Accurate phylogenetic trees are fundamental to evolutionary and comparative biology, but the almost simultaneous emergence of major animal phyla and diverse body plans during the Cambrian Explosion poses major challenges to reconstructing deep metazoan phylogenetic relationships.
This is particularly true for the second largest phylum, Mollusca, whose major lineages originated in the Cambrian period. The diverse fossil record, extreme morphological disparity among the eight living classes, and dramatic conflict among phylogenetic hypotheses due to diverse paleontological, morphological and molecular evidence hinder the understanding of molluscan phylogeny.
Recently, researchers from China, the U.S. and the U.K. have sequenced the first genomes of Scaphopoda or “tusk shells”—among the rarest and least-studied members of Mollusca—and found unprecedented ancient incomplete lineage sorting (ILS) that occurred during early molluscan cladogenesis.
These findings provide new insights into early molluscan evolution and explain why resolving molluscan class-level relationships has been a great challenge to evolutionary biologists.
The study was published in Proceedings of the National Academy of Sciences.
2023-09-18 16:00:03
Original from phys.org