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Fungivorous Pegomya flies: spatial and temporal variation in a guild of competitors

Gunilla Ståhls, Eugenia Ribeiro and Ilkka Hanski
Annales Zoologici Fennici
Vol. 26, No. 2 (1989), pp. 103-112
Stable URL: http://www.jstor.org/stable/23736061
Page Count: 10
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Fungivorous Pegomya flies: spatial and temporal variation in a guild of competitors
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Abstract

Fourteen species of Pegomya (Anthomyiidae) are the only significant primary fungivorous flies breeding in Leccinum (Boletaceae) sporophores in Finland. The length of the thorax in the flies is negatively correlated with the number of flies emerging from a sporophore, suggesting increasing larval competition with increasing numbers of larvae in sporophores. Further evidence of competition is provided by a geographical comparison: in Central Europe there are only 2 species of Pegomya that use Leccinum, but their abundance is as high as the pooled abundance of all Pegomya in Finland, i.e. 20 to 50 flies per sporophore. We demonstrate that Pegomya are intraspecifically aggregated amongst sporophores, which will contribute to the coexistence of many species in spite of competition. In Finland, the number of abundant species is about 7 throughout the country, though the species pool decreases from south (13) to north (7). Predation of full-grown larvae and pupae is also severe and may inflict up to 90% mortality. Prolonged diapause is common in Pegomya in Lapland but not in south Finland, probably because of increasing year-to-year variation in sporophore production with latitude.

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