Caterpillars did not evolve from onychophorans by hybridogenesis

Area of Science:

• Evolutionary Biology
• Developmental Biology
• Genomics

Background:

• Larval forms in animal life cycles exhibit complex patterns of similarity and difference.
• Morphological similarities exist between Onychophora (velvet worms) and insect caterpillars.
• A recent hypothesis proposed hybridization between velvet worm ancestors and insects, leading to "larval transfer".

Purpose of the Study:

• To evaluate the hypothesis of inter-lineage hybridization and "larval transfer" between Onychophora and insects.
• To test specific predictions derived from the hybridization hypothesis using existing genomic and life-history data.

Main Methods:

• Analysis of existing literature and comparative genomic data.
• Evaluation of morphological and life-history evidence in extant animal lineages.
• Assessment of the plausibility of hybridogenesis between distantly related taxa.

Main Results:

• The hypothesis of velvet worm-insect hybridization is contradicted by current data.
• Genomic and life-history evidence does not support a "larval transfer" event.
• Hybridogenesis between distantly related animals is not a general explanation for evolutionary patterns.

Conclusions:

• The proposed hybridization event between Onychophora and insects is unfounded.
• Existing genetic and morphological data provide strong evidence against this evolutionary scenario.
• Alternative explanations are needed for observed similarities in animal life cycles.