Spider Biodiversity Patterns and Their Conservation in the Azorean

Systematics and Biodiversity 6 (2): 249–282 Issued 6 June 2008 doi:10.1017/S1477200008002648 Printed in the United Kingdom C The Natural History Museum ∗ Paulo A.V. Borges1 & Joerg Wunderlich2 Spider biodiversity patterns and their 1Azorean Biodiversity Group, Departamento de Ciências conservation in the Azorean archipelago, Agrárias, CITA-A, Universidade dos Açores. Campus de Angra, with descriptions of new species Terra-Chã; Angra do Hero´ısmo – 9700-851 – Terceira (Açores); Portugal. Email: [email protected] 2Oberer Häuselbergweg 24, Abstract In this contribution, we report on patterns of spider species diversity of 69493 Hirschberg, Germany. the Azores, based on recently standardised sampling protocols in different hab- Email: joergwunderlich@ t-online.de itats of this geologically young and isolated volcanic archipelago. A total of 122 species is investigated, including eight new species, eight new records for the submitted December 2005 Azorean islands and 61 previously known species, with 131 new records for indi- accepted November 2006 vidual islands. Biodiversity patterns are investigated, namely patterns of range size distribution for endemics and non-endemics, habitat distribution patterns, island similarity in species composition and the estimation of species richness for the Azores. Newly described species are: Oonopidae – Orchestina furcillata Wunderlich; Linyphiidae: Linyphiinae – Porrhomma borgesi Wunderlich; Turinyphia cavernicola Wunderlich; Linyphiidae: Micronetinae – Agyneta depigmentata Wunderlich; Linyph- iidae: Erigoninae – Acorigone gen. nov. with its type species Acorigone zebraneus Wunderlich; Clubionidae – Cheiracanthium floresense Wunderlich; Cheiracanthium jorgeense Wunderlich; Salticidae – Neon acoreensis Wunderlich. Other major taxonomic changes are: Diplocentria acoreensis Wunderlich, 1992 (Linyphiidae) is transferred to Acorigone (comb. nov.), Leucognatha Wunderlich 1995 (Tetragnathidae) is not an endemic genus of the Azores but an African taxon and synonymous with San- cus Tullgren, 1910; Leucognatha acoreensis Wunderlich, 1992 is transferred to San- cus. Minicia picoensis Wunderlich, 1992 is a synonym of M. floresensis Wunderlich, 1992. For each species additional information is presented about its known distribution in the islands, its colonisation status, habitat occurrence and biogeographical origin. Key words Araneae, Azores, biodiversity patterns, biogeography, cave species endemic, islands, new taxa, Macaronesian Islands, spiders Introduction Due to the ability of many families of spiders to disperse over long distances using wind currents (‘ballooning’) these Spiders (Araneae) are an important component of arthropod organisms easily colonise isolated island archipelagos like the faunas (Wise, 1995), with their predatory behaviour being, for Azores and should have disproportionally higher species di- instance, of great relevance for biological control in agroe- versity. However, spiders are not a particularly attractive arth- cosystems. Members of this order play an important role ropod group for humans, and their current world and Azorean in most terrestrial foodwebs, may be very abundant in sev- taxonomic knowledge are far from being satisfactory. For in- eral habitats and are among the most numerous arthropods stance, in the Azores the rate of new species records and new from many samples in all kinds of habitats in the Azores species description indicates that only recently are we achiev- (Borges & Brown, 2001, 2004) and elsewhere (Basset, 1991). ing a satisfactory picture of the Azorean spider diversity (see Moreover, despite the importance of spiders in terrestrial eco- more details below). systems, in both species richness and abundance, this arachnid The difficulty in spider biodiversity assessment in the group is rarely considered in evaluating networks of protec- Azores seems to be related to the absence of historical ted areas (but see Skerl, 1999; Cardoso, 2004; Borges et al., expeditions focusing only on this group of arthropods and 2005a). on the high richness and variability in microhabitats they occupy. Historical investigations include the works of Denis ∗Corresponding author. (1964), that reported 70 species for the archipelago, and 249 250 Paulo A.V. Borges & Joerg Wunderlich Figure 1 Map of the studied region, showing the nine islands of the Azores. Wunderlich (1992), who listed 103 species and a few inde- and biogeographical origin; (iii) to estimate spider species rich- termined taxa. Special sampling protocols and a standardised ness in the Azores; and (iv) to plan some suggestions for the sampling of different habitats are urgently needed for the conservation of Azorean spider diversity. adequate inventory of spiders and other arthropod