COMPARATIVE BEHAVIORAL ECOLOGY OF THE SPIDER THERIDION GRALLATOR (SIMON) (ARANEAE : THERIDIIDAE) IN THE HAWAIIAN ARCHIPELAGO (EVOLUTION, ETHOLOGY, ARACHNID, SPECIATION).

摘要

Theridion grallator is endemic to mesophytic forests on O'ahu, Moloka'i, Maui and Hawai'i islands, in lower vegetational strata. Island populations show morphological differences, so a comparative study of the behavioral ecology of three populations on Maui (Makawao site) and Hawai'i (Puna and Manuka sites) was undertaken (1980-1984).;The spiders capture organisms which take shelter sub-foliarly. The spiders utilize leaf-borne vibrations in leaftop hunting without direct use of web-borne vibrations. The populations differed in responses to standardized vibrations. This extrinsic prey-monitoring system may explain web reduction. The Maui spiders forage for Cibotium sporangia. This facultative herbivory seems population-specific.;Captive birds ate Theridion grallator. Immature spiders were vulnerable to Lispocephala flies, which also are competitors. However, adult female spiders captured Lispocephala. This may explain maternal-specific foraging behaviors of T. grallator.;Theridion grallator exhibits a specialized cryptic diurnal posture. Two postural themes (linear and splayed) were described for six species of sub-foliar spiders. The diversity of taxa argues for convergence of cryptic function.;The spiders live under individual leaves of a subset of plant species (e.g., Broussaisia, and Osmanthus), showing distributions limited vertically and correlating with light intensity. Inter-populational differences were quantified. Spiders increased movement frequency and distance to vacate inappropriate sites, and chose distal, cryptic leaf sites exhibiting small-scale concavities. The importance of the three leaf site parameters is age-dependent. The spiders responded posturally to inclement weather.;Male spiders detect the status of conspecific web occupants via web-borne or leaf-borne cues. Males cohabit with and guard females, engaging in leg-grappling contests. Size affected contest outcome. Post-fighting copulation suggests sperm-precedence.;Inter-populational differences in male courtship were reflected by female responses to allo-populational males. Inter-island courtships never yielded copulations. Intra-island courtships demonstrated courtship success asymmetries or yielded copulations. Intra-island (Maui) copulatory courtships involved populations along a homogenous habitat band. Unsuccessful intra-island courtships (Hawai'i) involved populations separated by habitat breaks.;Maternal spiders feed and protect offspring. A low clutch size population (Puna) showed extended nurturing, larger dispersing offspring and greater competitive ability, relative to two other populations. Females accepted unrelated offspring. Parasitism by Baeus wasps may affect egg case topology.