CORDERO, Alicia M., Museum of Paleontology and Dept. of Integrative Biology, University of California, Berkeley, CA 94720-4780
Within the reproductive tract of many land snails is a dart apparatus that consists of calcareous darts and often a mucus gland. These darts, commonly referred to as "love darts" are incorporated into the courtship sequence of land snails in various ways. Sometimes the dart is ejected from the "shooter" and pierces the body wall of the "recipient." In other cases the dart is ejected from the "shooter" without entering the body of the "recipient." In some snails the dart is retained by the "shooter" and used to jab the "recipient." Many hypotheses have been presented to explain the evolutionary significance of the dart apparatus: (1) it is a calcium gift used to entice the partner to act as female; (2) it is a calcium gift used to entice the partner to act as male; (3) it is an honest signal of mate quality; (4) it facilitates species recognition; (5) it is a means of transporting chemicals to a potential mate; and (6) it is used to prevent unwanted matings. The occurrence of darts in land snails is widely distributed throughout many taxonomic groups, however, nearly all of the detailed observations of the reproductive behavior of land snails have been made on only two closely related helicoid species, Helix pomatia and Helix aspersa. The behavior of other species is largely unknown, but anecdotal reports show that in some species the dart may be used differently than in Helix. In order to determine the role the dart is playing in reproduction and whether or not it has the same role within different clades, the phylogenetic distribution of darts must be known and the behavior of more dart bearing land snails must be investigated.
In this study, I examine the distribution of darts in the helicoid land snail clade. Although the current state of land snail phylogenetic systematics is not ideal for assessing questions of character evolution in a comparative context, two phylogenetic hypotheses of the helicoids have been published. I use both of these trees to map the known dart apparatus characters for members of this group. I will use these results as part of a larger research project in which the refinement of the phylogenetic hypotheses and the incorporation of behavioral data will ultimately allow me to test questions regarding reproductive behavioral evolution and its link with morphology.