groups in the Azores. This contribution is part of a larger study conducted since 1998 in the Azorean islands (Project BALA – Materials and methods Biodiversity of the Arthropods of the Laurisilva of the Azores) (see Borges et al., 2000a, 2005a) that aims to Area of study: The Azores survey the Azorean arthropod fauna using standardised The Azorean Islands are volcanic in origin being located in the sampling protocols at different spatial scales covering most North Atlantic, roughly between the coordinates 37◦ to 40◦ N protected areas and native forests in seven of the nine Azorean latitude and 25◦ to 31◦ W longitude (Fig. 1). This archipelago islands. For this current contribution we use as a starting comprises nine main islands and some small islets and is point the last list of Azorean spiders (Wunderlich, 1992), located at the triple junction between the African–Eurasian and include data from recent field studies in pasturelands and North-American plates, emerging from the Azores Plat- (Borges, 1999; Borges & Brown, 1999, 2001, 2004), cav- eau, a topographic and gravity high near the Mid Atlantic ernicolous fauna (Borges & Orom´ı, in press), native forest ridge (MAR). The archipelago is situated over two tectonic and grassland habitats (Borges et al., 2000b, 2005a), and plates: the westernmost islands of Flores and Corvo lie over fruit orchards (Santos et al., 2005). The recently published the American plate and are separated from the eastern islands updated list of Azorean fauna and flora (Borges et al., 2005b) by the Mid-Atlantic Ridge (MAR); the other seven main is- also includes a revised list of Azorean spiders (Borges & lands are located in a large triangular plateau with a com- Wunderlich, 2005) that is reproduced with some updates and plicated structure known as ‘Azores Plateau’ (Nunes, 1999; additional information (e.g. new records, habitat distribution, França et al., 2003). The distance between the Azores and biogeographical origin) in Appendix 1 (which is available the European mainland is about 1584 km, calculated from as “Supplementary data” on Cambridge Journals Online: Cabo da Roca (the most westerly point of the European con- http://www.journals.cup.org/abstract_S1477200008002648) tinent). The nine islands are divided into three groups: the and will be the basis of our biodiversity pattern analysis. occidental group of Corvo and Flores; the central group of Studies on island biodiversity and island biogeographical Faial, Pico, Graciosa, Sao˜ Jorge and Terceira; and the oriental patterns for spiders are scarce globally (but see Baert & Jocque,´ group of Sao˜ Miguel and Santa Maria, plus the Formigas islets 1993; Real et al., 1999; Schoener et al., 2003). Therefore, (Fig. 1). The largest island is S. Miguel (757 km2), and the we are trying to make some headway by investigating some smallest is Corvo (17 km2). S. Maria is the southernmost island biodiversity patterns in the Azorean spider fauna. (37◦N, 25◦W), and Flores is the westernmost one (31◦W). The The purposes of this work are: (i) to update all the tax- most northerly one is Corvo (39, 7◦N). The distance between onomy data of the Azorean spider fauna, describing new taxa, Corvo and Santa Maria, the islands farthest apart, is about listing new records for individual islands and revising nomen- 615 km. Corvo lies approximately at the same distance from clature; (ii) to investigate some biodiversity patterns concern- the Iberian Peninsula and from Newfoundland. All the in- ing distribution between islands, habitats, colonisation status formation concerning the longitude (long.), latitude (lat.), area, Island spider diversity 251 maximum altitude, distances from the mainland and geological conservation management scheme, was launched covering age of each island are given in Table S1 in Supplementary Ma- about 13% of the area of Azores islands. Selected areas were terial. chosen both for the protection of selected species of birds (Spe- The acceptance of the Plate Tectonic Theory and the cial Protection Areas – SPAs; Portuguese ZPEs; n = 15) and confirmed volcanic origin of these islands, made the Azores a for the protection of habitats and (non-bird) species (Special totally oceanic archipelago. The eastern part of every Azorean Areas of Conservation – SACs; Portuguese SICs; n = 23). island is geologically the oldest. This is a consequence of the particular seismovolcanic mechanisms of this archipelago (Nunes, 1999; França et al., 2003). Spider sampling and databases Located at a mean latitude of 38◦30 and surrounded by Since 1994 spiders were sampled in a standardised way in dif- the Atlantic Ocean, the Azores enjoy the benefits of a mild ferent habitats. Data from semi-natural pastures and intensive and agreeable climate. The warm Gulf Stream is

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