rsg_book_2013

InvertebratesProject SummaryFeasibility: Field surveys by British Arachnological Society volunteers,initiated three years before the recovery began, confirmed the current status ofD. plantarius and identified potential new English receptor sites. Confirmation ofspecies’ status also came from checking records of its congener D. fimbriatus,with which it is easily confused, and from a public appeal for Dolomedessightings. Field survey work is ongoing.Implementation phase: By 2010 receptor sites had been identified andprioritized, and work undertaken to establish appropriate provenance of stock.The priority sites were on the same river system as the most vulnerable extantpopulation but with habitat much more similar to that of the more distant Englishpopulation. Although these two populations differed genetically, no evidence wasfound of either inbreeding depression or hybrid vigor when they were crossed incaptivity (Smith, 2011). It was therefore decided to stock new sites from bothpopulations to maximize genetic diversity. Introductions to new sites of spidersfrom the smaller and more vulnerable of the English populations (Smith, 2000)used three-month-old spiderlings that had been captive-reared in individual testtubes. With mean brood size of over 500 and survival to three months in captivityof >80%, large numbers of spiderlings were available for release from relativelysmall numbers of wild-caught females. These females were also retained incaptivity until they produced second broods (this species stores sperm) before rereleaseat their point of capture. Successful second brood production issignificantly greater in captivity than in the wild and so this method helped tooffset depletion of the source population. Females from the larger Englishpopulation were also caught from the wild carrying egg sacs and were retained incaptivity until their broods hatched. They were then released to new sites withtheir broods (this species shows maternal care), removing the risk of predation ofthe female and her egg sac.As well as establishing new site populations, the translocation program sought toexpedite recolonization ofrecently restored habitatwithin the more vulnerableEnglish site. Thepopulation there hadbecome confined to twosmall areas and hadundergone a sharp declinein genetic diversity over a20 year period (Holmes,2008). Captive rearedstock from these residualareas was released intotwo areas of restoredhabitat between 2010 and2012 and a chain of newponds excavated to helpSpider release into the wild © Sheila Tilmouth3