Abstract
To predict effects of global change on zooplankton populations, it is important to understand how present species adapt to temperature and how they respond to stressors interacting with temperature. Here, we ask if the calanoid copepod Eurytemora affinis from the Baltic Sea can adapt to future climate warming. Populations were sampled at sites with different temperatures. Full sibling families were reared in the laboratory and used in two common garden experiments (a) populations crossed over three temperature treatments 12, 17, and 22.5°C and (b) populations crossed over temperature in interaction with salinity and algae of different food quality. Genetic correlations of the full siblings’ development time were not different from zero between 12°C and the two higher temperatures 17 and 22.5°C, but positively correlated between 17 and 22.5°C. Hence, a population at 12°C is unlikely to adapt to warmer temperature, while a population at ≥17°C can adapt to an even higher temperature, that is, 22.5°C. In agreement with the genetic correlations, the population from the warmest site of origin had comparably shorter development time at high temperature than the populations from colder sites, that is, a cogradient variation. The population with the shortest development time at 22.5°C had in comparison lower survival on low quality food, illustrating a cost of short development time. Our results suggest that populations from warmer environments can at present indirectly adapt to a future warmer Baltic Sea, whereas populations from colder areas show reduced adaptation potential to high temperatures, simply because they experience an environment that is too cold.
Highlights
E. affinis to be adapted to different temperature regimes and that the species can adapt to higher temperature than present via indirect selection at 17°C, which can result in an adaptation at 22.5°C
Low variance in phenotypic plasticity is typically seen as a limit of the evolutionary response (Dam, 2013; Ghalambor et al, 2007; Lee, 2002; Oostra, Saastamoinen, Zwaan, & Wheat, 2018; Sgrò, Terblanche, & Hoffmann, 2016), it is possible to see its potential benefits because all genotypes are more prone to respond to both direct and indirect selection, and a short development time is likely beneficial at both 17 and 22.5°C
Our study shows that selection of development time at warmer temperatures of 17 and 22.5°C is positively correlated, and E. affinis can adapt to higher temperatures if they currently inhabit waters of ≥17°C because of indirect selection that reinforce adaptation to high temperatures
Summary
Global warming affects the distribution and ecology of populations (De Meester, Stoks, & Brans, 2018; Kratina, Greig, Thompson, Carvalho-Pereira, & Shurin, 2012; Parmesan, 1996; Urban et al., 2016); the magnitude of its effect will depend on the populations’ adaptation potential to changing environmental conditions (Aitken, Yeaman, Holliday, Wang, & Curtis-McLane, 2008; Merilä & Hendry, 2014; Urban, Richardson, & Freidenfelds, 2014) Both genetic and plastic variation may facilitate retention of. There are still important topics to address on how species may adapt to climate change, such as how contemporary populations can adapt to future conditions This can be estimated by quantifying indirect selection between present and future environments, which is revealed by the sign and strength of genetic correlations. Populations that originate from areas of different temperature, salinity, and primary production were compared to investigate local adaptations and trade-offs
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