Abstract Detail

The power of two: Marrying phylogeny and biogeography to reconstruct the evolutionary history of pteridophytes

Taylor, W. Carl [2], Hoot, Sara B. [1], Napier, Nancy S. [1].

Phylogeny and Biogeography of Isoetes on Oceanic and Terrestrial Islands.

Isoetes is an ancient genus of lycopods with approximately 250 or more species, ranging from ephemeral terrestrials to evergreen aquatics. They are found on every continent except Antarctica and on many islands. In this presentation, we explore two kinds of islands: 1) oceanic islands, often isolated considerable distances from continental land masses and 2) terrestrial, granitic outcrop islands found in the United States, South Africa, and Western Australia. Using a combination of nuclear ribosomal ITS, chloroplast rbcL-atpB spacer data, and a homolog of nuclear LFY intron 2 region (either separately or combined), we present phylogenies that show the likely origins of such oceanic island endemics as I. hawaiiensis, I. azorica, I. cubana, I. jamaicensis, I. taiwanensis, I. kirkii from New Zealand, I. habbemensis from New Guinea, I. gunnii from Tasmania, and several species from Australia. In general, the oceanic island species appear to have their origins from the nearest landmasses, although several of them (I. cubana and I. jamaicensis) are intriguing because they are among the earliest branching lineages within the family. The granite outcrop species of North America, South Africa, and Western Australia are found in distant clades and exhibit convergent evolution, having attained similar morphological characteristics in adapting to similar habitats. We hypothesize that the same dispersal agents (migratory birds) are mainly responsible for the distribution of progenitor species to islands and within and between continents as well. Long-range dispersal, widespread interspecific hybridization, and allopolyploidy have led to subsequent radiations that have effected speciation in both insular and continental species of Isoetes.

1 - University of Wisconsin-Milwaukee, Department of Biological Sciences, P.O. Box 413, Milwaukee, Wisconsin, 53201, USA
2 - Milwaukee Public Museum, Botany Department, 800 W Wells St., Milwaukee, Wisconsin, 53233, USA

Keywords:
biogeography
molecular phylogenetics
Isoetes.

Presentation Type: Symposium
Session: 34-2
Location: Ballroom 1 (Cliff Lodge)
Date: Tuesday, August 3rd, 2004
Time: 2:45 PM
Abstract ID:219