Developmental instability and phenotypic evolution in a small and isolated bear population

We explored fluctuating asymmetry (FA) and morphological integration (MI)
in the skull of the small, highly inbred and divergent Apennine bear
(Ursus arctos marsicanus), to explore its uniqueness and investigate any
potential effects of inbreeding depression. We used 3d geometric
morphometrics contrasting 17 Apennine bears with other two large outbred
bear populations (22 from Scandinavia and 9 from Kamchatka) as controls.
Shape divergence and variability were explored by a PCA on aligned
coordinates of 39 landmarks. Procrustes ANOVA, morphological disparity,
and the Global Integration (GI) index were performed both to detect FA and
to quantify shape variance and degree of MI. By remarking that Apennine
bears share a highly divergent phenotype, we recorded the highest FA and
deviation from self-similarity compared to the other two control
populations. We conclude that Apennine bears are likely facing
developmental instability as a consequence of inbreeding depression,
whereas the divergent trait covariance pattern may represent a potential
source of evolutionary novelties. We discuss the implications for the
conservation and management of this imperiled taxon.