Abstract Detail

Patterns and Processes of American Amphitropical Plant Disjunctions: New Insights

Whittall, Justen Bryant [1], Biro, Peter [2].

The age of amphitropic plant disjuncts coincides with the Great American Biotic Interchange.

Long-distance plant disjunctions are mysterious. There are over 130 closely related plants distributed both in California and South America, yet nowhere in between. Charles Darwin posited that avian dispersal created these large distributional gaps, known as amphitropic disjunctions. Yet, many of these plants lack characteristics that would seem to facilitate bird dispersal and most do not currently occupy habitats conducive to dispersal by the types of birds known to make such long distance migrations. Avian dispersal may not be the only mechanism to explain these plant distributions. Approximately 3.2 million years ago, the closing of the Isthmus of Panama afforded an unprecedented migration of primarily large, flocculent animals from North America to South America. This mammalian migration, known as the Great American Biotic Interchange (GABI), lasted until approximately 1.4 million years ago and provides an alternative hypothesis that may explain some amphitropic plant disjunctions. We examined the directionality and age of 75 amphitropic dispersal events across 38 genera by building phylogenetic trees using sequences from the nuclear-ribosomal-ITS region available in Genbank. We then used ancestral-state-reconstructions to infer the directionality of the dispersals and dated these events using the average substitution rate of the ITS region. The results strongly support GABI as a viable alternative to explain many amphitropic plant disjunctions. Ancestral-state-reconstructions indicate 55 of 75 events proceeded from North to South America – reflecting the primary direction of GABI. Furthermore, 81.3% of sampled disjuncts have dispersal dates that coincide with GABI. This provides a plausible, if not likely, alternative mechanism that helps explain the mystery of long-distance amphitropic plant disjunctions.

1 - Santa Clara University, Department Of Biology, 500 El Camino Real, Santa Clara, CA, 95053, USA
2 - Santa Clara University, Biology, 500 El Camino Real, Santa Clara, CA, 95053, United States

Keywords:
Plant disjunctions
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great american biotic interchange.

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: 4:15 PM
Number: C2011
Abstract ID:553
Candidate for Awards:None