{"id":273994,"date":"2019-02-19T15:13:37","date_gmt":"2019-02-19T18:13:37","guid":{"rendered":"http:\/\/revistapesquisa.fapesp.br\/?p=273994"},"modified":"2019-07-22T14:40:30","modified_gmt":"2019-07-22T17:40:30","slug":"how-snakes-arrived-in-the-galapagos","status":"publish","type":"post","link":"https:\/\/revistapesquisa.fapesp.br\/en\/how-snakes-arrived-in-the-galapagos\/","title":{"rendered":"How snakes arrived in the Gal\u00e1pagos"},"content":{"rendered":"

In November 2016, BBC One viewers were treated to a spectacular animal chase: dozens of runner snakes of the species Pseudalsophis occidentalis<\/em> crawled out of crevices and attempted to capture an iguana on a beach on Fernandina, a Gal\u00e1pagos island 1,000 kilometers (km) off the coast of Ecuador. The iguana outruns the snakes, scaling the cliffs to a successful escape. The 2-minute, 17-second film, which won a British Academy Television Craft Award in May 2017, depicted the struggle for survival and habits of a poorly studied group of vertebrates in the archipelago\u2014snakes.<\/p>\n

Brazilian and Ecuadorian biologists witnessed scenes like these as they collected snakes on the Gal\u00e1pagos Islands, an archipelago in Ecuador comprising 13 major islands, six smaller islands, and dozens of islets and rocky outcroppings, spanning an area of 8,000 km2<\/sup>. Morphological (external appearance, bones, and organs) and molecular (genetic) analyses of snake specimen from the islands allowed the researchers to reconstruct their colonization routes and identify three new species. The nine recognized species are of the genus Pseudalsophis. <\/em>They are between 35 and 85 centimeters (cm) in length and some occur only on specific islands of the archipelago.<\/p>\n

The article titled \u201cHow snakes arrived in the Gal\u00e1pagos<\/em>,\u201d published in issue no. 270 of Pesquisa FAPESP<\/em>, does not represent a public and permanent scientific record, nor does it constitute a nomenclatural act published in accordance with the guidelines of the International Code of Zoological Nomenclature (ICZN).<\/strong><\/div>\n

The common ancestor of the nine species no longer exists according to the study, which was published in August in the journal Systematics and Biodiversity<\/em>. With a body length of 50 cm, P. hoodensis<\/em> is thought to have been the first species derived from the hypothetical ancestor. Other species originated from it, in a process known as speciation. The ancestors of P. hoodensis<\/em> must have first arrived on now-submerged islands of the Gal\u00e1pagos archipelago about 7 million years ago, the researchers concluded. Their conclusions are consistent with the notion that there might have been a Proto-Gal\u00e1pagos as proposed by American oceanographers and geologists in a 1994 article in Nature<\/em>.<\/p>\n

According to the study, the ancestors of P. hoodensis<\/em> must have set out from the coast of Ecuador\u2014where their sister species, P. elegans<\/em>, is still to be found\u2014and arrived in Gal\u00e1pagos on pieces of roots and branches that broke off from the shoreline. P. hoodenis<\/em> is found only on Espa\u00f1ola Island\u2014the oldest of the current string of islands\u2014and adjacent islets. \u201cThe divergence of P. hoodensis<\/em> occurred about 4.5 million years ago, initiating a process of speciation that led to the colonization of other islands by other species in the archipelago,\u201d says biologist Hussam Zaher, a professor at the Museum of Zoology of the University of S\u00e3o Paulo (MZ-USP), who led the expedition.<\/p>\n

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Tribute to Darwin<\/strong>
\nGal\u00e1pagos is home to many endemic species of animals: of the estimated 5,000 species inhabiting the islands, around 2,000\u2014including birds, turtles, reptiles, and other groups\u2014occur nowhere else. The archipelago is famous as the setting in which Charles Darwin (1809\u20131882) found clues that led to his formulation of the principle of natural selection and the theory of evolution in 1859. He began to wonder whether one species could originate others after seeing that turtles and birds varied in body shape between the islands he had visited in 1835 on his voyage aboard the HMS Beagle<\/em>. \u201cDarwin reported seeing a green snake on Floreana Island,\u201d says Zaher, \u201cbut we did not find any there. They likely have become extinct.\u201d The snakes on the islands eat birds, iguanas, smaller lizards, insects, and fish and are predated by hawks.<\/p>\n

Of the three new Gal\u00e1pagos species, one was named P.<\/em> darwini<\/em> in tribute to Darwin. It is about 40 cm long and lives on the islet of Tortuga as well as on the larger islands of Isabela and Fernandina. Another species, which only occurs on Santiago Island and adjacent islets, was named P. hephaestus<\/em> after Hephaestus, the Greek god of fire, in allusion to the archipelago\u2019s volcanic origin. The third is P. thomasi<\/em>, a species found on Santiago Island and named after American biologist Robert Thomas. A professor at Loyola University, Thomas formulated a classification of Gal\u00e1pagos snakes that remained in use for 20 years.<\/p>\n

In a 1997 article in Herpetological Natural History<\/em>, Thomas reclassified the four then-known species and subspecies of Gal\u00e1pagos snakes into three different taxonomic genera, two of which are also found on Caribbean islands. \u201cMy research on Gal\u00e1pagos snakes was done using data on most specimens available at museums around the world. It was entirely morphological,\u201d says Thomas.<\/p>\n

