Ecology of the Ant Pogonomyrmex mayri: Distribution, Abundance, Nest Structure, and Diet

Abstract

Although the North American seed harvesting ants of the genus Pogonornyrmex have been studied for many years, this is the first report of the ecology of a South American species. The entire distribution of P. mayri seems limited to desert or very dry forest in northeast Colombia. Colonies are of moderate size for the genus, averaging 603 workers per nest. Nest density, however, is high, resulting in a biomass comparable to that of Pogonomyrmex with much larger colonies. Nests have hidden entrances and consist of only two levels and a few chambers. Nest relocation in the area studied was frequent and executed within four or five hours. Unlike most Pogonomyrmex so far studied, P. mayri is not granivorous, but rather relies mostly on dead arthropods for food. ANTS OF THE GENUS Pogonomyrmex are distributed throughout the western hemisphere from Patagonia to southern Canada (Kusnezov 1951). They are one of the most primitive genera of the extremely successful subfamily Myrmicinae. In order to understand this subfamily, its origins, and its radiation, it is important to study the biology of its more primitive members. Because of their large size, conspicuous nests, and remarkable habit of gathering and storing seeds, a few North American species of the subgenus Pogonomyrmex have received a great deal of attention for many years (see Wheeler 1910, Cole 1968, MacKay 1981 for references). Their obligate granivory, however, is almost certainly derived and unrepresentative of myrmicine ancestry. Within the genus are many species with apparently much less developed granivory (Creighton 1952, 1956; Kusnezov 1959; MacKay 1981), but their habits are little known, particularly those of the South American species. This, in fact, is the first ecological study of any South American Pogonomyrmex. Pogonomyrmex mayri is the sole member of the subgenus Forelomyrmex, which is morphologically most related to the less conspicuous members of the subgenus Ephebomyrmex (Kugler 1978b). Here we present observations on distribution, abundance, nest characteristics, and diet of Pogonomyrmex mayri. Elsewhere we will examine its foraging and territorial behavior (Ku-