title: The converse to Bergmann's rule in bumblebees, a phylogenetic approach.
abstract: Two patterns commonly emerge when animal body size is analyzed as a function of latitudinal distribution. First, body size increases with latitude, a temperature effect known as Bergmann's rule, and second, the converse to Bergmann's rule, a pattern in which body size decreases with latitude. However, other geographic patterns can emerge when the mechanisms that generate Bergmann's and the converse to Bergmann's clines operate together. Here, we use phylogenetic comparative analysis in order to control for phylogenetic inertia, and we show that bumblebees exhibit the converse to Bergmann's rule. Bumblebee taxa are distributed worldwide in temperate and tropical regions. The largest species are found in places with high water availability during the driest time of the year. Nonetheless, large body size is constrained by extreme temperatures. Bumblebees' body size could be related to a higher extent to the size of food rewards to be harvested than to the energetic advantages of thermoregulation. Moreover, we found that the body size of eusocial and cuckoo species responded in the same way to environmental variables, suggesting that they have not diverged due to different selective pressures.
authors.affiliation: Lab. de Ecología; UBIPRO Facultad de Estudios Superiores Iztacala Universidad Nacional Autónoma de México A.P. 314 Tlalnepantla 54090 México México.
authors.forename: Víctor Hugo
authors.initials: VH
authors.lastname: Ramírez-Delgado
authors.affiliation: Lab. de Ecología; UBIPRO Facultad de Estudios Superiores Iztacala Universidad Nacional Autónoma de México A.P. 314 Tlalnepantla 54090 México México.
authors.forename: Salomón
authors.initials: S
authors.lastname: Sanabria-Urbán
authors.affiliation: Laboratorio de Biología Evolutiva Centro Tlaxcala de Biología de la Conducta Universidad Autónoma de Tlaxcala Carretera Tlaxcala-Puebla km 1.590070 Tlaxcala México; Posgrado en Ciencias Biológicas Universidad Autónoma de Tlaxcala México.
authors.forename: Martin A
authors.initials: MA
authors.lastname: Serrano-Meneses
authors.affiliation: Lab. de Ecología; UBIPRO Facultad de Estudios Superiores Iztacala Universidad Nacional Autónoma de México A.P. 314 Tlalnepantla 54090 México México.
authors.forename: Raúl
authors.initials: R
authors.lastname: Cueva Del Castillo
keywords: Bergmann's rule; bumblebees; fecundity; life history