WYSOR, BRIAN. Department of Biology, University of Louisiana at Lafayette, P. O. Box 42451, Lafayette, LA 70504-2451, USA. - The Central American Isthmus: implications for intraspecific phylogeny and biogeography of a pantropical green alga.
An intraspecific phylogenetic study was undertaken to resolve the
evolutionary relationship of isolates of the green alga
Phyllodictyon anastomosans (Harv.) Kraft et Wynne that occur on
Atlantic and Pacific coasts of the Central American Isthmus. Patterns
of vicariance related to the emergence of the Central American Isthmus
were evident, but numerous examples of recent trans-oceanic and
trans-isthmian dispersal obscured the underlying pattern. This study,
one of the first studies to assess the impact of the emergence of the
Central American Isthmus in seaweed phylogeography, provided an ideal
opportunity to estimate the rate of sequence evolution using a single
time point. Using this newly calibrated molecular clock the timing of
an historical introduction across the isthmus is shown to be
concordant with a shallow water breach of the isthmus dated at
approximately 2.3-2.0 million years ago. This work contributes to a
growing body of literature that suggests marine algae are fairly
successful at dispersing over long distances in recent times.
Key words: Central American Isthmus, molecular clock, Phyllodictyon anastomosans, phylogeography, rDNA ITS, vicariance