The role of hybridisation in facilitating macroevolutionary change

Photography by Markaharper1/Wikimedia commons

Species boundaries can remain semipermeable for prolonged periods of time. Interspecific gene flow mostly occurs between sister-species but instances of hybridization are occasionally also recorded among distantly related clades. We are interested in understanding to what extent occasional gene flow can benefit recipient populations and under what circumstances introgressed genetic variants can eventually drive evolutionary change.

To study these questions, we use whole-genome resequence or exon-capture data and focus on two different organismal groups: (i) Birds-of-Paradise and (ii) Cryptoblepharus skinks.

Biodiversity genomics

Human induced environmental change has a severe impact on global biodiversity. While the decline in iconic species is well recorded, there are many organismal groups where we currently do not have a good view on the diversity of lineages and it therefore remains challenging to quantify the true impact of our changing environment. We utilise genomic approaches to characterise genetic diversity and use this information to study the evolutionary history of populations, species and the environment they live in. Moreover, we frequently utilise natural history collections in our research since they represent an important repository of biodiversity across time and space. Recent examples of our research include the study of genetic erosion in the extinct Paradise parrot, the phylogenetic placement of the extinct Cuban macaw and the discovery of a completely new member of the Lamproliidae family.

Lithograph of the extinct Cuban macaw

The evolution of convergence across time and traits

The role of natural selection in shaping phenotypic variation has been a central focus in evolutionary biology. The study of evolutionary convergence, the independent origin of similar phenotypes, has attracted the attention of biologists for decades since it has long been considered as a prime example of adaptation driven by natural selection. Traditionally, convergence research has mostly focused on the study of trait evolution in a comparative context, but the decreasing costs of high-throughput sequencing has led to a shift in focus from quantifying phenotypic similarity to characterizing the genomic basis of convergence.

Cryptoblepharus lizards are small diurnal lizards and we have previously shown that they are a promising group to study the genomic underpinnings of phenotypic convergence. Cryptoblepharus lizards have radiated across the Australian continent within the last 10 to 15 Myr’s and repeatedly switched habitat in the process. We have shown that these independent switches between rock formations and tree habitat have led to adaptive diversification and the emergence of habitat specific phenotypes (‘ecomorphs’). Moreover, phenotypic convergence within Cryptoblepharus is of particular interest since these convergence patterns can be observed at different scales of phylogenetic divergence and between traits with a different genetic architecture. We are currently applying for funding to investigate how genomic convergence evolves over time and how this might differ between different phenotypic traits.

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)