1998. P. A. Selden (ed.). Proceedings of the 17th European Colloquium of Arachnology, Edinburgh 1997. Sun, surf and spiders: taxonomy and phylogeography of Hawaiian Araneae Rosemary G. Gillespie, Malia A. J. Rivera and Jessica E. Garb Department of Zoology & Center for Conservation Research and Training, University of Hawaii, 3050 Maile Way, Honolulu, HI 96822, USA Summary The isolation of the Hawaiian archipelago has resulted in a fauna that shows high levels of endemism, and an associated vulnerability to anthropogenic disturbance and alien species invasion. Most of the initial collections of Hawaiian spiders were made by R. C. L. Perkins, and the species described by Eugène Simon. Some groups are represented by single (or a few) species, and may be relictual, or evolutionarily recent introductions. Major radiations are now known in the following groups: (1) the genus Theridion, a poorly known group, except for the single species T. grallator; (2) the genus Tetragnatha, which has been the focus of studies by R. G. Gillespie and colleagues; (3) the genus Argyrodes, which has been the subject of recent studies by M. A. J. Rivera; (4) rep- resentatives of Thomisidae and Philodromidae, which were studied by T. W. Suman, with more recent phylogenetic studies of the Thomisidae being conducted by J. E. Garb; and (5) representa- tives of Lycosidae, best known for their cave adaptations discovered by F. G. Howarth. Preliminary evidence from some of these radiations, based on morphological and/or molecular data, suggests that founder events (and the associated isolation) and adaptive shifts have been involved in species proliferation for at least some groups. Introduction The Hawaiian Islands Remarkable suites of endemic and often rare There are several geographic features that ren- species are characteristics of isolated land der the Hawaiian Archipelago an unparalleled masses. This is particularly true of the Hawaiian scientific laboratory for studying processes of Islands, where extreme isolation has been asso- evolution. First, the extreme isolation of the ciated with accentuation and acceleration of the Hawaiian Islands has allowed repeated and processes of both evolution and extinction. The explosive diversification of species from a biota is well known for its extraordinarily high single ancestor, often accompanied by radical levels of endemism: species frequently occupy shifts in morphology, ecology and behaviour. minute distributional ranges. At the same time, These radiations are associated with high fre- anthropogenic disturbance, either direct or quencies of endemism: more than 81% in birds indirect, is causing rapid species decline. No and an extraordinary 99% in terrestrial molluscs other area in the USA has such a high proportion and arthropods (Eldredge & Miller, 1995; Miller of endemic species nor suffers the impact from & Eldredge, 1996). Second, the tremendous as many new invading species as Hawaii. As a topographical range and consequent environ- consequence, the archipelago represents a mental diversity (wet and dry habitats; bogs, microcosm for studies in evolution and shrublands and forests; elevations from tropical conservation. coastlands to alpine deserts) provide a huge 42 Proceedings of the 17th European Colloquium of Arachnology, Edinburgh 1997 ecological spectrum for species differentiation. Hawaiian spider fauna. “The fauna of this arch- Third, the series of islands provides a replicated ipelago could be considered to be strongly spe- system for examining within-island patterns of cialized and rich relative to its area . The species formation across similar ranges of envi- diverse groups of arachnids here are very ronmental extremes. Finally, because the islands unevenly distributed. Of the 40 or so families are arranged by age from Kauai (oldest) to which are generally recognized today, 31 are Hawaii (youngest), the archipelago allows completely lacking [from the native fauna].” examination of species, formation within an (Simon, 1900). He recognized the speciose identifiable chronological framework (Carson & nature of closely knit lineages in the genera Clague, 1995). The initial stages of population Theridion (Theridiidae, described ten endemic subdivision can be found on the youngest island, species), Tetragnatha (Tetragnathidae, described with the dynamic volcanic state of the island seven endemic species), Sandalodes (Salticidae, providing shifting barriers to gene flow (Carson, described eight endemic species) and several 1990). Later stages in species formation can lineages in the crab spider families Thomisidae generally be found on the older islands. Upon and Philodromidae. Simon also recognized that this palette, the primary factors responsible for many (if not all) of the taxa