Discovery and delimitation of Manihot capsularis sp. nov. using integrative morphological and molecular data
摘要
We report the discovery and delimitation of a new Manihot species, here named Manihot capsularis, from Serra de Grão Mogol, Minas Gerais, Brazil. Integrating morphological and molecular evidence, we distinguish this taxon from its sister species, M. caerulescens. Morphologically, M. capsularis is characterized by pubescent vegetative and reproductive structures, capsular fruits, seeds with a well-developed caruncle, and darker green leaves, whereas M. caerulescens typically has glabrous, lighter green leaves, baccate fruits, and seeds that are ecarunculate or have an inconspicuous caruncle. Phylogenetic analyses of three nuclear gene regions (ch_metE, g3pdh, and nia-i3) recovered two well-supported clades corresponding to the two species. A ch_metE haplotype network corroborated these lineages, with no haplotype sharing observed between them. Microsatellite data further supported species distinctiveness and population structure: Bayesian clustering identified three genetic groups, with all M. caerulescens specimens forming a single cluster, whereas M. capsularis specimens split into two distinct clusters with limited admixture. Genetic diversity metrics indicated private alleles in all M. capsularis populations and high observed heterozygosity. The new species is endemic to Campos rupestres on sandy soils and can be recognized in the field and in herbaria. Given its restricted distribution (extent of occurrence < 100 km2) and habitat specificity, M. capsularis is provisionally assessed as Critically Endangered. This study highlights the value of combining molecular and morphological data for robust species delimitation in taxonomically complex groups and underscores the need for conservation attention to narrowly endemic taxa within Manihot.