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Local population differences in emergence of cabbage root flies from south‐west Lancashire: implications for pest forecasting and population divergence
Author(s) -
FINCH STANLEY,
COLLIER ROSEMARY H.,
SKINNER GARETH
Publication year - 1986
Publication title -
ecological entomology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.865
H-Index - 81
eISSN - 1365-2311
pISSN - 0307-6946
DOI - 10.1111/j.1365-2311.1986.tb00288.x
Subject(s) - biology , pest analysis , overwintering , divergence (linguistics) , larva , population , ecology , pupa , crop , mating , zoology , botany , demography , linguistics , philosophy , sociology
.1 Emergence of cabbage root fly, Delia radicum (L.), from overwintering populations of puparia collected from twenty‐one sites in south‐west Lancashire, was extremely variable. 2 The patterns of emergence indicated that there were two extreme biotypes, one with early‐ and the other with late‐emerging flies. There was also evidence of an intermediate biotype, tending more to early than to late emergence. 3 This gradient of biotypes, or clinal divergence, was maintained by populations breeding at different times and by females mating close to their sites of emergence. Non‐dispersive females then perpetuated their genotype within their own locality. 4 The time of emergence was not obviously associated with the type of host‐crop on which larvae had developed. 5 The late‐emerging biotype was most prevalent around Halsall. The minimum distance between populations of the late‐ and the early‐emerging biotypes was 16 km. 20 km south‐east from Halsall only half of the fly population was early‐emerging, possibly a result of a displacement of the Halsall biotype by the prevailing NW wind. 6 Regional‐based forecasts will need to take into account the emergence characteristics of the populations to predict the peak periods of cabbage root fly activity adequately in south‐west Lancashire and other areas where emergence patterns differ.