Flora Of Guatemala

Abstract

The flora of Guatemala (Standley and Stey ermark '45, Smith 1889-1907) is the richest and most (lixersified of any in Central America for a variety of reasons. This is (itle not only to a combination of varied climatic, physiographic, and edaphic conditions, l)lt also to a long and (liverse geological hi story. Extremes range from lhot deserts. seashores, and lowlan(l rain forests to cool temperate oak-pine, fir, or ctupresstus forests, moist cloud forests, alpiiie meadows, and volcanic stummits; temnlperatures range from 16? F in the highlands to around 100? F in the Motagnta desert; altitudes vary between seale-el and 4,210 meters on the summit of Volcan (le Tajurnulco; rainfall from 6 inches to 200 inches annually, and varying from a dry season of half a year to almost (daily rains throughout the year; topographic features range through plains and everglade-like country, mountain lakes, sulfur fumaroles and springs, waterfalls, steep canyons, caves, clear spring-fed mountain streams to (lark browxln waters of lowland areas, an(l rocks varying from limestones and sandstones to marbles, serpentine, gneisses and mica-schists to granites, diorites, pumice, basalt, and volcanic ash (Griscom '32). The 14 major volcanoes are all of Pleistocene and Recent origin. The present limestone plains and hills of Peten in northern Guatemala resulted from the marine inundations of Tertiary times (Schuchert '35). But the most interesting parts of Guatemala are the old mountains of the southern part (fig. 1) that extend in an east-west direction from the Sierra de los Cuchumatanes to the Sierra (le Chuacus and Sierra de las Minas. These mountains, formed of Paleozoic and Mesozoic rocks, are part of an ancient nuclear core of Central Amnerica (Sapper 1894), and have been available for plant occupation since the end of the Cretaceous period. Many genera whose ancestry dates back to late Cretaceous and early Tertiary times occur only in this area of ancient strata. The family Magnoliaceae, of proved ancient lineage, and occurring at present in eastern Asia and eastern North America as well as in Central and South America, is represented in Guatemala by the genera M1ayniolba, Talauoia, andl Drilivs, which occur in Guatemala only on these old strata. Likewise, are found Osinitnda, Ceratofazaiia, Taxodiumn, Tavls s, fitiperits, Podocar pus, Car points, Jfuianis, Alfaroa, I)istyliitlfl, Liqitidaniibar, Mllattdaea, P/a tains, A4cer, Sarcococca, and Befaria-and all limited to these older rocks. None of these or similar groups are found on the youthful slopes of the volcanoes formed in Pleistocene times, or on the Tertiary lowlands of Peten, or on the Pleistocene formations of the lowlands of Izabal or the Pacific bocacosta. Just as some genera in the United States, such as Cladrastis, Cotinus, and others, are represented by fossil ancestors which prove their existence back to late Cretaceous or early Tertiary times, and now are confined to the old Appalachian-Ozark plateau, which has been available for plant occupation since the end of the Paleozoic era, so do similar examples in Guatemala point to anciently distrib uted types. Upon this area of old rocks are found some of the most remarkable genera endemic to Guatemala, such as Tintinnabiltaria and Gutaniatela. To this area are restricted such peculiarly isolated species as M41itchlella repenis, Gelseinhiiu serperzvirens, Part/ieiiocissus qfiti qitefolia, Rhus radicans, and Berclienmia scandens, otherwise known only from the United States and northern Mexico. The remarkable parasite, Mitrastemon, is also found in the area of older strata. Likewise, the greater variety of the

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