Diversity of recent subterranean and paratethyan ostrocods

The interest for comparative studies which allow to understand the ecology of Ancient lakes is actually high. Lake Pannon in Central Europe was in existence for about eight Mya during Upper Tertiary. Crustacean ostracods represents an optimal group to investigate evolutionary-ecological topics within a palaeolimnological context. We will use experience gained on the Recent subterranean ostracods for better understand how we can use fossil ostracods of the Pannonian facies in the western part of the Lake Pannon in order to reconstruct in a precise way the dynamics of the (palaeo)environment where they occur. Specifically, we will chose sampling sites for the Recent groundwater ostracods from the flood-plain of the Danube which display some similarities with the Panonian facies in some of our sampling areas. In pilot studies using geometricmorphometric analysis we noted that the carapace of several living subterranean ostracod species are ecologically and evolutionarily plastic, i.e. they display differences within populations located in contrasted environments and/or in geographically separated sites. The experience gained will be further used for fossil ostracods where the palaeoenvironment can not be easily reconstructed using common geologic and palaeoecologic information. Parallel to the morphologic diversity (disparity) we will describe also the taxonomic diversity of whole ostracod assemblages from various sampling sites. It is expected that combination of both approaches will offer a rich information on the palaeoenvironment and its changes during various time periods. It is also foreseen to test the evolutionary ecological hypothesis that some of the ostracod groups where able to migrate from the western part of the Lake Pannon towards the eastern and southern parts of this basin and further on outside of this basin. This will allow to gain a new insights in the historical (palaeo)biogeography of the Danube Basin. Knowledge derived from living groundwater ostracods and groundwater ecology for palaeoecology and systematics of fossil Paratethyan ostracods represents a premiere within the micropalaeontology. Extended usage of geometric morphometrics for palaeoenvironmental reconstructions opens a new era in the research of the Pararatethys ostracods. It allows also to better define (i.e. in an objective and quantitative way) ostracod taxa which one can further integrate in other research projects.

Ostracods represent a unique material for ecological and palaeoecological studies because of their wide distribution in both marine and limnic (non-marine) habitats. The main topic of the project deals with comparative studies between Recent (living) ostracods from groundwater systems and fossil ostracods, mainly from the palaeo-ancient Lake Pannon, which derived about 11 Million years ago from the central part of the Paratethys Sea. Many so- called `Ancient Lakes` and groundwater systems (aquifers) have in common a long persistence of their environment (thousands of years) and in many cases a very wide spatial distribution (up to hundreds of kilometres). It was therefore interesting to compare the ostracod diversity of both systems, in the present case of the Lake Pannon who was in existence for about six million years and which is located mainly in Central Europe, with the living European groundwater ostracod fauna. For the groundwater ostracod fauna, we reviewed the morphology and systematics of two groups, Pseudocandona, the group eremita and Cryptocandona, the group vavrai, as well as those of the new genus Dolekiella which displays similarities with fossil groups either from Lake Pannon or even from more ancient aquatic systems. For the former two groups we noticed a higher taxonomic diversity in groundwater than existing in European surface- water systems, while the latter genus has no close relatives in the present day fauna and can be labelled metaphorically as a `living fossil` group. For the Lake Pannon we studied three groups, Herpetocyprella, Amplocypris and Cyprideis. Additionally a large group, the Candoninae, is ongoing studied for its morphological diversity. We confirmed for the Cyprideis group higher species diversity on the western part Lake Pannon as compared to the present-day Cyprideis in Europe. The opposite situation appears for Herpetocyprella and Amplocypris. A revision of these two groups showed a more reduced diversity than earlier accepted. The comparative study of specific European groundwater ostracod groups with those of Lake Pannon allowed us to use the productive scientific method of `reciprocal illumination`, respectively ideas and scenarios based on our studies from one domain where used to construct possible explanations for the origin and development of the ostracod diversity in the alternative domain. We noticed for instance that one characteristic of the groundwater Candoninae ostracods (specifically the case of the Pseudocandona eremita group) has the high potentiality to change the morphology of limbs related to slight changes in the morphology of the valves. We applied this observation to fossil ostracod Candoninae and Cyprididae from the Lake Pannon and its satellite post-lakes, which allowed to better understand the morphological and taxonomical diversity of these latter.