Inbreeding reduces fitness of seed beetles under thermal stress

Abstract

Human-induced environmental change can influence populations both at the global level through climatic warming and at the local level through habitat fragmentation. As populations become more isolated, they can suffer from high levels of inbreeding which contributes to a reduction in fitness, termed inbreeding depression. However, it is still unclear if this increase in homozygosity also results in a corresponding increase in sensitivity to stressful conditions, which could intensify the already detrimental effects of environmental warming. Here, in a fully factorial design, we assessed the life-long impact of increased mutation load and elevated temperature on key life history traits in the seed beetle, Callosobruchus maculatus. We found that beetles raised at higher temperatures had far reduced fitness and survival than beetles from control temperatures. Importantly, these negative effects were exacerbated in inbred beetles as a result of increased mutation load, with further detrimental effects manifesting on individual hatching probability and lifetime reproductive success. These results reveal the harmful impact that increasing temperature and likelihood of habitat fragmentation due to anthropogenetic changes in environmental conditions could have on populations of organisms worldwide.

Genetic and thermal variation influence adaptation to fluctuating temperature in the seed beetle, Callosobruchus maculatus

“…A multitude of studies have shown the negative impact of increasing mean temperature on important life history traits in invertebrate species (Bauerfeind & Fischer, 2014; Rogell et al , 2014; Vasudeva et al , 2014; Berger et al , 2017; Chen et al , 2018; Klepsatel et al , 2019; Ivimey-Cook et al , 2021). In particular, heat stress caused by high temperatures outside of a species’ thermal optimum can disrupt reproduction, reduce longevity and survival in insects (Berger et al ., 2017; Ivimey-Cook et al , 2021), particularly if outside of a species Thermal Fertility Limit (TFL, reviewed in Walsh et al , 2019).…”