Comparative phenomics: a new approach to study heterochrony.

Area of Science:

• Developmental biology
• Evolutionary biology
• Quantitative biology

Background:

• Understanding the interplay between development and evolution is a major biological challenge.
• Heterochronies, or evolutionary changes in developmental timing, are key to evolutionary change but difficult to quantify.
• Previous methods oversimplify development, limiting understanding of how timing shifts impact broader developmental processes.

Purpose of the Study:

• To develop and apply a novel method for quantifying organismal development and its evolutionary implications.
• To investigate the relationship between heterochronies and high-dimensional phenotypic changes.
• To explore the evolutionary significance of altered developmental event timings.

Main Methods:

• Development of 'Energy proxy traits' (EPTs) by analyzing energy spectra in video pixel values of embryonic development.
• Application of EPTs to three freshwater pulmonate mollusc species (Lymnaea stagnalis, Radix balthica, Physella acuta).
• Construction of continuous functional time series from time-lapse video to create high-dimensional developmental landscapes.

Main Results:

• High-dimensional phenotypic transitions in EPTs correlated with known heterochronies between species.
• Variations in developmental event timings within species were linked to shifts in high-dimensional phenotypic space.
• EPTs provide a continuous quantification of developmental changes, moving beyond discrete event timings.

Conclusions:

• Energy proxy traits (EPTs) offer a powerful new approach to studying the evolutionary impact of heterochronies.
• Reimagining the phenotype as energy spectra allows for continuous, high-dimensional quantification of developmental changes.
• This methodology has the potential to significantly advance the study of heterochrony and broader developmental biology.