Aetana Huber, 2005

Aetana Huber, 2005a: 72–73 .

Type species: A. omayan Huber, 2005 .

Diagnosis

Even though the cladistic analysis identifies only two synapomorphies for Aetana, the genus is fairly easily distinguished from the putatively closest relatives by the following characters: retrolateral trichobothrium on leg 1 very proximal (at <5% of tibia length) and presence of curved hairs on tibiae and / or metatarsi (both in contrast to Spermophora, Khorata Huber, 2005, Savarna, and an undescribed genus from Sarawak, below called ‘Gen.n. Borneo’); sternum not dark, retrolateral trichobothrium on male palpal tibia in very distal position, and presence of epiandrous spigots (all in contrast to Khorata, Savarna, and ‘Gen.n. Borneo’); male legs without spines and male palpal coxa unmodified (both in contrast to ‘Gen.n. Borneo’); ALS with only two spigots, epigynal plate without external pair of pockets, and female genitalia without unpaired posterior pocket (all in contrast to Spermophora). Most characters previously thought to be diagnostic (Huber 2005a) are rendered invalid due to the newly described species.

Description

Male

MEASUREMENTS. Total body length ~2.5–4.5 (smallest species in A. kinabalu group; largest species in A. omayan group); carapace width 0.9–1.8; leg 1 length ~27–44; tibia 1 length ~6.0–11.0; tibia 2/tibia 4 length 0.92–1.08; tibia 1 L/d ~55–95 (the largest species, A. omayan, has the relatively thickest legs; the smallest species, A. gaya, has the relatively thinnest legs).

COLOR. In life mostly ochre-gray with brown and black marks (e.g., Figs 51–56, 105–110), only A. libjo Huber, sp. nov. and A. baganihan Huber, sp. nov. with light brown to orange prosoma and palps (Figs 8–12); sternum never dark; legs usually with indistinct darker rings on femora (subdistally) and tibiae (proximally and subdistally); darker rings missing in A. libjo Huber, sp. nov. and A. baganihan Huber, sp. nov.

BODY. Carapace either with shallow median furrow restricted to frontal part (Figs 63–64, 198) or without furrow (Figs 118, 130); ocular area raised, eye triads on short stalks directed toward lateral, in some species with median process (Figs 77, 96) or with pair of processes arising from near ALE (Figs 221, 226). AME absent. Clypeus high, either unmodified, with small paired processes (Fig. 191), with large median process (Figs 59, 77), or with indistinct lateral ridges (Figs 221, 226). Abdomen from slightly longer than high (Figs 51–56) to almost cylindrical (Figs 8, 102), pointed at spinnerets. Male gonopore with four epiandrous spigots in all species examined with SEM (e.g., Figs 37, 143, 162); each ALS with large widened spigot and pointed spigot, without further cylindrically shaped spigots (Figs 68, 210); PMS with two spigots each.

CHELICERAE. Very variable, distal apophyses ranging from short processes in frontal position (Figs 15, 40) to long processes in lateral position (Figs 191, 226), absent in A. kiukoki group; proximal apophyses usually present, large in A. kiukoki group (Fig. 66), absent in A. ocampoi group (Figs 15, 40); chelicerae without modified hairs; without stridulatory ridges.

PALPS. Coxa unmodified; trochanter usually with one retrolateral to ventral process, sometimes provided with scales or teeth (Fig. 158), in A. ocampoi group fused to femur (Figs 14, 27); trochanter in some species with additional prolateral apophysis (Fig. 189); femur rarely simple (Fig. 27), usually with one or more processes, in A. kinabalu group with complex set of up to four processes (e.g., Figs 150–151); patella either triangular in lateral view or ventral side longer than usual (e.g., Figs 14, 58); tibia either of usual shape (e.g., Figs 14, 127) or rather small and slender ( A. kiukoki group; e.g., Fig. 58), with retrolateral trichobothrium in very distal position (close to tibia-tarsus joint; Figs 27, 114); palpal tarsus small, usually with capsular tarsal organ (Figs 134, 203), exposed in A. libjo Huber, sp. nov. (Fig. 35) (not clear in A. ocampoi Huber, sp. nov. and A. baganihan Huber, sp. nov.); procursus usually complex with proximal and distal parts connected by membranous hinge; procursus in A. kiukoki group unusually long (Figs 58, 76), in A. ocampoi group reduced to simple semi-transparent process (Figs 14, 27); bulb either with weakly sclerotized embolus as only process (Figs 114, 159), in A. kiukoki group with additional short membranous process (Figs 58, 75), in A. ocampoi group with additional novel processes (Figs 13–14, 26–27).

LEGS. Without spines; with curved hairs on tibiae and/or metatarsi (Fig. 133); usually without or with few vertical hairs, only in A. libjo Huber, sp. nov. and A. baganihan Huber, sp. nov. with one dense row retrolatero-dorsally on each tibia; retrolateral trichobothrium on tibia 1 very proximal (at 2–4% of tibia length), prolateral trichobothrium absent on tibia 1, present on other tibiae. Tarsus 1 usually with ~25–30 pseudosegments, fairly distinct distally; tarsus 4 with single row of ventral comb-hairs of a modified Belisana - type (cf. Huber & Fleckenstein 2008; Figs 32, 69, 82, 209).