with distributions generating the high diversity of endemic species outside Hawaii were probably introduced. are: (1) small population sizes, (2) species inter- Recognition of this has become increasingly actions, and (3) habitat fragmentation. important as the onslaught of alien species has risen dramatically in recent years. History of arachnology in Hawaii Understanding of the biological associations and evolutionary origins of species that currently The pioneering work on the Hawaiian fauna occur on the islands is critically important to the was carried out by R. C. L. Perkins, who was interpretation of any biogeographic study. sent out to the islands from the UK in the late Until very recently, the only work that had 1800s. He spent over ten years in Hawaii, col- been carried out on the native Hawaiian spiders lecting just about everywhere, and against all since the time of the Fauna Hawaiensis (Simon, odds: “I was obliged to carry a limited supply of 1900, 1904; Perkins, 1913) was that of Ted oil and a small oil stove on account of the diffi- Suman (1970), who worked on the crab spider culty or impossibility of making a fire . during families Thomisidae and Philodromidae. Here, the continuous and heavy rains . for the pur- we discuss some of the recent work that has pose of cooking rice. This with coffee and sugar been, and is being, conducted on Hawaiian and one or two kinds of tinned meats (in addi- spiders, a group that is providing fascinating tion to a tent, clothing and apparatus) will be found as much as the collector will care to pack insights into patterns and processes of evolution. in so rough a country, and I found the stove and The biogeographic pattern that predominates oil a sore burden, very reluctantly assumed.” in most Hawaiian taxa is a tendency for both (Perkins, 1913). species proliferation and population differentia- Perkins’s contribution to Hawaiian biology tion to occur in a step-like manner down the was such that his work is still a primary refer- island chain from the oldest to the youngest ence for many of the Hawaiian insect groups. islands. In addition, species (or populations) Unfortunately, by his own admission, his collec- tend to have the narrowest ranges on the older tion of spiders was very inadequate. He spent islands (Gillespie, 1997). Species on the more than half his time collecting birds, the rest youngest island (Hawaii) tend to be widely dis- of the time looking for insects, the spiders all tributed over the island (in some groups these being collected while he was involved in pursuit species are shared with Maui). A number of dif- of the latter. ferent within-island patterns have been superim- Perkins sent his collection of Hawaiian posed on these general patterns. Here we discuss spiders to Eugène Simon at the Muséum two broad categories of patterns found in the National d’Histoire naturelle in Paris. Despite native Hawaiian taxa: (1) Singleton species— the paltry representation of many species, Simon single representatives of a lineage throughout recognized the extraordinary nature of the the islands, and (2) Species radiations. Gillespie et al.: Hawaiian Araneae 43 Singleton species Gillespie, 1991a, 1992a, 1994); (2) the genus Argyrodes (Simon, 1900; Rivera, in prep.); A number of species of spiders have been (3) representatives of the crab spider families described recently from Hawaii that have wide- Thomisidae and Philodromidae (Suman, 1970; spread distributions and have not differentiated Garb, in prep.); (4) the genus Theridion (Simon, in the archipelago. This is particularly true at 1900); and (5) representatives of the wolf spider low elevations, where almost all of the spiders family Lycosidae (Gertsch, 1973). Radiations are introduced. It is also likely that all of the may also exist in the genus Sandalodes native Hawaiian spider fauna is endemic. (Salticidae) and Cyclosa (Araneidae), although Among the endemic fauna are a number of there is little conclusive evidence for these lineages represented by single species. These groups. Recent work by Gustavo Hormiga (pers. may be recent introductions, or relicts from comm.) suggests that there are more species in largely extinct radiations. the genus “Labulla” (Linyphiidae) than the two Single representatives among relictual taxa. originally described by Simon (1900). Certain taxa are characterized by a suite of apo- morphies, which, in some cases, has even caused them to be placed in monotypic genera. Systematic status of radiations For example, Doryonychus raptor (Tetragnathidae) 1. Theridion. Radiation within the genus has abandoned the web-building behaviour Theridion is well known, but again, little work characteristic of the family, and developed long has been done on this group, and many species claws