Abstract Detail


Nguyen, Khoa [1], Laport, Robert [1].

Investigating the origins of the American Amphitropical Disjuncts Larrea tridentata and Larrea divaricata.

One of the key modes of plant diversification is long distance dispersal to a novel range. Some of the most striking examples of closely related species (or populations of conspecifics) that have diversified after long distance dispersal are the American Amphitropical Disjunctions (AADs) 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 chloroplast DNA sequence data obtained from living and herbarium specimens originating from throughout the respective ranges of the species, we investigated the phylogenetic relationships, the potential geographic origin of the most recent common ancestor, and the timing of divergence between L. tridentata and L. divaricata. Our analyses are consistent with a relatively recent divergence (Pliocene or early Pleistocene), though other estimates range widely from ~8.6 to 1.0 mybp, but the geographic origin of the most recent common ancestor is less clear given broad haplotype sharing between the two extant species.

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2 - Rhodes College, Department Of Biology, 2000 North Parkway, Memphis, TN, 38112, United States

long distance dispersal
new world deserts
adaptive radiation

Presentation Type: Poster
Session: P, Biogeography Posters
Location: Virtual/Virtual
Date: Monday, July 27th, 2020
Time: 5:00 PM Time and date to be determined
Number: PBG001
Abstract ID:109
Candidate for Awards:None

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