Phenotypical Variation in Leucocytherella Sinensis Huang, 1982 (ostracoda): A New Proxy for Palaeosalinity in Tibetan Lakes

Leucocytherella sinensis, a ubiquitous and the most abundant ostracod endemic to the Tibetan Plateau, can account for > 98% of the ostracod association. These low-diversity associations are hard to interpret using community palaeoecology alone, but environmentally driven phenotypic variation may provide clues to palaeoenvironmental factors. L. sinensis displays several morphological forms, characterised by different tubercle formation on their valves. These morphological forms were described as diverse species. We present a taxonomical revision and a first description of the soft parts of L. sinensis. We also redescribe the genus and confirm its assignment to the subfamily Limnocytherinae Klie, 1938. Analysis of L. sinensis associations from surface sediments of 12 Tibetan lakes shows a connection between tubercle formation and specific conductivity (SC) of the ambient water with lower tubercle number at higher salinity. Tubercles are less common in low SC populations and highest within the beta-oligohaline range. However, high Ca2+ concentrations suggest a combined effect of salinity and Ca2+ ion concentration on tubercle formation. The phenomenon of tubercle formation can be used to trace salinity changes recorded by fossil L. sinensis valves from Tibetan Holocene lake sediments.