Preliminary Study On Molecular Phylogeny Of The Main Lineages Of Orbiculariae And The Evolution Of Their Webs

Web-spinning spiders, whose habitats or biology are diverse, construct many types of aerial webs. Most species of spiders belonging to Deinopoidea and Araneoidea use orb-webs to capture prey. Orb-webs share several key features: all having a sticky capture thread placed spirally on radial threads converging on the hub; typical orb-webs being highly regular structures more or less circular and planar. Has the orb-web a monophyletic or a polyphyletic origin? In other words, is Orbiculariae (Deinopoidea + Araneoidea) monophyletic or polyphyletic? There is a considerable dispute about phylogenetic relationship between Deinopoidea and Araneoidea. Additionally, in superfamily Araneoidae, with the exception of orb-weavers building orb webs, there are many nonorb-weavers building sheet webs or gumfoot webs which are very different from typical orb webs. The phylogenetic relationship between orb-weavers and nonorb-weavers of superfamily Araneoidae has been the subject of argument.In the present study, mitochondrial 12S, 16S and nuclear 18S, 28S rDNA fragments of ten species of spiders were amplified and sequenced. Using neighbor-joining (NJ), maximum parsimony (MP), maximum likelihood (ML) methods and Bayesian analyses, the phylogenetic relationship between Deinopoidea and Araneoidea was inferred from the combined DNA sequences of 12S, 16S, 18S and 28S rDNA fragments. The resulting phylogeny indicated that: Deinopoidea and Araneoidea did not form single clade. This finding well supports that the orb-web similarities between Deinopoidea and Araneoidea are more likely the result of convergent rather than homologous evolution. In addition, the reconstructed phylogenetic tree based on cDNA and DNA sequences encoding C-terminal non-repetitive region of MaSp1 (Major ampullate spidroin-1) also showed that Deinopoidea and Araneoidea are not sister groups.Secondly, mitochondrial 12S rDNA and nuclear 18S rDNA gene fragments of nine species of spiders were amplified and sequenced. The phyolgenetic trees of Araneoidea were reconstructed with NJ, MP and ML methods. The resulting phylogeny indicated that: (1) Araneidae and Tetragnathidae, which build orb webs, are not a sister group in the superfamily Araneoidea; (2) Theridiidae and Linyphiidae, which build nonorb webs, are also not monophyletic, The results also corroborated the independent origins of linyphiid sheet webs and theridiid gumfoot webs; (3) The phylogenetic placement of linyphiid closer to tetragnathid than to araneid implies that the similarities of male palpal organ between linyphiids and araneids may be homoplastic rather than homologous.