An interspecific test of Bergmann's rule reveals inconsistent body size patterns across several lineages of water beetles (Coleoptera: Dytiscidae). (25th November 2018)

• Record Type: Journal Article
• Authors: Pallarés, Susana; Lai, Michele; Abellán, Pedro; Ribera, Ignacio; Sánchez‐Fernández, David
• Is Part Of: Ecological entomology. Volume 44:Number 2(2019)
• Page Start: 249
• Page End: 254
• Publication Date: 2018-11-25
• Subjects: Aquatic insects -- biogeography -- habitat -- inland waters -- latitude -- lentic -- lotic -- phylogeny; Insects -- Ecology -- Periodicals; Entomology -- Periodicals; 595.7
• DOI: 10.1111/een.12701
• Languages: English
• ISSNs: 0307-6946

Abstract

Abstract : 1. Bergmann's rule sensu lato, the ecogeographic pattern relating animals' body size with environmental temperature (or latitude), has been shown to be inconsistent among insect taxa. Body size clines remain largely unexplored in aquatic insects, which may show contrasting patterns to those found in terrestrial groups because of the physiological or mechanical constraints of the aquatic environment. 2. Bergmann's rule was tested using data on body size, phylogeny and distribution for 93 species belonging to four lineages of dytiscid water beetles. The relationship between size and latitude was explored at two taxonomic resolutions – within each independent lineage, and for the whole dataset – employing phylogenetic generalised least‐squares to control for phylogenetic inertia. The potential influence of habitat preference (lotic versus lentic) on body size clines was also considered. 3. Within‐lineage analyses showed negative relationships (i.e. converse Bergmann's rule), but only in two lineages (specifically in those that included both lotic and lentic species). By contrast, no relationship was found between body size and latitude for the whole dataset. 4. These results suggest that there may be no universal interspecific trends in latitudinal variation of body size in aquatic insects, even among closely related groups, and show the need to account for phylogenetic inertia. Furthermore, habitat preferences should be considered when exploring latitudinal clines in body size in aquatic taxa at the interspecific level. Abstract : This study explored latitudinal variation in body size across species of four lineages of dytiscid water beetles, accounting for the effects of taxonomic resolution, phylogenetic inertia, and habitat constraints. Two lineages showed a decrease of species size with latitude (converse Bergmann's rule), but no relationship was found for the other two, or for the pooled four lineages. Latitudinal patterns of body size are inconsistent across aquatic insect groups and influenced by phylogenetic effects and differential constraints on size and dispersal between lotic and lentic habitats.