Morphological Variation in the Striped Field Mouse Across Three Countries.

Area of Science:

• Zoology
• Ecology
• Evolutionary Biology

Background:

• Morphological variation is key to understanding species adaptation.
• Ecogeographic rules predict how environmental factors influence animal morphology.
• The striped field mouse (Apodemus agrarius) is a widespread rodent species in Europe.

Purpose of the Study:

• To investigate morphological variation in Apodemus agrarius across geographic gradients in Europe.
• To assess the influence of latitude, longitude, age, sex, and temporal trends on mouse morphology.
• To test the adherence of Apodemus agrarius morphology to Bergmann's and Allen's rules.

Main Methods:

• Analysis of morphological traits (body mass, body length, tail length, hind foot length, ear length) from specimens collected between the 1980s and 2020s.
• Geographic data included Slovakia, Lithuania, and Estonia, covering south-north and west-east gradients.
• Generalized Linear Models (GLM) were used to assess the impact of environmental and demographic factors.

Main Results:

• Significant adherence to Bergmann's rule: body size increased with latitude (northward).
• Significant adherence to Allen's rule: appendage size (tail, ear) decreased with latitude.
• Longitudinal gradients showed reduced body and appendage length eastward. Temporal analysis revealed dynamic body size changes, with sex-based dimorphism varying by location and time.

Conclusions:

• Apodemus agrarius exhibits clear morphological adaptations to geographic and climatic variations, supporting ecogeographic rules.
• The findings highlight the species' ecological plasticity and capacity for evolutionary responses to environmental pressures.
• Understanding these patterns is crucial for predicting species' resilience and distribution shifts in response to climate change.