Snailing the South Seas

11th September 2014

News, Alumni news

The remarkable story of the endangered Partula tree snails and their role in the development of evolutionary biology is detailed in a new book by Wadham alumnus Dr Justin Gerlach (1988, Zoology).

  • Justin Gerlach

    Justin Gerlach

  • Partula

    A Partual shell

  • Snail hunting

    Snail hunting

In Snailing round the South Seas - the Partula story, Justin describes how, at the start of the 20th century, the naturalist approach of collection and observational natural history, characterised by the expeditions of Captain Cook and Charles Darwin in the 19th Century, were superseded by a new generation of biologists, eager to combine field data with the concepts of genetics and statistics.

According to Justin, the most remarkable of these was Henry Crampton, already a notable biologist by the time he turned to Partula. Crampton started one of the most remarkable studies ever undertaken: the analysis of variation and evolution of the tree-snails of every single valley across the Society Islands in the South Pacific Ocean. Although Crampton never finished his work on the quarter of a million snails that he collected, the results that he did publish inspired other researchers. With them the study of evolution in the wild became the study of genetics.

Gerlach explains: “For over 200 years Partula were at the heart of the development of the biological sciences. All this came to an end after 1974 when carnivorous snails were introduced to Tahiti in a catastrophic attempt at biological control. Within the space of 20 years one of the most dramatic extinction events unfolded, devastating a remarkable group of island species. Today just a handful of species survive, as tiny relict populations in the wild, or in a captive breeding programme. Partula remain at the heart of cutting-edge projects, but now those are dedicated to the precarious task of keeping species from extinction.”

After completing his Zoology degree at Wadham (with College tutors David Mabberley and Robin McCleery) Justin stayed on for his DPhil, researching 'The ecology of the carnivorous snail Euglandina rosea', a species introduced around the world's tropical islands as a biological control for pest snails.

Describing the inspiration for his book Justin said: “I've always been interested in conservation and had known since the 1980s that Euglandina had exterminated dozens of species of snail, rather than eating the intended target - the tough giant African snails. Why it was such a problem in the south Pacific but apparently not in the Indian Ocean was a question that intrigued me. The Christopher Welch Scholarship enabled me to put together my own research programme, then with the support of Wadham and London Zoo I was able to get out to the islands and collect some of the last surviving Partula snails. Some species haven't survived but descendants of some of the snails I collected are now in several zoos, but sadly with little prospect for putting them back into the wild.”

Justin, who is now based  in Cambridge, is currently studying the Partula collection at the Philadelphia Museum, some quarter of a million specimens.