Abstract Detail

Patterns and Processes of American Amphitropical Plant Disjunctions: New Insights

Simpson, Michael [1], Guilliams, Matt [2].

What are American amphitropical disjunctions and why are they interesting?

Plants with an American amphitropical disjunction (AAD) are those that occur on either side of the American tropics but not within, a biogeographic pattern that has been recognized for some time for a number of groups. We consider first the biogeographic boundaries of AAD plants and the obvious need to evaluate vegetation regions or ecological zones and the correlated features of climate, topography, and geological substrate in assessing distributions. The taxonomic entities to be evaluated for AAD need to be clearly evaluated, whether infraspecific, conspecific, or congeneric pairs (e.g., sister species), or closely related species groups (ideally clades). AAD plants are often assumed to have arisen by natural (non-human) events, but possible introductions by humans in historical times can now be assessed. Character evolution is quite interesting to trace with AAD plants, both possible preadaptations to dispersal, such as self-compatibility and propagule morphology and physiology (e.g., endozoochory versus ectozoochory), and possible adaptations following dispersal, such as shifts in perenniality or chromosome number. One of the more interesting aspects of this line of research is evaluating the mechanism by which plants originally attained a current AAD distribution. The ruling dogma is that the great majority of AAD plants attained their current distributions by long distance dispersal. Under this scenario, seeds or fruits may have moved between the continents in a single dispersal event, e.g., between two desert or Mediterranean-type climate regions, or via two or more shorter dispersal events, e.g., in a stepping-stone fashion along the American Cordillera, but vicariance hypotheses might also be considered. Assessing the number and timing of dispersal events is now possible with molecular dating methods. Here we summarize knowledge of AAD plants and give examples of each of the preceding facets of investigation. With continued research on AAD plants, we may accumulate enough data to evaluate if events resulting in AAD distributions exhibit signals of a common pattern among taxonomic groups, these correlated with past geologic or climatic events or with life history features that have shaped the survival and evolution of these plants in novel habitats.

1 - San Diego State University, Department of Biology, San Diego, CA, 92182, USA
2 - Santa Barbara Botanic Garden, Conservation & Research, 1212 Mission Canyon Road, Santa Barbara, CA, 93105, USA

Keywords:
Biogeography
amphitropical
Distribution.

Presentation Type: Colloquium Presentations
Session: C2, Patterns and Processes of American Amphitropical Plant Disjunctions: New Insights
Location: 204/Savannah International Trade and Convention Center
Date: Tuesday, August 2nd, 2016
Time: 1:30 PM
Number: C2001
Abstract ID:916
Candidate for Awards:None