Geographical variation of body size in sigmodontine rodents depends on both environment and phylogenetic composition of communities

Abstract

Aim Body size variation in animal assemblages is a widely addressed pattern in biogeographical studies, and is affected by both environmental gradients and phylogenetic constraints. However, no study has yet explored to what extent the association between body size variation and environmental gradients across broad spatial scales is influenced by the biogeographical distribution of different phylogenetic lineages. In this study, we discriminate the influences of environmental variables and phylogenetic community composition on body size variation in South American sigmodontine rodents.Location South America.Methods We computed the mean body mass of sigmodontine species cooccurring in 1 9 1°cells across South America. For each cell we recorded mean values for three environmental variables. We characterized the phylogenetic composition of sigmodontine assemblages within each cell using phylogenetic fuzzy-weighting and principal coordinates of phylogenetic structure (PCPS). We then partitioned out the influence of environmental factors and the phylogenetic community composition on mean body size.Results Mean body size variation was mostly explained by shared influence of phylogenetic community composition (PCPS) and environmental factors (68%), while exclusive influence of PCPS was low (19%), and of environment was even lower (0.47%). Increases in body size were related to increases in annual mean temperature, and the influence of environment on body size was mediated by the distribution of sigmodontine lineages across South America.Main conclusions Environment alone was not sufficient to explain body size variation in sigmodontine assemblages. Rather, environmental gradients interacted with historical processes to determine body size variation in the Neotropical assemblages. These results have implications for the way we think of body size gradients across species assemblages, because any gradient in a trait may be a result of differences in the biogeographical distribution of lineages across space, which should be considered in an explicit context.

Using phylogenetic clade composition to understand biogeographical variation in functional traits

“…This is a spatial legacy intrinsic to nature, and should be interpreted instead of corrected for (Hawkins 2012). Full details on the methods can be found in Maestri et al (2016aMaestri et al ( , 2017a. The predictor variables were taken as follows.…”

“…Moreover, size and shape variation can be linked to different sets of predictors Elton 2009, Maestri et al 2016c), suggesting that an analysis of both traits is necessary. Exploration of assemblage-level patterns of variation in size and shape was useful for detection of unknown patterns of trait variation, and to elucidate the role of historical biogeography and macroecological adaptation in the diversification of sigmodontine traits (Maestri et al 2016a(Maestri et al , 2017a.…”

“…However, this approach makes it difficult to investigate how much of the CWM is explained jointly by environmental variables and the phylogenetic distribution of lineages (the portion of variation corresponding to phylogenetic niche conservatism at the metacommunity level; see Pillar and Duarte 2010). Since the distribution of species belonging to distinct phylogenetic lineages across geographical space determines which species are present in a community, and by extension, the CWM, explicit consideration of the distribution of these lineages across an array of metacommunities may be important (Maestri et al 2016a(Maestri et al , 2017a. Failure to account for this distribution may lead to the detection of a spurious correlation between CWM and environmental factors, which could arise simply due to different spatial distributions of the ancestors that gave rise to entire clades (assuming clades with shared traits), distributed in allopatry across space (Lawing et al 2016, Polly et al 2017.…”

“…Maestri (2017) and Maestri et al (2016aMaestri et al ( , 2017a aimed to investigate how the phylogenetic distributions of lineages interact with environmental variables to explain mean trait distribution across metacommunities. CWM was calculated using univariate body size (Maestri et al 2016a) and, for the first time, using multivariate shape (Maestri et al 2017a).…”

“…CWM was calculated using univariate body size (Maestri et al 2016a) and, for the first time, using multivariate shape (Maestri et al 2017a). I analyzed the data using a variance-partitioning analysis framework, whereby the effects of environmental variables and clade composition, both singly and jointly, can be teased apart (Fig.…”