Spatial distribution and ecology of the Recent Ostracoda from Tangra Yumco and adjacent waters on the southern Tibetan Plateau: A key to palaeoenvironmental reconstruction

Abstract

• Distribution and ecology of modern freshwater ostracods from a remote region, Tibetan Plateau. • Ecology of living ostracods from extremely high altitudes freshwater ecosystems. • Contribution to biodiversity and taxonomy of Tibetan Recent ostracods. • Baseline data for palaeolimnological investigations using Tibetan ostracods. We elucidate the ecology of Recent Ostracoda from a deep brackish lake, Tangra Yumco (30°45′—31°22′N and 86°23′—86°49′E, 4595 m a.s.l.) and adjacent waters on the southern Tibetan Plateau. Ostracod associations (living and empty valves) in sixty-six sediment samples collected from diverse aquatic habitats (lakes, estuary-like water and lagoon-like water waters, rivers, ponds and springs) were quantitatively assessed. Eleven Recent Ostracoda were found (nine living and two as empty valves only). Cluster analysis established two significant (p < 0.05) habitat specific associations; (i) Leucocytherella sinensis , Limnocythere inopinata , Leucocythere ? dorsotuberosa , Fabaeformiscandona gyirongensis and Candona xizangensis are lacustrine fauna . (ii) Tonnacypris gyirongensis , Candona candida , Ilyocypris sp., Heterocypris incongruens and Heterocypris salina are temporary water species . Ostracod distribution and abundance are significantly (p < 0.05) correlated to physico-chemical variables. The first two axes of a canonical correspondence analysis (CCA) explain 30.9% of the variation in the species abundance data. Conductivity and habitat types are the most influential ecological factors explaining the presence and abundance of ostracods. Spearman correlation analysis reveals that: (i) Two species, L .? dorsotuberosa (r = 0.25) and L. inopinata (r = 0.36) have a significant positive correlation with conductivity while one species, T. gyirongensis (r = −0.68) displays a significant negative correlation with conductivity. Limnocythere inopinata correlates significantly positive (r = 0.37) with alkalinity. Fabaeformiscandona gyirongensis correlates significantly positive (r = 0.28) with water depth. Key indicator living assemblages are: (i) L . sinensis dominates Ca-depleted brackish waters although ubiquitously distributed; (ii) L. ? dorsotuberosa dwells in fresh to brackish waters; (iii) L . inopinata predominates in mesohaline to polyhaline waters; (iv) F. gyirongensis inhabits exclusively brackish-lacustrine deeper waters; (v) C . candida populates freshwaters; (vi) T . gyirongensis and Ilyocypris sp. are restricted to shallow temporary waters; (vii) H . incongruens occurs in ponds. Water depth indicators are F . gyirongensis and L.? dorsotuberosa , useful in ostracod assemblages for palaeo-water depth reconstruction. Our results expand the knowledge of the ecological significance of Recent Tibetan Ostracoda ecology. This is a new insight on habitat chacteristics of both living assemblages and sub-Recent associations of ostracods in mountain aquatic ecosystems. The new modern ostracod dataset can be used for the quantitative reconstruction of past environmental variables (e.g., conductivity) and types of water environment. The key indicator ostracods are relevant in palaeolimnological and climate research on the Tibetan Plateau.