Three new Eustala ( Araneae , Araneidae ) species from the Galápagos Islands ( Ecuador )

three new Eustala species are described from the Galápagos archipelago: Eustala occidentalis sp. nov. with a western distribution, Eustala orientalis sp. nov. with an eastern distribution and Eustala meridionalis sp. nov. with a distribution restricted to the southern island Floreana.


Introduction
Because they construct conspicuous orbwebs, araneidae are among the most prominent group of spiders.With 169 genera and more than 3000 described species, it is also one of the largest spider families (Jocqué et al. 2013;Platnick 2014 ).On the Galápagos Islands, the family is represented by nine genera: Cyclosa Menge, 1866, Galaporella Levi, 2009, Gasteracantha Sundevall, 1833, Mastophora Holmberg, 1876, Metazygia F.O.Pickard-Cambridge, 1904, Metepeira F.O.Pickard-Cambridge, 1903 and Neoscona Simon, 1864 are represented by one species each, and Argiope audouin, 1826 by two species (Baert et al. 2008;Baert 2013).In this paper, I report on the ninth genus, Eustala Simon, 1895, which is the most speciose araneid genus of the archipelago with three species, here described as new.
the american continent harbours 82 species of the genus Eustala, of which half are found in South america.Most of these (35 species) occur in the eastern and southern part (Guyana, Brazil, Uruguay and argentina) of the South american mainland.Only six species are cited from the western part, more precisely from Peru, but none from ecuador (Platnick 2014).
the Eustala specimens found on the Galápagos have so far been assigned to one species: Eustala vegeta (Keyserling, 1865) (Baert et al. 2008;Garrett et al. 2008).However, a more detailed analysis of the male palp and the female scapus shows that they belong to a complex of three different species, each with a well defined, segregated distribution over the islands of the archipelago.The males can easily be distinguished by the structure of their terminal apophyses, the females by the shape of their scapus.
the type material of the three species is deposited in the collections of the royal Belgian Institute of Natural Sciences, Brussels (Belgium).
Specimens were examined and measured with a Wild M5 stereo-microscope, and illustrated using a Wild M10 stereomicroscope.the electron microscope photographs were made with an eSeM FeI QUaNta 200 microscope.the colour photographs were made with a Nikon D7000 with an aF Micro Nikkor 60 mm objective.all measurements are in mm. the left male palps are depicted, except the right one for E. orientalis.the female genitalia were cleared in a methylsalicylate solution.

Diagnosis of the genus
the carapace has a deep longitudinal cleft in the thoracic region.the abdomen has a triangular shape with a dorsal folium pattern and a ventral white patch.the posterior median eyes are usually slightly smaller than the anterior median eyes.the males are smaller than the females.the distal margin of the male first coxa has a distinct hook, which fits into a groove on the second femur.The palpal patella has one very long macroseta.the bulb has a huge, variably-shaped conductor and a conspicuous white, cone-shaped median apophysis produced downward on the ventral side of the large bulb.Females are characterized by the scapus of the epigyne projecting forward.the males of the three species described here differ from all known Eustala species by the structure of the terminal apophysis, the subterminal apophysis and the embolus, the females by the shape of the anteriorly projecting scapus.the males of these three Galápagos species differ from each other by the structure of their terminal apophysis (Fig. 6) while the females are recognized by the shape of their scapus (Figs 1C,3C,4C).

Diagnosis
Male: terminal apophysis needle-like, short and slightly curved, its apical and caudal ridges equal in length and structure.

Etymology
the species name refers to its distribution in the western part of the archipelago.Other material examined originating from the islands Fernandina, Isabela (Volcán Sierra Negra, Volcán alcedo, Volcán Darwin), Marchena, Pinta and Santiago (see table 1).
CarapaCe.Colour (in alcohol) yellowish with clypeus and eye region black, dorsal cephalic part black with central yellow V; two short, diverging combs of long, thin, white hairs starting from PMe and PLe.Chelicerae black with few yellow stains.Labium black with white apical edge.endites black with white apical and inner edges.Sternum white with irregular blackish suffused border.Pedipalps with striped yellow-black appearance.Legs yellow with variable black annulations.
abdomen.Dorsum white with distinct dorsal dark folium pattern (colour pattern a), with six sclerotized apodemes; venter black with central white patch; spinnerets dark.pedIpalp (Figs 1a-b, 5a).One very long patellar seta, slightly longer than bulbus.Cymbium with conspicious t-shaped tarsal hook, its transverse bar slightly curved and with rounded extremities.terminal apophysis (Fig. 6 a) needle-like, slightly bent, short, apical and caudal ridges equal in shape and length; embolus short, sharp tip, slightly curved at tip, lying in excavation of small, whitish conductor.
abdomen.Creamy white, faintly speckled with cream spots, four apodemes; grey patches extend laterally of the proximal dots; three branched, dirty-grey lines run backwards in distal half of dorsum; venter cream with central white patch; spinnerets orange brown.

