The evolution of body size under environmental gradients in ectotherms: why should Bergmann's rule apply to lizards?

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The evolution of body size under environmental gradients in ectotherms: why should Bergmann's rule apply to lizards?

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dc.contributor.author Pincheira-Donoso, Daniel en_GB
dc.contributor.author Hodgson, David J. en_GB
dc.contributor.author Tregenza, Tom en_GB
dc.date.accessioned 2008-09-28T19:35:43Z en_GB
dc.date.accessioned 2011-01-25T11:47:01Z en_US
dc.date.accessioned 2013-03-20T14:48:28Z
dc.date.issued 2008-02-27 en_GB
dc.description.abstract Background The impact of environmental gradients on the evolution of life history traits is a central issue in macroecology and evolutionary biology. A number of hypotheses have been formulated to explain factors shaping patterns of variation in animal mass. One such example is Bergmann's rule, which predicts that body size will be positively correlated with latitude and elevation, and hence, with decreasing environmental temperatures. A generally accepted explanation for this phenotypic response is that as body mass increases, body surface area gets proportionally smaller, which contributes to reduced rates of heat-loss. Phylogenetic and non-phylogenetic evidence reveals that endotherms follow Bergmann's rule. In contrast, while previous non-phylogenetic studies supported this prediction in up to 75% of ectotherms, recent phylogenetic comparative analyses suggest that its validity for these organisms is controversial and less understood. Moreover, little attention has been paid to why some ectotherms conform to this rule, while others do not. Here, we investigate Bergmann's rule in the six main clades forming the Liolaemus genus, one of the largest and most environmentally diverse genera of terrestrial vertebrates. A recent study conducted on some species belonging to four of these six clades concluded that Liolaemus species follow Bergmann's rule, representing the only known phylogenetic support for this model in lizards. However, a later reassessment of this evidence, performed on one of the four analysed clades, produced contrasting conclusions. Results Our results fail to support Bergmann's rule in Liolaemus lizards. Non-phylogenetic and phylogenetic analyses showed that none of the studied clades experience increasing body size with increasing latitude and elevation. Conclusion Most physiological and behavioural processes in ectotherms depend directly upon their body temperature. In cold environments, adaptations to gain heat rapidly are under strong positive selection to allow optimal feeding, mating and predator avoidance. Therefore, evolution of larger body size in colder environments appears to be a disadvantageous thermoregulatory strategy. The repeated lack of support for Bergmann's rule in ectotherms suggests that this model should be recognized as a valid rule exclusively for endotherms. en_GB
dc.identifier.citation BMC Evolutionary Biology 2008 8:68 en_GB
dc.identifier.doi 10.1186/1471-2148-8-68 en_GB
dc.identifier.uri http://hdl.handle.net/10036/38234 en_GB
dc.publisher BioMed Central en_GB
dc.relation.url http://www.biomedcentral.com/1471-2148/8/68 en_GB
dc.relation.url http://creativecommons.org/licenses/by/2.0 en_GB
dc.rights Copyright © 2008 Pincheira-Donoso et al; licensee BioMed Central Ltd. en_GB
dc.title The evolution of body size under environmental gradients in ectotherms: why should Bergmann's rule apply to lizards? en_GB
dc.type Article en_GB
dc.date.available 2008-02-27 en_GB
dc.date.available 2008-09-28T19:35:43Z en_GB
dc.date.available 2011-01-25T11:47:01Z en_US
dc.date.available 2013-03-20T14:48:28Z
dc.identifier.issn 1471-2148 en_GB
dc.identifier.journal BMC Evolutionary Biology en_GB
dc.identifier.pmcid 2268677 en_GB
dc.identifier.pmid 18304333 en_GB


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