Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Atlantic lowlands |
Pacific lowlands |
Identification
Minor worker (La Selva): head length 0.54mm, head width 0.47mm, scape length 0.39mm, Webers length 0.67mm (n=1). Head somewhat flattened behind; promesonotum evenly arched, mesonotal suture absent; propodeal spines small but distinct; face smooth and shining, pronotum feebly punctatorugose dorsally, with large smooth and shiny patches on sides, mesonotum and propodeum foveolate; dorsal pilosity abundant, short, suberect, flexuous; color orange.
Major worker (La Selva): head length 1.04mm, head width 0.78mm, scape length 0.42mm (n=1). Anterior margins of frontal carinae in the form of distinct teeth, elevated and projecting from face; face entirely and coarsely punctatorugose, vermiculate rugae obliquely oriented in middle, irregular on sides, and transverse on vertex lobes; hypostomal margin nearly flat, with pair of sharp teeth located about one third distance from midline to recessed teeth flanking mandibles; dorsal pilosity abundant, short, somewhat lanose; sides of head with appressed to subdecumbent short pilosity, without conspicuous erect setae.
Variation: major workers from the Pacific side of Costa Rica have relatively wider heads (head length 1.06mm, head width 0.91mm, n=1), the hypostomal margin more concave, and the hypostomal teeth much smaller (n = 4 Pacific slope collections, 3 Atlantic slope collections).
Range
Panama (type locality Bugaba), Costa Rica (Atlantic and southern Pacific lowlands).
Natural History
This species is an obligate inhabitant of Piper myrmecophytes. Nests are in the clasping petioles, and may extend into the stem. Longino observed a colony in Corcovado National Park with 45 major workers, 70 minor workers, 7 adult males, 1 dealate queen, and brood. Most colonies observed by Longino have been monogynous, but one at Carara (Bijagual) was polygynous.
This species has been the subject of extensive ecological studies by Letourneau:
Letourneau, D. K. 1983. Passive aggression: an alternative hypothesis for the Piper-Pheidole association. Oecologia 60:122-126.
Letourneau, D. K. 1990. Code of ant-plant mutualism broken by parasite. Science 248:215-217.
Letourneau, D. K. 1991. Parasitism of ant-plant mutualisms and the novel case of Piper. Pp. 390-396 in C. Huxley and D. Cutler, eds. Ant-Plant Interactions. Oxford University Press, Oxford.
A recent study is:
Fischer, R. C., Wanek, W., Richter, A. and Mayer, V. 2003. Do ants feed plants? A 15N labelling study of nitrogen fluxes from ants to plants in the mutualism of Pheidole and Piper. Journal of Ecology 91:126-134.
The summary is as follows:
1 Nutrient fluxes play a significant role in the interaction of myrmecophytic plants and their symbiotic ants. There is a clear flux from plants to ants via nectar or food bodies but nutrient fluxes from ants to plants are less obvious.
2 We report on a nitrogen flux from ants to plants in the association between Pheidole bicornis (Formicidae-Myrmicinae) and two myrmecophytic Piper species (P. fimbriulatum and P. obliquum, Piperaceae). Pulse experiments were performed by feeding ants with 15N-labelled glycine supplied in sucrose solution. Workers passed ingested label on to other ants and the brood by trophallaxis.
3 The distribution of label within the colony showed highest incorporation rates in larvae and in the working caste, while the reproductive caste received only a small amount of the 15N-labelled food.
4 Nutrient transfer from ants to plants occurred remarkably fast. Within 6 days, up to 25% of the nitrogen ingested by the ants was incorporated by the plants.
5 However, ant distribution within P. fimbriulatum plants did not correlate with the intra-plant uptake pattern of 15N, and ant-mediated nitrogen uptake by myrmecophytic P. fimbriulatum accounted for less than 1% of the plants' above-ground nitrogen demand.
Page authors:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu
Stefan Cover, Museum of Comparative Zoology, Harvard University, Cambridge MA 02138 USA. scover@oeb.harvard.edu
Date of this version: 3 March 2003.
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