Consequences of a translocation between two divergent lineages of theParatya australiensis(Decapoda:Atyidae) complex: reproductive success and relative fitness

Abstract

When 2 populations are mixed for whatever reason, the outcome can be difficult to predict. In 1993, 2 populations of an atyid shrimp (Paratya australiensis:Atyidae) from different subcatchments of the Brisbane River, Queensland, Australia, were mixed as a result of a translocation. At the time, they were thought to represent slightly divergent populations of a single species. However, subsequent molecular analysis showed that they were significantly divergent. An analysis of patterns at one of the sites in 2001 suggested that the translocated lineage might be sending the resident population extinct in one of the streams. Analysis of mitochondrial deoxyribonucleic acid (DNA) and 3 allozyme loci indicated that the explanation for the outcome might be related to asymmetrical hybridization and nonviability of hybrids between resident females and translocated males. We present data for 2002 and an analysis of samples that had been collected prior to the 2001 study, but not analyzed. We tested 3 hypotheses: 1) the translocated genotypes would continue to increase in relative frequency at sites above the translocation site because their site of origin was at higher altitudes, to which they were expected to be better adapted; 2) at intermediate sites, the relative frequency of translocated alleles in juveniles would increase relative to in their parents; and 3) resident genotypes would survive better than translocated genotypes within a generation, especially at lower and intermediate elevations. Translocated genotypes increased extremely rapidly at the most upstream site. Consistent evidence was present for higher relative frequency of translocated alleles in juveniles relative to their parents, both in the generation following the 2001 study and in the pre-2001 samples. With the exception of in the upstream site, translocated genotypes had lower fitness within a generation than resident genotypes. Thus, the translocated genotypes had a higher reproductive success but were less well adapted to their local environment than residents, a situation that decreased population fitness overall. Such an outcome demonstrates a rarely reported effect of translocations and mixing of divergent lineages.

Spatial distributions and environmental relationships of two species complexes of freshwater atyid shrimps

“…Indeed, this has been suggested as important in the distribution of atyid shrimps by previous authors based on laboratory experiments on the two lineages (Fawcett et al. ).…”

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

“…An early study showed that some hybridization between the lineages had occurred but that lineage 4 had dispersed more than 1.5 km upstream of the translocation site and had sent lineage 6 almost extinct in all sites higher and 2 sites lower of than the original translocation site (Hughes et al, 2003). Two years later, lineage 4 sill dominated high elevation sites (In the Branch Creek-translocated stream) but had not moved further to low elevation sites (Fawcett, Hurwood & Hughes, 2010). It was hypothesized that lineage 4 is adapted to higher elevations, as they quickly colonized the upper reaches of the stream which is approx.…”

“…This was supported by a small laboratory experiment in which individuals of the 2 lineages were incubated in separate tanks and water temperature was increased by 1 • C every 3 days. Lineage 4 was less tolerant to increasing temperature than lineage 6, dying at a lower temperature (Fawcett, Hurwood & Hughes, 2010). Ten years later, in Branch Creek following very heavy rainfall over 2 summers, lineage 4 had shifted further to downstream, which was suspected to be due to lower temperatures caused by heavy rainfall (Wilson, Schmidt & Hughes, 2016), favoring lineage 4 over lineage 6.…”

Strong interactions of Paratya australiensis (Decapoda:Atyidae) on periphyton in an Australian subtropical stream

“…Paratya australiensis (Decapoda: Atyidae) is a small freshwater shrimp which is widespread in eastern Australia (Williams andAltmann 1980, Choy andHorwitz 1995) and is one of the most conspicuous and abundant macroinvertebrates in small headwater streams in southeastern Queensland (Hancock and Bunn 1997). The species has been extensively studied in terms of genetics, dispersal, behaviour and systematics (Hughes et al 1995, Baker et al 2004, Fawcett et al 2010, Bool et al 2011), but its role in transforming periphyton and sediments has not been studied experimentally.…”