Molecular evidence for mid-Pleistocene divergence of populations of three freshwater amphipod species (Talitroidea:Chiltoniidae) on Kangaroo Island, South Australia, with a new spring-associated genus and species

Recent molecular and morphological analyses have shown that chiltoniid amphipods, once thought to be a relictualgroup,are adiverseandspeciosefamily ofAustralianfreshwater amphipods.As partofalarger examinationofthe family,chiltoniidsfromKangarooIslandinSouthAustraliawerecollectedandanalysedusingmolecular(COIand28S)and morphologicalmethodsinordertounderstandspecies distributional patterns andrelationships.Kartachiltonia moodyigen. nov.,sp.nov.,aspring-associatedspeciesendemictotheisland,wasdiscoveredandpopulationsofthreeadditionalmainland species(Austrochiltoniaaustralis,A.dalhousiensisandA.subtenuis)wereexamined.TheislandpopulationsofA.australis, A.dalhousiensisandA.subtenuiswerefoundtoformnaturalgroupswithdifferinghaplotypecoalescencetimesdatingfrom the Early to Mid-Pleistocene. Numerous cycles of regional climate change throughout the Pleistocene are likely to have driven speciation in chiltoniid amphipods in southern Australia and the presence of multiple chiltoniid species at Kangaroo Islandindicatesthatitexistsatalikelyconvergenceofspeciesdistributionpatterns.Threepossiblehypothesestoexplainthe evolutionanddiversityofchiltoniidsinsouthernAustraliaarediscussedasareevidenceforpotentialintroductionandlong- distance dispersal events.