Shifts in frog size and phenology: Testing predictions of climate change on a widespread anuran using data from prior to rapid climate warming

Abstract

Changes in body size and breeding phenology have been identified as two major ecological consequences of climate change, yet it remains unclear whether climate acts directly or indirectly on these variables. To better understand the relationship between climate and ecological changes, it is necessary to determine environmental predictors of both size and phenology using data from prior to the onset of rapid climate warming, and then to examine spatially explicit changes in climate, size, and phenology, not just general spatial and temporal trends. We used 100 years of natural history collection data for the wood frog, Lithobates sylvaticus with a range >9 million km2, and spatially explicit environmental data to determine the best predictors of size and phenology prior to rapid climate warming (1901–1960). We then tested how closely size and phenology changes predicted by those environmental variables reflected actual changes from 1961 to 2000. Size, phenology, and climate all changed as expected (smaller, earlier, and warmer, respectively) at broad spatial scales across the entire study range. However, while spatially explicit changes in climate variables accurately predicted changes in phenology, they did not accurately predict size changes during recent climate change (1961–2000), contrary to expectations from numerous recent studies. Our results suggest that changes in climate are directly linked to observed phenological shifts. However, the mechanisms driving observed body size changes are yet to be determined, given the less straightforward relationship between size and climate factors examined in this study. We recommend that caution be used in “space‐for‐time” studies where measures of a species’ traits at lower latitudes or elevations are considered representative of those under future projected climate conditions. Future studies should aim to determine mechanisms driving trends in phenology and body size, as well as the impact of climate on population density, which may influence body size.

Northward expansion of the bivoltine life cycle of the cricket over the last four decades

“…Recent decreases in body size of ectotherms are often explained by the general negative relationship between adult body size and temperature in relation to climate warming (Gardner, Peters, Kearney, Joseph, & Heinsohn, ; Scheffers et al, ; Sheridan & Bickford, ). It was shown that increasing temperature caused decreases in the body size over several decades in butterflies (Bowden et al, ), beetles (Tseng et al, ), fishes (Baudron, Needle, Rijnsdorp, & Tara Marshall, ; Daufresne, Lengfellner, & Sommer, ), amphibians (Caruso, Sears, Adams, & Lips, ; Reading, ; Sheridan, Caruso, Apodaca, & Rissler, ), and reptiles (López‐Calderón, Feriche, Alaminos, & Pleguezuelos, ). In a frog, Lithobates sylvaticus , and a few species of salamanders, the magnitude and the direction of the body size response differed geographically, and depended on the change in temperature and precipitation (Caruso et al, ; Sheridan et al, ).…”

“…It was shown that increasing temperature caused decreases in the body size over several decades in butterflies (Bowden et al, ), beetles (Tseng et al, ), fishes (Baudron, Needle, Rijnsdorp, & Tara Marshall, ; Daufresne, Lengfellner, & Sommer, ), amphibians (Caruso, Sears, Adams, & Lips, ; Reading, ; Sheridan, Caruso, Apodaca, & Rissler, ), and reptiles (López‐Calderón, Feriche, Alaminos, & Pleguezuelos, ). In a frog, Lithobates sylvaticus , and a few species of salamanders, the magnitude and the direction of the body size response differed geographically, and depended on the change in temperature and precipitation (Caruso et al, ; Sheridan et al, ). In the present results, however, the decreased body size at the middle latitudes cannot be explained simply by the negative relationship between adult body size and temperature, because the increase in the length of the season available for growth caused by increasing temperature was not larger at the middle latitudes than that at the other latitude (Figure ).…”

Peer Review #2 of "The role of ambient temperature and body mass on body temperature, standard metabolic rate and evaporative water loss in southern African anurans of different habitat specialisation (v0.1)"

“…Our results suggest that the significance of M b in influencing key physiological factors is not universal (at least for EWL) and should also be looked at in the context of species ecology as M b did not influence T b , EWL and SMR in the principally aquatic X. laevis (see Olalla-Tárraga & Rodriguez, 2007;Gouveia et al, 2019). Understanding how species with different ecologies will respond to climate change is particularly important in anurans where some species may respond by altering their body sizes (e.g., Sheridan et al, 2018). Despite the pronounced sexual dimorphism in anurans, sex did not influence the relationship of T a with all physiological variables considered.…”

Museum specimens provide novel insights into changing plant–herbivore interactions

“…Animals are also shifting their phenology with climate change; many species are migrating sooner, advancing seasonal breeding times, and insects are emerging earlier [56]. Natural history collections have been valuable in demonstrating how animal species respond to climate warming [57,58]. Thanks to the biases of early Victorian naturalists and their attractiveness to contemporary collectors, the Lepidopterabutterflies and moths, which in their immature stages are herbivorous-have been collected more comprehensively than many other groups and are thus the subject of a large proportion of collections research on animals [59].…”