RELATIONSHIP BETWEEN REPRODUCTIVE SECURITY AND INTERSEXUAL SELECTION IN A JUMPING SPIDER PHIDIPPUS JOHNSONI (ARANEAE: SALTICIDAE).

Abstract

The jumping spiders (Salticidae) are noted foir their highly developed vision (Land, 1972), sexually dimorphic and often extravagant coloration, and elaborate courtship displays in which the males dance, gesture, and posture in front of the watching females (Crane, 1949). Early interest in these spiders was very much associated with debate over the importance of sexual selection (e.g., Poulton, 1890; Wallace, 1890). Peckham and Peckham (1889, 1890, 1909) described the displays of many North American species and used their observations to support the Darwinian concept that choice by females of males with particular characteristics (intersexual selection) has been an important evolutionary process. During subsequent years, interest in sexual selection apparently subsided; but after the clarification of certain concepts, such as proximate and ultimate causation (Mayr, 1961), that were blurred during earlier discussions, interest in sexual selection has again become intense (Campbell, 1972; Blum and Blum, 1979). However, current studies of salticid sexual behavior have been little affected by this renaissance. The early objections to the Peckhams' assertions concerning female choice were multiple and complex, and many of these do not presently seem very germane. However, two stand out as particularly damaging. (1) The Peckhams made many of their observations under laboratory conditions with spiders in abnormally high densities. Under these conditions, females sometimes rejected courting males, but the Peckhams provided few data concerning the characteristics of the rejected males. (2) Later workers often indicated that salticid females mate only once, that females probably encounter courting males in nature one-at-a-time, and that females tend to copulate with the first conspecific male that courts. During the course of a recent study of the mating strategy of a North American salticid, Phidippus johnsoni Peckham and Peckham (Jackson, 1980), I made some observations that are relevant to these two objections. It was found that females of this species sometimes copulate with more than one male, and two specific hypotheses were suggested by the data: (1) females of P. johnsoni discriminate between males and copulate preferentially with ones having particular characteristics, and (2) non-virgin females discriminate more strongly than virgin females.