Systematics Section / ASPT
Peterson, Paul M. .
Evolution of the Muhlenbergiinae (Poaceae: Chloridoideae: Cynodonteae) in México.
MEXICO is clearly a center of Chloridoideae diversity where there are 319 native species (29.7%) out of the 1043 grasses indigenous to the country. The five largest native chloridoid genera in Mexico include: Muhlenbergia (108 spp.), Bouteloua (51 spp.), Eragrostis (36 spp.), Sporobolus (29 spp.), and Chloris (10 spp.). The subtribe Muhlenbergiinae currently consists of 10 genera and 173 species almost entirely restricted to the New World. A phylogenetic analysis based on internal transcribed spacer (ITS) and trnL-F sequences indicates that all nine of the smaller genera, Aegopogon (4 spp.), Bealia (1 sp.), Blepharoneuron (2 spp.), Chaboissaea (4 spp.), Lycurus (3 spp.), Pereilema (4 spp.), Redfieldia (1 sp.), Schaffnerella (1 sp.), and Schedonnardus (1 sp.), are nested within a paraphyletic Muhlenbergia (152 spp). The hot, arid to semi-arid climate of northern Mexico coupled with the fault-block uplifting of the Mexican Plateau and further development of the Sierra Madre Occidental and Sierra Madre Oriental in the Eocene created an environment well suited for the evolutionary diversification of the Muhlenbergiinae. Species diversity within the Muhlenbergiinae is greatest in Mexico where there are 125 (72.3%) indigenous species, and 55 of these are endemic. There are 48 endemic species of Muhlenbergia in Mexico, and 12 of these are known only from a single state. Well-supported clades include species that exclusively exhibit PCK leaf anatomy (Muhlenbergia subg. Muhlenbergia, Aegopogon, and Pereilema), species that have sclerosed phloem and a crown of inflated cells associated with primary vascular bundles (Muhlenbergia subg. Trichochloa), and species that usually have 3-nerved and/or toothed upper glumes (Muhlenbergia montana complex). A taxonomic revision of the Muhlenbergiinae for Mexico is in preparation. -DU
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Smithsonian Department of Botany
1 - Smithsonian Institution, Department of Botany, MRC-166, National Museum of Natural History, PO Box 37012, Washington, DC, 20013-7012, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Wednesday, August 2nd, 2006
Time: 2:45 PM