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Recruitment, kin and the spatial genetic structure of a caddisfly Plectrocnemia conspersa in a southern English stream
Author(s) -
WILCOCK HELEN R.,
BRUFORD MICHAEL W.,
HILDREW ALAN G.,
NICHOLS RICHARD A.
Publication year - 2005
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1111/j.1365-2427.2005.01424.x
Subject(s) - caddisfly , biology , larva , ecology , population , microsatellite , genetic structure , spatial distribution , zoology , streams , population genetics , genetic variation , geography , demography , allele , remote sensing , sociology , gene , computer network , biochemistry , computer science
Summary 1. Our objectives were to examine small‐scale patterns in oviposition and genetic relatedness in a population of the stream‐dwelling caddis Plectrocnemia conspersa and, in particular, to look for any evidence of the spatial proximity of close kin and, therefore, ‘patchy recruitment’. 2. In order to examine the distribution of related larvae at the beginning of the aquatic phase, we searched the stream for egg masses. Spatially and temporally structured samples of larvae were then collected from the stream over four sample dates within one generation. The genetic relatedness of these field‐collected larvae, estimated using six polymorphic microsatellite loci, was subsequently compared with that of larvae reared from individual egg masses in the laboratory. 3. Egg masses were laid in clusters or ‘hot spots’ along the stream. The mean relatedness coefficient within reared egg masses ranged from 0.327 to 0.525, and differed significantly from that estimated for the population as a whole (0.070), indicating that the markers were sufficiently powerful to identify groups of siblings. Each egg mass was likely to be the progeny of one father, although the possibility of a small contribution from a second male could not be excluded for a few masses. 4. Mean relatedness within the spatially structured groups of larvae in the stream, even those in close proximity to each other, did not differ from the background population level estimate, suggesting that siblings disperse away from each other very quickly and that kin structure does not persist over time. 5. Changes in spatial genetic structure late in the larval life indicated that neighbouring larvae were less closely related than the population overall, possibly suggesting some direct or indirect means of avoiding kin when approaching the onset of pupation. 6. Our counts of egg masses suggested that survival through the egg stage and early larval life was apparently very high (>50%) for a non‐social insect, and may be a consequence of the colonial net that is briefly occupied by first instar larvae. 7. The number of egg masses laid in the stream (approximately 400 in the sample year), the lack of a spatial genetic structure showing evidence of families even early in larval life, and the high survival of eggs and early instar larvae, all refute the ‘patchy recruitment hypothesis’ for this species.