Variation
the males in our samples vary in length between 4.9 and 7.4 mm, the females between 5.7 and 10.6 mm. a great diversity in abdominal colouration, independent of island origin, can be observed (Figure 2). the abdominal colour can vary from uniform light cream (Pattern a: for example ♂ of sample B.88/317: Santa Cruz, surroundings of CDrS, 17 Feb. 1988; allotype ♀ from Santa Cruz and ♀ from Marchena, 26/I/1977, leg.Reeder), to very dark (Pattern B: for example ♀ specimen from Santa Cruz, Media Luna, 620 m alt., 3 May 1980, leg.reeder), with all possible variations in between.the colour may be uniform or with a faint or a very conspicuous folium (patterns on Fig. 2a, 2D-F), showing two sinuous lines converging backwards.Some specimens, male and females, have a black abdomen with two large white shoulder spots (pattern, Fig. 2C: for example ♂ specimen from sample P.92/179: Tagus cove, Volcán Darwin, 22 May 1992, but also some specimens from Santa Cruz, Volcán Sierra Negra, Pinta and Santiago), a few with a dorsal longitudinal white band (Fig. 2D, F) and some with a white abdomen with median black folium (Fig. 2e).Cephalothorax also variable, with or without marked black stains.

Distribution
E. occidentalis sp.nov.has a western distribution within the archipelago (Fig. 7): Fernandina (up to 600 m alt.); the Isabela volcanoes Volcán Sierra Negra (arid zone and above 900 m alt.), Volcán alcedo (above 300 m alt.), Volcán Darwin and Beagle Crater (coastal arid zone); Marchena; Pinta (from coast to summit); Pinzon (above 300 m alt.); rábida; Santiago (from coast to summit); Seymour Norte; South Plaza and Santa Cruz (from coast up to 600 m alt.).there is apparently no preferred vegetation zone.It also occurs along the walls of buildings (cf.CDrS buildings of the dormitorio).CarapaCe.Colour (in alcohol) yellow brown with clypeus and eye region black, dorsal cephalic part yellow brown with central, faintly suffused, blackish V; two short combs of long white hairs diverge from between PMe and PLe.Chelicerae yellow with central, faintly suffused, blackish stain.Labium and endites pale yellow with white margin.Sternum yellow with faintly suffused, blackish stains in front of coxae.Pedipalps yellow-brown with some black stain.Legs pale yellow with black annulations, variable between specimens; coxae and proximal part of femora whitish.

Eustala orientalis
abdomen.Dorsum creamy white with small, black median triangle in front, two small, white central stains and distinct dark sepia folium with dark brown margins and ten brown apodemes arranged as 4-2-2-2, becoming smaller caudally and towards the sides; venter whitish, slightly suffused with black; colulus and spinnerets dark.
abdomen. as in male, but more uniform grey; shoulders white; venter sepia with white stains; spinnerets orange brown.

Variation
the males in our samples vary in length between 4.6 and 6.9 mm, the females between 5.1 and 8 mm.
the colour variation of the abdomen is comparable to that of the previous species.

Distribution
E. orientalis sp.nov.has an eastern distribution within the archipelago (Fig. 7): española (arid zone), Islote Gardner near española, Genovesa (arid zone), San Cristóbal (coastal arid zone and above 500 m alt.) and Santa Fé.We cannot detect a preference for a certain kind of vegetation zone, as most islands are low in altitude.

Diagnosis
Male: Differing from E. occidentalis and E. orientalis in the structure of the terminal apophysis, which is flat and broadening towards tip, apical ridge being slightly longer than caudal ridge.The female differs from both species by having a shorter and thicker scapus.

Etymology
the species name refers to its distribution in the southern part of the archipelago.

Type material
Holotype ♂, ISLa FLOreaNa, Cerro Pajas at the edge of Scalesia forest, alt.335 m, 18 apr.1996 (P.96/55), leg.S. Peck.CarapaCe.Colour (in alcohol) yellowish with black suffused striae and marked yellow V in cephalic region; two short combs of long, white hairs diverge from between PMe and PLe.Chelicerae black with yellowish inner sides.Labium black with white apical edge.endites black with white apical and inner margins.Sternum light yellow with broad, blackish suffused border.Pedipalps dark.Legs pale yellow with black annulations, variable among specimens; coxae and proximal part of femora whitish.
CarapaCe.Cream with some faint brown stains in cephalic area; eyes with black rings.Chelicerae cream.Labium yellow brown with white apical edge.endites yellow brown with white apical and inner   4 B-C).Scapus 0.35 mm long, 0.21 mm thick, L/D = 1.67.Spermathecae separated; scapus broader at tip (in ventral view), straight and very broad in the middle (in lateral view).

