Sunday, September 18, 2016

Speaker Report - Sept 2016 - On Spiders

Dr Ron Atkinson lived and worked in Toowoomba, so is familiar to some of our members. Accompanied by his wife and daughters, he was made welcome on Friday night, and all listened with great interest to his talk titled “The Twenty-first Century Spiderman”. Enormous changes have been made within the field of spider taxonomy since the 19th century, and Ron outlined some of them.

A small spider field guide with black and white illustrations published in 1968 is now almost completely obsolete. Mascord’s “Australian Spiders in Colour”, published in 1970 and owned by some of us, was a great improvement as images were in colour, but is probably now 50% incorrect. “A guide to the Spiders of Australia” by Volker Framenau and others, full of information and containing excellent colour photographs was published only two years ago but already needs revision. 

The early scientists describing Australia’s wildlife, including spiders and insects, used genera and family names familiar to them from their work in the Northern hemisphere, but they proved to be inaccurate, so changes were later made. Spiders once allotted to the genus Epeira in Australia, are now placed in at least seven different spider families. The common spider, Eriophora transmarina, the garden orb weaver, has had nine name changes since it was first described in 1865.

Two funnel-web spiders were named in 1873 and 1877 by Koch and Pickard-Cambridge respectively, Hadronyche cerbera and Atrax robustus; now these have been expanded to more than 30 Hadronyche species, many named for their locations – H. lamingtonensis, H. alpina, H. Tambo, H. monaro. The three Atrax are probably incorrectly named since taxonomic convention says that the first published generic name for the group should apply for all others of the same kind of spider.

 Some spiders show strong sexual dimorphism, like Mopsus mormon, a jumping spider. This was confusing for some taxonomists, especially when more females than males are found, or vice versa, and they were first thought to be separate species. There are various reasons for these name changes. Early scientists working on spiders could only communicate by letter, and mail services within Australia and overseas were of course much slower than they are today. This meant that many species which were identical were given different names by different people describing them. A paper which was written in Eastern Australia and published in the UK might take years before it arrived at the home of a biologist in a different part of Australia. 

Technology of course has vastly improved since the 1870s. Taxonomists then relied on line drawings to illustrate their descriptions, and some were much better artists than others. At that time some did not realise what features were important - Funnel web spiders are separated into species in some cases merely by bulge sand spurs on their legs or by the shape of their palps or epigynum (sexual parts).

Microscopes have been vastly improved since those times, allowing more specific descriptions. For example only one white-tailed spider was known in 1989, the species named Lampona cylindrata. But Norman Platnickin 2000 examined all specimens of white-tailed spiders held in collections in Australia and overseas and was able to separate them into 56 species of Lampona, plus 145 species in 21 other genera; an amazing 201 separate species in all. The internet, macro lenses and digital photography have all made huge improvements in speed and accuracy of communication and image quality, and today every good museum and research centre now has access to a scanning electron microscope, enabling the minutest hairs on a spider’s leg to be seen in great detail. At least some of these minute features have taxonomic value. 

Over the last few years, the optimum tool in examining relationships between life-forms, DNA profiling, has become more accessible. For simplicity’s sake, mitochondrial DNA of spiders is being examined, not the whole genome. DNA analysis makes the whole process of classification more objective because it reveals the evolutionary changes that have led to the spider species we have today. Charts called “clades” can be created using the data – these look and are complex, but they show clearly the similarities, differences and relationships between spider families, genera and species. Some spider families have been altered, divided or combined, and in some cases new names given. This process is being used to revolutionise the taxonomy of other life forms as well, including human ancestry. 

Ron explained the origin of and how to use his “Find-a-spider” website – on this very useful site he has provided several ways for interested spider-hunters to identify their catches – by family, by species name, and by photographs. Ron updates his site when a change appears on the “World Spider Catalogue”, the High Court of Arachnology. The Atlas of Living Australia also has links to old and new spider names. Several questions were asked by members at the end of his talk. All showed their appreciation of Ron and his family for travelling from Brisbane to speak to us on such an interesting topic.
(Article and photos by Glenda Walter) 

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