Genetic assessment of the rare freshwater shrimp Caridina logemanni endemic to Hong Kong and its hybridisation with a widespread congener

The lack of information is one of the major impediments to effective conservation of rare, endemic species. One of which concerns the freshwater atyid shrimp Caridina logemanni known only from three streams in Hong Kong, with an area of occupancy of less than 20 km(2), further threatened by harvesting for aquarium trade and potential introgressive hybridisation with a ubiquitous congener C. cantonensis. Here, we delineated the genetic diversity and population structure of C. logemanni, and examined its extent of hybridisation with C. cantonensis, using one mitochondrial (COI), one nuclear (NaK intron) and six microsatellite markers. The two examined populations of C. logemanni exhibited strong genetic differentiation at a spatial scale of <1.5 km apart, and generally low genetic diversity. Historic introgressive hybridisation is evident from the sharing of COI haplotypes between species and the more extensive inter-specific microsatellite admixture than inter-population admixture, such that both C. logemanni populations were of hybrid origin. Future conservation efforts on C. logemanni should aim at (1) minimising waterway modifications to prevent potential anthropogenic hybridisation, (2) fortifying conservation legislations to stop its harvesting, and (3) conducting continuous monitoring in case of stochastic events associated with small population size and linear habitat.

Automated summary

This study investigated the genetic diversity and population structure of the rare freshwater atyid shrimp Caridina logemanni in Hong Kong. The results showed strong genetic differentiation and low genetic diversity among the populations of C. logemanni. Historic hybridisation was evident, indicating that both populations were of hybrid origin. Future conservation efforts should focus on preventing anthropogenic hybridisation, prohibiting harvesting, and conducting continuous monitoring.