THERIDIIDAE AND ITS RELATIVES

Agnarsson, Ingi, 2004, Morphological phylogeny of cobweb spiders and their relatives (Araneae, Araneoidea, Theridiidae), Zoological Journal of the Linnean Society 141 (4), pp. 447-626 : 463-464

PLACEMENT OF THERIDIIDAE AND ITS RELATIVES

This analysis tested the placement of Synotaxus (formerly an argyrodine theridiid) in a matrix containing argyrodine theridiid genera. In concordance with Forster et al. (1990), Griswold et al. (1998) and Agnarsson (2003c), Synotaxus is not a theridiid. The web, egg-sac guarding web and general somatic morphology make Synotaxus unlike any theridiid ( Fig. 95A–D ). Instead, it is sister to the theridioids (clade 55), as also suggested by Griswold et al. (1998), who informally named the clade containing cyatholipoids (cyatholipids plus synotaxids) and theridioids as the spineless femur clade (clade 57).

Forster et al. (1990) expressed doubts concerning the position of Carniella within Theridiidae , based on the basal position of the ‘paracymbium’ ( Fig. 36C ) and the lack of flattened AG spigots ( Fig. 36I ) so typical of theridiids. However, the results of this study strongly support such a placement (see Thaler & Steinberger, 1988) as sister to the clade ( Pholcomma , Robertus ) ( Fig. 102 ). Knoflach (1996) suggested affinities between Carniella and Theonoe , based on the absence of the male palpal tibial trichobothrium and modification of the cymbial tip ( Fig. 36A–C ). Theonoe shares several additional features with the clade containing Carniella , Pholcomma and Robertus and thus Knoflach’s argument seems well founded.

As suggested by Berland (1932), Gertsch (1949), Wunderlich (1978) and Forster et al. (1990) hadrotarsines are related to theridiids, and here form the sister clade to the remaining theridiids. Hadrotarsine monophyly is supported by an array of morphological peculiarities, making them unlike any other theridiid. They also lack several characteristics typical of other theridiids (see below). For these reasons, revalidating Hadrotarsidae seems logical. However, such an act has major nomenclatural consequences and is currently contradicted by molecular evidence (see Arnedo et al., 2004). Therefore, the elevation of Hadrotarsinae to family rank will be reconsidered following combined analysis (see ‘Note’ above).

Figures

Figure 36. Carniella siam, male. A–D, palp. A, mesial; note knob on tegulum that may be the remains of the conductor (arrow). B, ventral. C, ectal; note basal cymbial hook (arrow, 32-0). D, tibia. E, prosoma. F, clypeus. G, dorsal posterior part of prosoma; note stridulating ridges (128-1). H, area around pedicel on abdomen; note pairs of SPR (arrows), and nubbins. I, spinnerets; note presence of AG, FL (219-1). Scale bars: A–D, H, 50 Mm; E–G 100 Mm; I, 10 Mm.

Figure 95. A, typical ‘chicken-wire’ web (225-2) of Synotaxus monoceros, characteristic of this genus (Bartika, Guyana). B, S. waiwai, female guarding egg sac in a simple ‘egg sac web’. (Gunn’s landing, Guyana) C, S. monoceros, female guarding egg sac in an identical web (Bartika, Guyana). D, male of S. monoceros (Bartika, Guyana). E, Selkirkiella luisi (Puyehue, Chile) in an egg-guarding web typical of the genus, superficially similar to Synotaxus. Note that the dense silk mat in Selkirkiella covers the loosely woven egg sac entirely. Enoplognatha ovata is similar (e.g. Nielsen, 1932: 41)

Figure 102. Single most parsimonious cladogram (L = 759, CI = 37, RI = 73) and preferred phylogenetic hypothesis of theridiid spiders with major groups identified and the family Theridiidae shown with thick lines. Numbers above branches indicate Bremer support; below branches are bootstrap values (above 50%). Parsimony jackknife scores were nearly identical and are not shown.