Adaptive latitudinal variation of the duration and thermal requirements for development in the ground beetle Amara communis (Panz.) (Coleoptera, Carabidae)

Abstract

The data are obtained on development time at six constant temperatures (12, 14, 16, 18, 20, 22°C) and thermal requirements for preimaginal development in a ground beetle Amara communis from Arkhangelsk (64°34′N) and St. Petersburg (59°53′N). The larval and pupal development times were found to be significantly shorter in the Arkhangelsk than in the St. Petersburg population under all temperatures. As a result, total preimaginal development appeared to be shorter by 6.2–6.6% in the Arkhangelsk population. The regression lines of the larval, pupal and total (egg-to-adult) development rate on temperature for the Arkhangelsk population run above and steeper than the respective lines for the St. Petersburg population. Both populations share the similar values of the thermal thresholds (7.2–8.2°C). This explains faster preimaginal development in the northern population under all temperatures above the threshold. Thus, the slope of the regression lines increases, i.e., the sum of degree-days decreases, whereas the thermal threshold for development exhibited no distinctive changes from south to north in this species. Adults from Arkhangelsk reared in the experiments appeared heavier on the average in comparison with those from St. Petersburg, especially at 18–22°C. Temperature did not significantly affect adult weight, except the fact that the beetles were slightly heavier at 20 and 22°C. Consequently, the well-known “temperature-size rule” is violated in this species. Relative growth rate in larvae of A. communis increased considerably with temperature rise from 14 to 22°C. It was significantly higher in the beetles from Arkhangelsk at 18–22°C. There were no differences in larval growth rate between the two populations at 14 and 16°C.