Bermuda land snails, scientific name Poecilozonites, are an endemic genus of pulmonate land snail in the family Gastrodontidae (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005). 12 species are known from the fossil record, and 4 of these species (bermudensis, nelsoni, circumfirmatus, reinianus) survived into modern times, but due to the highly negative effects of human development, the extant species has been reduced down to only bermudensis and circumfirmatus.[1]
Scientists believe that Poecilozonites colonised the mid-Atlantic island of Bermuda at least 300,000 years ago. Poecilozonites makes up 95% of Bermuda's terrestrial fossils. Only one other large pulmonate, Succinea, has been found as a fossil.
Research
The major contributor to the natural history of Poecilozonites was HarvardpaleontologistStephen Jay Gould who did his doctorate and early academic research on Bermuda's snails. On December 21, 1999, Dr. Gould described to The Royal Gazette of first visiting Bermuda as a deckhand on a Woods Hole Research Center boat in 1959. "I was a geology major. I had a look around and found all these wonderful fossil snails in all their variety. The geology of Bermuda had already been worked out by then and I thought these snails would become a pretty good PhD."
Poecilozonites is a member of the Gastrodontidae family and is likely to have colonised Bermuda from North America as one specimen via flotsam. Gould cites research which uses the "probability of self-impregnation" as the justification of this view.
Gould claims the proto-poecilozonites "underwent a vigorous and presumably rapid adaptive radiation" and diversified into three subgenera and 15 species, ranging in size from P. nelsoni (max dia. 46mm) to the subspecies' of P. gastrelasmus and P. discozonites which were found to rarely exceed 5mm.[clarification needed] Although extinction of various species occurred in prehistoric times, with the introduction of predators by man in the 16th century, namely hogs, dogs, cats, and rats, the snail suffered, but has apparently hung on.
It was the introduction of the predator snails Euglandina and Gonaxis in the 1950s and 1960s and the increased use of pesticides that led to the presumed extinction of the surviving Poecilozonites species by the 1970s.
The apparently accidental introduction of the edible snail, Otala in the mid-1920s set the die for the destruction of Poecilozonites as by the 1950s, Otala had become a pest and measures were taken to control their numbers. By the time of Gould's research in the mid-1960s, P. bermudensis and P. circumfirmatus were still common. He wrote of talking to an elderly woman who remembered a time when the shells were collected and burned for lime. By the mid-1970s, a Bermuda Biological Station scientist remembers opening his kitchen door and seeing none other than Gould exclaim "If I could only find one alive!"
In Eight Little Piggies, a book from 1993, Gould wrote: "I don't even think Euglandina has even dented Otala but it devastated the native Poecilozonites. I used to find them by the thousands throughout the Island. When I returned in 1973... I could not find a single animal alive. Last year (1991) I relocated one species, the smallest and most cryptic, but the large P. bermudensis, the major subject of my research, is probably extinct."
(Poecilozonites) are part of a class that are uniquely found on islands. Islands have these strange fauna because of their isolation. Back when I was studying them, we did not know where they came from or their closest relative. That can be done now with genetic research. Poecilozonites had a very impressive radiation in Bermuda. By far one of the largest for a species. It is a wonderful example of an experiment in local evolution. It's just that people did not realise that with the Euglandina, it would eat other snails too. Not just Otala, which by then had become a pest. No one ever said that Poecilozonites ever caused them trouble. It certainly is a tragic story.
In 2002, a Bermuda Aquarium, Museum and Zoo summer intern, Alex Lines, was sent out to Gould's old sites and is understood to have found a clutch of survivors. Several dozen snails were sent to London to aid their propagation.
Poecilozonites circumfirmatus is protected in Bermuda under the Protected Species Act (2003) and a Protected Species Recovery Plan was published for it in 2010 by the Bermuda Government, Department of Conservation Services.
In 2014 it was reported in The Royal Gazette that a live colony of Poecilozonites bermudensi (greater Bermuda land snail) had been found in an overgrown alley in Hamilton. The colony was apparently isolated from the rest of the island, including the effects of invasive species, by colonizing the alley early on.[3] A captive breeding program was carried out at Chester Zoo and the Zoological Society of London in the UK, resulting in the release of more than 4,000 snails into nature reserves on the island by June 2019.[4]
In 2020, Chester Zoo also reintroduced 800 lesser Bermuda land snails to the island, which were thought to have been extinct from the island since 2004.[5] The IUCN Red List considers both extant species to be Critically Endangered, with P. circumfirmatus being possibly extinct in the wild.[6][7]
Species
Species in the genus Poecilozonites include:[8][9]
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point. Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly "reappears" after a period of apparent absence.
