Taxonomic and Cytogenetic Complexity Complicate Forecasts of Climate-Driven Habitat Change in Rhexia (Melastomataceae)

Abstract Rhexia (Melastomataceae), a temperate genus composed of 13 species in eastern North America, provides a useful system for evaluating how taxonomic and cytogenetic complexity influence projections of climate-driven habitat change. Ecological niche models (ENMs) incorporating climatic and edaphic variables were used to estimate current and future habitat suitability for diploid, polyploid, and mixed-cytotype species. Habitat suitability was strongly associated with soil texture, hydrologic conditions, and precipitation, with suitable environments characterized by sandy, acidic, and seasonally moist habitats. Projections under future climate scenarios revealed highly variable, species-specific responses, with some taxa exhibiting substantial expansions in suitable habitat and others experiencing pronounced contractions. Contrary to expectations, ploidal level was not consistently associated with niche breadth or climate response, as both diploid and polyploid species displayed a wide range of outcomes. These findings highlight the need for flexible, habitat-focused conservation strategies that consider hydrologic and edaphic variables and demonstrate how taxonomic and cytogenetic complexity can complicate forecasts of biodiversity change under future climate scenarios.