Environmental stressors alter multiple determinants of individual reproductive output in the acid-tolerant mayfly Leptophlebia vespertina

1. Environmental stressors such as acidification modify community composition in freshwater habitats through their direct and indirect effects on individuals. However, the effect of acidification on various aspects of individual fitness is poorly known in aquatic insects, a key group in many freshwater habitats. 2. Here, the influence of acidification (acidity and Al toxicity), food quality and habitat properties on the reproduction of an acid-tolerant mayfly Leptophlebia vespertina (Linnaeus, 1758) in a group of Central European lakes is explored. The focus is on last-instar larvae as the short-lived, semelparous adults cannot mitigate stress experienced by the larvae. 3. It is shown that the environment affects multiple determinants of individual reproductive output both directly by affecting body size and fecundity in last-instar larvae, and indirectly by releasing the larvae from density dependence. Populations tended to be denser in more acidic sites and individuals in denser populations were substantially smaller and had lower size-dependent fecundity and reproductive effort. All else being equal, larvae from colder sites were larger, suggesting an important role of the temperature-size rule in this species. Size-dependent fecundity and reproductive effort increased with better food conditions as expected, but neither reproductive measure was affected by acidity or temperature. Finally, a weak egg size-number trade-off with slightly smaller eggs in more fecund females was detected. 4. These results imply that indirect ecological feedbacks and food quality, rather than the direct effects of stressful environment, may dominate the effects of environmental stressors on the reproductive output of acid-tolerant species such as L. vespertina.

Automated summary

The study shows that indirect ecological feedbacks and food quality, rather than the direct effects of a stressful environment, may play a dominant role in influencing the reproductive output of acid-tolerant species like Leptophlebia vespertina in freshwater habitats.