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Egg Hatching and Resource Partitioning in Stoneflies (Plecoptera): Ten British Species in the Family Nemouridae
J. M. Elliott
Journal of Animal Ecology
Vol. 57, No. 1 (Feb., 1988), pp. 201-215
Published by: British Ecological Society
Stable URL: http://www.jstor.org/stable/4773
Page Count: 15
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(1) The objective was to compare variations in egg hatching between three Protone-mura spp., two Amphinemura spp., Nemurella pictetii and four Nemoura spp. (interspecific variations) and between populations of each species (intraspecific variations). There were significant interspecific, but not intraspecific, differences in female size, adult life-span and egg production. (2) There were interspecific, but not intraspecific, differences in the percentage of eggs hatching within the range 3.8-22.1 degrees C in the laboratory; optimum temperatures being 4.7 degrees C (A. standfussi), 6.5-6.7 degrees C (P. montana, N. erratica) and 8.7-9.5 degrees C (P. praecox, P. meyeri, A. sulcicollis, N. pictetii, N. cambrica, N. avicularis, N. cinerea). Over 50% of the eggs hatched in the range 5-15 degrees C, the only exception being A. standfussi (2-9 degrees C for 50% hatched). (3) There were interspecific, but not intraspecific, differences in the incubation period and the length of the hatching period in the laboratory; both variables were adequately represented by a negative power-function in relation to water temperature over the relevant range (3.8-12.1 degrees C for A. standfussi, 3.8-22.1 degrees C for other species). Degree-days could also be used to predict hatching time in P. montana (336 degrees days), N. erratica (356 degrees days), N. cambrica (289 degrees days). For all ten species, the power-functions obtained from the laboratory data provided good estimates of incubation periods for egg batches placed in a Lake District stream. (4) Interspecific differences in egg development in the ten species are related to their different larval habitats and flight periods (months in which adults are present). These differences ensure a continual succession of species throughout the year and a reduction in competition between closely-related species; this reduction being almost total for the cold-water stenotherms (A. standfussi, P. montana, N. erratica) and species living in still or very slow running water (N. avicularis, N. cinerea), but only partial for the remaining species. This investigation and a previous one on six Leuctra spp. (Elliott 1987) provide examples of a physiological mechanism by which complex resource partitioning can occur in closely-related species.
Journal of Animal Ecology © 1988 British Ecological Society