Morphological variability and developmental instability in
the badger in Denmark
Journal
Journal of
Biogeography, Volume 30,Number 6, June 2003, pp. 949-958(10)
Blackwell Publishing
Authors
Pertoldi C.; Bach L.A.; Madsen
A.B.; Randi E.; Loeschcke V.
Abstract
Local populations from different geographical regions may differ in the
selection regimes to which they are exposed. Differences in environmental
factors and population density may affect the relative importance of different
selective forces (e.g. natural vs. sexual selection). We suggest a direction of
investigation concerned with the developmental instability of morphological
traits. The goal is to disclose putative small-scale geographical differences in
the evolutionary forces, which may be hard to detect.
Craniometrical investigations were carried out on ninety-eight skulls and
teeth of the Eurasian badger (Meles meles) collected during the period
1995–97 from three different populations in Denmark. One of these thrives at low
population density, whereas the two others are characterized by high local
density.
The skulls were investigated for developmental
instability (DI) using fluctuating asymmetry (FA) as its estimator. FA
was measured on canines, molars, premolar teeth and other skull and
mandible traits.
Evidence was found suggesting differentiation among populations in mean
degree of FA, and the FA values measured on canines were higher in the
high-density populations. FA of the canines was significantly higher in males
than females, in contrast to FA of the other traits. Evidence of a negative
relationship between canine size and their FA was found, whereas no significant
correlations were found between the molar and premolar teeth measures and their
FA.
Our results suggest that canines could be under directional selection
stemming from intrasexual competition, which may be stronger in high-density
zones. The other teeth investigated seem to be under a stabilizing regime hence
their FA is mainly affected by environmental stresses. The negative relationship
between canine size and FA found in males suggests the capacity of badgers to
respond in an evolutionary way to environmental changes, despite the low genetic
variability previously found at the molecular level.
Keywords
Fluctuating asymmetry; developmental instability;
badger; sexual selection; population density
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