Body size responses to the combined effects of climate and land use changes within an urban framework

Abstract

Alterations in body size can have profound impacts on an organism's life history and ecology with long-lasting effects that span multiple biological scales. Animal body size is influenced by environmental drivers, including climate change and land use change, the two largest current threats to biodiversity. Climate warming has led to smaller body sizes of many species due to impacts on growth (i.e., Bergmann's rule and temperature-size rule). Conversely, urbanization, which serves as a model for investigating the effects of land use changes, has largely been demonstrated to cause size increases, but few studies have examined the combined influences of climate and land use changes on organism size. We present here the background theory on how each of these factors is expected to influence body size, summarize existing evidence of how size has recently been impacted by climate and land use changes, and make several recommendations to guide future research uniting these areas of focus. Given the rapid pace of climate change and urbanization, understanding the combined effects of climate and land use changes on body size is imperative for biodiversity preservation.

Geographical Variation in Body Size and the Bergmann’s Rule in Andrew’s Toad (Bufo andrewsi)

“…Like those of most other ectotherms [ 67 , 105 , 106 ], anuran life-history traits (e.g., age at sexual maturity, mean age, and longevity) vary with environmental conditions [ 66 , 82 , 107 , 108 ]. For instance, populations experiencing longer growth seasons have younger ages at sexual maturity, mean age, and longevity than populations experiencing shorter growth seasons in previous studies that discussed geographical variation in B. andrewsi age structure [ 22 , 45 ].…”

“…The skeletochronology was used to estimate the ages of each sampled individual [ 22 ]. To produce histological sections for age determination, we used paraffin sectioning and Harris’s haematoxylin staining (see details in [ 66 , 97 ]). With a LEITZ dialux 40 microscope, we selected the cross-sections of the phalanx that had the smallest medullar cavity and the thickest cortical bone (13 m thick) to count the lines of arrested growth (LAG).…”

“…For instance, individuals living in harsh environments devote more time and energy to growing, which causes them to become older and to grow larger, and, thus, these individuals are of a larger body size [ 62 ]. Furthermore, some species display sex-specific relationships between environmental factors and body size because males and females suffer distinct selection pressures in the same environment [ 63 , 64 , 65 , 66 , 67 ]. As such, the extent to which these hypotheses explain the ecogeographic patterns of body size variation remains uncertain.…”

“…The anuran is an ideal model for exploring the influence of environmental changes on body size, since their highly permeable skin, unshelled eggs, low vagility, and frequent territoriality are particularly vulnerable to environmental stresses (e.g., temperature, precipitation, and ultraviolet radiation) [ 68 ]. However, few studies exploring body size variation have been conducted, of which only nearly 5% of all amphibian species have been studied, and there is much controversy as to whether the effects of environmental changes on body size variation support Bergmann’s rule [ 45 , 55 , 57 , 61 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 ]. Although the effect of temperature on body size is contested, precipitation, as a proxy for productivity, has been found to affect the body size of frogs [ 24 , 83 ].…”

What's going to be on the menu with global environmental changes?

“…Climate warming has been suggested as the driver of observations of size shifts in several taxa including invertebrates (Polidori et al, 2020; Tseng et al, 2018), fish (Forster et al, 2012), amphibians (Caruso et al, 2014), birds (Prokosch et al, 2019), and mammals (Ozgul et al, 2009; Yom‐Tov et al, 2010). Body size is a fundamental trait for any organism that affects all physiological and ecological processes including the structuring of consumer–resource interactions (Martin & Sheridan, 2022). For example, Polidori et al (2020) suggested shrinking sizes of social wasps ( Dolichovespula sylvestris ) could lead to reduced foraging distances and the exclusion of large prey items previously accessible.…”