floras and faunas between India and Eurasia during the Eocene.

Genomic data reveals potential for hybridization, introgression, and incomplete lineage sorting to confound phylogenetic relationships in an adaptive radiation of narrow‐mouth frogs

The microhylid frog genus Kaloula is an adaptive radiation spanning the edge of the Asian mainland and multiple adjacent island archipelagos, with much of the clades diversity associated with an endemic Philippine radiation. Relationships among clades from the Philippines, however, remain unresolved. With ultraconserved element (UCE) and mitogenomic data, we identified highly supported differences in topology and areas of poor resolution, for each marker set. Using the UCE data, we then identified possible instances of contemporary hybridization, past introgression, and incomplete lineage sorting (ILS) within the Philippine Kaloula. Using a simulation approach, and an estimate of the Philippine Kaloula clade origin (12.7—21.0 mya), we demonstrate that an evolutionary history including inferred instances of hybridization, introgression, and ILS leads to phylogenetic reconstructions that show concordance with results from the observed mitogenome and UCE data. In the process of validating a complex evolutionary scenario in the Philippine Kaloula, we provide the first demonstration of the efficacy of UCE data for phylogenomic studies of anuran amphibians.

Lizards of the lost arcs: Mid-Cenozoic diversification, persistence and ecological marginalization in the west pacific

Regions with complex geological histories often have diverse and highly endemic biotas, yet inferring the ecological and historical processes shaping this relationship remains challenging. Here, in the context of the taxon cycle model of insular community assembly, we investigate patterns of lineage diversity and habitat usage in a newly characterized vertebrate radiation centred upon the worlds most geologically complex insular region: island arcs spanning from the Philippines to Fiji. On island arcs taxa are ecologically widespread, and provide evidence to support one key prediction of the taxon cycle, specifically that interior habitats (lowland rainforests, montane habitats) are home to a greater number of older or relictual lineages than are peripheral habitats (coastal and open forests). On continental fringes, however, the clade shows a disjunct distribution away from lowland rainforest, occurring in coastal, open or montane habitats. These results are consistent with a role for biotic interactions in shaping disjunct distributions (a central tenant of the taxon cycle), but we find this pattern most strongly on continental fringes not islands. Our results also suggest that peripheral habitats on islands, and especially island arcs, may be important for persistence and diversification, not just dispersal and colonization. Finally, new phylogenetic evidence for subaerial island archipelagos (with an associated biota) east of present-day Wallaces Line since the Oligocene has important implications for understanding long-term biotic interchange and assembly across Asia and Australia.

A New Cryptic Species of Salamander, Genus Oedipina (Caudata: Plethodontidae), from Premontane Elevations in Northern Nicaragua, with Comments on the Systematic Status of the Nicaraguan Paratypes of O. pseudouniformis Brame, 1968

Abstract We describe a new species of Oedipina (subgenus Oedipina) from premontane elevations of three isolated mountains in northern Nicaragua. The new cryptic species differs in molecular characters from its closest relatives: Oedipina cyclocauda (an Atlantic lowland species with a distributional range from central Panama to extreme southeastern Nicaragua) and Oedipina pseudouniformis. We regard all Nicaraguan specimens previously referred to as O. pseudouniformis to be conspecific with the new species herein described and restrict O. pseudouniformis as a Costa Rican endemic species. We also record the fourth known locality (and southernmost) of the Nicaraguan endemic O. nica and discuss additional species of Oedipina that are likely to be found in Nicaragua as field research continues in the country.