The power of two: Marrying phylogeny and biogeography to reconstruct the evolutionary history of pteridophytes
Haufler, Christopher H. , Smith, A. R. , Ranker, T. A. , Schneider, Harald .
A tale of two mechanisms: Discovering how dispersal and vicariance contributed to the pattern of species diversity in the “polygrams”.
Ferns assigned to the long-recognized families Polypodiaceae and Grammitidaceae (the “polygrams”) yield a study in contrasts. Their sori lack “derived” indusia, but polygrams are relatively young lineages. Both “families” are circum-tropical and have equivalent numbers of species, but the grammitids are a younger clade with New World polypod ancestors. Some New and Old World polypod species share similar morphologies, but they do not share common ancestors. These relatively recent revelations spark biogeographic questions. Where did the groups originate? Can the roles of dispersal and vicariance in the history of the groups be identified? Although preliminary, we can begin to assess the “nativity” of some well-studied groups and extrapolate general patterns and processes from these examples. Lecanopteris demonstrates an apparently rapid and regional radiation in Sulawesi, whereas Microgramma (including Solanopteris) is an example of a primarily New World radiation, where it joins with sister taxa Niphidium and Campyloneurum to form a ±90 species clade of simple-bladed taxa. These specific examples are consistent with the following general trends. Sister to the Davalliaceae, the Polypodiaceae appeared in the late Cretaceous in southeastern Asia. Originating as simple-bladed epiphytes, ancient radiations led to considerable diversity in tropical Asia. A single dispersal event to the New World led to early radiations of simple-bladed Campyloneurum, once-pinnate Polypodium triseriale and relatives, and the hugely successful grammitids (variously dissected). A subsequent large radiation generated the diversity of Central American polypods and lastly the temperate P. vulgare group. Basal-most grammitids are entirely neotropical (Terpsichore). Early radiations and at least 8 episodes of long-distance dispersal led to extensive diversification on islands and in Africa/Madagascar. Overall, the paucity of pantropical polygram genera and the many groups with regionally restricted diversification provide strong evidence of a recent origin, rare long-distance dispersal, and most speciation occurring within geographically limited tropical and subtropical areas.
1 - University of California, Berkeley, Integrative Biology, University and Jepson Herbaria, 1001 Valley Life Sciences Building, Berkeley, California, 94720-2465, USA
2 - University of Kansas, Dept. Ecol. & Evol. Biol. and Natural History Museum, 1200 Sunnyside Ave., Lawrence, Kansas, 66045-7534, USA
3 - University of Goettingen, Department of Systematic Botany, Albrecht von Haller Institute for Plant Sciences, Untere Karspuele 2, Goettingen, D-37073, Germany
4 - University of Colorado, University Museum & Department of Ecology and Evolutionary Biology, 265 UCB, Boulder, Colorado, 80309-0265, USA
Presentation Type: Symposium
Location: Ballroom 1 (Cliff Lodge)
Date: Tuesday, August 3rd, 2004
Time: 5:00 PM