Description of six new species of Loxosceles (Araneae:
Sicariidae) endemic to the Canary Islands and the utility of DNA barcoding for their fast and accurate identification
ENRIC PLANAS and CARLES RIBERA*
Institut de Recerca de la Biodiversitat (IRBio) and Departament de Biologia Animal, Facultat de
Biologia, Universitat de Barcelona, Avinguda Diagonal 643, 08028, Barcelona, Spain
Received 21 May 2014; revised 20 October 2014; accepted for publication 29 October 2014
We conducted an integrative taxonomic study of a radiation of Loxosceles spiders endemic to the Canary Islands combining molecular (mtDNA and nDNA) and morphological data. This led to the formal description of six new species: Loxosceles mahan sp. nov. endemic to Fuerteventura, Lanzarote, and adjacent islets; Loxosceles bentejui sp. nov. and Loxosceles tazarte sp. nov. both endemic to Gran Canaria; Loxosceles guayota sp. nov. and Loxosceles tibicena sp. nov. both endemic to Tenerife; and Loxosceles hupalupa sp. nov. endemic to La Gomera and El
Hierro. These new species are included in the Loxosceles rufescens group, and are clearly distinguished from L. rufescens by a conspicuous dark V-mark posteriorly on the pars cephalica, the embolus length, and the shape of seminal receptacles. Given that a crucial step for the development of proper health management is the correct identification of the species involved in bite accidents, we additionally tested the efficacy of DNA barcoding as a fast and reliable tool for identifying the Loxosceles species found in the Canary Islands, including the human-introduced
L. rufescens. © 2015 The Linnean Society of London, Zoological Journal of the Linnean Society, 2015, 174, 47–73. doi: 10.1111/zoj.12226
ADDITIONAL KEYWORDS: arachnids – arthropods – leg elongation – loxoscelism – Macaronesia – medically important spiders – species delimitation – spider – taxonomy.
The importance of oceanic islands as natural laboratories for evolutionary studies was acknowledged by
Darwin and Wallace (Wallace, 1855; Darwin, 1859).
Since then, numerous evolutionary studies conducted on islands, especially oceanic islands such as the
Galapagos, the Hawaii archipelago, and the Canary
Islands, have served to uncover fascinating processes and patterns that ultimately led to general theories such as ‘The theory of island biogeography’ (MacArthur & Wilson, 1967; Wagner & Funk, 1995; Whittaker,
Triantis & Ladle, 2008). To achieve these objectives, biologists generally have relied on species as the basic units on which to conduct evolutionary studies and to elucidate general patterns (de Queiroz, 2005). Thus, a complete inventory of rigorously delineated species is an essential first step (Dayrat, 2005).
With more than 500 species in the Canary Islands (Macías, 2010), spiders are amongst the most diverse and well-known groups of arthropods in the archipelago (Cardoso et al., 2010). Thus, the recent discovery of an endemic Canarian clade of Loxosceles Heineken & Lowe, 1832, spiders, distributed across the archipelago was an exceptional case (Fig. 1; Planas & Ribera, 2014). Loxosceles comprises 107 species (Platnick, 2014) distributed predominantly in temperate and tropical areas in North, Central, and South America (Gertsch, 1967; Gertsch & Ennik, 1983; Binford et al., 2008), although some species are located in Africa (Lotz, 2012) and two in the Mediterranean basin (Ribera & Planas,*Corresponding author. E-mail: firstname.lastname@example.org bs_bs_banner
Zoological Journal of the Linnean Society, 2015, 174, 47–73. With 15 figures © 2015 The Linnean Society of London, Zoological Journal of the Linnean Society, 2015, 174, 47–73 47 2009; Duncan et al., 2010). This diversity is strongly biased towards those areas where extensive taxonomic revisions have been conducted (e.g. most of the American Loxosceles species were described in three monographs; Gertsch, 1958, 1967; Gertsch & Ennik, 1983), and recent studies based on molecular evidence have suggested that the existent diversity could be highly underestimated (Binford et al., 2008; Duncan et al., 2010; Planas & Ribera, 2014). One of the factors that has hampered a comprehensive view of the present diversity is the subtle variation in genitalia characters. This difficulty was noted by Brignoli (1969: 142) in his Italian and Maltan revision of the genus when he stated that ‘. . . è evidente che la tassonomia dei
Loxosceles è di singolare difficoltà . . .’ [it is evident that the taxonomy of Loxosceles is singularly difficult], and by Gertsch & Ennik (1983: 273), who concluded that in Loxosceles, ‘. . . degrees of difference in genitalic characters are less great or perhaps less easy to describe verbally or pictorially than those of some other spiders . . .’, notwithstanding that they had described most of the currently accepted Loxosceles species.
Nevertheless, these difficulties are not exclusive to
Loxosceles, and systematists working on morphologically homogeneous spider groups (e.g. mygalomorphs) have encountered similar obstacles (e.g. Hamilton et al., 2014 and references therein). Thus, it is especially in these ‘cryptic’ species groups sensu Bickford et al. (2007) (i.e. two or more species classified as a single nominal species because they are at least superficially indistinguishable morphologically) that the usage of DNAbased methods has been successful in uncovering the existent diversity, and in delimiting species boundaries. Currently, it is generally accepted that evidence from multiple and complementary disciplines (e.g. additional molecular markers, ecological information, morphological characters) should be integrated when possible to improve our level of confidence when formalizing species hypotheses (Dayrat, 2005; Padial et al., 2010).
In this study, we followed this reasoning and obtained additional sets of data [i.e. morphological and nuclear molecular markers (nDNA)] to test the taxonomic status of the Canarian endemic Loxosceles evolutionary lineages previously delimited with mtDNA markers (Planas & Ribera, 2014).