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.

Over the past thirty years, late Quaternary environments in the arid interior of western North America have been revealed by a unique source of fossils: well-preserved fragments of plants and animals accumulated locally by packrats and quite often encased, amberlike, in large masses of crystallized urine. These packrat middens are ubiquitous in caves and rock crevices throughout the arid West, where they can lie preserved for tens of thousands of years. More than a thousand of these deposits have been dated and analyzed, and middens have supplanted pollen records as a touchstone for studying vegetation dynamics and climatic change in radiocarbon time (the last 40,000 years). Now, similar deposits made by other mammals like hyraxes are being reported from other parts of the world. This book brings together the findings and views of many of the researchers investigating fossil middens in the United States, Mexico, Africa, the Middle East, and Australia. The contributions serve to open a forum for methodological concerns, update the fossil record of various geographic regions, introduce new applications, and display the vast potential for fossil midden analysis in arid regions worldwide. The findings presented here will serve to foster regional research and to promote general studies devoted to global climate change. Included in the text are more than two hundred charts, photographs, and maps.

Encompassing tropical and temperate forests, arid lands, and the Gulf of California, northern Mexico is one of the most biologically diverse areas in the world. Representing the collaborative efforts of ecologists in the U.S.

Environmental and specific diversity in the Chihuahuan desert in general, and in the Cuatro Ciénegas Basin in particular, has long been recognized as outstanding. This book provides a global ecological overview, together with in-depth studies of specific processes. The Chihuahuan desert is the warmest in North America, and has a complex geologic, climatic and biogeographical history, which affects today’s distribution of vegetation and plants and generates complex phylogeographic patterns. The high number of endemic species reflects this complex set of traits. The modern distribution of environments, including aquatic and subaquatic systems, riparian environments, gypsum dunes and gypsum-rich soils, low levels of phosphorous and organic matter, and high salinity combined with an extreme climate call for a range of adaptations. Plants are distributed in a patchy pattern based on punctual variations, and many of them respond to different resources and conditions with considerable morphological plasticity. In terms of physiological, morphological and ecological variability, cacti were identified as the most important group in specific environments like bajadas, characterized by high diversity values, while gypsophytes and gypsovagues of different phylogenies, including species with restricted distribution and endemics.

This volume investigates the contemporary fauna that inhabit the Cuatro Ciénegas Basin. Divided into 15 chapters, it addresses and describes their diversity, taxonomic and biogeogaphic affinities, and ecological characteristics. The Cuatro Ciénegas Valley is a unique oasis in the south-central region of the State of Coahuila, part of the Sonoran Desert, in Mexico. Several clues, specially derived from the study of the microbiota, suggest a very ancient origin of the valley and its permanence through time. This condition had promoted a high level of endemism and led to unique interactions between the resident species.