Signatures of increasing environmental stress in bumblebee wings over the past century: Insights from museum specimens

Abstract

1. Determining when animal populations have experienced stress in the past is fundamental to understanding how risk factors drive contemporary and future species' responses to environmental change. For insects, quantifying stress and associating it with environmental factors has been challenging due to a paucity of time-series data and because detectable population-level responses can show varying lag effects. One solution is to leverage historic entomological specimens to detect morphological proxies of stress experienced at the time stressors emerged, allowing us to more accurately determine population responses.2. Here we studied specimens of four bumblebee species, an invaluable group of insect pollinators, from five museums collected across Britain over the 20th century. We calculated the degree of fluctuating asymmetry (FA; random deviations from bilateral symmetry) between the right and left forewings as a potential proxy of developmental stress.3. We: (a) investigated whether baseline FA levels vary between species, and how this compares between the first and second half of the century; (b) determined the extent of FA change over the century in the four bumblebee species, and whether this followed a linear or nonlinear trend; (c) tested which annual climatic conditions correlated with increased FA in bumblebees.

Land-use-associated stressors interact to reduce bumblebee health at the individual and colony level

“…Bees with lower foraging activity also pollinate fewer flowers and thus affect the reproductive output of plants. Furthermore, we have shown that insecticide exposure reduced body size (here wing size) and increased wing asymmetry (a measure of developmental stability), both of which are connected to larval development [ 63 ], while a recent study using specimens from museums could link increasing wing asymmetry to climatic conditions such as increasing temperature [ 87 ]. Thus, acetamiprid and a lack of nutrients affect bumblebee larval development and cause a decrease in body size.…”

Bee species richness through time in an urbanizing landscape of the southeastern United States

“…Multiple studies have used museum specimens to fill in temporal data gaps to answer questions about bee diversity patterns (e.g., Bartomeus, Ascher, et al., 2013; Jacobson et al., 2018; Mathiasson & Rehan, 2019), response to environmental stress (Arce et al., 2023), and pollination networks (Mathiasson & Rehan, 2020). Studies that looked at diversity patterns using museum specimens either investigated across multiple time periods, finding weak declines in richness that were non‐significant except for some wild bee species (e.g., some Bombus species, Bartomeus, Ascher, et al., 2013), or split the data into two time periods (historic vs. contemporary; e.g., Jacobson et al., 2018; Mathiasson & Rehan, 2019).…”

Leveraging natural history collections to understand the impacts of global change

“…Clearly, specimens from museums provide a wealth of opportunities to explore how phenotypes might change through time. For example, in Journal of Animal Ecology , Arce et al (2023) document the degree of fluctuating asymmetry—a potential proxy for developmental stress—in the forewings of four bumblebee species from five natural history collections over 100 years. They found that fluctuating asymmetry generally increased over the course of the 20th century, which could have implications for the health of bumblebee populations.…”