Variation
the few males in our samples vary between 4.70 and 5.90 mm in length.the male caught at the base of Cerro Pajas (P.96/62) shows the same two broad white spots as some E. occidentalis sp.nov.specimens (see colour pattern C of E. occidentalis sp.nov., Fig. 2C). the other males all have a much lighter appearance.their abdomen has more white and their cephalothorax is as light as that of the female allotype.

Distribution
E. meridionalis sp.nov.has only been found above 300 m alt. in the Scalesia zone of Cerro Pajas and its vicinity on the centrally located southern island Floreana (Fig. 7).

Discussion
the three Eustala species described here differ consistently from all mainland species: the males by the shape of the palpal terminal apophysis, the females by the shape of the epigyne scapus and the configuration of the spermathecae.Chickering (1955) previously wrote that the colour pattern of the Central american Eustala species is highly variable.He therefore did not attribute much importance to this character in his species descriptions.this observation was later corroborated by Levi (1977: 96) in his generic diagnosis of Eustala: "Most species are variable in colouration with dark and light individuals, but most have a folium pattern on the dorsum, exceptions being some specimens of E. anastera that are contrastingly coloured with black patches on white in alcohol (figs.219, 222)".The colour patterns as given here by Levi coincide strikingly with the patterns observed in Eustala species from Galápagos (Fig. 2, patterns a-B and e).
the three species show a very distinctive segregated distribution over the archipelago.E. occidentalis sp.nov.has the broadest range over the central (Santa Cruz), the western (Santiago, Isabela and Fernadina) and two of the northern islands (Pinta and Marchena).this part of the archipelago is younger than 2.3 my (Geist et al. 2013).E. meridionalis sp.nov.lives on the isolated southern island of Floreana which has an age between 1.5 and 2.3 my (Geist et al. 2013).E. orientalis sp.nov.shows a peculiar distribution which I cannot explain.Its presence on the eastern islands San Cristóbal and española may be logical and understandable, these islands being the oldest ones (between 2.4 and 4.0 My, Geist et al. 2013).But its presence on the "eastern" islands Santa Fé and Genovesa is less explicable, since the distance separating Santa Fé and Santa Cruz, where E. occidentalis sp.nov.lives, hardly exceeds 17.5 km.Moreover, Genovesa belongs to the very young northern islands (age between 0.3 and 0.8 my according to Geist et al. 2013), lying on a straight line north of Santa Fé along the 90° W longitude, at a distance of approximately 125 km, but only some 50 km east of the central northern island Marchena.Odo desenderi Baert, 2009 has a similar distribution.It occurs on Santa Fé and Genovesa but in an inexplicable way also on Marchena.
Eustala species are, like most araneids, probably good ballooners, which can easily be transported by wind.One should expect E. orientalis sp.nov. to be able to bridge the short northwest distance between Santa Fé and Santa Cruz, and to be found on that central island.this has apparently not happened, although the prevailing winds come from the southeast.the distribution of E. orientalis sp.nov. on the older southeastern islands and E. occidentalis sp.nov. on the younger central and northwestern islands fits the line of the progression rule pattern, paralleling the geological formation of the islands (Wagner & Funk 1995;Parent et al. 2008).

Natural History
Eustala species are apparently nocturnal (Levi 1977: 97) and remove their web during daytime.they seem to have no retreat, but rest on a branch of the vegetation in which they live (Levi 1977: 97).they were mostly caught by sweeping in daytime and were sometimes caught at night.
Other material examined from the islands of Genovesa, San Cristóbal and Santa Fé (see table 2).
DiagnosisMales differ from E. occidentalis sp.nov.by the structure of the terminal apophysis: flat and broadening towards the tip, its caudal ridge being longer than the apical ridge.Females differ from E. occidentalis sp.nov.by the shape of the scapus.Etymologythe species name refers to its distribution in the eastern part of the archipelago.
Distribution map of Eustala occidentalis sp.nov., Eustala occidentalis sp.nov.andEustalameridionalis sp.nov.edges.Sternum whitish with broad, yellowish brown border.Legs yellowish brown with annulations fainter than in male.abdomen.Dorsum lighter than in male; venter cream with three white stains.Colulus and spinnerets black with orange tinge.