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Sexual size dimorphism (SSD) is the difference in body size between males and females. One of the most studied patterns in allometric size difference between sexes is Rensch's rule, which describes an increase of SSD with increasing species size when males are the larger sex. However, few studies have tested this rule in bats, and morphological structures other than body size have rarely been included. The objective of this paper was to analyze the patterns of SSD across 28 New World bat species and assess their conformity to Rensch's rule. To do this, I obtained measurements of forearm length, length of the third digit, and length of the fifth digit from 1,151 bat specimens, and through t-tests and reduced major axis regressions, I analyzed patterns of SSD and Rensch's rule. I found high variation in size and wing morphology, with a modest female-biased size in more than half the species, which fails to support Rensch's rule. Larger wing structures in females can improve flight performance to overcome aerodynamic challenges during reproduction when carrying pups and foraging for food. Mechanisms other than body size in females, geographic variation, and the set of species selected may explain the isometric pattern between sexes, which invalidates Rensch's rule for Neotropical bats. Further studies should encompass a broader range of bat species from different lineages, but it is also necessary to analyze SSD based on various traits related to resource use, such as wing and nasal morphology, as well as include the influence of geographic variation and environmental factors. El dimorfismo sexual del tamaño (DST) es la diferencia en el tamaño corporal entre machos y hembras. Uno de los patrones mas estudiados en la diferencia de tamaño alométrico entre sexos es la regla de Rensch que describe un aumento del DST con el aumento del tamaño de la especie cuando los machos son el sexo más grande. Sin embargo, existen pocos estudios realizados en murciélagos y en contadas ocasiones se han incluido estructuras morfológicas distintas del tamaño corporal para probar esta regla. El objetivo de este artículo fue analizar los patrones de DST en 28 especies de murciélagos neotropicales y evaluar la validez de la regla de Rensch. Para ello, obtuve medidas de la longitud del antebrazo, longitud del tercer y quinto dígito de 1,151 especímenes de murciélagos, y a través de pruebas t y de regresiones de eje mayor reducido, analicé patrones de DST y la regla de Rensch. Encontré una gran variación en el tamaño y la morfología alar con un ligero aumento de las hembras en más de la mitad de las especies, lo cual no respalda la regla de Rensch. Estructuras alares más grandes en las hembras pueden mejorar el rendimiento de vuelo para superar los desafíos aerodinámicos durante la reproducción cuando cargan a las crías y buscan alimento. Mecanismos distintos del tamaño corporal en las hembras, así como la variación geográfica, y el conjunto de especies seleccionadas pueden explicar el patrón de isometría entre sexos que invalida la regla de Rensch para murciélagos neotropicales. Futuros estudios deberían abarcar una mayor variedad de especies de murciélagos de diferentes linajes, pero también es necesario analizar el DST en función en diversos rasgos relacionados con el uso de recursos, como la morfología alar y nasal, además de incluir la influencia de la variación geográfica y los factores ambientales. [ABSTRACT FROM AUTHOR]

Bergmann's rule is one of the most vigorously debated ecogeographic patterns but has rarely been examined in Neotropical bats. Herein, I examined Bergmann's rule in Carollia perspicillata and Artibeus lituratus along an elevation gradient of 2500 m at both inter- and intraspecific level. I measured 384 specimens from collections belonged to C. perspicillata (89 ♀, 102 ♂) and A. lituratus (89 ♀, 104 ♂). The size of C. perspicillata increased with increasing elevation and decreasing temperature, whereas A. lituratus showed the converse pattern. For both species, females did not differ between elevation categories, contrary to males that were larger above 1000 m in C. perspicillata, but smaller in A. lituratus. Conformity to Bergmann's rule depends on bat size and sex. Despite C. perspicillata follows the pattern, the explanatory mechanisms still need to be understood. By contrast, A. lituratus follows the converse of Bergmann's rule due to naked and highly vascularized wings that aid thermoregulation in warmer environments. Male size is more sensitive to changes in temperature for both species which may be partially explained by sexual selection. Elevation and temperature are not the only factors related to bat morphology and other mechanisms may explain size in bats. [ABSTRACT FROM AUTHOR]