Effects of Quaternary climate changes on morphological variability of aquatic invertebrates (ostracodes) within the ICDP project NamCore

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The interplay between the evolution of the mountainous environments, monsoonal fluctuations and orbitally-forced climate changes resulted in the Tibetan Plateau (TP) being a montane biodiversity hotspot. Diversification of many modern lineages occurred between 2 Ma and 150 ka assumed to result from climate fluctuations and associated environmental changes. The exact origin and development of most ecosystems, especially lakes, on the TP is however largely unknown. Hence, relationships between monsoonal changes, local or regional environmental responses, and species distribution or diversity are not recognized so far. The main aim of the Nam Co Drilling project is to establish a continental record of detailed monsoon history on orbital to suborbital timescales back to 0.5-1 Ma on sediments of the Tibetan lake Nam Co (Co = lake). This long continuous record enables to investigate Quaternary biotic dynamics (species diversity and distribution, evolution) in relation to climate changes. Understanding the morphological variability of aquatic organisms can make a valuable contribution, as it depends on environmental and genetic influences. Ostracodes (Arthropoda, Crustacea) are ideal bioindicators to answer these questions since they are the only aquatic invertebrates in lacustrine settings forming skeletal carbonates which are easily and abundantly preserved, and can provide plenty of paleoenvironmental information due to their (species-specific) sensitivity for ecological changes. We suggest to investigate the long-term evolution of ostracode distribution and their morphological variability in Nam Co. This will reveal if the lake served as glacial refugium and was continuously populated by ostracodes, or if ostracodes became extinct when climate was cooling during glacials and repeatedly colonized the lake with, e.g., increasing temperatures. Characterization of morphology-environment relationships of modern populations will help to understand if morphological variability of the fossil ostracodes reflect environmental changes (e.g., temperature) or intra- and/or interspecific differentiation. Analyzes will be based on morphometric data of valve size, shape and ornamentation of L. sinensis-L. dorsotuberosa, the most dominant ostracode species in Nam Co. Identification of ecophenotypical characteristics will disclose how environmental changes impact ostracode valve morphology, and in particular which morphological traits are sensitive indicators for specific ecological parameters. This novel approach will therefore provide new insights on responses of the ostracodes to climate change and their effects on ostracode evolution and (paleo)ecology in general and in particular for the TP.