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Occupation of environmental and morphological space: climatic niche and skull shape in Neotoma woodrats
Soberón, Jorge Martínez-Gordillo, David
Soberón, Jorge
Martínez-Gordillo, David
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Abstract
Background: Theoretical and empirical studies suggest that in some circumstances niche
evolution may be very slow – a phenomenon called ‘niche conservatism’. Evidence for niche
conservatism comes mainly from studies of niches whose axes are climatic variables with broad
ranges of spatial covariance (coarse-grained niche variables). The geographic area inside the
physiologically viable climatic extreme values (i.e. climate tolerances) is usually large and may
expose populations to a wide range of finer-grained selective pressures.
Hypothesis: Coarse-grained niche variables lead to different evolutionary patterns than do
finer-grained niche variables.
Data: Skulls from museum specimens of rats of the genus Neotoma provided data on lateral,
ventral, dorsal, and mandibular aspects. Climate data were assembled for each place where
a specimen had been caught.
Key assumption: Rats of the genus Neotoma respond to selective pressures that are
coarse-grained in space, whereas their cranial dimensions respond to fine-grained selective
pressures. The volume of a minimally enclosing ellipsoid in the principal component (PCA)
space of either climatic or morphological variables is a surrogate for the species’ breadth of
occupation of climatic and morphological spaces.
Methods: We measured and analysed overall variance in climatic variables and morphology
using geometric morphometry methods. We analysed ellipsoid volumes, together with summaries
of skull shape and climatic tolerances, as to the influence of phylogeny on patterns of variation.
And we also searched for contrasting patterns of morphological and climatic features.
Conclusions: Patterns in climatic and morphological variables were different. Climatic PC
axes were mostly uncorrelated with morphological PC axes. Ellipsoid volumes of the climatic
variables were significantly smaller than those of the morphological variables. Blomberg’s K
did show that the evolution of most of the PC axes (four morphological and three climatic)
cannot be distinguished from Brownian motion. However the evolution of two PCs – the PC
dominated by dryness and the one dominated by ventral view of the skull – have been restricted
by phylogeny.
Description
This is the publisher's version, which the author has permission to share. The original version may be found online at the following link: http://www.evolutionary-ecology.com/issues/v14/n04/kkar2777.pdf
Date
2012
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Evolutionary Ecology
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Keywords
fundamental niche, geometric morphometry, Neotoma, niche conservatism, North America, realized niche, skull
Citation
Soberón, J. and Martínez-Gordillo, D. 2012. Occupation of environmental and morphological space: climatic niche and skull shape in Neotoma woodrats. Evolutionary Ecology Research 14(4): 503-517.