Ontogeny of fluctuating asymmetry in the rodent skull
As part of a broader study of the ontogenetic dynamics of the variance throughout the postnatal development of the rodent skull, this study compared symmetric and asymmetric components of the variation in the rodent skull. To this end, we investigated ontogenetic dynamics of both overall magnitude and the multivariate pattern of variation of these two components, including patterns of integration and modularity.
2004. Software SAGE: Symmetry and Asymmetry in Geometric Data. University of Michigan, Ann Arbor. [ DOWNLOAD Win32 Win64
Márquez, E.J.; Zelditch, M.L.
2005. Canalization and developmental stability of the rodent skull. VII International Congress of Vertebrate Morphology, Boca Raton, FL. [ SLIDESHOW ]
Ontogenetic dynamics of components of skull shape variance in Mus
Concerted evolution in developmental modules of the mandible
In a related project, we ask whether morphological divergence has accumulated preferentially within developmental modules in the rodent skull. In this case, the focus is on the amount of divergence accrued within each module in different species, which is compared across modules. The correlation between module-specific disparity values (termed "co-disparity") is thus interpreted as a measure of the extent to which a specific developmental process or functional interaction (e.g., chondrogenesis) has disproportionately influenced or undergone evolutionary divergence.
2007. Software CORIANDIS: Correlation analysis based on distances. University of Michigan, Ann Arbor. [ DOWNLOAD Win32 Win64
Contribution of each mandible region to the total disparity of 11 rodent species
Geographic variation in mice skulls
ABSTRACT: The composite nature of the species Oryzomys albigularis Tomes, 1860 has long been recognized from the karyological heterogeneity of diploid and fundamental numbers, with at least two sets of populations in the eastern and northern Andes with 2n = 66 and 2n = 80, respectively. The aim of this study was to test for differences among populations within the species using cranial morphometrics. Populations for the multivariate analyses were defined according to differences in autosomal arm numbers within a single modal diploid number from six locations in two mountain systems of Venezuela, in northern South America. Principal component and canonical variate analyses clearly discriminated among the karyomorphs, the variation at the interorbital, palatal, and incisive foramen regions being the most informative. These traits explained most of the total variance, after adjusting for size effects. We found no evidence for congruence between the patterns of morphometric variation and geographical distance among karyomorphs, but similarity patterns among samples resulted in congruence when morphometric and karyological data were considered. Since variation of these last two datasets can be considered independent of each other, the observed congruence is suggestive of a phylogenetic structure in the data. Our results are consistent with a composite nature for the species, as most of the observed cranial variation appears to be associated with major karyotypic differences. Given the theoretical relevance of the implied karyotypic changes as a means of reproductive isolation, morphometric evidence is used to support the splitting of the "albigularis" form in at least two distinct species.
Márquez, E.J.; Aguilera, M.M.; Corti, M. 2000. Morphometric and chromosomal variation in populations of Oryzomys albigularis from Venezuela Multivariate aspects. Zeitschrift fuer Saeugetierkunde 65: 84-99.
Present and Past Projects