We describe a novel species Cheiracanthium ilicis sp. n. (Araneae, Eutichuridae) collected in the province of Toledo (Central Spain). It was found during a systematic sampling campaign carried out in an agricultural landscape with isolated Holm oaks Quercus ilex and small forest patches. Its morphology and affinities with other species of the genus are discussed. Furthermore, one mitochondrial gene was sequenced to confirm species membership and its differentiation from other Cheiracanthium species. The molecular phylogenies based on mitochondrial and nuclear genes showed a close relationship of C. ilicis sp. n. with C. inclusum and C. mildei, with which it also shares morphological similarities. Nonetheless, the sparse sampling of the phylogeny, due to the low number of sequences available, impedes drawing any definitive conclusion about these relationships; it is first necessary to perform an extensive review of the genus worldwide and more thorough phylogenies. C. ilicis sp. n. also shares certain ecological and phenological characteristics with C. inclusum and C. mildei. Like them, C. ilicis sp. n. is an obligate tree dweller that prefers a tree canopy habitat and reproduces primarily in late spring and summer. From a conservation perspective, the present study suggests the need to preserve isolated trees in agricultural landscapes. They are not only the refuge of common forest organisms but also of novel species yet to be discovered.

Cheiracanthium ilicis sp. n., DNA taxonomy, Iberian Peninsula, isolated trees, molecular phylogeny

Cheiracanthium C. L. Koch, 1939 is the only genus of the family Eutichuridae Lehtinen, 1967 in Europe. This genus was transferred from the family Clubionidae Wagner, 1887 to Miturgidae Simon, 1886 (Ramírez et al. 1997) and, more recently, to the family Eutichuridae Lehtinen, 1967 (Ramírez 2014). The debate on the taxonomical status of this genus of spiders still remains open, since Wunderlich (2012) revalidated the genus Chiracanthops Mello-Leitão, 1942, which would include some of the species currently ascribed to Cheiracanthium. The spiders of this latter genus would be characterized by certain structures of the external sexual organs: male pedipalp apophysis and female copulatory ducts (Wunderlich, 2012).

Cheiracanthium has worldwide distribution and is only absent from the polar regions. Of the 209 known species of this genus in the world (World Spider Catalog 2016), 29 have been found in Europe, 14 of which on the Iberian Peninsula (Morano et al. 2014). With regard to the Iberian Peninsula, Urones (1987) provided the first extensive report on this genus including data on taxonomy, biology, habitat and geographical distribution of the 12 species cited up to that time. Later, Piñol et al. (2010) and Wunderlich (2012) increased this list by adding two new species observed in the Ibero-Balearic region.

Spiders of this genus are swift hunters on woody or herbaceous plants, and their dense claw tufts help them to crawl along inclined surfaces. Their body colours usually range from yellow to greenish, with orange and brownish tones in some species. Cheiracanthium spiders belong to the group known as “sac spiders” because they spin small silk bags which shelter these nocturnal hunters during the day. These bags are quite conspicuous, as often the spiders build them on top of tall grass shoots and so they are easily seen in wet meadows, on crops and besides paths.

In this article we describe a novel species of Cheiracanthium found during a sampling campaign carried out in Central Spain. Different habitats were periodically sampled in an agricultural landscape with isolated oaks and forest fragments interspersed between crop fields and grasslands. In addition to its morphological description we sequenced two genes (mitochondrial and nuclear) to build a molecular phylogeny and assess its status with respect to those species of the genus for which molecular data were available in GenBank. Finally, we provide data on habitat selection and phenology recorded during a one-year long systematic sampling.

A total of 6048 spiders were collected throughout the whole sampling campaign. During the examination of the specimens a novel species of Cheiracanthium was found. It was the only species of the genus Cheiracanthium found in the study area and a total of 179 individuals were collected: 162 immatures and 17 adults (six males and 11 females).

We describe a novel species of Cheiracanthium that can be easily diagnosed based on male and female genitalia from other species in the genus. The amount of genetic divergence in DNA barcode sequence (cox1) (7 to 11 % from closest relatives) provides further support for its distinctiveness.

Morphologically, Cheiracanthium ilicis sp. n. resembles C. inclusum and C. mildei. Like them, C. ilicis sp. n. males have a pedipalp with a relatively stout cymbial apophysis, a strongly sclerotized, stout median apophysis and no tegular apophysis. Also, in these three species the embolus is on the retrolateral margin of the bulbus and females have relatively stout copulatory ducts that do not encircle the two pairs of receptacula seminis on the vulva. C. ilicis sp. n. shares other characteristics with these species, such as a weakly developed or absent thoracic fissure and basal cheliceral articles that, at least in C. mildei, are smaller in females and not pigmented in the distal half. Male chelicera do not have modified basal articles and are powerful and more elongated than in females, especially in C. inclusum and less in C. mildei. In C. mildei male pedipalps have an additional dorsal tibial apophysis. In turn, in C. mildei females the copulatory ducts are placed in the middle of a strongly sclerotised epigyne. The phylogenetic analysis of the concatenated cox1+28S data matrix also supports the close relationship of the new species with C. mildei and C. inclusum. The two last species are included in Chiracanthops, a genus recently resurrected by Wunderlich (2012), which may suggest that the new species actually belongs to the genus Chiracanthops. Unfortunately, the sparse sampling of our phylogeny, only six species out of the 209 known species worldwide, deters us to draw any definitive conclusion about these relationships.

