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

Area of Science:

• Evolutionary biology
• Conservation genetics
• Morphometrics

Background:

• The Apennine bear (Ursus arctos marsicanus) is a small, inbred, and divergent population facing unique evolutionary pressures.
• Understanding developmental instability and morphological integration is crucial for assessing the health of isolated populations.

Purpose of the Study:

• To investigate fluctuating asymmetry (FA) and morphological integration (MI) in the Apennine bear skull.
• To assess potential effects of inbreeding depression on Apennine bear development.
• To compare Apennine bears with outbred populations to understand their uniqueness.

Main Methods:

• Utilized 3D geometric morphometrics on skull landmarks.
• Employed principal component analysis (PCA) for shape divergence and variability.
• Applied Procrustes ANOVA, morphological disparity, and global integration index to analyze FA and MI.

Main Results:

• Apennine bears displayed the highest FA and deviation from self-similarity compared to Scandinavian and Kamchatka bear populations.
• A highly divergent phenotype was observed in the Apennine bear.
• Trait covariance patterns were distinct in the Apennine bear population.

Conclusions:

• Apennine bears likely experience developmental instability, potentially linked to inbreeding depression.
• The observed divergent trait covariance may represent a source of evolutionary novelty.
• Findings have implications for the conservation and management of this endangered taxon.