Systematic review of a new orb-weaving spider genus (Araneae: Araneidae), with special reference to the Australasian-Pacific and South-East Asian fauna

Abstract

The Australasian-Pacific and South-East Asian species of the new orb-weaving spider genus Plebs with Plebs eburnus (Keyserling, 1886) as type species are revised. Following this study, Plebs includes a total of 22 species of which seven are here described new. Seven species are found in Australia, two in the Pacific region (New Caledonia, Vanuatu), and two in South-East Asia (Papua New Guinea, The Philippines). Eleven Asian species are transferred to the new genus. Plebs represent comparatively small orb-weaving spiders of c. 1.2-15.0 mm body length with a slightly elongated abdomen and humeral (shoulder) humps. Males of most species have two to three stout setae on the ventral side of their fourth coxae. Male pedipalps are characterized by the presence of a single macroseta on the patella, the presence of a paramedian apophysis as basal extension of the conductor, and an apical tegular protrusion. The female epigyne has a scape that is generally much longer than wide. It does not have a terminal pocket and is frequently broken off in a number of species. A phylogenetic analysis of 15 species of Plebs (those for which both sexes are known), 13 Australian/Pacific orb-weaving spider species representing the most commonly collected clades with paramedian apophysis, three species of Nearctic Eriophora Simon, 1864, and Araneus diadematus Clerck, 1758, as outgroup, identified a single synapomorphy of Plebs based on 35 morphological and three behavioural characters: a distinct, inverted U-shaped light pattern on the ventral side of the abdomen with two additional white spots anterolateral to the spinnerets. This analysis recovered a monophyletic clade of all Asian Plebs, suggesting a single colonization event of the genus that putatively originated in Australia. Most Plebs species appear to be active during the day. They build a regular orb-web with vertical stabilimentum in grass and low shrubs.

Phylogeny of the orb‐weaving spider family Araneidae (Araneae: Araneoidea)

“…Recent revisionary work has clarified the taxonomy of some of the more common Australian members of the “Backobourkiines”, for example the treatments of Plebs (Fig. G) and Backobourkia (Framenau et al., ; Joseph and Framenau, ), but species such as Eriophora transmarina and Eriophora_sp_64 represent a new Australian genus ( NGEN01 ). No known morphological synapomorphies currently confirm this group, but the Bayesian (PP = 0.98) support value is high.…”

“…The inclusion of Singa nitidula , a Palearctic species in the Backobourkiines, requires further investigation. However, other species of the Backobourkiines putatively dispersed into South‐East Asia and the Indian subcontinent after Australia collided with the Sunda shelf, for example in the genus Plebs , which has highest diversity in Australia (Joseph and Framenau, ).…”

A giant spider from the Jurassic of China reveals greater diversity of the orbicularian stem group

“…The third leg is very short (<0.5× length of leg 1) in Orbiculariae and in Mongolarachne ; in other web spiders, it is also usually the shortest, but less so (>0.5× length of leg 1) (measurements from specimens and the following literature: Kraus 1956; Gertsch 1958; Hoffman 1963; Catley 1994; Gray 1994; Harvey 1995; Ramírez and Grismado 1997; Opell 1983; Yin et al 2002; Penney 2003; Chang and Tso 2004; Joseph and Framenau 2012). Third leg: 0 short, 1 long.…”

Generic and family transfers, and numina dubia for orb-weaving spiders (Araneae, Araneidae) in the Australasian, Oriental and Pacific regions

“…About 30 putative new genera have been identified for Australia (V.W. Framenau & N. Scharff unpublished data; Scharff et al in press) in addition to some that have recently been established as part of ongoing revisions of the Australian orb-weaving spiders (Framenau 2011;Framenau et al 2010a;Harmer and Framenau 2008;Joseph and Framenau 2012). The review of type material as part of this revisionary work also found that a number of Australian species currently listed in Araneus belong to well-established genera.…”