Female

Similar to male but eye triads on lower humps (Figs 64, 80, 119) and closer together than in male (sexual dimorphism low in A. ocampoi group; in other groups, eye triads in females often less than half as wide apart as in males); clypeus and chelicerae unmodified; legs slightly shorter than in males (tibia 1 ~4.0–9.0). Females in A. omayan group with stridulatory apparatus between prosoma (elongate median plate on carapace posteriorly; Figs 186–188) against abdomen (indistinct hairless area frontally). Epigynum weakly to heavily sclerotized, sometimes with scape of variable length and shape (Figs 28, 60), never with external pair of pockets in anterior epigynal plate but in A. kinabalu and A. omayan groups sometimes with internal sclerotized pockets originating from ventral wall of uterus externus (Figs 111, 192–194), and in A. omayan group with pair of membranous external pockets in posterior epigynal area (Figs 192, 194, 222). Internal genitalia with pair of pore plates, in A. libjo Huber, sp. nov. and A. baganihan Huber, sp. nov. with unique median membranous structure (Figs 29, 44); in A. kiukoki group with distinctive serrated ridges (Figs 61, 73, 79).

Monophyly and relationships

Morphologically, the monophyly of Aetana appears weakly supported. Only two characters support this node (Fig. 1), both of them without homoplasy within the taxa included in the matrix but with considerable homoplasy among more distant Pholcinae relatives: (1) the very proximal position of the retrolateral trichobothrium on the leg tibiae (char. 30); and (2) the presence of curved hairs on leg tibiae and/or metatarsi (char. 31). However, preliminary analyses of molecular data (including many more potential close relatives) (A. Valdez-Mondragón, D. Dimitrov, B.A. Huber, unpubl. data) consistently support the monophyly of Aetana with high support values.

The sister group of Aetana appears much better supported by morphology. Four characters suggest that three genera together ( Khorata, Savarna, and ‘Gen.n. Borneo’) are sister to Aetana . This, however, is in conflict with our preliminary molecular data that suggest a closer relationship between Aetana and East Asian Spermophora (incl. S. estebani) than between Aetana and Khorata, Savarna, and ‘Gen.n. Borneo’. Such a close relationship with East Asian Spermophora was actually proposed in the original description (Huber 2005a), at that time without a formal cladistic analysis.

Within Aetana, four species groups receive strong support both from the morphological analysis herein (Fig. 1) and from our preliminary molecular data. Conflict exists regarding relationships among these groups. The present analysis supports a sister group relationship between the Aetana kinabalu and A. omayan groups, and at least one of the three characters supporting this node is a unique feature (the long retrolateral membranous process on the procursus; char. 21). Our preliminary molecular data do not strongly support any sister group relationships among the four species groups within Aetana .

Natural history

Most species were collected in forests, from well protected spaces close to the ground, under rocks and logs, in small holes and cavities. Few species occur higher in the vegetation, even in places directly reached by the sun, most notably the closely related A. libjo Huber, sp. nov. and A. baganihan Huber, sp. nov. and the putatively close relatives A. kinabalu and A. lambir Huber, sp. nov. An exception is the type species A. omayan, which was mainly collected in a cave but also among rocks in a treeless ravine.

All species seem to build simple domed sheet webs (like most other pholcids studied), but the sheets are unusually strongly domed in A. libjo Huber, sp. nov. and A. baganihan Huber, sp. nov., and in A. kinabalu and A. lambir Huber, sp. nov. a second sheet occurs a few cm under the main sheet.

In six cases, two species were found to share a locality, sometimes in different microhabitats (e.g., at Baganihan: A. kiukoki Huber, sp. nov. near the ground; A. baganihan Huber, sp. nov. among vegetation), sometimes in what seemed to be identical microhabitats (e.g., at Mt. Banahaw: A. manansalai Huber, sp. nov. and A. banahaw Huber, sp. nov., both close to the ground).

In most species, males and females were often found together sharing a web. This was never observed in A. libjo Huber, sp. nov. and A. baganihan Huber, sp. nov., where males and females were sometimes observed very close to each other but in separate webs.

When disturbed, Aetana spiders tend to run toward the periphery of the web rather than to vibrate in the ‘typical’ pholcid way. Some do then vibrate vigorously for a very short time before becoming motionless and pressing their body against the substrate; others stop vibrating and start to gently move the abdomen in circles ( A. libjo Huber, sp. nov. and A. baganihan Huber, sp. nov.). The closely related A. poring Huber, sp. nov. and A. indah Huber, sp. nov. barely reacted to disturbance.

Composition

The genus now includes 18 described species. The high species turnover in the Philippines and in northern Borneo, together with the wide distribution of one species group ( A. omayan group; Philippines to Fiji Islands) and the huge sampling gaps in eastern Indonesia, New Guinea, and east to Fiji suggest that at least several dozen further species are likely to exist.

Distribution

Ranging from northern Borneo and the Philippines to Fiji (Fig. 2). Most gaps and missing records are probably due to lack of adequate sampling, but the absence of records from two areas might reflect real absence. First, our intensive collecting in western Sarawak (at seven localities ranging from the Pueh foothills in the west to Niah in the east) did not result in a single specimen of Aetana, while many specimens were collected at all eight localities in eastern Sarawak (east of Niah) and Sabah. Second, northern Australia is relatively well sampled, but a revision of all the material available in collections (Huber 2001) did not reveal any Aetana .