The new species Araneus bonali Morano, sp. n. (Araneae, Araneidae) collected in central and western Spain is described and illustrated. Its novel status is confirmed after a thorough revision of the literature and museum material from the Mediterranean Basin. The taxonomy of Araneus is complicated, but both morphological and molecular data supported the genus membership of Araneus bonali Morano, sp. n. Additionally, the species uniqueness was confirmed by sequencing the barcode gene cytochrome oxidase I from the new species and comparing it with the barcodes available for species of Araneus. A molecular phylogeny, based on nuclear and mitochondrial genes, retrieved a clade with a moderate support that grouped Araneus diadematus Clerck, 1757 with another eleven species, but neither included Araneus bonali sp. n. nor Araneus angulatus Clerck, 1757, although definitive conclusions about the relationships among Araneus species need more markers examined and a broader taxonomic coverage. The new species was collected on isolated holm oaks and forest patches within agricultural landscapes. Adults were mostly trapped on tree trunks, where their lichen-like colours favour mimicry, while juveniles were collected on tree branches. Specimens were never found either in ground traps or grass samples. This species overwinters as egg, juveniles appear in early spring, but reproduction does not take place until late summer-early autumn. Araneus bonali Morano, sp. n. was found in the same locality from where another new spider species was described. Nature management policies should thus preserve isolated trees as key refuges for forest arthropods in agricultural landscapes, as they may be hosting more unnoticed new species. After including Araneus bonali Morano, sp. n. and removing doubtful records and synonymies, the list of Araneus species in the Iberian Peninsula numbers eight.

DNA barcoding, Iberian Peninsula, isolated trees, mimicry, molecular phylogeny, Quercus ilex

The genus Araneus Clerck, 1757 includes 641 species of orb weaver spiders distributed worldwide (World Spider Catalog 2018), of which ten species have been cited in the Iberian Peninsula (Morano et al. 2014; Nentwig et al. 2018). It initially comprised species now included in different genera such as Araniella Chamberlin & Ivie, 1942, Larinioides Chamberlin & Ivie, 1942 or Aculepeira Caporiacco, 1934. While copulatory organs of the species in the younger genus are quite uniform, those of the species remaining in Araneus are highly heterogeneous (Dondale et al. 2003), suggesting that the genus is still far to form a natural grouping. The genus Araneus has never been revised and currently constitutes a melting pot of species that superficially resemble the type species Araneus angulatus Clerck, 1757. For example, some species described from Australia most likely do not really belong to Araneus (see Framenau 2012). Moreover, recent studies based on analyses of species from North America, Europe, and Australia have shown that Araneus is polyphyletic (Gregoric et al. 2015), which has been further corroborated by recent phylogenomic studies (Kallal et al. 2018).

Here, a new species, Araneus bonali sp. n. (Araneae, Araneidae), collected at several localities in western and central Spain is described. The comparison of Araneus bonali with reference material from the Iberian Peninsula and the south-western Mediterranean Basin available at the National Museum of Natural Sciences (Madrid) confirmed that the specimens represent a new species. In addition, a bibliographic review of the descriptions of Holarctic Araneus species was performed (Levi 1971, 1973, 1991; Dondale et al. 2003, Simon 1929; Nentwig et al. 2017; Grasshoff 1968; Šestáková et al. 2009, Yin et al. 1997, Tanikawa 2007, 2009). A special focus was paid to the species catalogues from northern Africa, where the spider fauna is still insufficiently known. In total seven species of Araneus, three of which are doubtful, have been cited in five countries: Egypt (Audouin 1826; Cambrigde 1876; Denis 1945), Tunisia (Pavesi 1880; Simon 1885), Lybia (Cambridge 1872; Simon 1908; Caporiacco 1934), Algeria (Lucas 1846; Simon 1899) and Morocco (Thorell 1875; Simon 1909; Denis 1945; Jocqué 1997).

Due to the challenging taxonomy of Araneus, the generic delimitation of the new species was queried by using morphological and molecular data. For the morphological analyses, the criteria exposed in the cladistic analysis of the family Araneidae performed by Scharff and Coddington (1997) were followed. For the molecular analyses a nuclear gene (28SrRNA) was sequenced and blasted in GenBank to assess the closer genera in terms of raw sequence similarity. Additionally, a fragment of the barcoding mitochondrial gene cytochrome oxidase I was sequenced and compared with the sequences of Araneus available in GenBank and BOLD (Barcoding of Life Datasystem). All the evidence pointed to the same conclusion: a new species of the genus Araneus had been collected.

Most of the specimens of the new species were collected during an extensive sampling campaign carried out in central Spain, in the same site where a new Eutichuridae spider was recently described, namely Cheiracanthium ilicis (Morano & Bonal, 2016). As in the case of C. ilicis, Araneus bonali sp. n. was found on the branches and trunks of holm oaks Quercus ilex interspersed within agricultural fields. Based on a one-year-long systematic sampling, the habitat selection and the phenology of the new species were analysed, testing whether juveniles and adults showed different patterns. Finally, the literature was consulted and all the Araneus species cited from the Iberian Peninsula listed. Their taxonomic status is discussed and the number of species updated after removing dubious species records and including Araneus bonali sp. n.

