A Biogeographical Analysis of the Chihuahuan Desert through its Herpetofauna

The Mexican Plateau, in its magnificent dimensions and material wealth, stood among the first and perhaps most alluring discoveries of European explorers. Bur­ ied deeper in the verbal histories of a now vanquished people, the American Indians, must be the primordial human awareness of the inverted complex triangle that dominates the Mexican topography, climate and biota. It always has been viewed by man as a source of wealth and a center of authority. The plateau is the pillar upon which all Mexican conquerors have erected their capitols, tilled their crops and mined for their treasure, and from which they dispersed the forces of their authority. Ironically, the same size and diversity that give the plateau its value, also make it an immense barrier. Its broad desert and three to five thousand meter high crests constitute severe obstacles in the path of North American man. What has just been said of mankind in general, can be applied to the biologist in particular. He too has termed the goliath southern plateau as the crucible of the arid biotas of the continent (i. e. , 'Madro-Tertiary'). The biologist found the plateau to be a region of tremendous richness and diversity. But he also has been inhibited both physically and intellectually by its high mountain and vast desert barriers.

Contenu

I. Introduction.- II. Sources, Methods and Analytical Procedures.- Data Sources.- Methods of Data Compilation and Presentation.- Analytical Procedures.- III. Climate.- Existing Conditions.- Causal Factors.- Comparative Climates of North American Deserts.- IV. The Physiography of the Chihuahuan Desert.- Geography and Dimensions.- Topography.- Geological History.- Adjacent Topographical Features.- Soils.- Hydrology.- V. Vegetation.- A. Chihuahuan Desert Vegetation.- B. Non-Desert Relict and Border Vegetation.- VI. Definitions, Terminology and the Base map of the Chihuahuan Desert.- The Concept of a Desert.- Biogeographical Terminology.- Historical Résumé of the Chihuahuan Desert as a Biogeographical Unit.- Definition of the Chihuahuan Desert and the Base map.- VII. The Herpetofauna.- Systematic Problems in the Classification of Chihuahuan Herpetofauna.- A Statement of Systematic Positions.- A Checklist of Extant Amphibian and Reptilian Species Occurring within the Geographical Chihuahuan Desert.- Addenda to the Checklist of Amphibian and Reptile Species Occurring within the Geographical Chihuahuan Desert.- VIII. The Ecological Affinities of the Chihuahuan Herpetofauna.- Ecological Affinities and Faunal Assemblages in a Biogeographical Unit.- Correlations between Plant Associations and the Habitat Distribution.- A. Chihuahuan Desert Scrub Association.- B. The Mesquite Grassland Ecotone.- C. Chaparral Association.- D. Desert Riparian Associations (Woodland & Marsh).- E. Juniper-Piny on Woodland Association.- F. Montane Coniferous Forest.- Analysis of Ecologically Based Herpetofauna Assemblages.- Habitat Displacement or Restriction.- Habitat Segregation and the Influence of Geographical Faciations.- IX. A Spatial Analysis of the Chihuahuan Herpetofauna.- Objectives.- Preliminary Evaluation of the Primary Area.- Subdivisions of the Chihuahuan Desert.- The Affinities of the Chihuahuan Desert Herpetofauna with those of Adjacent Non-Desert Provinces.- Chihuahuan Desert Filter Barriers and Extralimital Desert Relict Herpetofaunas.- The Affinities among North American Desert Herpetofaunas.- Montane Relict Herpetofaunas.- Riparian Herpetofaunas within the Chihuahuan Desert.- X. A Historical Biogeography of the Chihuahuan Herpetofauna.- The Cretaceous Period.- Paleogene Period.- Early Neogene Period.- The Mexican Plateau as an Evolutionary Center.- Late Pliocene Epoch.- The Pleistocene.- The Glacials.- The Interglacials.- The Pluvial Period, Post Wisconsin.- The Xerothermic Period, Post Wisconsin.- XI. Summary.- Literature.- Appendix I. Biogeographical Features.- Appendix II. Species Distribution Maps.