ALBERT

Description: Animal locomotory morphology, i.e. morphological features involved in locomotion, is under the influence of a diverse set of ecological and behavioral factors. In teleost fish, habitat choice and foraging strategy are major determinants of locomotory morphology. In this study, we assess the influence of habitat use and foraging strategy on important locomotory traits, namely the size of the pectoral and caudal fins and the weight of the pectoral fin muscles, as applied to one of the most astonishing cases of adaptive radiation: the species flock of cichlid fishes in East African Lake Tanganyika. We also examine the course of niche partitioning along two main habitat axes, the benthic vs. limnetic and the sandy vs. rocky substrate axis. The results are then compared with available data on the cichlid adaptive radiation of neighbouring Lake Malawi. We find that pectoral fin size and muscle weight correlate with habitat use within the water column, as well as with substrate composition and foraging strategies. Niche partitioning along the benthic–limnetic axis in Lake Tanganyikan cichlids seems to follow a similar course as in Lake Malawi, while the course of habitat use with respect to substrate composition appears to differ between the cichlid assemblages of these two lakes.

Description: In marine climate change research, salinity shifts have been widely overlooked. While widespread desalination effects are expected in higher latitudes, salinity is predicted to increase closer to the equator. Here, we use the steep salinity gradient of the Baltic Sea as a space‐for time design to address effects of salinity change on populations. Additionally, genetic diversity, a prerequisite for adaptive responses, is reduced in Baltic compared to Atlantic populations. On the one hand, adaptive transgenerational plasticity (TGP) might buffer the effects of environmental change, which may be of particular importance under reduced genetic variation. On the other hand, physiological trade‐offs due to environmental stress may hamper parental provisioning to offspring thereby intensifying the impact of climate change across generations (non‐adaptive TGP). Here, we studied both hypothesis of adaptive and non‐adaptive TGP in the three‐spined stickleback (Gasterosteus aculeatus) fish model along the strong salinity gradient of the Baltic Sea in a space‐for‐time experiment. Each population tolerated desalination well, which was not altered by parental exposure to low salinity. Despite a common marine ancestor, populations locally adapted to low salinity lost their ability to cope with fully marine conditions, resulting in lower survival and reduced relative fitness. Negative transgenerational effects were evident in early life stages, but disappeared after selection via mortality occurred during the first 12‐30 days post hatch. Modeling various strengths of selection, we showed that non‐adaptive transgenerational plasticity accelerated evolution by increasing directional selection within the offspring generation. Qualitatively, when genetic diversity is large, we predict that such effects will facilitate rapid adaptation and population persistence, while below a certain threshold populations suffer a higher risk of local extinction. Overall, our results suggest that transgenerational plasticity and selection are not independent of each other and thereby highlight a current gap in TGP studies.