Heterochronic detection through a function for the ontogenetic variation of bone shape

Area of Science:

• Evolutionary Biology
• Developmental Biology
• Comparative Anatomy

Background:

• Heterochrony, changes in developmental timing and rates, drives evolutionary change.
• Long bone growth analysis offers a window into developmental processes.
• Understanding heterochrony requires quantitative methods to assess evolutionary modifications.

Purpose of the Study:

• To develop and test a novel function (sigma (t)) for quantifying ontogenetic variation in bone shape.
• To detect evolutionary modifications in the timing (t(m)) and rate (beta) of long bone growth.
• To investigate the influence of phylogenetic history on bone shape variation in birds.

Main Methods:

• A function sigma (t) was formulated using Gompertz curves for endochondral and periosteal ossification.
• The timing parameter t(m) and rate parameter beta were derived from the sigma (t) function.
• Permutational phylogenetic regressions were employed to analyze 13 Anseriformes and 17 other neornithine species.
• Bone shape was optimized onto a phylogenetic tree to estimate ancestral conditions.

Main Results:

• The sigma (t) function successfully modeled ontogenetic variation in bone shape.
• Significant phylogenetic effects were identified, influencing adult bone shape variation.
• The method allows for the detection of hypomorphosis, hypermorphosis, deceleration, and acceleration in developmental timing and rates.
• Ancestral conditions for bone shape were estimated for Anas platyrhynchos.

Conclusions:

• The developed method provides a robust framework for detecting heterochrony through long bone growth analysis.
• Phylogenetic history significantly shapes bone morphology, necessitating its consideration in evolutionary studies.
• This approach offers insights into the evolutionary pathways of developmental modifications in birds.