Structural constraints of secondary asymmetry in male externalgenitalia of Noctuidae

摘要

The basic architecture of the external genitalia of Noctuidae ("genital capsula") is bilaterally symmetric. Secondary asymmetry is well-known in different subfamilies and tribes. We review and interpret the functions and processes which may be responsible for secondary asymmetry (i.e., dissymmetry) of these structures in terms of structural vs. behavioural working hypotheses. We consider the genital structures as correlated elements of a complex structure ("bauplan") in which some changes in detailscan be explained by selection due to optimization of the reproductive success. Major pathways of changes are, however, delimited by some structural constraints which appear in parallel in different phyletic lines of trifine Noctuidae. One of these constraints is the subsistence of symmetry in structures with own musculature. On the other hand, some rigid parts without own musculature can evolve more rapidly and divergently in connection with the different allocation of functions. Such asymmetric structures may have some selective advantages due to the more effective stimulation, on one side, and fixation of genital parts during copulation, on the other. Asymmetric structures can effectively enhance the variations of the spatial geometry but without change of the "bauplan" which can be preserved in parallel in different taxonomical groups. It means that the originally symmetric "bauplan" with its homologies can be considered as a phyletic "heritage", while the functional dissymmetrisation driven by selective optimization is the "habitus" in which numerous homoplasies can occur.