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The same species, not the same invader: Metabolic responses of genetically distinct invasive populations of Dikerogammarus villosus and their intraspecific hybrid to environmental stresses

Jermacz, Łukasz1; Podwysocki, Krzysztof2, 3; Desiderato, Andrea3; Bącela-Spychalska, Karolina3; Rewicz, Tomasz3; Szczerkowska, Eliza3; Augustyniak, Mateusz1; Gjoni, Vojsava4; Kobak, Jarosław1

Published Jun 10, 2025 on Dryad. https://doi.org/10.5061/dryad.5tb2rbpft

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Jun 10, 2025 version files 146.99 KB

Abstract

Climate change has a profound impact on ectotherms, which suffer suboptimum thermal conditions in their native areas or spread to previously unavailable locations. However, it is often neglected that responses to environmental changes are likely at a population level, rather than species-specific phenomenon.

Two groups (Western and Eastern) of the invasive Ponto-Caspian amphipod Dikerogammarus villosus independently spread in Europe from two geographically isolated and genetically distinct source populations living in the Danube and Dnieper deltas, respectively. They are expected to meet in the near future in Polish inland waters. This makes this species a perfect model to investigate the intraspecific variability in responses to environmental changes, as well as effects of hybridization between different genetic units on invasiveness.

We scaled maximal metabolic rate (MMR), standard metabolic rate (SMR), and aerobic scope (AS, a measure of physiological performance) of D. villosus at different temperatures (15 and 25 oC) and oxygen levels (9.5 or 7.5 mg/l at a temperature of 15 and 25 oC, respectively and 5.5 mg/l at both temperatures) to test for differences in responses to environmental changes among the distinct invasive groups and their hybrid.

Large Western Group individuals showed a lower AS at a high temperature, compared to low temperature and to the Eastern group individuals, whereas small animals exhibited similar AS irrespective of temperature and group identity. Moreover, large individuals from both groups experienced a reduction in MMR and AS under low oxygen conditions, whereas small animals did not change these parameters in response to oxygen reduction. Although parental groups reduced their AS in response to oxygen reduction, AS of the hybrid remained unchanged.

In conclusion, organism responses to climate change depend on intraspecific variation, which should be considered in studies related to this topic. Furthermore, D. villosus appears sensitive to oxygen deficits and temperature changes (especially the Western group and large individuals), but intraspecific hybridisation can enhance the environmental tolerance of invaders.