Population‐specific responses of an insect herbivore to variation in host‐plant quality

Abstract

Anthropogenic climate change poses a substantial challenge to many organisms, to which they need to respond to avoid fitness reductions. Investigating responses to environmental change is particularly interesting in herbivores, as they are potentially affected by indirect effects mediated via variation in host‐plant quality. We here use the herbivorous insect Pieris napi to investigate geographic variation in the response to variation in food quality. We performed a common garden experiment using replicated populations from Germany and Italy, and manipulated host quality by growing host plants at different temperature and water regimes. We found that feeding on plants grown at a higher temperature generally diminished the performance of P. napi, evidenced by a prolonged development time and reduced larval growth rate, body mass, fat content, and phenoloxidase activity. Genotype by environment interactions (G × E) were present in several performance traits, indicating that Italian populations (1) respond more strongly to variation in host‐plant quality and (2) are more sensitive to poor food quality than German ones. This may reflect a cost of the rapid lifestyle found in Italian populations. Consequently, German populations may be more resilient against environmental perturbations and may perhaps even benefit from warmer temperatures, while Italian populations will likely suffer from the concomitantly reduced host‐plant quality. Our study thus exemplifies how investigating G × E may help to better understand the vulnerability of populations to climate change.

Factors shaping the abundance of two butterflies sharing resources and enemies across a biogeographic region

“…Cooler temperatures can slow down metabolic processes of insects, reducing energy consumption and potentially extending their lifespans (Karl & Fischer, 2009; Karlsson & Wiklund, 2005). In the same way, lower temperatures can enhance the persistence of host plants in ideal conditions for larval development (Kuczyk et al., 2021; Stefanescu et al., 2022). Overall, these factors will increase reproductive success and, hence, population size, explaining the observed higher population abundance in the cooler regions of our studied species.…”