Control of Fecundity in Pieris rapae. V. Comparisons Between Populations

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Abstract
(1) It was found previously that genetic variation for larval development rate in P. rapae is restricted within a fixed pattern. The same pattern of variation applies to pupal development rate too. (2) Australian, British, Canadian, French, Italian and Spanish P. rapae have the same temperature thresholds, development rates and pupal weights: but there are intrinsic differences between populations for adaptation to host plants, and for timing of entry into-and emergence from-diapause. (3) In insects, the temperature thresholds and heat requirements for development and for postdiapause emergence, obey general rules. (4) The empirical results, in this and previous papers, contradict the orthodox theory of natural selection, which considers only the genetic variation between individuals. An extended theory, incorporating a second level of genetic variation, accounts for the ecological observations and for the widespread occurrence of sexual reproduction.