[2 phases of form development realized during microevolution]

Area of Science:

• Evolutionary biology
• Developmental biology
• Population genetics

Background:

• Animal structure "plan" evolves via alterations in body proportions and size.
• Understanding population differentiation is key to evolutionary studies.

Purpose of the Study:

• To present a method for estimating population differentiation based on body proportions and size.
• To analyze the distinct phases of form development during population differentiation.

Main Methods:

• Analysis of animal structure evolution.
• Estimation of population differentiation using morphometric parameters.
• Identification of developmental phases in microevolution and intra-population dynamics.

Main Results:

• Population differentiation involves two primary phases of form development.
• The initial microevolutionary stage is characterized by changes in body proportions.
• Subsequent stages are dominated by alterations in body size, observable at both inter- and intra-population levels.

Conclusions:

• Morphogenesis during population differentiation proceeds sequentially, initially through proportion changes, then size changes.
• Selection can drive increased differentiation in individual body proportions within a population.