Species, ESUs or populations? Delimiting and describing morphologically cryptic diversity in Australian desert spring amphipods

Abstract

Cryptic species are frequently being discovered in refugial habitats, such as desert springs and groundwater systems. Unfortunately, many of these taxa remain as unnamed entities years after their initial discovery. Recent advances in the use of molecular data and coalescent analyses allow DNA-based delimitation of species to move from single locus, tree-based methods to multilocus coalescent analyses. This study compares two DNA-based approaches to delimit species of putatively cryptic freshwater amphipods (Chiltoniidae) from desert springs in central Australia. In addition, a morphometric analysis of 11 characters was undertaken to determine whether the DNA-delimited species were morphologically distinguishable. The single locus method results in identification of lineages that are not supported as species under the multilocus coalescent analyses. We conclude that Wangiannachiltonia guzikae King, 2009, as currently circumscribed, represents six genetically distinct amphipod species, and we describe and name these species despite no clear diagnosable morphological differences. Critically, all of these newly recognised species have extremely limited distributions, which increases the biodiversity significance of their desert spring habitat.