In paleontology, a Lazarus taxon is a taxon that disappears for one or more periods from the fossil record, only to appear again later. Likewise in conservation biology and ecology, it can refer to species or populations that were thought to be extinct, and are rediscovered. The term Lazarus taxon was coined by Karl W. Flessa & David Jablonski in 1983 and was then expanded by Jablonski in 1986. Paul Wignall and Michael Benton defined Lazarus taxa as, "At times of biotic crisis many taxa go extinct, but others only temporarily disappeared from the fossil record, often for intervals measured in millions of years, before reappearing unchanged". Earlier work also supports the concept though without using the name Lazarus taxon, like work by Christopher R. C. Paul.
Pleistocene megafauna is the set of large animals that lived on Earth during the Pleistocene epoch. Pleistocene megafauna became extinct during the Quaternary extinction event resulting in substantial changes to ecosystems globally. The role of humans in causing Pleistocene megafaunal extinctions is controversial.
Gould's mouse, also known as the Shark Bay mouse and djoongari in the Pintupi and Luritja languages, is a species of rodent in the murid family. Once ranging throughout Australia from Western Australia to New South Wales, its range has since been reduced to five islands off the coast of Western Australia.
The flora and fauna of Bermuda form part of a unique ecosystem due to Bermuda's isolation from the mainland of North America. The wide range of endemic species and the islands form a distinct ecoregion, the Bermuda subtropical conifer forests.
Neontology is a part of biology that, in contrast to paleontology, deals with living organisms. It is the study of extant taxa : taxa with members still alive, as opposed to (all) being extinct. For example:
The poʻo-uli or black-faced honeycreeper, is an extinct species of passerine bird that was endemic to the island of Maui in Hawaiʻi. It is considered to be a member of the Hawaiian honeycreepers, and is the only member of its genus Melamprosops. It had a black head, brown upper parts and pale gray underparts. This bird inhabited only the wetter, easternmost side of Maui, where it had rapidly decreased in numbers. With extinction threatening, efforts were made to capture birds to enable them to breed in captivity. These efforts were unsuccessful; in 2004, only two known birds remained, and since then, no further birds have been sighted. A 2018 study recommended declaring the species extinct, citing bird population decline patterns and the lack of any confirmed sightings since 2004, and in 2019, the species was declared extinct.
Euglandina rosea, the rosy wolfsnail or cannibal snail, is a species of medium-sized to large predatory air-breathing land snail, a carnivorous terrestrial pulmonate gastropod mollusk in the family Spiraxidae.
Partula faba is an extinct species of air-breathing tropical land snail, a terrestrial pulmonate gastropod mollusk in the family Partulidae. This species was endemic to Ra'iātea and Tahaa, neighbouring islands which share the same lagoon, in French Polynesia. The species was the first Partula to be recorded.
Partula suturalis, common name the moorean viviparous tree snail or sutural partula, is a species of air-breathing tropical land snail, a terrestrial pulmonate gastropod mollusk in the family Partulidae. This species was endemic to the island of Moorea, French Polynesia. It is now extinct in the wild. It was previously listed as extinct in the IUCN Red List of Threatened Species, but has been moved to extinct in the wild since 2009. This error was the result of changing taxonomy.
An endling is the last known individual of a species or subspecies. Once the endling dies, the species becomes extinct. The word was coined in correspondence in the scientific journal Nature. Alternative names put forth for the last individual of its kind include ender and terminarch.
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Otala lactea, known as the milk snail or Spanish snail, is a large, edible species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk, in the family Helicidae, the typical snails.
Chelonoidis is a genus of turtles in the tortoise family erected by Leopold Fitzinger in 1835. They are found in South America and the Galápagos Islands, and formerly had a wide distribution in the West Indies.
Chelonoidis alburyorum is an extinct species of land tortoise that lived from the late Pleistocene to around 1400 CE. The species was discovered and described by Richard Franz and Shelley E. Franz, the findings being published in 2009.
↑ Gulick, Addison (1904). "The Fossil Land Shells of Bermuda". Proceedings of the Academy of Natural Sciences of Philadelphia. 56 (2): 406–425. JSTOR4062982.
Gould, Stephen Jay Allometry in Pleistocene land snails from Bermuda: The influence of size upon shape, Journal of Paleontology, v. 40 p.1131-1141.
Gould, Stephen Jay (December, 1969) An Evolutionary Microcosm: Pleistocene and recent history of the land snail P. (Poecilozonites) in Bermuda, Bulletin of the Museum of Comparative Zoology, v. 138(7) P. 407–532.
Gould, Stephen Jay (September 1969) Land Snail Communities and Pleistocene Climates in Bermuda: a Multivariate Analysis of Microgastropod Diversity, Proceedings of the North American Paleontological Convention, p.486-521.
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