Abstract Detail

Dynamics and Demography of Alpine Islands

Steinmann, Victor [1], Hernández-Cárdenas, Rodrigo [2], Arredondo-Amezcua, Libertad [3], Ramírez-Amezcua, Yocupitzia [4].

Islands of alpine vegetation in central Mexico.

The alpine vegetation of central Mexico occurs as small islands in a sea of coniferous forest. Globally, this ecosystem is found on frigid mountaintops above treeline in both tropical and temperate regions. Although much more extensive during Pleistocene glacial episodes, its current distribution is scattered and restricted. In central Mexico, alpine vegetation is confined to the 11 highest peaks of the Trans-Volcanic Mexican Belt (TVMB), a volcanically active, east–west oriented cordillera that extends across the country. In this region the lower boundary of alpine vegetation usually occurs at approximately 3900 m and the upper boundary at 4700 m, above which vascular plants cease to exist. There are only 150 km2 of alpine vegetation within the TMVB, and the size of these alpine islands ranges from 0.03 km2 on Cerro Telapón to nearly 50 km2 on Pico de Orizaba. In total, 232 alpine species have been documented from the area, all but 12 of which are native. Perennial herbs are the dominant life form, and annuals are very rare. Forty-five percent of the species occur in three families: Asteraceae (43 spp.), Poaceae (42 spp.), Caryophyllaceae (20 spp.); none of the remaining 42 families have more than 10 species. Five species are strict endemics, and 13 others are restricted to alpine vegetation but also occur outside the study area, mostly in the páramos of Central and South America. An additional eight species are near endemics and otherwise grow only above 3500 m in the adjacent subalpine forests of the TVMB. Whereas ten species occur on all of the peaks, 86 species are known from a single peak. The most diverse alpine island is Iztaccíhuatl (167 spp.), and the least diverse is the Nevado de Colima (31 spp.). The size of the alpine area is not a correlated with diversity, and the largest alpine island on the Pico de Orizaba surprisingly has less species than the nearby Cofre de Perote, which is nearly 30 times smaller. Instead, important factors affecting alpine diversity appear to be the time since and extent of the last volcanic activity, in addition to the distance from other alpine islands. In terms of biogeographic affinities, 126 species are also distributed in Central or South America, and 44 occur in the United States or Canada. Fifteen species are also native to the Old World. Seventy-seven species are endemic to Mexico, 35 of which are endemic to the TVMB.

1 - Universidad Autónoma de Querétaro
2 - Universidad Autónoma Metropolitana-Iztapalapa
4 - Plant Sales

Alpine plants
Trans-Volcanic Mexican Belt.

Presentation Type: Colloquium Presentations
Number: 0004
Abstract ID:491
Candidate for Awards:None

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