EXPERIMENTAL-ANALYSIS OF REPRODUCTIVE ISOLATION OF 2 SYMPATRIC SPECIES OF SPIDERS - LYCOSA-THORELLI (KEYSERLING) AND LYCOSA-CARBONELLI COSTA-ET-CAPOCASALE

Four experimental groups were used: (A) males Lycosa thorelli x female L. thorelli; (B) male Lycosa carbonelli x female L. carbonelli; (C) Male L. thorelli x female L. carbonelli; (D) male L. carbonelli x female L. thorelli. Males were placed in a field with conspecific sexual pheromone and confronted to anesthetized virgin females. Male L. thorelli showed a greater tenacity than male L. carbonelli in the maintenance of the copulatory position. The typical copulation pattern (intraspecific groups) became atypical in interspecific groups. Only one typical interspecific copulation was observed in group C. Male L. carbonelli showed a good specific discrimination when mounting the female, while male L. thorelli showed a low discrimination level. The maintenance of the copulatory position could be determined by a modal number of ejaculations in the case of male L. carbonelli and by a modal duration in the case of male L. thorelli. Atypical copulations might indicate a mechanical incompatibility between the genitalia of the two species. Typical copulations produced offspring, indicating the absence of postcopulatory isolation mechanisms.