Complexity in Polyploid Species Origin and Establishment: Arctostaphylos mewukka (Ericaceae)

Abstract

Abstract— Lineage recombination is an important source of genetic and morphological variation in species-rich groups of plants. Tetraploids that are intermediate in morphology and ecology with respect to sympatric diploids are regularly hypothesized to be the products of hybridization. Arctostaphylos mewukka is one such intermediate tetraploid long regarded as the result of hybridization and genome duplication among divergent and geographically overlapping diploids widely distributed across the western slope of the Sierra Nevada. Here we set out to test this hypothesis leveraging the notion that allopolyploids arise repetitively and may show signs of reciprocal organellar exchange among species between maternal and paternal progenitors. We compared nuclear ribosomal and plastid sequence data acquired from samples within and outside this target species complex. Molecular sequence data show striking patterns indicative of widespread reticulation and chloroplast capture events across the genus Arctostaphylos. Results support the notion that outcrossing, long-lived woody plant species such as members of the genus Arctostaphylos can retain a secured morphological identity despite ongoing influence of interspecific gene flow that would otherwise render species boundaries vulnerable to dissolution.