Diversity trends and their ontogenetic basis: an exploration of allometric disparity in rodents

Abstract

It has been hypothesized that most morphological evolution occurs by allometric differentiation. Because rodents encapsulate a phenomenal amount of taxonomic diversity and, among several clades, contrasting levels of morphological diversity, they represent an excellent subject to address the question: how variable are allometric patterns during evolution? We investigated the influence of phylogenetic relations and ecological factors on the results of the first quantification of allometric disparity among rodents by exploring allometric space, a multivariate morphospace here derived from, and encapsulating all, the ontogenetic trajectories of 34 rodent species from two parallel phylogenetic radiations. Disparity was quantified using angles between ontogenetic trajectories for different species and clades. We found an overlapping occupation of allometric space by muroid and hystricognath species, revealing both clades possess similar abilities to evolve in different directions of phenotypic space, and anatomical diversity does not act to constrain the labile nature of allometric patterning. Morphological features to enable efficient processing of food serve to group rodents in allometric space, reflecting the importance of convergent morphology, rather than shared evolutionary history, in the generation of allometric patterns. Our results indicate that the conserved level of morphological integration found among primates cannot simply be extended to all mammals.

Ontogenetic Allometry and Cranial Shape Diversification Among Human Populations From South America

“…A complex picture emerges from these studies, since in some cases the shape variation associated with the evolution of size seems to be channeled in particular directions, resulting from extensions or truncations along common ontogenetic allometries (Marroig and Cheverud, 2001;Cardini and Thorington, 2006;Marroig, 2007). In contrast, other studies found that the pattern of size-related shape changes during ontogeny is not always conserved, and thus, the direction of the ontogenetic allometries can be altered resulting in morphological differences among populations, and in turn, among species (Strand Vidarsdottir et al, 2002;Cobb and O'Higgins, 2004;Gerber et al, 2004;Mitteroecker et al, 2004;Adams and Nistri, 2010;Willson and Sanchez Villagra, 2010). Despite their discrepancies, these studies remark the importance of growth changes during ontogeny in patterning the shape differentiation among populations and species, which may be related to ecological or evolutionary factors (Klingenberg, 2010).…”

Walk the line: 600000 years of molar evolution constrained by allometry in the fossil rodent Mimomys savini

“…This is in accordance with the conclusions from the recent meta-analysis by Voje et al [6] supporting a constraining role of static allometry on trait divergence on timescales less than a million years. Over larger time and taxonomic scales, larger changes in allometric coefficients are commonly observed [6], as claimed for rodent skull traits [48,49].…”

Skeletogenesis and sequence heterochrony in rodent evolution, with particular emphasis on the African striped mouse, Rhabdomys pumilio (Mammalia)

“…Additionally, several studies have concentrated upon the role of growth heterochrony in rodent evolution, using morphometric approaches (e.g. Creighton and Strauss 1986;Hautier et al 2008Hautier et al , 2009Monteiro et al 2005;Wilson and Sánchez-Villagra 2010;Zelditch et al 2006).…”