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Aspects of the Ecology of Three Species of Ants (Myrmecocystus spp., Aphaenogaster sp.) in Desertified Grassland in Southeastern Arizona, 1958- 1993

Robert M. Chew
The American Midland Naturalist
Vol. 134, No. 1 (Jul., 1995), pp. 75-83
DOI: 10.2307/2426484
Stable URL: http://www.jstor.org/stable/2426484
Page Count: 9
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Aspects of the Ecology of Three Species of Ants (Myrmecocystus spp., Aphaenogaster sp.) in Desertified Grassland in Southeastern Arizona, 1958- 1993
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Abstract

From 1981 to 1993 the density of colonies of Myrmecocystus depilis and Aphaenogaster cockerelli decreased after being stable from 1958-1981. The density of Myrmecocystus mexicanus declined after consistently increasing from 1958-1981. The declines after 1981 were principally due to decreases in rates of founding of new colonies. Aphaenogaster cockerelli became locally extinct by 1993, possibly because of thermal stress or dampness within its shallow nests. Both Myrmecocystus species may have been affected by shading by an increasing vegetation cover. Myrmecocystus mexicanus nests that were experimentally shaded either died or moved entrances away from the shade. The only naturally shaded colonies of M. depilis that survived from 1981 to 1993 had moved their entrances beyond shade. Estimates of average and maximum life spans of colonies were: M. depilis 8.6 yr and 35 yr, M. mexicanus 8.9 yr and 23 yr, A. cockerelli 5.2 yr and 23 yr.

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