Advisors: Martin Schwentner & Luise Kruckenhauser

Master's Defensio

Thursday December 12th, 2024, 15:00 CET
SR 1.4, UBB
Djerassiplatz 1, 1030 Vienna

Abstract

This study investigated the population dynamics of the freshwater tadpole shrimp Lepidurus apus (L., 1758) (Branchiopoda, Notostraca), the only representative of this genus in Austria. Large Branchiopoda are adapted to temporary freshwater habitats via resting egg banks that persist through fluctuations and maintain populations across generations. Both spatial and temporal perspectives on the large branchiopod L. apus were explored: Spatially, recent genetic variation among L. apus populations across Austria, alongside individuals from Slovakia, was analysed to assess the extent of genetic differentiation. Temporally, the L. apus collection of the NHM Vienna spanning from the 1960s to the early 2000s provided a unique opportunity to investigate genetic changes over time. Population genomic methods applied ddRAD sequencing for recent material, while hyRAD was used for historic, fragmented DNA, in combination with two library preparation approaches to convert single- to double-stranded DNA, enhancing data recovery from degraded samples. Additionally, the whole genome of L. apus was assembled as a reference for analysing the ddRAD and hyRAD data. Results showed a clear genetic pattern in recent individuals, with Austrian and west Slovakian individuals grouping separately from those in east and south Slovakia. This pattern reflects geographic influences coupled with effective short-distance dispersal of resting eggs within the Austrian/west Slovakian group, contrasted by limited gene flow between this group and east/south Slovakia. Artefactual SNPs, detected primarily in historic libraries, were corrected to reduce their impact on genetic inference and population structure. Nonetheless, additional high missingness and low coverage made it challenging to reach clear conclusions about genetic change over time, emphasising the difficulties when working with degraded DNA in temporal studies of population dynamics.