Mosaic foreleg convergence disentangles phylogeny from ecology in Cretaceous amber crickets
Mosaic evolution assembles organisms from ancestral and derived parts, and traits shaped by convergent selection can mislead phylogenetic reconstruction while recording ecology. Disentangling these two signals within the same anatomy is a challenge for placing fossils and reconstructing evolution in deep time. We present a character-partitioning framework that fixes a molecular backbone of living species, projects fossils onto it with partitioned morphological matrices, and quantifies each anatomical module's contribution to phylogenetic placement and ecological prediction. In mid-Cretaceous Myanmar amber crickets, which combine a cricket-like body with mole-cricket-like digging forelegs, the foreleg module drove most phylogenetic distortion and carried most ecological information: removing it restored a convergent living control species to its family and collapsed habitat-prediction accuracy from 77.8% to below the 44.4% baseline. Partitioning convergent modules thus separates phylogenetic signal from ecological information, turning mosaicism from a confound of fossil interpretation into a quantitative record of history and niche.