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A comparison of the capacity for increase at a low temperature of foreign and Australian populations of Sitophilus oryzae (L.) and S. granarius (L.)
Author(s) -
EVANS D. E.
Publication year - 1979
Publication title -
australian journal of ecology
Language(s) - English
Resource type - Journals
eISSN - 1442-9993
pISSN - 0307-692X
DOI - 10.1111/j.1442-9993.1979.tb01201.x
Subject(s) - sitophilus , biology , range (aeronautics) , ecology , zoology , horticulture , botany , composite material , materials science
The capacity for increase (r c ) of three populations of S. oryzae and three populations of S. granarius from Great Britain and Canada was determined over 15 and 24 weeks respectively at 15°C in wheat of 14% moisture content. The fertility of these populations at 27°C, their body weight and chill‐coma threshold was also measured. With both S. oryzae and S. granarius , values of r c for the foreign populations fell within the range previously observed when several Australian populations were reared under the same conditions. The cohort generation times (T c ) of the foreign S. oryzae populations were significantly shorter than those of the Australian populations because of the shorter immature development periods ( D ) of the former. Two of the foreign S. granarius populations had lower values for D than all but one of their Australian counterparts but their values of T c were within the range previously observed for Australian weevils. When the Australian and foreign populations were considered together, the value of r c was more strongly correlated with fertility at 27°, an optimal temperature, than with body weight in both S. oryzae and S. granarius. With S. oryzae , r c was correlated with the chill‐coma threshold of cold‐acclimated weevils only. There were no correlations between r c and chill‐coma thresholds in S. granarius. It was concluded that the observed differences in r c were related to differences in the vigour of the populations rather than to physiological differences in cold‐tolerance. The likelihood of grain weevils becoming cold‐tolerant as a result of grain aeration is discussed and the practical significance of differences in r c considered.