title: Body Size Adaptations to Altitudinal Climatic Variation in Neotropical Grasshoppers of the Genus Sphenarium (Orthoptera: Pyrgomorphidae).
abstract: Altitudinal clines in body size can result from the effects of natural and sexual selection on growth rates and developing times in seasonal environments. Short growing and reproductive seasons constrain the body size that adults can attain and their reproductive success. Little is known about the effects of altitudinal climatic variation on the diversification of Neotropical insects. In central Mexico, in addition to altitude, highly heterogeneous topography generates diverse climates that can occur even at the same latitude. Altitudinal variation and heterogeneous topography open an opportunity to test the relative impact of climatic variation on body size adaptations. In this study, we investigated the relationship between altitudinal climatic variation and body size, and the divergence rates of sexual size dimorphism (SSD) in Neotropical grasshoppers of the genus Sphenarium using a phylogenetic comparative approach. In order to distinguish the relative impact of natural and sexual selection on the diversification of the group, we also tracked the altitudinal distribution of the species and trends of both body size and SSD on the phylogeny of Sphenarium. The correlative evidence suggests no relationship between altitude and body size. However, larger species were associated with places having a warmer winter season in which the temporal window for development and reproduction can be longer. Nonetheless, the largest species were also associated with highly seasonal environments. Moreover, large body size and high levels of SSD have evolved independently several times throughout the history of the group and male body size has experienced a greater evolutionary divergence than females. These lines of evidence suggest that natural selection, associated with seasonality and sexual selection, on maturation time and body size could have enhanced the diversification of this insect group.
authors.affiliation: Laboratorio de Ecología, UBIPRO, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México (UNAM), A.P. 314, Tlalnepantla, 54090 México, México.
authors.forename: Salomón
authors.initials: S
authors.lastname: Sanabria-Urbán
authors.affiliation: Department of Entomology, Texas A&M University, 2475 TAMU, College Station, Texas, United States of America.
authors.forename: Hojun
authors.initials: H
authors.lastname: Song
authors.affiliation: Instituto de Investigaciones en Ecosistemas y Sustentabilidad, UNAM, Morelia, 58190 Michoacán, México.
authors.forename: Ken
authors.initials: K
authors.lastname: Oyama
authors.affiliation: Instituto de Investigaciones en Ecosistemas y Sustentabilidad, UNAM, Morelia, 58190 Michoacán, México.
authors.forename: Antonio
authors.initials: A
authors.lastname: González-Rodríguez
authors.affiliation: Laboratorio de Biología Evolutiva, Centro Tlaxcala de Biología de la Conducta, Universidad Autónoma de Tlaxcala, Carretera Tlaxcala-Puebla Km. 1.5, 90062, Tlaxcala, México.
authors.forename: Martin A
authors.initials: MA
authors.lastname: Serrano-Meneses
authors.affiliation: Laboratorio de Ecología, UBIPRO, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México (UNAM), A.P. 314, Tlalnepantla, 54090 México, México.
authors.forename: Raúl
authors.initials: R
authors.lastname: Cueva Del Castillo
mesh_terms: D000220:Adaptation, Biological; D000531:Altitude; D000818:Animals; D005075:Biological Evolution; D049628:Body Size; D002980:Climate; D005260:Female; D006110:Grasshoppers / Q000235:genetics / Q000254:growth & development*; D008297:Male; D058885:Multilocus Sequence Typing; D010802:Phylogeny; D012727:Sex Characteristics