Araneus bonali sp. n. exhibits a combination of somatic and genital characters typical of Araneus according to the cladistic analyses performed by Scharff and Coddington (1997), which established the intergeneric relationships within the family Araneidae. These traits include a hairy carapace in both sexes and in males the presence of an endite tooth, coxa I with hook and curved tibia II with strong macrosetae. Male genitalia were thoroughly analysed (including the expanded bulb) and has two patellar setae, a median apophysis with spines and hooks, stipes and two apophysis (subterminal and terminal) separated from distal hematodocha. The cap on the tip of the embolus present in virgin males was not found in the individuals analysed. Females showed the pockets near the tip of the epigynal scape characteristic of the genus (Levi 1991; Scharff and Coddington 1997). The molecular analyses supported genus membership of the new species by identifying Araneus angulatus (the type species of the genus) and the common Araneus diadematus as the two closest species, and the 28S gene tree showed the new species within the Araneus group along with other species of the genus.

The morphology of the male and female genitalia clearly distinguished the new species from any other Araneus species. Moreover, large uncorrected genetic distance to the closest relative (11.7%), further confirms its species status (Ratnasingham and Herbert 2007). Araneus bonali colouration is similar to that of Araneus circe (Audouin, 1826), however, the presence of the latter species in the Iberian Peninsula has not been confirmed (see discussion about the taxonomic status of Iberian Araneus spp. below). Moreover, A. circe is a large orbweaver (female length more than 20 mm), about three times bigger than A. bonali. The new species resembles another three small European araneids, namely Gibbaranea gibbosa, Araneus sturmi (Hahn, 1831) and Araneus triguttatus (Fabricius, 1775) and, like them, inhabits trees. It could be confused with the first species due to the greenish body (Figure 1). However, the new species lacks the prominent humps on the opisthosoma typical of G. gibbosa. Their genitalia are also different, in G. gibbosa male median apophysis has a broad base and a tapering, curved spur and the scape of female epigyne finishes in a characteristic spoon-shaped tip. Regarding the other two species, the lichen-like and greenish grey opisthosoma of Araneus bonali distinguishes it from the orangish red colour of A. sturmi and A. triguttatus. In addition, the structure and morphology of the copulatory organs (especially the straight scape of female epigyne and the three small teeth of the median apophysis of male palps in A. bonali) allow their differentiation.

A thorough revision of the literature was carried out including reports and descriptions of Araneus in Northern Africa (Audouin 1826; Cambridge 1872; Thorell 1875; Cambrigde, 1876; Pavesi 1880; Simon 1885; Lucas 1846; Simon 1899; Simon 1908; Simon 1909; Caporiacco 1934; Denis, 1945; Jocqué 1997) and three species not cited in Europe were found, namely Araneus arganicola (Simon, 1909), Araneus klaptoczi (Simon, 1908) and Araneus v-notatus (Thorell, 1875). The specimens of A. klapotczi and A. v-notatus could not be examined but, based on the original descriptions, they cannot be mistaken with A. bonali. In the first case, the description matches that of the modern genera Pararaneus Caporiacco, 1940, Larinia Simon, 1874 or Siwa Grasshoff, 1970. In the case A. v-notatus, the scape of the female genitalia has the characteristic “S” shape of Araneus sturmi. In spite of the different body colour, Simon (1929) included this species as a variety of A. sturmi when it was collected in France. The syntypes of A. arganicola deposited at the collection of the National Museum of Natural Sciences (Madrid) (voucher MNCN 20.02/12093) could be examined. They were collected by Martínez Escalera in Mogador (Morocco) in the nineteenth century. After a detailed inspection it was concluded that they were two subadults (♀ and ♂), as can be appreciated in Figure 10 where the outlines of female epigyne and swollen male palps can be observed. Both specimens probably belong to the species Neoscona subfusca (CL Koch, 1837). Besides these specimens, there were other two collected by the same person in Morocco (vouchers and collecting sites: MNCN 20.02/12120 -Mogador- and MNCN 20.12/12115 -Tanger-). They were labelled as A. circe but, after a detailed morphological analysis, we concluded that they were two females de A. angulatus.

Figure 10. 

Araneus arganicola syntype specimens. A dorsal view B ventral view C data labels.

