Meeting Abstract
Reproductive behavior in animals can vary seasonally, potentially in part because of seasonal changes in selection pressures on males and/or females. We examined seasonality in mating behavior in a North American species of Opiliones in the Leiobunum clade (animals commonly known as daddy longlegs or harvestmen), for which little is know about behavior or ecology. In general, species in this clade mate face to face, with the male inserting a penis into the female genital opening. Males may chase females prior to mating and guard them afterwards. We provide the first formal description of mating behavior in Leiobunum ventricosum, and test for seasonality in behavior. We collected males and females from a population in Inver Grove Heights, MN in mid-June, the middle of their mating season. They were housed overnight in the lab, and the following day we ran male-female mating trials. We ran a second set of mating trials 15 days later, and then compared the precise timing, frequency, and sequence of mating behaviors between the mid- and late-June trials (e.g., male attempts to mate; female resistance to mating; eversion, insertion, and withdrawal of penis; and male guarding). We found significant increases in male mating attempts, successful copulations, the duration of male mate guarding, and female resistance to male mating attempts. These seasonal shifts in mating behavior may reflect changes in selection due to decreased mate availability later in the season, when we have observed decreased population density in the field. Notably, male attempts and female resistance suggest increased conflict in mating interests in the sexes as the season progresses.
