Decreases in beetle body size linked to climate change and warming temperatures

Abstract

Body size is a fundamental ecological trait and is correlated with population dynamics, community structure and function, and ecosystem fluxes. Laboratory data from broad taxonomic groups suggest that a widespread response to a warming world may be an overall decrease in organism body size. However, given the myriad of biotic and abiotic factors that can also influence organism body size in the wild, it is unclear whether results from these laboratory assays hold in nature. Here we use datasets spanning 30 to 100 years to examine whether the body size of wild-caught beetles has changed over time, whether body size changes are correlated with increased temperatures, and we frame these results using predictions derived from a quantitative review of laboratory responses of 22 beetle species to temperature. We found that 95% of laboratory-reared beetles decreased in size with increased rearing temperature, with larger-bodied species shrinking disproportionately more than smaller-bodied beetles. In addition, the museum datasets revealed that larger-bodied beetle species have decreased in size over time, that mean beetle body size explains much of the interspecific variation in beetle responses to temperature, and that long-term beetle size changes are explained by increases in autumn temperature and decreases in spring temperature in this region. Our data demonstrate that the relationship between body size and temperature of wild-caught beetles matches relatively well with results from laboratory studies, and that variation in this relationship is largely explained by interspecific variation in mean beetle body size. This long-term beetle dataset is one of the most comprehensive arthropod body size datasets compiled to date, it improves predictions regarding the shrinking of organisms with global climate change, and together with the meta-analysis data, call for new hypotheses to explain why larger-bodied organisms may be more sensitive to temperature.

Eco‐evolutionary processes underlying early warning signals of population declines

“…Such a phenotypic trait, for example, could be body size. Body size is a quantitative trait fundamental to life‐history theory and population dynamics (Gibert, Allen, Hruska, & DeLong, ; Pigeon, Ezard, Festa‐Bianchet, Coltman, & Pelletier, ), which has been shown to decline in response to decreases in resource availability (Clements & Ozgul, ), increases in temperature (Forster, Hirst, & Atkinson, , ; Gardner, Peters, Kearney, Joseph, & Heinsohn, ; Tseng et al, ) and increases in harvest rate (Clements et al, ). In our model, the optimum environmental change will affect the dynamics of the phenotype.…”

“…To evaluate the efficacy of trait-based EWS (Clements & Ozgul, 2016), information from mean phenotype z was incorporated with the leading indicators in an additive manner. We z-standardized the , which has been shown to decline in response to decreases in resource availability (Clements & Ozgul, 2016), increases in temperature (Forster, Hirst, & Atkinson, 2011Gardner, Peters, Kearney, Joseph, & Heinsohn, 2011;Tseng et al, 2018) and increases in harvest rate (Clements et al, 2017). In our model, the optimum environmental change will affect the dynamics of the phenotype.…”

The influence of ecological and life history factors on ectothermic temperature–size responses: Analysis of three Lycaenidae butterflies (Lepidoptera)

“…Ecological rules such as the temperature-size rule (TSR) and Bergmann's rule (latitude-size clines) have led to the prediction that body size declines will be a "universal" response to climate change (Daufresne, Lengfellner, & Sommer, 2009;Gardner, Peters, Kearney, Joseph, & Heinsohn, 2011). Specifically, the TSR predicts that individuals developing in cool conditions will be larger as adults than those developing in warm conditions, and this has been shown to be the case for many species (Daufresne et al, 2009;Gardner et al, 2011;Ghosh, Testa, & Shingleton, 2013;Horne et al, 2015;Irie, Morimoto, & Fischer, 2013;Ohlberger, 2013;Sheridan & Bickford, 2011;Tseng et al, 2018). However, it has also recently been shown that some species increase in size with increasing temperature, whereas some species appear to show no temperature-size response (Classen, Steffan-Dewenter, Kindeketa, & Peters, 2017;Fenberg, Self, Stewart, Wilson, & Brooks, 2016;Horne et al, 2015;Høye, Hammel, Fuchs, & Toft, 2009;Scriber, Elliot, Maher, McGuire, & Niblack, 2014;Shelomi, 2012;Upton, Price, Percy, & Brooks, 2016).…”

Evolutionary dynamics and diversification in changing environments

“…With gradual environmental change, the phenotype of a species generally has to evolve in step with the movement of the centre of the carrying capacity, because otherwise the carrying capacity of that species will fall to very low values, making the environment inviable for that species. Such effects can be observed in various populations (Gienapp et al 2008;Baym et al 2016;Tseng et al 2018). For example, numerous studies indicated a global tendency of various species to decrease in body size in warming environments (Guillemain et al 2005;Y.…”

“…Body size is an important physiological characteristic that strongly influences metabolism and thermoregulation. For example, decreased body-size due to changing temperature regimes was observed in beetles both in natural and laboratory populations (Tseng et al 2018).…”