Contrasting insights provided by single and multispecies data in a regional comparative phylogeographic study

Abstract

Many single-species freshwater phylogeographic studies have been carried out in south-east Queensland; however comparative phylogeography requires multiple lines of evidence to infer deep, significant relationships between landscape and biota. The present study aimed to test conclusions resulting from single taxon studies in a multispecies comparative framework: (1) how influential are river basins in the genetic structure of freshwater species; (2) are there biogeographic frontiers between groups of basins; and (3) could deep intraspecific lineages be explained by a single event? New and existing data from 33 freshwater species (23 fishes and 10 crustaceans) were combined, and both standard single-species analyses (haplotype networks, genetic distances, FST) and multispecies methods (hierarchical ABC) were carried out for 1814 sequences from eight basins. More than half of the species displayed a high phylogeographic structure and contained at least two distinct lineages. Almost all of the lineage divergences displayed an element of north/south geographic breaks, with the most influential boundary being between the Mary and Brisbane rivers. Of the 11 basin-pair multispecies coalescent analyses, four implied a single divergence as being most likely. A regional analysis of deep lineages within 16 taxon-pairs resulted in a strongly supported inference of a single divergence, probably dating to the Pleistocene. Basin boundaries are a key determinant of phylogeographic patterns for most of these freshwater species, although the specific biogeographic relationship between basins often varies depending on the species. There are a number of influential biogeographic frontiers, with the Brisbane-Mary being the most important. The finding that a single event may be responsible for multiple deep lineages across the region implies that a highly influential climate change event may have been detected.