A new species of jumping spider Neonella Gertsch, with notes on the genus and male identification key (Araneae, Salticidae)

Abstract The American genus Neonella Gertsch, 1936 consists of very small jumping spiders whose biology is not well known. The genus currently includes eleven valid species, of which eight are known from both sexes and two are only known from one sex. This paper describes and illustrates a new species Neonella acostae sp. n., demonstrates male palpal variation in Neonella montana Galiano, 1988, and provides some information on the ecology of three sympatric species. New records of Neonella montana and Neonella minuta Galiano, 1965 are reported. Because the previously described species of Neonella were well illustrated and diagnosed, a dichotomous key to males is given along with genital illustrations of both sexes for all known species.

Neonella jumping spiders are very small and easily unnoticed. The females are usually less than 2 mm in body length and the males are even smaller (Galiano 1998). This genus is similar to Neon Simon, 1876 (another genus of small jumping spiders) but can be distinguished by: 1) the absence of fovea; 2) the presence of abdominal scutum in males; and 3) the epigynal openings inside funnel-like atria (see Galiano 1988; and more detail in Gertsch 1936). The shorter distal embolus with thick tip is no longer considered a diagnostic character after Edwards (2003) described N. camillae, the first Neonella that has long and twisted embolus ("a retrolateral spiral with a proximal embolar disk"; see Edwards 2003, Fig. 5), and this kind of coiled retrolateral embolus was subsequently described for N. salafraria (see Ruiz and Brescovit 2004, Fig. 3) and N. noronha (see Ruiz et al. 2007, Fig. 13).
Recent phylogenetic analyses suggest that Neonella belongs to the subfamily Euophryinae, and falls within a clade with the Neotropical genera Ecuadattus Zhang & Maddison, 2012, Belliena Simon, 1902and Ilargus Simon, 1901(Zhang and Maddison 2013. Morphological characters indicate Neonella may be most closely related to Darwinneon Cutler, 1971 (not included in phylogenetic analyses), both of which are very small jumping spiders usually with a distinctive proximal tegular lobe (TL) and short RTA on male palp, and short and wide copulatory duct (Zhang and Maddison 2015).
The biology of these species is not well known. They have been found on the ground, e.g., N. lubrica and N. nana inhabiting leaf litter or underneath and in rotten wood (Galiano 1988), N. camillae in Australian pine litter no more than one cm in depth (Edwards 2003), N. minuta on grassland up to 40 cm high (Galiano 1965) and N. montana under small rocks (Galiano 1988). Probably their poor biological and taxonomic knowledge are due to their hidden habitat and the small size of individuals. As a result of an ecological study in Córdoba city, Argentina, several specimens of both sexes of three species of Neonella were collected: N. minuta, N. montana and an undescribed species. In this paper we describe and illustrate the new species, which we name N. acostae sp. n., show a variation of the male palp in N. montana, and provide some information on their ecology. Because the previously described species of Neonella were well illustrated and diagnosed, a dichotomous key for males to all known species is also given with this contribution.

Material and methods
Specimens were collected in different sites in Córdoba city (central Argentina), using a Garden-Vacuum method to suck spiders from the vegetation (for details on the method, see Rubio and González 2010). We collected on thirty sites around Córdoba city, in urban and peri-urban habitats (in November 2013, springtime), from which nine sites provided Neonella species (Fig. 1A). Sites that were positive for Neonella were re-sampled the following February-March 2014 (summertime) and July-August 2014 (wintertime). The study area is located within the Espinal ecoregion (Brown et al. 2006), a thorny deciduous shrubland forest (Fund 2014), but has been historically subjected to intense anthropogenic disturbance and modifications (including deforestation, urbanization and agriculture). The sampling sites ranged from forest remnants to urban parks (Fig. 1B, C).
Description formats and morphological terms follow Ruiz and Brescovit (2004), Zhang and Maddison (2015), and Ramírez (2014). Female epigynum was dissected and cleared in clove oil to study the internal structures as in Levi (1965); the male bulb was similarly prepared. Temporary preparations were examined using a Leica DM500 compound microscope and a Leica M60 stereomicroscope. All measurements are in millimeters, were made with an ocular micrometer, and were measured as in Galiano (1963: 275). Leg measurements are shown as total length (femur, patella and tibia, metatarsus, tarsus). Specimens examined are deposited at the arachnological collections of: Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", Buenos Aires (MACN-Ar, C. Scioscia), Instituto de Biología Subtropical, Misiones (IBSI-Ara, G. Rubio) and Centro de Relevamiento y Evaluación de Recursos Agrícolas y Naturales, Córdoba (CREAN, C. Argañaraz).
Drawings in Figure 4 were modified from the following original sources: The three species were collected together or at different locations. In order to explore the strength of the association or the degree to which two species occur jointly in a number of locations, Cole´s index (1949) was utilized. This association coefficient has been used in various applications over animals and plant ecology (Warrens 2008). The index was constructed by 2 × 2 contingency tables and χ 2 . A site was considered positive when a species was detected at least once either in the spring or the summer sampling (n = 9 sites). Significant associations could indicate interspecific interactions or similar responses to the same environment (Soosairaj et al. 2005).
Etymology. The specific name is a Latinized patronym in honor of Dr. Luis E. Acosta, arachnologist of Universidad Nacional de Córdoba, who was major professor for the PhD of G.D.R. and advisor for the bachelor thesis of C.I.A.
Sexual dimorphism. Males and females differ only slightly in their somatic morphology. Females are slightly larger than males, mainly due to their larger abdomen. The carapace is somewhat more pigmented in males than in females. Note. The holotype was requested for study but so far it is unavailable. However, we do not consider this a major drawback since in a recent contribution, Ott et al. (2015) synonymized N. cabana with N. montana based on specimens collected in southern Brazil, which had been noted as a possibility by Galiano (1998). In agreement with Ott and collaborators, we found that males of N. montana have variations in both somatic and reproductive structures. Therefore, an updated diagnosis including both sexes and an additional re-description of the male including the variation found in the palp of specimens from Argentina (near the type locality) are given below.

