Whole-genome sequencing distinguishes the two most common giant kelp ecomorphs.

This article investigates the genetic divergence and evolutionary history of two morphological variants, or ecomorphs, of giant kelp (Macrocystis pyrifera)—namely M. "pyrifera" and M. "integrifolia"—across populations in the Northern and Southern Hemispheres. Using whole-genome sequencing and single-nucleotide polymorphism (SNP) analyses of 18 populations from Chile and California, the study finds clear genetic distinctions between the two ecomorphs, with the largest divergence occurring between hemispheres and subsequent divergence between morphs within hemispheres. The results suggest that the integrifolia ecomorph evolved independently in each hemisphere, representing a case of parallel incipient speciation rather than a single origin followed by dispersal. The study identifies candidate genes under selection potentially related to morphological differences and highlights the need for further research to clarify the environmental drivers and genetic mechanisms underlying this convergent evolution.