Abstract Detail

Population Genetics/Genomics

Landis, Jacob [1], Gaynor, Michelle [2], Deanna, Rocío [3], O'Connor, Tim [4], Nguyen, Khoa [5], Ng, Julienne [5], Laport, Robert [6].

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

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, AADs remain a frustrating biogeographic puzzle with important questions pertaining to the biogeographic origins, evolutionary timing, and mechanisms of dispersal remaining unanswered. 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 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 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. To fully leverage the RAD capture data, we assembled draft genomes for both species to map raw reads for SNP calling. Comparative genomic analyses were performed on the assembled genomes to look for major differences between the two species, however with no suitable outgroup determining directionality of changes remains difficult. 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 unclear. Different levels of data filtering and underlying models can potentially bias interpretations of the evolutionary patterns observed.

1 - Cornell University
2 - University of Florida
3 - 1350 20th St. Apt A-29, Prestamo BID PICT 2017 CONICET N 2370, Córdoba, X, 5000, Argentina
4 - University of Chicago
5 - University of Colorado
6 - Rhodes College, Department Of Biology, 2000 North Parkway, Memphis, TN, 38112, United States

Keywords:
long distance dispersal
polyploidy
new world deserts
adaptive radiation
Zygophyllaceae
RAD capture.

Presentation Type: Oral Paper
Number: PGG1003
Abstract ID:175
Candidate for Awards:None