The somatic traits of this species are a combination of characteristics common to several afro-tropical species–such as C. aculeatum Simon, 1884, C. denisi Caporiacco, 1939 and C. furculatum Karsch, 1879, and species with a wide geographic distribution C. inclusum (Hentz, 1847) (New World, Africa and Reunion) (Lotz 2007a; Bayer 2014; World Spider Catalog 2015). Cheiracanthium ilicis sp. n. presents the tegular apophysis with a configuration similar to C. denisi, although the rest of the bulb differs in the cymbial spur and the retrolateral tibial apophysis. In the case of the epigyne, it resembles those of C. furculatum and C. inclusum, yet it differs in the wide septum that separates the depressions where the copulatory openings are located and in the way these are oriented antero-dorsally in the latter; whereas in C. ilicis sp. n. it is lateral and mid-positioned. By contrast, the shape of the vulva is more similar to C. furculatum and even to C. mildei L. Koch, 1864, as in both cases the copulatory ducts form a loop analogous to that found in C. ilicis sp. n.

The new species is sympatric with Cheiracanthium mildei, which is native to Southern Europe (Bryant 1951) and could thus co-exist with it. The information about the distribution of C. mildei on the Iberian Peninsula is recent and scarce. It is present in the north (provinces of Guipúzcoa) (Castro 2003; Castro 2009) and on the Mediterranean coast (province of Valencia) (Barrientos et al. 2010). There is not available information for the centre and the northwest of Iberia (Morano et al. 2014). C. mildei has been found to co-exist with C. inclusum in North America, where C. mildei is an invasive species (Hogg and Daane 2011). However, C. ilicis sp. n. was the only species of the genus found in our study area.

We agree with Bayer (2014) regarding the need to perform an extensive review of the Cheiracanthium genus for Europe, the Mediterranean Basin, Africa and the Middle East. For example, the type material of some species like C. salsicola Simon, 1932 was insufficiently described and, unfortunately, it seems to be lost, as we could not find it even after trying to do so. There is a need to study the intraspecific variability as well as to characterise lesser known species and their affinities; the discovery of this novel species in the Iberian Peninsula supports this claim. Furthermore, it would be worthwhile to sequence the genes commonly used for DNA barcoding, such as the mitochondrial cox1, in the existing species and in all the potentially novel ones. There are DNA sequences available in Gen-Bank for very few species of this genus; only if this number increases will we be able to build more thorough phylogenies that can establish reliable phylogenetic relationships among species.

The spiders of this genus occupy different habitats and can be found in grasslands, under stones, on shrubs and trees, etc (Dondale and Redner, 1982; Urones, 1988; Lotz, 2007a; Nentwig et al. 2016). In the case of C. ilicis sp. n. it has a preference for tree canopies, where most of the individuals were collected. Closely related C. inclusum and C. mildei have also been found in woody habitats (Corrigan and Bennett 1987; Hogg and Daane 2011), in which adults reproduce. We have found silk sacks in the empty acorn cups that remained attached to the oak shoots after the acorns are dropped. Only immatures were collected on the tree trunks, where they are likely to find shelter, and just three in the grasslands, probably immatures dispersing between trees. In fact, the dispersal abilities of species like C. inclusum by excreting a long silk thread that is carried by the wind (ballooning) are well known (Peck et al. 1970). The good dispersal abilities of these spiders may also explain the lack of a spatial autocorrelation among trees in the number of spiders collected.

Based on Ysnel and Canard (1986)C. ilicis sp. n. would be a spring stenocorus species, characterized by a short biological cycle with a brief adult presence in late spring and early summer. As in the case of C. inclusum in temperate North America (Peck et al. 1970), then was when we collected adults and reproduction takes place. After that, samples are dominated by juveniles and later mostly by subadults during winter and early spring. This is because the species is probably annual like other species of the genus; adults mate in early summer and then die in winter. The number of individuals and reproducing adults collected from each tree was closely related to size (canopy surface). Foliage biomass is greater in large trees and positively correlated with the abundance of herbivore insects on which spiders prey (Halaj et al. 1998). Caterpillar samplings in our study site have indeed shown that their numbers are higher in large Holm oaks (unpublished data). Also, large trees are older and the probability of tree colonisation in fragmented landscapes increases with time (Floren et al. 2011).

Cheiracanthium spp. spiders are nocturnal hunters and all of the individuals that we collected during the day by branch beating were quite inactive. They are very effective predators, which probably explains their success as invaders in areas outside their distribution range (Hogg et al. 2010). These spiders feed on Lepidoptera eggs, caterpillars, leafhoppers, leafminers and other herbivorous insects, some of them being insects that feed on cultivars of economic interest (e. g. vineyards, apple tree orchards). In fact, some studies have highlighted the potential role of these spiders in pest control (Corrigan and Bennett 1987; Hogg and Daane 2011). In the case of C. ilicis sp. n. inhabiting Holm oaks Quercus ilex, the main tree species of man-made savannahs used for livestock rearing (so called dehesas and montados in Spain and Portugal, respectively), this role has to be taken into account. Lastly, the present study supports many others that emphasise the importance of isolated trees in agricultural landscapes (Manning et al. 2006). They not only harbour common forest organisms but are also refuges for species yet to be discovered.

This work was financed by the projects PII1C09-0256-9052 (JCCM and ESF), PPII-2014-01-PJCCM ESF and AGL2014-54739-R (MINECO). RB was funded by a contract of the Atracción de Talento Investigador Programme (Gobierno de Extremadura TA13032). Marisa Hernández helped with the lab work. The Editor and reviewers Jan Bosselaers and Henrik Krehenwinkel provided helpful comments that improved earlier drafts of the manuscript. We thank Susan Rutherford for the English language edition. We are indebted to the local authorities and landowners of Huecas for allowing working on their properties.