Phylogeography and ecological speciation of fishes

– Isolation by Adaptation and Sea Level Changes in Silverside Fishes from the Pampas and Patagonia
We were arguably the first to describe a scenario of fish speciation in South America driven by divergent natural selection. We showed that niche divergence due to estuarine colonization by marine silverside fish (genus Odontesthes) led to isolation by adaptation and speciation in the presence of high gene flow – one of the most convincing reports of parapatric speciation in an aquatic organism from the Southern Hemisphere. In another study, we explored the role of adaptive diversification and recent sea-level changes as evolutionary drivers. That study pioneered phylogeographic reconstructions of radiations in South America (the coastal freshwater Odontesthes perugiae group), and also reported some of the most rapid speciation rates for a vertebrate (see publications below). Team members and collaborators: L Beheregaray, P Sunnucks (Monash), A Gosztonyi (Centro Nacional Patagónico, Argentina).

– Comparative Phylogeography and Speciation of Amazonian Fishes
In 2002 we implemented a research program on evolution of fishes in Amazonia, the basin home to the world’s richest freshwater fish fauna. This ambitious program started as a collaboration with Universidade do Amazonas (Brazil) and Yale University (USA), and was later funded by the ARC (DP0556496, Beheregaray 2005-2007). It aims to clarify the relative roles of natural selection and drift in population adaptation, divergence and speciation in the complex and understudied Amazonian fish fauna. So far, we have conducted nine field-expeditions in Amazonia that together covered over 6,000 Km of waterways and collected >4,000 samples from co-distributed fish species. We have produced several papers that pioneered the combination of genome scans with large-scale population genetics and phylogeographic datasets to understand evolution in Amazonia. Our findings indicate adaptive divergence and ecological speciation due to hydrochemical differences between major Amazonian rivers (i.e. differences in water colour and pH). In the Rio Negro basin, we have reported multiple cases of ancient cryptic species in lowland flooded-forest fish that likely evolved in response to Andean tectonic history. Team members and collaborators: L Beheregaray, G Cooke, M Sistrom, M Piggott and S Corrigan (Macquarie), N Chao (UFAM, Brazil), G Caccone (Yale).

– Comparative Phylogeography and Ecological Speciation of Elasmobranchs from the Gulf of California
The Gulf of California (GC) shows high ecological diversity, complex oceanography and active geological history, characteristics that make it suitable to study ecological speciation. This work aims to elucidate ecological and biogeographic factors that have shaped genetic structure and speciation in co-distributed elasmobranchs from the Gulf of California (GC) and the Pacific coast of Baja California Peninsula, in Mexico.  Study groups include sharks and rays from the genera Rhinobatos, Squatina, Mustelus and Rhizoprionodon. Our results suggest previously unsuspected cryptic species that have probably diverged ecologically and also distinct populations that should be managed separately. These findings provide urgently needed information for conservation management of the heavily exploited elasmobranch fisheries in the region. This work represents the first comparative genetic analysis in elasmobranchs from the iconic GC ecosystem and has important implications for the study of the Gulf’s biodiversity and its origin and for improving our understanding about speciation in the sea. Team members and collaborators: J Sandoval-Castillo and L Beheregaray (Flinders), Oscar Sosa-Nishizaki (Center of Scientific Research of Ensenada, Mexico).

– Comparative Phylogeography and Phylogenetics of Australian Wobbegong Sharks
Wobbegongs sharks (Orectolobidae) are endemic to the temperate and tropical waters of the western Pacific and eastern Indian oceans, but are most diverse in Australian waters. We have proposed hypotheses about speciation and the biogeographic history of this family and provided evidence for recent events of diversification in this shark group. We have also reported on genetic evidence for a new species of wobbegong and are exploring phylogeographic history in co-distributed wobeggong sharks from the east coast of Australia. Team members and collaborators: S Corrigan (Macquarie), L Beheregaray, C Huveneers (Flinders).

– Phylogeography of perches and basses
This project aims to elucidate historical and current population genetic structure in golden perch, Macquarie perch, Australian bass, and estuary perch. We have reported on the influence of past climate and coastal oceanography in generating phylogeographic divergence and provided key information for conservation management of these recreationally important species. Team members and collaborators: L Beheregaray (Flinders), L Faulks, K Shaddick, T Schwartz (Macquarie), D Jerry (James Cook University), C Burridge (UTAS), W Fulton (DPI Fisheries VIC).