Castañeda-Posadas, Carlos , Cevallos-Ferriz, Sergio .
Miocene plants form Tlaxcala, central Mexico, their saying to explain biodiversity.
In the Late Miocene sediments of Panotla, Tlaxcala, a great number of vegetative organs, including wood fragments, have been collected. Presences of members of five genera, Terminalia, Cedrela, Hypodaphnis, Pterocarpus, and Podocarpus have been documented base on wood anatomy. Terminalia and Hypodaphnis strongly suggest that an evergreen tropical forest was present at that time in the area. Today they live at altitudes below 900 m, with temperatures between 20Â° y 25Â°C, and precipitation between 2500 and 4000 mm. These conditions contrast with today xeric characteristics of the area. The palynological record of the region suggests that during the last ca. 15 ma humidity dropped dramatically, while temperature varied far less in the area. Vegetation during the Pliocene changed to a conifer-oak forest, during the Pleistocene to a conifer forest and more recently, during the Holocene to bushes. The drying of a lake accompanied this vegetation changes. An ecosystem may be explained as reflecting the interactions between biotic (e.g., plants, animal) and abiotic (topographic edaphologic, latitudinal, altitudinal, climatological, geological, etc.) factors. The geographic location of Mexico, in the limits of the tropical zone and more than 50 % of its territory with elevations above the 1000masl, facilitated the presence of different geobiological scenarios, selecting diverse biological communities. The history being excavated from the Panotla rocks exemplifies how the scenarios changed trough time in Mexico, and how these were important in selecting the communities establishing in them, highlighting the importance of explaining biodiversity as part of a great system, the Earth System, in which biotic and abiotic factors interact continuously.
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1 - Instituto de Geologia, UNAM, Posgrado de Ciencias Biologicas, Ciudad Universitaria, Delegacion Coyoacan,, Mexico, Distrito Federal, 04510, Mexico
2 - Department of Palentology, Instituto De Geología, Mexico, 01900, Mexico
Presentation Type: Oral Paper:Papers for Sections
Location: Williford A/Hilton
Date: Wednesday, July 11th, 2007
Time: 10:45 AM