Three species of tilapia native to Zimbabwe, Oreochromis mossambicus, O. mortimeri and O. macrochir are not naturally sympatric, but because of transplantation they have been brought into sympatry. Allozymes of fish examined from Lakes Kariba, Kyle and Chivero showed evidence of introgressive hybridization. The data showed non‐random mating populations in Lakes Kariba and Kyle. All three reservoirs displayed individuals with intermediate principal component scores and hybrid index scores indicating hybridization.
A study of the ant populations was made through a transect of mid-continent North America from Churchill on Hudson Bay and various localities around the Great Lakes to Iowa and northern Illinois. Data were obtained from extensive personal collecting and from literature sources. The results were assembled and discussed within an ecological framework provided by Merriam’s life zones, and showed a regular diminution in the variety and wealth of the ant faunas progressing from south to north. Though the number of species at Churchill is extremely reduced, ants nevertheless do occur there as established reproducing colonies, even in the presumed tundra habitats. These forms which exist so far north represent a highly impoverished remnant of richer faunas further south. Although none of the species is peculiar to the area, each must be tolerant of high boreal environments. A total of 135 species and subspecies are listed for the Carolinian and Alleghenian zones combined, 43 taxa for the Canadian Zone, 4 taxa for the Hudsonian Zone, and 4 also for the Arctic Zone. Comparisons with the recorded ant faunas of the Rocky Mountains of Colorado were made with respect to the corresponding zones, namely, the Plains (Upper Sonoran), Foothills or Submontane (Transition), Montane (Canadian), Subalpine (Hudsonian), and Alpine (Arctic) zones, and appropriate similarities and differences noted.
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