Impact of warming on functional traits of a keystone grazer in Arctic lakes

Athina Karapli-Petritsopoulou , Dörthe Becker, Dagmar Frisch 

Temperature rise is one of the most pronounced abiotic changes currently affecting Αrctic ecosystems. Knowledge about the adaptation capacity of their key species is urgently needed to better understand the ecological consequences for these sentinel ecosystems. Previous work on a keystone zooplankton grazer, the obligatory parthenogenetic Daphnia pulicaria, from a lake in South-West Greenland revealed a decreased thermal tolerance over the course of a decade. To assess its thermal responses in more detail, we compared physiological and life history traits of four clones from the same population that originate from two time periods a decade apart. The tested clones represent two closely related genetic clusters. Both were present in the 2022 population, but only one was present also in 2011. Two of the clones were previously resurrected from the sediment dating to ca. 2011. We tested three temperatures to reflect future climate warming scenarios: 14°C, 16°C, and 18°C. The tested temperature range did not alter most of the measured traits, but there were pronounced differences between clones at all temperatures. Results indicated that genetic cluster membership, rather than time period of origin, determined the clones’ responses. The clone representing the genetic cluster detected only in 2022 had consistently higher stress and lower fitness across all tested temperatures. To better understand the implications for the lake ecosystem, a more comprehensive survey of clonal diversity and the survival capacity of additional clones present in the population under projected warming scenarios is needed.