|The Ants of
CHAPTER 3 - Mosaics - Evidence from Cameroun - 1 - Jackson
|Introduction - Cameroun 2 - Cameroun 3|
The single published work appears to be extracted from the author's doctoral thesis. It described a study, during 1979-1980, of three small plots of cocoa at the governmental cocoa research station, Nko'emvon (2°49'N, 11°7'E), in the extreme south of the country (see Map 7). The plots each measured 30 m X 50 m and contained mixtures of Trinitrario and Amelonado cocoa, planted at 3 m X 3 m spacing some 14-15 years earlier and then 4-5 m tall.
The arboreal mosaic was investigated by manual examination up to
1.6 m of every tree in two of the plots on a single occasion. These two
plots and the results of the survey are shown in the Plan.
Plot A (133 trees) was dominated by Crematogaster africana (on 34 trees, 22 with > 50 workers), Oecophylla longinoda (44/37) and Tetramorium aculeatum (40/27). Also present was a ground-dweller Pheidole species 2 (8/2).
Plot B (117 trees) was dominated by Crematogaster gabonensis (48/42) and Tetramorium aculeatum (33/29). Also present was Pheidole species 2 (34/4).
Mapping of the four arboreal species showed clear separation of the colonies and strong negative associations were found between all tested pairs. Crematogaster africana was associated with dense canopy but no information was given as to the nest sites or their location. The other three arboreal species were not significantly affected by canopy density and Jackson thought their distribution probably was determined simply by priority of colony establishment.
The study added to earlier knowledge by incorporating an investigation of the terrestrial ant community. In plots A and B, pitfall traps, with and without bait, were used.
The most abundant species was Pheidole species 2, found in over half the traps, and generally twice as abundant as any other species. It was similarly the most common in the third plot K, where traps and ground search techniques were used.
Each of the plots, however, had a different spectrum of other common species. In plot A the second species was Pheidole speculifera, in plot B it was Monomorium species 1, in plot C it was Myrmicaria opaciventris.
Camponotus flavomarginatus and Paratrechina species 2 both occurred in moderate numbers in all three plots.
Other species listed were Pheidole species 3 (plot A), Anoplolepis tenella (plots A and B), Lepisiota (as Acantholepis) crinita (plot B) and Tapinoma species 4 (plot K).
In plot K Crematogaster africana was a common ground forager, with the only demonstrable negative associations with the other species.
Myrmicaria opaciventris and Pheidole species 2 were found to compete for resources in plot K, with the larger Myr. opaciventris reducing the foraging success of the other ant.
Finally, without details of species, Jackson described finding up to 16 species of surface foragers in plot A, and an average in plots A and B of 9.6 and 8.3 species per grid-square, an area of 1.25 m² comprising 5 hand-searched quadrats.
She concluded that there were no clearly obvious terrestrial territories, perhaps due to the greater species density, comparing this with Room's (1971) figure of an average 5.7 species per cocoa tree. An added factor was that the arboreal environment had a much greater resource of the food supply provided by Homoptera aggregations. Such aggregations were very low in the herb layer. It appears, however, that no mapping of terrestrial species, e.g. of nest sites, was undertaken. The more recent taxonomic papers (especially those of Bolton 1982 onwards) contain a number of new species which Jackson had collected, both on trees and in leaf litter samples.
©1998 - Brian Taylor CBiol FSB FRES
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