Genetic and morphological evidence support the specific status of the endemic Erica andevalensis (Ericales, Ericaceae)

Abstract

Assessing the taxonomic status of closely related taxa is crucial in plant systematics and can have important implications for conservation and human plant use. Erica andevalensis Cabezudo & Rivera is a metallophyte endemic species from highly metal-polluted soils of SW Iberian Peninsula, an area with a mining history going back more than 5,000 years. Erica andevalensis is closely related to Erica mackayana Bab., a northern Iberian species also present in western Ireland. The status of E. andevalensis as a species or subspecies subordinated to E. mackayana is subject to debate. Here, we assessed the genetic and phenotypic relationship between both species, including the population structure of E. andevalensis. We used high throughput sequencing to determine genome-wide Single Nucleotide Polymorphisms (SNPs), and morphometric analyses from 35 reproductive and vegetative traits. The morphological analysis showed at least eight characters that can discriminate the two species, from which ovary hairiness and the size of leaf glandular hairs were the most informative. Genetic analyses showed that each species formed a monophyletic cluster with full support, separated by an interspecific genetic distance >4-fold higher than intra-specific distance. Population genetic analyses of E. andevalensis shows that populations are highly structured, with the Portuguese one as the most isolated and less variable. These results support the recognition of E. andevalensis as a distinct species with a highly constrained ecological requirements and a narrow geographic distribution, but with a limited gene flow between populations. We discuss the implications of these outcomes in conservation policies and potential uses of E. andevalensis such as decontamination of polluted soils.