Population structure and intraspecific ecological niche differentiation point to lineage divergence promoted by polyploidization in Psidium cattleyanum (Myrtaceae)

Polyploidy is defined as the presence of more than two complete chromosome sets in an organism and has frequently occurred throughout the history of angiosperms. Polyploidization is a process that typically results in instant speciation. Using Psidium cattleyanum, a natural polyploid complex with several cytotypes, we aim to test two hypotheses regarding speciation in polyploids: polyploidization promotes (1) interruption of gene flow and (2) intraspecific niche divergence. We analyzed 12 natural populations of P. cattleyanum, integrating population genetics data, accessed by microsatellite markers, and climatic niche analysis, using environmental niche modeling, to provide insights about polyploid speciation. We found strong genetic structure in populations and cytotypes and low environmental niche similarity between cytotypes. Genetic diversity declines with increasing ploidy levels which is probably associated with asexual reproduction. Our results corroborate that polyploidy is generating a reproductive barrier and is associated with niche divergence among cytotypes. Therefore, we infer future divergent lineages between cytotypes of P. cattleyanum and confirm the role of polyploidy as an evolutionary step in speciation in this group. Additionally, this study provides new information for the discussion about how polyploidy affects the genetic diversity of taxa and ecological niches.

Automated summary

This study uses Psidium cattleyanum as a research subject, and through the analysis of genetic data of natural populations and climate niche analysis, it confirms two hypotheses about speciation in polyploids promoted by polyploidization and provides new information on the genetic diversity and ecological niches affected by polyploidy.