An evolutionary study of the genus Marina (Fabaceae): phylogenomic systematics, overlooked biodiversity and drought adaptations of the false prairie clovers

Abstract

Marina (Fabaceae) is a primarily Mexican genus of seasonally dry tropical forests and arid deserts, including many rare and narrowly endemic species. Despite recent increases in Marina collections, five species are still known from a single locality and many species have very limited data on their distribution and biology. In a time of rapid land conversion and climate change, the urgency to document biodiversity is urgent. However, the species' circumscriptions and the intriguing evolutionary hypotheses introduced in the last monograph of Marina, almost fifty years ago, have not been revisited. Our goal is to use novel phylogenomic approaches and sequencing technologies to revise the taxonomy for this group, test hypotheses about species' ages and origins, and use Marina to understand questions on legumes' potential for adapting to highly seasonal environments. After studying Marina in the field and across herbaria in USA and Mexico, we developed a densely sampled phylogeny using target capture methods to test taxonomic hypotheses at the species level and above. We used this phylogeny to date lineages, elucidate evolutionary history, and explore correlations between relatedness and nutrient cycling. We tested whether leaflet traits of Marina and related genera were explained by climate or by phylogeny and determined that precipitation is the best explanation for the variation we found of intrinsic water use efficiency across our samples. We generated morphological, ecological, and genetic support and completed the necessary descriptions for a monotypic genus sister to Marina, six undescribed species and one new combination within Marina. In conclusion, we have a revised taxonomy that will provide an up-to-date understanding to inform conservation decisions for the genus and a better understanding of how taxa may adapt facing drier, hotter conditions.