ScienceDaily (Oct. 21, 2009) — Researchers from the United States and Slovenia have discovered a new, giant Nephila species (golden orb weaver spider) from Africa and Madagascar.
This photo shows a giant golden orb-web exceeding 1 meter in diameter: Nephila inaurata, Rodrigues, Indian Ocean. (Credit: Photo M. Kuntner)
The findings are published in the Oct. 21 issue of the journal PLoS ONE. Matjaž Kuntner, chair of the Institute of Biology of the Slovenian Academy of Sciences and Arts and a Smithsonian research associate, along with Jonathan Coddington, senior scientist and curator of arachnids and myriapods in the Department of Entomology at the Smithsonian's National Museum of Natural History, also reconstructed size evolution in the family Nephilidae to show that this new species, on average, is the largest orb weaver known. Only the females are giants with a body length of 1.5 inches (3.8 centimeters) and a leg span of 4-5 inches (10-12 centimeters); the males are tiny by comparison.
More than 41,000 spider species are known to science with about 400-500 new species added each year. But for some well-known groups, such as the giant golden orb weavers, the last valid described species dates back to the 19th century.
Nephila spiders are renowned for being the largest web-spinning spiders. They make the largest orb webs, which often exceed 3 feet (1 meter) in diameter. They are also model organisms for the study of extreme sexual size dimorphism and sexual biology.
Giant golden orb weavers are common throughout the tropics and subtropics. Thousands of Nephila specimens that have been collected are in natural history museums. Past taxonomists collectively recognized 150 distinct Nephila species, but in his doctoral thesis, Kuntner recognized only 15 species as valid. Linnaeus described the first Nephila species in 1767, and Karsch described the last genuinely new Nephila in 1879. All more recent descriptions turned out to be synonyms.
"It was surprising to find a giant female Nephila from South Africa in the collection of the Plant Protection Research Institute in Pretoria, South Africa, that did not match any described species," said Kuntner, who first examined the specimen in 2000.
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Discovery of the Largest Orbweaving Spider Species: The Evolution of Gigantism in Nephila
Matjaž Kuntner1,2*, Jonathan A. Coddington2
1 Institute of Biology, Scientific Research Centre of the Slovenian Academy of Sciences and Arts, Ljubljana, Slovenia,
2 Department of Entomology, National Museum of Natural History, Smithsonian Institution, Washington D. C., United States of America
Abstract Top
Background
More than 41,000 spider species are known with about 400–500 added each year, but for some well-known groups, such as the giant golden orbweavers, Nephila, the last valid described species dates from the 19th century. Nephila are renowned for being the largest web-spinning spiders, making the largest orb webs, and are model organisms for the study of extreme sexual size dimorphism (SSD) and sexual biology. Here, we report on the discovery of a new, giant Nephila species from Africa and Madagascar, and review size evolution and SSD in Nephilidae.
Methodology
We formally describe N. komaci sp. nov., the largest web spinning species known, and place the species in phylogenetic context to reconstruct the evolution of mean size (via squared change parsimony). We then test female and male mean size correlation using phylogenetically independent contrasts, and simulate nephilid body size evolution using Monte Carlo statistics.
Conclusions
Nephila females increased in size almost monotonically to establish a mostly African clade of true giants. In contrast, Nephila male size is effectively decoupled and hovers around values roughly one fifth of female size. Although N. komaci females are the largest Nephila yet discovered, the males are also large and thus their SSD is not exceptional.
Citation: Kuntner M, Coddington JA (2009) Discovery of the Largest Orbweaving Spider Species: The Evolution of Gigantism in Nephila. PLoS ONE 4(10): e7516. doi:10.1371/journal.pone.0007516
Editor: Thomas Buckley, Landcare Research, New Zealand
Received: July 31, 2009; Accepted: September 13, 2009; Published: October 21, 2009
This is an open-access article distributed under the terms of the Creative Commons Public Domain declaration which stipulates that, once placed in the public domain, this work may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose.
Funding: NSF (PEET to G. Hormiga and J. Coddington) and Sallee Charitable Trust (to I. Agnarsson and M. Kuntner) funded the 2001 expedition, EU 6th FP (Marie Curie IRG to M. Kuntner) and Slovenian Research Agency (ARRS to M. Kuntner) funded the 2006 expedition, Ezemvelo KZN Wildlife supplied the collect and export permits. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
* E-mail: kuntner@gmail.com
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