Neonella montana Galiano, 1988
Diagnosis. Males of N. montana are similar to those of N. colalao in sharing a comblike, branched lamella of embolus (LE), but can be distinguished from this species by having non bifurcated terminal apex of the embolus (Fig. 3E; and Galiano (1998): Figs 11, 12, compare with Figs 7-10). Females of N. montana can be distinguished from the other species of Neonella by having only one opening on the epigynal plate, formed by a large, trapezoid atrium (Fig. 4E;and Galiano 1988: 447, Figs 14, 21).
Description. Male from Ciudad de Córdoba (IBSI-Ara 00243) (Fig. 3) brown; cymbium yellow. Femur and patella black proximally, with a hook-shaped retrolateral apophysis (PA). Copulatory bulb light brown, with conspicuous tegular lobe (TL) and embolus base (EB). Embolus (E) short, with comb-like lamella (LE). Abdomen light brown, with a few scattered black hairs; with a pair of longitudinal dark stripes on the abdomen in anterior half, and the posterior half with chevrons. Dorsal abdomen completely covered with a scutum (DS). Spinnerets pale yellow. Variation (n=10): some specimens from Córdoba vary in thickness and shape of embolus and LE respectively; for comparison see Figure 4E; in addition, the blackish irregular bands of the femora may be less developed.
Distribution. Central and southeast Argentina: in Córdoba (Fig. 1A) and Buenos Aires provinces, and southern Brazil: Rio Grande do Sul.
Ecology of the collected species. The three species of Neonella were collected during the spring and the summer but were not detected in the winter samples. They were found in the lower strata of vegetation (0 to 35 cm), consisting mainly of grasses and forbs. Neonella acostae was collected both within the urban environment (Fig. 1A, B) and in more natural sites on the periphery of the city (Fig. 1A, C), while N. montana and N. minuta were mostly collected from more natural sites with dense vegetation on the city periphery ( Fig. 1A, C). Based on Cole's index (1949), N. acostae was negatively associated with N. minuta (-0.44 ± 0.42; mean association ± standard error) and N. montana (-0.13 ± 0.11), suggesting moderately dissimilar habitat disturbance tolerances because N. acostae was collected at a wider range of sites in terms of plant cover, or alternatively a moderate degree of interspecific competition because they occasionally occurred at the same site. Cumming and Wesolowska (2004) explained high Salticidae richness in small suburban areas as a result of strong host-plant associations. More detailed studies of microhabitat use should be carried out to confirm these explanations. Neonella minuta and N. montana were not significantly associated (0.1 ± 0.11), suggesting independent occurrences of the species.

Provisional identification of species groups of Neonella
Known species of Neonella are more easily distinguished if based on the morphology of male organs; however, males with long and spiral embolus could have conspecificity with females having copulatory openings as two simple round holes and, apparently, without window of epigynum (W) or median septum (MS) (Fig. 4). All species included in the genus, 11 plus one described here, can be separated into two large main groups; 1) those with long spiral embolus: N. camillae, N. salafraria, N. noronha, and N. acostae (Fig. 4A-D), and 2) the remainder having short and generally more stout embolus. Within this latter group we can distinguish two subgroups; 2 a ) species having a visible branched lamella of embolus (LE): N. montana and N. colalao (Fig. 4E, F) and 2 b ) without such lamella or is very difficult to see, but in this case unbranched: N. vinnula, N. minuta, N. antillana, N. lubrica, and N. nana (Fig. 4G-K). Although it has been found that N. noronha has a tiny lamella of embolus (paraembolic projection sensu Ruiz et al. (2007)), this species has a long spiral embolus. Neonella mayaguez is known only from females (Fig. 4L).
The following key to species has some limitations because it is constructed based only on the males. Males have diagnostic characters which are much more apparent and applicable. On the other hand, in females, the diagnostic characters are mainly in the internal genitalia (ducts and spermathecae) in ventral and dorsal views (vulva), and these are more ambiguous. Therefore, we consider the need to complement this contribution with a comprehensive review of the genus to provide a key with both sexes in the future.