Age pyramid of a local population and viability fitness of phenotypical fractions in Carabus auronitens (Coleoptera, Carabidae)

Abstract

The population dynamics of a local population of Carabus (Chrysocarabus) auronitens Fabricius, 1792 has been studied in the Westphalian Lowlands on an area of 0.2 ha since 1982. During the activity seasons of this species pitfall traps were opened overnight twice a week. Beetles were individually marked and released again after every capture. In summer 1992 the area was closed by a beetle‐proof fence ‐ C. auronitens is a spring breeder. During the autumn season, freshly hatched beetles are obligatorily active in foraging, whereas surviving old beetles are dormant from the end of the spring season until the next spring season. The probability of surviving from autumn until spring was mostly around 75%; survival probability from the 1st until the 2nd spring season was about 65%; from the 2nd until the 3rd spring about 60%; from the 3rd until the 4th spring about 55%; from the 4th until the 5th spring season about 40%. The phenotypical plasticity of the generations A ‘92, A ‘93 and A ‘94 is described in terms of the following traits: seasonality (date of hatching, start and end of the spring season), body size, post‐ecdysial maturation, weight development during spring and capture rate in the spring seasons. These traits were examined with respect to their influence on individual fitness of viability. The probability of surviving from the autumn until the first spring season was affected in the following way: (1) Time of hatching per se did not influence the survival probability. (2) Early hatching beetles that are small showed an enlarged mortality risk. Concerning the probability of surviving a spring season, it was observed: (3) The individual survival probability was higher, the later a beetle was caught for the first time in a spring season. The relative weight of early appearing females was relatively low at first capture; however, surviving and non‐surviving females of this fraction did not differ with respect to their mean relative weight. (4) Females and males frequently caught in a spring season had a reduced chance of surviving; most of these animals belonged to the fraction of late disappearing specimens. On the other hand, late females and males that had been less frequently caught had a high viability fitness. (5) There were distinct, but non‐uniform influences of body size upon survival probability: in males, the probability of surviving the 1st spring season was highest in a lower middle class of size; the probability of surviving the 2nd spring season was relatively low in small females and males. The main points of discussion are (1) possible objections to the measurement of viability fitness by capture‐recapture data; (2) the heritability of variable phenotypical traits; (3) the question whether the selection‐responding polymorphisms detected can contribute to the genetic adaptation of this local population to environmental changes.