Genetic structure of Australian glass shrimp, Paratya australiensis, in relation to altitude.

Sharmeen Rahman,Daniel Schmidt,Jane M Hughes

doi:10.7717/peerj.8139

Abstract

Paratya australiensis Kemp (Decapoda: Atyidae) is a widely distributed freshwater shrimp in eastern Australia. The species has been considered as an important stream organism for studying genetics, dispersal, biology, behaviour and evolution in atyids and is a major food source for stream dwelling fishes. Paratya australiensis is a cryptic species complex consisting of nine highly divergent mitochondrial DNA lineages. Previous studies in southeast Queensland showed that “lineage 4” favours upstream sites at higher altitudes, with cooler water temperatures. This study aims to identify putative selection and population structure between high elevation and low elevation populations of this lineage at relatively small spatial scales. Sample localities were selected from three streams: Booloumba Creek, Broken Bridge Creek and Obi Obi Creek in the Conondale Range, southeast Queensland. Six sample localities, consisting of 142 individuals in total were sequenced using double digest Restriction Site Associated DNA-sequencing (ddRAD-seq) technique. Among the 142 individuals, 131 individuals shared 213 loci. Outlier analysis on 213 loci showed that 27 loci were putatively under selection between high elevation and low elevation populations. Outlier analysis on individual streams was also done to test for parallel patterns of adaptation, but there was no evidence of a parallel pattern. Population structure was observed using both the 27 outliers and 186 neutral loci and revealed similar population structure in both cases. Therefore, we cannot differentiate between selection and drift here. The highest genetic differentiation was observed between high elevation and low elevation populations of Booloumba Creek, with small levels of differentiation in the other two streams.

Highlights

Genetic variation within and among populations arises as a result of a number of factors, namely-mutation, genetic drift, gene flow/dispersal and natural selection (Slatkin, 1985)
Five types of barcodes were used ranging from 4 bp to 8 bp in size. ddRAD libraries prepared from the 142 individuals from high elevation and low elevation populations of all 3 streams were sequenced using Illumina NextSeq500 platform of the Australian Genomic Research Facility (AGRF)
The Booloumba Creek High (BOH) population had a number of private alleles, which reflects the isolation of the high elevation population from the low elevation population and suggests extremely limited dispersal

Summary

Introduction

Genetic variation within and among populations arises as a result of a number of factors, namely-mutation, genetic drift, gene flow/dispersal and natural selection (Slatkin, 1985). Widespread gene flow homogenizes genetic variation among populations whereas restricted gene flow creates genetic divergence among populations due to genetic drift and/or natural selection (Slatkin, 1985; Hughes, Schmidt & Finn, 2009). In a dendritic stream network, geneflow and population connectivity may be influenced by the stream’s physical features resulting in population structuring within and between subcatchments within a larger stream catchment (Meffe & Vrijenhoek, 1988; Hughes, Schmidt & Finn, 2009). How to cite this article Rahman S, Schmidt D, Hughes JM. Genetic structure of Australian glass shrimp, Paratya australiensis, in relation to altitude.

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