During the middle Pliocene seven principal arborescent plant communities occupied the zone between sea level and the highest elevations of the eastern Transvolcanic Belt—manglar (mangrove swamps; Rhizophora), bosque caducifolio (deciduous or Quercus/ Liquidambar woods), bosque de encino (oak woods; Quercus, both lowland tropical and upland temperate types), bosque de pino (pine woods; Pinus), bosque de pino y encino, and bosque de oyamel (high-altitude Abies/Pinus woods). The presence of Picea, now confined in Mexico to the northern mountains 1000 km distant from the fossil locality in south-eastern Veracruz state, and the poor representation of the selva alta perennifolia (tropical rain forest) suggest cooler mean annual temperatures estimated at 2-3°C below the present. A downward shift in ecotones of about 500-1000 m is suggested, with a maximum altitude in the region of about 2500 m (the present maximum is 5650 m; present altitudinal range of Abies in eastern Mexico is 2400-3600 m). In southern Central America (Costa Rica, Panama) all modern anologues of taxa recently reported from late Eocene and early Miocene palynofloras can be accommodated in a zone between sea level and 1200-1500 m (current maximum elevations c. 3500-4000 m). Tertiary temperature fluctuations were muted by the insular environment of proto-Central America, and altitudinal shifts in ecotones are not evident in the fossil floras.

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Acta botanica neerlandica

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Koninklijke Nederlandse Botanische Vereniging

A. Graham. (1989). Late tertiary paleoaltitudes and vegetational zonation in Mexico and Central America. Acta botanica neerlandica, 38(4), 417–424.