Translocation causes extinction of a local population of the freshwater shrimp Paratya australiensis

Published source details Hughes J., Goudkamp K., Hurwood D., Hancock M. & Bunn S. (2003) Translocation causes extinction of a local population of the freshwater shrimp Paratya australiensis. Conservation Biology, 17, 1007-1012.
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Summary

For some threatened species, introducing individuals from elsewhere into small populations has been suggested as a way of maintaining or increasing genetic diversity. Such translocations have been used in attempts to replenish depleted stocks of various fish species. It is recognized, however, that mixing of genetically differentiated stocks of a species may have detrimental effects on one or other of the two stocks.

In 1993, as part of another study, freshwater shrimps Paratya australiensis (Atyidae) were translocated between pools from two different subcatchments within the same drainage system in southeast Queensland, Australia. Subsequent analysis revealed that populations in the two subcatchments represented monophyletic lineages that were 6% divergent. Thus, it was decided to determine the effects of the translocation on resident populations.

Translocation and sampling: In 1993 approx. 9,500 shrimp were moved from a pool in Kilcoy Creek to a similar pool in Branch Creek in the headwaters of the Stony Creek subcatchment, and approximately 6,500 shrimp were likewise moved from the Branch Creek pool to the Kilcoy Creek pool.

In December 2000, samples of 30–100 adult shrimp from the site of introduction in Branch Creek and from five pools above and five pools below the introduction site were taken. In May 2001, samples of juvenile shrimp (carapace length <5 mm; offspring of adults from the previous summer) from the same sites were collected. In June 2001, samples were taken from the translocation site and pools above and below it in Kilcoy Creek.

Genetic analysis: Analysis of nuclear (allozymes) and mitochondrial genes ( COI ) was undertaken.

After only 7 years (equivalent to seven generations), the resident P.australiensis genotype had become extinct at one of the sites. Evidence from gene analysis suggests that this loss may be explained by a mating preference of females (resident and translocated) for translocated males, and a low viability of crosses between resident females and translocated males. There appears no obvious morphological or behavioral reason for a mating preference.

The results of this study highlight that translocations and interbasin water transfers in general, should be undertaken only with extreme caution and consideration for genetic contamination of isolated populations within them.

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http://www.blackwell-synergy.com/doi/full/10.1046/j.1523-1739.2003.01636.x