Taxon of the Week: Amphinectidae

Male of Metaltella simoni, a South American spider that has become established in the southern United States. Photo by johnnyn.

The Amphinectidae are a family of spiders described from Australia, New Zealand and South America. They are members of the 'amaurobioid' group of spiders, and share all the issues of poor definition associated with that group. Indeed, Davies (2002) made the admission that "there is no clear diagnosis of the family Amphinectidae". In general, most amphinectids are ground-dwelling (like many other 'amaurobioids'), and they are active hunters or construct small sheet-webs. They have two nearly straight rows of four eyes each at the very front of the cephalothorax. The metatarsi of the thrid and fourth legs have preening combs (Griswold et al., 2005). Since the Amphinectidae was originally established for a group of sixteen New Zealand genera, it has been enlarged to include the Australian and South American subfamily Metaltellinae (Davies, 1998) and the Tasmanian Tasmarubriinae (Davies, 2002). A further subfamily, the Kababininae, was initially regarded as amphinectid but has since been removed (Davies, 1999). Oddly enough, while the use of the names "Metaltellinae" and "Tasmarubriinae" would seem to imply an "Amphinectinae" (probably for the original New Zealand genera), I haven't been able to find a single case of such a name being used. Norm Platnick's World Spider Catalog simply lists the genera in this family in alphabetical order, without using subdivisions.

Metaltellinae are a reasonably distinct group - they differ from all other 'amaurobioids' in that the embolus (the intromittent part of the male genitalia through which the end of the sperm duct passes) turns anticlockwise rather than clockwise as in other families (Davies, 1998). Of the ten genera included in this subfamily by Davies (1998), eight are Australian and two (Metaltella and Calacadia) are South American, but I would not be surprised if this difference simply reflects the better-studied nature of Australian spiders. A single South American species, Metaltella simoni, has been introduced to southern North America with records from Florida to California. A relationship between Amphinectidae and Metaltellinae was first supported by Griswold et al. (1999), with the supporting characters being a proximal dorsal process on the tibia of the male pedipalp and possession by the females of a convoluted vulva*. The subfamily Tasmarubriinae was established by Davies (2002) and distinguished from Amphinecta (but not necessarily the other amphinectid genera, which were not examined) on the basis of features of the male genitalia.

*Davies (1998) had already transferred the Metaltellinae into the Amphinectidae on the basis that her own phylogenetic analysis "showed" the Metaltellinae to be closer to the Amphinectidae than to the Amaurobiidae (among which they had previously been included). However, Davies' analysis only included representatives of Amaurobiidae, Amphinectidae and Metaltellinae, with the single amaurobiid set as the outgroup, so it would have been impossible for the analysis to have shown anything else.


Unidentified amphinectid from Southland, New Zealand. Photo from here.

Other analyses have not supported an exclusive Amphinectidae-Metaltellinae connection. Davies (1999) included representatives of New Zealand Amphinectidae, Tasmarubriinae and Metaltellinae in an analysis of 'amaurobioid' spiders; while Tasmarubriinae and Amphinectidae formed a clade (supported by the first leg in females being shorter than the fourth leg, the presence of metatarsal preening combs, and a rounded conductor as part of the male genitalia), Metaltellinae were not part of that clade. Griswold et al. (2005) placed their included representatives of the two as successive outgroups to a clade of Desidae (marine spiders) and Dictynidae (slater spiders)*. Griswold et al. (1999) recognised a "fused paracribellar clade" including Amphinectidae, Desidae, Agelenidae, Stiphidiidae and Neolana, supported by features of the silk-spinning organs. This clade was still recognised by Griswold et al. (2005) but with slightly different contents, including the Dictynidae and excluding the Stiphidiidae.

*It is also noteworthy that neither of the two analyses by Griswold et al. (1999, 2005) have supported a close connection between Amphinectidae and Neolana, a genus included in Amphinectidae by Platnick's Spider Catalog, but placed in its own family by many other authors.

One final thing, which has nothing to do with the previous paragraphs, but which I felt compelled to include. The following passage is taken from a description of a New Zealand genus of Amphinectidae in Forster & Forster (1999):

Although the Otago species, Akatorea otagoensis, was occassionally found in rotting logs like its Fiordland relative, it was surprisingly rare until a sudden emergency with drains on our Dunedin property required an excavation. A metre or so below the surface of our lawn the likely answer to the true home of these spiders was revealed. There, lining the cracks and crevices in the clay subsoil, were webs (and eggsacs) all inhabited by these pale straw-coloured spiders, which proved to be the previously rare Akatorea otagoensis.

Science is often a matter of detailed planning and careful investigation. However, never underestimate the importance on many an occassion of sheer dumb luck.

REFERENCES

Davies, V. T. 1998. A revision of the Australian metaltellines (Araneae : Amaurobioidea : Amphinectidae : Metaltellinae). Invertebrate Taxonomy 12: 211-243.

Davies, V. T. 1999. Carbinea, a new spider genus from north Queensland, Australia (Araneae, Amaurobioidea, Kababininae). Journal of Arachnology 27 (1): 25-36.

Davies, V. T. 2002. Tasmabrochus, a new spider genus from Tasmania, Australia (Araneae, Amphinectidae, Tasmarubriinae). Journal of Arachnology 30 (2): 219-226.

Forster, R. R., & L. M. Forster. 1999. Spiders of New Zealand and their Worldwide Kin. University of Otago Press: Dunedin (New Zealand), and Otago Museum: Dunedin.

Griswold, C. E., J. A. Coddington, N. I. Platnick & R. R. Forster. 1999. Towards a phylogeny of entelegyne spiders (Araneae, Araneomorphae, Entelegynae). Journal of Arachnology 27: 53-63.

Griswold, C. E., M. J. Ramírez, J. A. Coddington & N. I. Platnick. 2005. Atlas of phylogenetic data for entelegyne spiders (Araneae: Araneomorphae: Entelegynae) with comments on their phylogeny. Proceedings of the California Academy of Sciences, Fourth Series 56 (suppl. 2): 1-324.