Primary productivity explains size variation across the Pallid bat's western geographic range

Abstract

Body size is associated with many aspects of the life history, ecology and physiology of animals. Within a species, body size can vary substantially across space and time, and the mechanisms generating these patterns have been the focus of evolutionary and ecology research. Bergmann’s rule predicts a negative relationship between body size and temperature across the geographic range of endothermic animals; larger animals have a lower surface to volume ratio, which would allow for greater heat conservation. Despite the broad support for this pattern, its underlying mechanisms are heavily debated. Numerous alternative explanations have been proposed to explain why larger animals are found in colder climates and vice versa, including heat dissipation, environmental seasonality and resource availability. We used the Pallid bat, Antrozous pallidus, as a model to evaluate Bergmannian size patterns and the relative support for major explanatory hypotheses of geographic body size variation. We tested the hypothesis that geographic size variation is predicted by productivity, as opposed to seasonality, heat conservation or dissipation, or some combination of these processes. Additionally, we investigated the potential ecomorphological consequences of size variation in Pallid bats by determining if skull shape (an indicator of bite performance) varies with size. Whereas we did find that Pallid bat populations in northern latitudes are composed of larger individuals, our results suggest that net primary productivity and, to a lesser extent heat conservation, best explain size variation throughout the western range of this species. We also found that skull shape in Pallid bats changes in tandem with skull size, with larger bats having cranial traits associated with greater bite force production. The results of our study indicate that variation in resource availability may be a key factor underlying spatial patterns in size, morphology and, possibly, feeding performance within wide‐ranging bat species. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.13092/suppinfo is available for this article.

The patterns and possible causes of global geographical variation in the body size of the greater horseshoe bat (Rhinolophus ferrumequinum)

“…In contrast, the predictions of James's rule have been thoroughly supported at the intraspecific level in mammals (Kubo & Takatsuki, ; Meiri, ; Pincheira‐Donoso, ; Rodríguez & Hawkins, ) and birds (Ashton, ). In bats, some studies have indicated that larger body sizes were found in cooler environments, consistent with the predictions of Bergmann's rule/James's rule (Bogdanowicz, ; Burnett, ; Dietz et al, ; Kelly et al, ; Storz et al, ). However, several studies have shown the inverse of James's rule in the greater horseshoe bat, and have suggested that resource rules (relating to resource abundance, availability, and size) may be used to explain this pattern (Budinski et al, ; Kryštufek, ; Wu et al, ).…”

“…In contrast, the predictions of James's rule have been thoroughly supported at the intraspecific level in mammals (Kubo & Takatsuki, 2015;Meiri, 2011;Pincheira-Donoso, 2010;Rodríguez & Hawkins, 2010) and birds (Ashton, 2002). In bats, some studies have indicated that larger body sizes were found in cooler environments, consistent with the predictions of Bergmann's rule/James's rule (Bogdanowicz, 1990;Burnett, 1983;Dietz et al, 2006;Kelly et al, 2018;Storz et al, 2001).…”

“…However, relative to birds and other mammals, little is known about ecogeographical variations in bat body size. Bergmann's rule/James's rule has been shown in several bat species, including Antrozous pallidus (Kelly, Friedman, & Santana, 2018), Rhinolophus mehelyi (Dietz, Dietz, & Siemers, 2006), Cynopterus sphinx (Storz et al, 2001), Myotis daubentonii (Bogdanowicz, 1990) and Eptesicus fuscus (Burnett, 1983). However, analyses of other bat species, such as Pipistrellus kuhlii (Tomassini et al, 2014), R. ferrumequinum (Budinski et al, 2015;De Paz, 1995;Wu et al, 2014), Plecotus auritus and P. austriacus (Postawa, Zagorodniuk, & Bachanek, 2012) have failed to support James's rule.…”

Functional diversity of phyllostomid bats in an urban–rural landscape: A scale‐dependent analysis

“…Endemism is one of the main factors predicting the risk of extinction in bats, that is associated with habitat specialist species (Welch & Beaulieu, 2018). Besides landscape composition and structure, other factors such as primary productivity may influence bat traits related to vagility and food intake (Kelly, Friedman, & Santana, 2018). Thus, bat responses to environmental degradation are probably not linear, and its predictability may depend on a methodological framework that incorporates the multidi-…”

Global patterns of body size evolution are driven by precipitation in legless amphibians

“…For example, while heat production implies high metabolic expenditure of energy for endotherms, the dependence of ectotherms on environmental heat neutralises such pressures (Brown et al 2004, Angilletta 2009); finally 3) the 'seasonality (or 'fastingendurance') rule', predicts that increasing seasonality selects for increased body size to enhance tolerance to unstable environments (Lindsey 1966, Boyce 1979, Calder 1984. Given the contrasting mechanisms that these hypotheses offer to explain the same phenomenon, evidence supporting them has been conflicting across lineages (Meiri et al 2005, Yom-Tov and Geffen 2006, Olalla-Tarraga and Rodriguez 2007, Olalla-Tarraga et al 2009, Oufiero et al 2011, Pincheira-Donoso and Meiri 2013, Gouveia and Correia 2016, Kelly et al 2018, Amado et al 2019). Furthermore, our understanding of body size macroecology has fundamentally been advanced based on above-ground organisms, while analyses on fossorial lineages remain anecdotal (Meiri and Dayan 2003, Measey and Van Dongen 2006, Feldman and Meiri 2014.…”