The 28S gene tree confirmed that the only non-Holartic species that was in the analysis (28S sequence available), namely the Australian Araneus dimidiatus, does not belong in the Araneus spp. group (fig. 28S tree) (Framenau 2012) and supports our decision of not including them in further phylogenetic analyses. The Araneus clade included species of other genera such as Larinioides and Neoscona, probably due to the lack of informative characters in this short fragment. The concatenated phylogenetic tree of the Holartic Araneus spp. recovered a low supported clade (PP = 0.82) that grouped Araneus diadematus with another eleven species. Neither Araneus bonali nor Araneus angulatus or Araneus sturmi seem to belong to this group. Nonetheless, the poor resolution of our tree caution against drawing any major conclusions. New phylogenetic analyses based on a more thorough taxonomic sampling and a larger combination of molecular markers would be required to confirm some of our results and provide a fully resolved phylogenetic hypothesis for the genus and its close allies.

The new species is a tree-specialist: in addition to the more intensively studied area, it was found in holm oaks in the other localities of central and western Spain sampled. However, microhabitat selection did differ among life stages. While juveniles were in all cases collected in the branches, adults were more often caught in trunk traps. The differences in colouration might explain such a contrast in some extent. Juveniles are greenish, similar to oak new shoots, whereas adults show a greyish green colour remarkably similar to the lichens that cover the oak trunks (Figure 3). This mimicry might help them to remain undetected by prey and/or avoid predators, as has been found in other species (Théry and Casas 2002). This lichen-like appearance is not unique to the new species but also shared by another closely related species, namely the American Araneus bicentenarius (McCook, 1888) (Figure 6), so called `giant lichen orbweaver´, which was collected on trees among lichens (Levi 1971). The new small Iberian species would thus have a “giant” counterpart on the other side of the Atlantic, as the females of A. bicentenarius (total length 28 mm) are more than four times larger than those of A. bonali (total length 6 mm).

The number of individuals of the new species collected at each tree was not spatially correlated, what suggests that A. bonali is able to disperse even in a landscape in which trees are isolated. Its small size may favour ballooning dispersal, a behaviour previously described in different araneids (Bell et al. 2005). Nonetheless, adult and juvenile numbers were significantly related at the tree level, what also points to the relative importance of local reproduction. With the exception of one individual in February, juveniles were present from mid-spring onwards and the first adults did not appear until late summer. Based on Schaeffer (1977) and Ysnel and Canard (1986) classification, A. bonali would be an autumn stenocorus species, characterized by a short biological cycle with a brief adult presence between late summer and early autumn and a wintering period as egg. This life-cycle phenology is the most common in European Araneus spp. (Nentwig et al. 2017), although in the new species adult presence extends a little more into early autumn, probably due to the warmer temperatures in the Mediterranean climate.

The morphological and genetic analyses confirm that Araneus bonali is a new species, hence, the list of Araneus in the Iberian Peninsula now numbers eight species: A. angulatus, A. bonali, A. diadematus, A. marmoreus, A. pallidus, A. quadratus, A. sturmi, and A. triguttatus. The inclusion of A. circe and A. grossus remains to be confirmed.

The geographical distribution of the new species remains to be fully delimited to confirm whether it is widespread or, similar to other species (e.g., Araneus pallidus), its distribution is restricted to the western Mediterranean Basin. The fact that it has not been collected elsewhere in Europe before suggests a potential small geographical range, however, it is true that due to its habitat preferences it may have gone unnoticed, as tree trunks are not so frequently sampled. In the case of Spain, this is the second new species collected in isolated holm oaks within croplands (the first, Cheiracanthium ilicis was sampled in the same study site; see Morano and Bonal 2016). Hence, sampling efforts on tree branches and trunks in further spider field surveys are encouraged. From a conservation perspective, the preservation of isolated trees and forest patches in croplands should be high in the agenda of nature management policies (Guevara et al. 2005, Manning et al. 2006, Bonal et al. 2012).

This research was financed by the projects PII1C09-0256-9052, PPII-2014-01-PJCCM (JCCM and ESF) and AGL2014-54739-R (MINECO). RB was funded by a contract with the Atracción de Talento Investigador Programme (Junta de Extremadura TA13032). Marisa Hernández helped with the field work.

Dra. Begoña Sánchez Chillón, curator of arthropod collection of National Museum of Natural History, Madrid (CSIC) for information and the opportunity to study material of Martinez Escalera´s collection; Dra. Aracéli Anadón & Dr. Carlos Lastra (University of Oviedo) for the permit to study material of Franganillo´s collections and Christine Rollard, curator of the National Museum of History Natural of Paris, for the information about Dufour´s material.

The first author thanks Carlos Antonio Ruiz de la Hermosa, Manuel Carrasco Redondo and Alfonso Díaz-Cambronero Astilleros for the trust and help they provided to the project, and the workers and guards of the National Park of the Tablas de Daimiel, who helped me with the field work. We thank the local authorities of Huecas and the private landowners in Dehesa Casablanca (Enrique Vega) for allowing us to work in their properties.

Comments of the Editor (Dr. Miquel Arnedo) and two reviewers (Dr. Robert Kallal and Dr. Nicolaj Scharff) contributed to improve previous versions of the article.