Using RAD capture sequences to investigate the origins of the American Amphitropical Disjuncts Larrea tridentata and Larrea divaricata

LAPORT, ROBERT; LANDIS, JACOB; GAYNOR, MICHELLE; O'CONNOR, TIMOTHY; DEANNA, ROCÍO; NGUYEN, KHOA

Online

Conferencia; Botany 2021; 2021

Botanical Society of America

Long distance dispersal to a novel range, and subsequent evolution, represents a major mode of plant diversification. American Amphitropical Disjunctions (AADs) represent some of the most striking examples of closely related taxa that have diversified after long distance dispersal, comprising more than 200 vascular plant lineages distributed on either side of the tropics of North and South America. Despite intense research focus over the last ~200 years, AADs remain a frustrating biogeographic puzzle with important questions pertaining to the biogeographic origins, evolutionary timing, and mechanisms of dispersal remaining unanswered. For example, little is known about the centers of dispersal from within the major geographic regions occupied by AAD taxa, which is particularly problematic for widespread taxa that may also have experienced range shifts over time. The genus Larrea (Zygophyllaceae) comprises dominant, long-lived evergreen shrubs widespread throughout xeric regions of North and South America. In North America, Larrea tridentata is distributed across the warm deserts of the southwestern US and northern Mexico, while its closest relative, Larrea divaricata, is widespread in arid areas of Argentina, Chile, Bolivia, and Peru. While the northern portion of the current South American range (e.g., northern Argentina) is hypothesized to represent the ancestral home of the common ancestor of extant L. divaricata and L. tridentata because of geographic proximity to North America, there are no explicit tests of this hypothesis using modern molecular and computational tools. Using Restriction site Associated DNA sequencing of probe captured DNA targets ("RAD capture") obtained from living and herbarium specimens originating from throughout the respective ranges of the species, we investigated the phylogenetic relationships and the potential geographic origin of the most recent common ancestor between L. tridentata and L. divaricata. Our analyses are consistent with a relatively recent divergence, but the geographic origin of the most recent common ancestor of the two extant species remains less clear.