Premium
Thermal Requirements for Development in Chrysopa Oculata: A Geographically Stable Trait
Author(s) -
Tauber Catherine A.,
Tauber Maurice J.,
Nechols James R.
Publication year - 1987
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1939231
Subject(s) - diapause , biology , voltinism , trait , ecology , larva , computer science , programming language
Chrysopa oculata from five widespread localities (southern Canada to montane Mexico), exhibited remarkable similarities in their thermal requirements for nondiapause development. Lower thermal thresholds (t) varied by only 1.2°C., and the degree—days required for total preimaginal development (K) differed among the populations by °85°d. Despite the similarities among populations, the results suggest that the thermal requirements for development are genetically variable. However, two factors may limit the geographical expression of this variation: (1) the multivoltine life cycle could result in seasonal oscillations in the magnitude and projection of directional selection on the nondiapause thermal responses, and/or (2) the thermal thresholds for development and the rates of development above the thresholds may be functionally correlated and constrained in their evolution. Males from all populations emerged slightly but consistently earlier than females. Temperature did not affect sex or survival, other than at 15.6.° where mortality was significantly increased. Among the five populations, only one large difference occurred in the thermal responses; under low temperatures, a relatively high proportion of the two northern populations entered diapause. The differences in diapause induction resulted from the differential effect of temperature on the critical photoperiod for diapause induction, rather than on the developmental rates.