Biology subjects

Donnellan, S. C.

Publications and source records attributed to Donnellan, S. C..

5 recordsLinked to original sources

bioRxiv2026

Phylogenomic assessment of microhylid frogs reveals widespread taxonomic confusion in the Asterophryinae and establishes the timing of diversification in Australia

Microhylid frogs are a hyper-diverse family thought to have radiated explosively around the Cretaceous-Paleogene boundary. Roughly half of microhylid species richness is concentrated into a single subfamily, the Asterophryinae, which is centered in New Guinea and surrounds, and has been a rich source for species discovery over the past 50 years. However, resolving Asterophryinae phylogenetics has remained a challenge, with frequent taxonomic reshuffling. To address this instability, we generated a sequence-capture molecular dataset to investigate the phylogenetics of the group. This included 71 species of Asterophryinae, across 13 of 17 recognized genera representing extensive sampling of the New Guinea radiation and full sampling of Australian microhylid species. Our dated species tree supports an explosive diversification of microhylids in New Guinea near the start of the Miocene, approximately 20 million years ago. Asterophryinae expansion into northern Australia occurred much later ([~]10 ma) and is marked by well supported clades of Austrochaperina and Cophixalus that show temporally consistent splits from their New Guinea sister taxa. Our phylogeny allows us to identify several instances of polyphyly, which are at odds with our current understanding of intergeneric relationships within the Asterophryinae. We suggest that this confusion is a result of rapid radiation and morphological variability across some poorly defined genera. This work establishes a reliable phylogenetic framework that can form a foundation for a more stable taxonomy of the Asterophryinae. HighlightsO_LIA phylogenomic assessment of the globally distributed frog family Microhylidae C_LIO_LIThe subfamily Asterophryinae radiated explosively in New Guinea C_LIO_LIAustralian species represent two distinct clades C_LIO_LIAssignments of species to genera by morphological means are often unreliable C_LI

evolutionary biology↗

bioRxiv2023

Integrating Genomics, Collections, and Community Science to Reveal Speciation in a Variable Monitor Lizard (Varanus tristis)

--The accurate characterization of species diversity is a vital prerequisite for ecological and evolutionary research, as well as conservation. Thus, it is necessary to generate robust hypotheses of species limits based on the inference of evolutionary processes. Integrative species delimitation, the inference of species limits based on multiple sources of evidence, can provide unique insight into species diversity and the processes behind it. However, the application of integrative approaches in non-model organisms is often limited by the amount of data that is available. Here, we show how data relevant for species delimitation can be bolstered by incorporating information from tissue collections, museum specimens, and observations made by the wider community. We show how to integrate these data under a hypothesis-driven, integrative framework by identifying the processes generating genetic and phenotypic variation in Varanus tristis, a widespread and variable complex of Australian monitor lizards. Using genomic, morphometric (linear and geometric), coloration, spatial, and environmental data we show that disparity in this complex is inconsistent with intraspecific variation and instead suggests that speciation has occurred. Based on our results, we identify the environmental factors that may have been responsible for the geographic sorting of variation. Our workflow provides a guideline for the integrative analysis of several types of data to identify the occurrence and causes of speciation. Furthermore, our study highlights how community science and machine learning--two tools used here--can be used to accelerate taxonomic research.

evolutionary biology↗

bioRxiv2023

Populating a Continent: Phylogenomics Reveal the Timing of Australian Frog Diversification

The Australian continents size and isolation make it an ideal place for studying the accumulation and evolution of biodiversity. Long separated from the ancient supercontinent Gondwana, most of Australias plants and animals are unique and endemic, including the continents frogs. Australian frogs comprise a remarkable ecological and morphological diversity categorized into a small number of distantly related radiations. We present a phylogenomic hypothesis based on an exon-capture dataset that spans the main clades of Australian myobatrachoid, pelodryadid hyloid, and microhylid frogs. Our time-calibrated phylogenomic-scale phylogeny identifies great disparity in the relative ages of these groups which vary from Gondwanan relics to recent immigrants from Asia and include arguably the continents oldest living vertebrate radiation. This age stratification provides insight into the colonization of, and diversification on, the Australian continent through deep time, during periods of dramatic climatic and community changes. Contemporary Australian frog diversity highlights the adaptive capacity of anurans, particularly in response to heat and aridity, and explains why they are one of the continents most visible faunas.

evolutionary biology↗

bioRxiv2020

Phylogenomics of monitor lizards and the role of competition in dictating body size disparity

Organismal interactions drive the accumulation of diversity by influencing species ranges, morphology, and behavior. Interactions vary from agonistic to cooperative and should result in predictable patterns in trait and range evolution. However, despite a conceptual understanding of these processes, they have been difficult to model, particularly on macroevolutionary timescales and across broad geographic spaces. Here we investigate the influence of biotic interactions on trait evolution and community assembly in monitor lizards (Varanus). Monitors are an iconic radiation with a cosmopolitan distribution and the greatest size disparity of any living terrestrial vertebrate genus. Between the colossal Komodo dragon Varanus komodoensis and the smallest Australian dwarf goannas, Varanus length and mass vary by multiple orders of magnitude. To test the hypothesis that size variation in this genus was driven by character displacement, we extended existing phylogenetic comparative methods which consider lineage interactions to account for dynamic biogeographic history and apply these methods to Australian monitors and marsupial predators. We use a phylogenomic approach to estimate the relationships among living and extinct varaniform lizards, incorporating both exon-capture molecular and morphological datasets. Our results suggest that communities of Australian Varanus show high functional diversity as a result of continent-wide interspecific competition among monitors but not with faunivorous marsupials. We demonstrate that patterns of trait evolution resulting from character displacement on continental scales are recoverable from comparative data and highlight that these macroevolutionary patterns may develop in parallel across widely distributed sympatric groups.

evolutionary biology↗

bioRxiv2019

Whole genome duplication potentiates inter-specific hybridisation and niche shifts in Australian burrowing frogs Neobatrachus

Polyploidy has played an important role in evolution across the tree of life but it is still unclear how polyploid lineages may persist after their initial formation. While both common and well-studied in plants, polyploidy is rare in animals and generally less well-understood. The Australian burrowing frog genus Neobatrachus is comprised of six diploid and three polyploid species and offers a powerful animal polyploid model system. We generated exome-capture sequence data from 87 individuals representing all nine species of Neobatrachus to investigate species-level relationships, the origin and inheritance mode of polyploid species, and the population genomic effects of polyploidy on genus-wide demography. We resolve the phylogenetic relationships among Neobatrachus species and provide further support that the three polyploid species have independent autotetraploid origins. We document higher genetic diversity in tetraploids, resulting from widespread gene flow specifically between the tetraploids, asymmetric inter-ploidy gene flow directed from sympatric diploids to tetraploids, and current isolation of diploid species from each other. We also constructed models of ecologically suitable areas for each species to investigate the impact of climate variation on frogs with differing ploidy levels. These models suggest substantial change in suitable areas compared to past climate, which in turn corresponds to population genomic estimates of demographic histories. We propose that Neobatrachus diploids may be suffering the early genomic impacts of climate-induced habitat loss, while tetraploids appear to be avoiding this fate, possibly due to widespread gene flow into tetraploid lineages specifically. Finally, we demonstrate that Neobatrachus is an attractive model to study the effects of ploidy on the evolution of adaptation in animals.

evolutionary biology↗