Research

Hybridization and introgression across evolutionary time scales
It is now well known that species boundaries can remain semipermeable for a prolonged period of time and hybridization frequently occurs between sister species. Yet in some groups, hybridization occurs long after incipient speciation and species that are phylogenetically distinct continue to exchange genetic variants. I have previously characterized the ecological and temporal context of interspecific gene flow within Cryptoblepharus skinks, where introgression has persisted between distinct ecomorphological species that diverged millions of years ago. Although I used sequence-capture data for the Cryptoblepharus project, I am currently learning how to employ a whole-genome approach and focus on introgression between various genera within the Birds-of-Paradise family.

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Photography by Tim Laman/National Geographic

Birds-of-Paradise are an iconic family of birds that are renowned for their extraordinary variety of sexually selected traits and behaviors, but instances of hybridization among genera have been frequently recorded. These contrasting observations, seemingly strong selection for pre-zygotic isolation and ongoing hybridization, have motivated us to study the evolutionary history of the complete family and dissect patterns of (adaptive) introgression.

 

  

phylomorphospace_plot

3D phylomorphospace plot illustrating the divergence in ecologically functional traits between arboreal (green), rock (red) and littoral (blue) ecomorphs. Species relationships are projected and highlight repeated convergence (Blom et al., 2016)

Ecological context of diversification during continental radiation
Understanding how population level processes promote macroevolutionary change is a major objective in evolutionary biology. Whereas many studies have focused on incipient speciation and changes in speciation dynamics across major clades, our understanding of the continuous nature between both ends of the spectrum remains relatively limited and mostly derives from the study of adaptive radiations in insular system. For my dissertation research, I focused on a recent continental radiation of Australian skinks and highlighted how ecologically mediated divergent selection has repeatedly promoted habitat specialization and phenotypic convergence. Simultaneous cryptic diversification within habitat, suggests that both divergent selection between and uniform selection across habitats have jointly stimulated lineage diversification at a continental scale.

 


Summary-Coalescent species tree estimation with NGS datasets
The number of phylogenetic markers available for empiricists have greatly increased with the introduction of NGS technology. Yet, full coalescent-based species tree estimation with a large number of tips and loci remains challenging. Summary-coalescent methods provide a tractable alternative but depend on the accuracy of gene tree estimation. Using a sequence-capture dataset for a recent radiation of Australian skinks, we have explored the importance of gene tree accuracy and demonstrate a straight forward approach to quantify the impact of gene tree accuracy on species tree estimation.


Biogeography and trait dependent dispersal
Range evolution is an important determinant in promoting species diversification and has shaped the macroevolutionary history of many taxa. But the importance of long-distance dispersal and how ecology might promote or constrain such events, remains uncertain and has been debated among biogeographers for many decades. The genus Cryptoblepharus is the most widespread group within the Scincidae family, even though they are a relatively young clade (~10 Myr). Extant taxa can be found across the Pacific, Indo-Australia and the Malagasy region. I am collaborating with researchers from CIBIO (Portugal), UC Berkeley (USA) and various museums throughout the world, to examine the evolutionary and biogeographic history of this group. We incorporate probabilistic modeling to explore whether habitat specialization (i.e. coastal vs. non-coastal species) has been an important component in shaping the widespread distribution Cryptoblepharus skinks.

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