The NSS Bulletin - ISSN 1090-6924
Volume 42 Number 3: 53-60 - July 1980
A publication of the National Speleological Society

Climatic Change and the Evolution of Cave Invertebrates in the Grand Canyon, Arizona
Stewart B. Peck

Abstract

The invertebrate cave faunas of three stream caves, located in the lower part of the Upper Sonoran Desert life zones of the Grand Canyon, Arizona, were investigated. Of the 15 species found, all are terrestrial and five are probably now limited to stream caves in the canyon as troglobites or disjunct populations of troglophiles. These five species probably descended from forest litter-inhabiting ancestors living near the caves during past glacial-pluvial climates. These climates, with their cooler and/or wetter conditions, should have allowed a lowering of at least some components of nearby spruce-fir montane forest communities from the Kaibab Palteau some 1000 m down into the middle elevations of the Grand Canyon, in the vicinity of the caves. This "life zone" lowering occurred most recently from 24,000 to 14,000 years ago. When the forest retreated upwards at the beginning of the present interglacial (about 8,000 years ago), some of the litter invertebrates which had entered the caves were locally isolated in them when adjacent epigean populations went extinct. Examples may be a rhagidid mite and a campodeid dipluran, and these could represent the most recent wave of invaders in a climatically controlled taxon cycle of cave occupation, isolation, and possible adaptation (or extinction). A telemid spider and a leiodid beetle are troglobites at a low level of specialization and probably resulted from an earlier (probably the Sangamon) interglacial wave of cave isolation and adaptation. An entomobryid collembolan is assumed to represent an even earlier period of subterranean isolation.

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