New Species of Endemic Kleptoparasitic Spiders of the Genus Argyrodes (Araneae: Theridiidae) in the Hawaiian Islands

This study examined the endemic species of kleptoparasitic spiders in the genus Argyrodes from the Hawaiian Islands, a lineage previously known in the archipelago from only a single described species, Argyrodes hawaiiensis Simon. Here, two additional endemic species are described, A. ilipoepoe Rivera and Gillespie, n. sp., and A. laha Rivera and Gillespie, n. sp., with their biogeographical patterns, and the allotype female and paratypes of A. hawaiiensis are designated. As with A. hawaiiensis, both new species are commonly found as kleptoparasites on the sheet webs of large nocturnal spiders in the genus Orsonwelles (Linyphiidae). Hawaiian Argyrodes are characterized by small and rounded abdomens, unpronounced clypeal projections, and variably long fangs. Argyrodes hawaiiensis; A. ilipoepoe, n. sp.; and A. laha, n. sp., include all the known endemic representatives of the group in the Hawaiian Islands, which mostly occur in wet and mesic forests. The Hawaiian archipelago is well known for being host to many diverse terrestrial arthropod assemblages, yet many of these lineages, including those of the endemic spider fauna (Gillespie et al. 1998, Gillespie 1999), have remained poorly understood. Although work on Hawaiian spiders has recently had an increased focus, efforts have largely been limited to groups with extensive species radiations, for example those in the genera Tetragnatha Latreille (Tetragnathidae) (Karsch 1880, Simon 1900, Okuma 1988, Gillespie 1991, 1992, 1994, 2002, 2003), Mecaphesa Simon (Thomisidae) (Simon 1900, Suman 1970, Lehtinen 1993, Garb 1999), and Orsonwelles Hormiga (Linyphiidae) (Hormiga 2002). More recently, a small group of endemic spiders has been discovered in the Hawaiian Islands that belongs to the genus Argyrodes Simon (Theridiidae). The genus Argyrodes is a part of the subfamily Argyrodinae, a large and cosmopolitan lineage of well over 200 described species worldwide that contains spiders with a diverse array of morphological features and foraging behaviors, including kleptoparasitism and free-living araneophagy (Exline and Levi 1962, Whitehouse 1987, Cangialosi 1997). Taxonomic relationships within the Argyrodinae have been a subject of debate over the last several decades, resulting in several of the originally described genera being collapsed into the single composite genus Argyrodes by Exline and Levi in 1962. However, a number of researchers did not agree with the composite designation and recent cladistic investigations have resulted in the resurrection of five of these genera (Agnarsson 2004). Today, in addition to the genus Argyrodes, several genera (Ariamnes Thorell; Rhomphaea Koch; Faiditus Keyserling; Neosphintharus Exline, 1950; Spheropistha Yaginuma, 1957) are again recognized in the subfamily Argyrodinae, and cladistic support is provided for the Pacific Science (2010), vol. 64, no. 2:221–231 doi: 10.2984/64.2.221 : 2010 by University of Hawai‘i Press All rights reserved 1 This work has been supported by grants from the Ecology, Evolution, and Conservation Biology Program and the Haumana Graduate Program at the University of Hawai‘i at Mānoa. Manuscript accepted 14 July 2009. 2 Hawai‘i Institute of Marine Biology, University of Hawai‘i at Mānoa, 46-007 Lilipuna Road, Kāne‘ohe, Hawai‘i 96744 (phone: 808-235-9301; fax: 808-235-9300; e-mail: [email protected]). 3 Environmental Science, 137 Mulford Hall, University of California, Berkeley, CA 94720. monophyly of the group (Yoshida 2002, Agnarsson 2004). In Hawai‘i, taxonomic treatments of endemic spiders primarily have been limited to the early descriptions of Simon (1900) and collections of Perkins (1913). In fact, Argyrodinae spiders in the Islands were known from only two species, A. hawaiiensis Simon and Ariamnes corniger Simon. Recently, Gillespie and Rivera (2007) described 10 new endemic species of Hawaiian Ariamnes, a diverse lineage of the subfamily Argyrodinae that appears to have undergone an adaptive radiation in the Islands. The endemic Ariamnes spiders are generally free-living nocturnal araneophages, though some may be facultative kleptoparasites on the sheet webs of the linyphiid spiders of the genus Orsonwelles. Although the genus Ariamnes contains many diverse endemic species in the Islands, the current study reveals that the endemic members of Hawaiian Argyrodes are limited to only three species. All three appear to be obligate kleptoparasites and to date have been found occurring only in the sheet webs of endemic Orsonwelles species. Despite their close relationship to Ariamnes, the Hawaiian Argyrodes can easily be distinguished by their fundamentally different body forms. Kleptoparasites are very small with rounded abdomens, whereas the free-living araneophages are generally larger, with variably long, slender abdomens. An introduced kleptoparasitic species, Argyrodes argentatus O. P. Cambridge, is also present in the Hawaiian Islands (Beatty 2000) and to date has commonly been found kleptoparasitizing both the orb webs of introduced spiders and the sheet webs of endemic Orsonwelles. Argyrodes argentatus is widely distributed from Madagascar through Southeast Asia and South America (Cambridge 1880, Exline and Levi 1962) and is easy to distinguish from the Hawaiian species. Argyrodes argentatus has been treated extensively elsewhere (Cambridge 1880, 1897, Exline and Levi 1962, Chrysanthus 1963, Zhu and Song 1991). The current study focuses only on the Hawaiian endemic members of the genus Argyrodes and is the second of two descriptive papers of Hawaiian Argyrodinae. materials and methods Morphological measurements were made according to Exline and Levi (1962) on the shape of the carapace, clypeus, fangs, and abdomen. The length of the whole body, carapace, abdomen, and segments of the first leg; the form and organization of the genitalia of both males and females; and the abdominal coloration pattern were also examined for gross morphology. All measurements and illustrations were made with the aid of a camera lucida. Ten to 20 specimens of each species were assessed, and six to 12 individuals per species were measured for variation. Abbreviations are as follows: TL, total length; CL, carapace length; AL, abdomen length; FeI, first femur; FeII, second femur; FeIII, third femur; and TaI, first tarsus. Genitalia of females were dissected from the abdomen using a fine scalpel and tissue dissolved by treatment with a 35% KOH solution for approximately 5 min., followed by several rinses in distilled water. In addition to illustrations, measurements of the epigynes were made with a dissecting microscope equipped with a metric-ruled eyepiece. Dissected epigynes were then placed in microvials along with the female specimen. Palps of males were examined by positioning the specimen under the microscope to allow a ventral view of the palpal organ without having to remove the palp from the body. This was done with the aid of fine sand to hold the spider in place for illustration and measurement. To complement the type descriptions and illustrations, scanning electron microscopy was used to examine the palps of paratype males from each of the species. Palps were removed from the specimen, placed in capsules, submerged in an alcohol series (70%, 85%, 95%, and 100%), and dried using a critical point drier (Autosamdri-810). Palps were then placed on stubs with silver paste, sputter coated with gold, and viewed with an SEM (Hitachi S-800). Holotype male and allotype female specimens of the new species were deposited at the Bernice Pauahi Bishop Museum in Honolulu, Hawai‘i (bpbm); all para222 PACIFIC SCIENCE . April 2010