Two years later, in the Bulletin of the American Museum of Natural History<\/em>, Zaher proposed that the species form a unique lineage more closely related to the species P. elegans<\/em> of the South American west coast than to Caribbean lineages. His study was based on variation of the hemipenis\u2014the male reproductive organ, usually located within the tail\u2014in two species of snakes in the archipelago and in species representing South American lineages. Years later, molecular studies by his group confirmed his findings.<\/p>\n

In a 2009 paper published in the journal Pap\u00e9is Avulsos de Zoologia<\/em>, Zaher and biologist Felipe Grazziotin, a researcher at Instituto Butantan, proposed a classification that better reflected these findings, integrating the Gal\u00e1pagos species, then considered by Thomas to be a subspecies, and the mainland species P. elegans,<\/em> into a single genus called Pseudalsophis<\/em>. The proposed classification was accepted by other experts.<\/p>\n

In molecular analysis of samples collected on the expedition to the Gal\u00e1pagos, Grazziotin found that the species in the archipelago were related to their sister species on the coast of Ecuador and therefore must have come from the mainland. This further supported the Brazilian researchers\u2019 hypothesis and ruled out the possibility that some species could also have come from the Antilles.<\/p>\n

Believing that three different lineages had colonized the archipelago, Thomas had included the Gal\u00e1pagos snakes in the genera Philodryas, Antillophis,<\/em> and Alsophis<\/em>. The genus Philodryas<\/em> includes aggressive species, which could indicate that the ones in the archipelago are also aggressive. However, the researchers noted that the snakes were aggressive only toward animals they prey on for food, such as iguanas. \u201cWe weren\u2019t sure whether the Gal\u00e1pagos species could be aggressive or venomous like some snakes of the genus Philodryas<\/em> in Brazil, but none of them attempted to bite us,\u201d notes Grazziotin, who joined the expedition as a doctoral student under Zaher. \u201cThe most they did was defecate, a common defense behavior in this family of snakes.\u201d<\/p>\n

The mainland species\u2014P. elegans<\/em>\u2014and the oldest Gal\u00e1pagos species\u2014P. hoodensis<\/em> and P. biserialis<\/em>\u2014average 60 cm in length. According to Zaher, this ancestral morphological pattern evolved in the archipelago, forming two distinct lineages termed as large and small insular species. The two lineages spread from east to west, cohabiting the larger islands (Santiago, Santa Cruz, Fernandina, and Isabela). Large insular species, which were 75 cm long, began to colonize the islands 3.3 million years ago, while the small species, around 25 cm long, began to occupy the younger islands 2.2 million years ago (see infographic<\/a><\/em>).<\/p>\n

Curiously, says Grazziotin, larger and smaller snakes\u2014one species of each\u2014can either live alone on some islands or share the same space with each other, but never with more ancient, medium-size species. \u201cLarge and small snakes can coexist without competing for food,\u201d says Zaher. \u201cThe larger ones live on rocks and prey on adult lava lizards, young iguanas, and birds, while smaller ones can find food in more restricted environments, such as crevices in rocks, feeding on lizards and insects.\u201d<\/p>\n

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Miguel T. Rodrigues\/USP<\/span><\/a> Fernandina Island, the youngest of the Gal\u00e1pagos IslandsMiguel T. Rodrigues\/USP<\/span><\/p><\/div>\n

The voyage<\/strong>
\nThe expedition to Gal\u00e1pagos took place in June 2008. After the voyage came the laborious work of describing the species and performing genetic testing on collected samples, generating a wealth of information that took many years to be interpreted. Four Brazilian researchers\u2014Zaher and Grazziotin along with Miguel Rodrigues and Luciana Lobo, both also from USP\u2014and four Ecuadorian researchers\u2014Yanes-Mu\u00f1oz, Altamirano-Benavides, Cruz Marques, and park ranger Simon Villamar\u2014spent two weeks at sea aboard the Queen Mabel,<\/em> along with four crew members. Except for the rare nights at hotels on the larger islands, they left the boat only to collect snakes in the early morning or late afternoon.<\/p>\n

The researchers visited 14 islands and adjacent islets, many of which are closed to visitors other than researchers, where they collected 149 specimens, of which 47 were sampled and released and the remainder were stored for detailed laboratory testing. The dominant species (44 specimens of the total) was P. occidentalis<\/em>, from Fernandina Island.<\/p>\n

The Gal\u00e1pagos archipelago is home to about 25,000 people, of whom 18,000 live in the city of Puerto Ayora on Santa Cruz Island. Pollution, especially plastic packaging, has been a concern for local authorities due to its potential adverse effects on wildlife. \u201cBecause of the litter,\u201d Zaher remarked, \u201csome islands are quite degraded.\u201d<\/p>\n

Project<\/strong>
\nOrigin and evolution of snakes and their diversification in the neotropical region: A multidisciplinary approach (no. 2011\/50206-9<\/a>); Grant Mechanism<\/strong> Thematic Project; Program<\/strong> Biota FAPESP; Principal Investigator<\/strong> Hussam El Dine Zaher (USP); Investment<\/strong> R$4,921,754.91.<\/p>\n

Scientific articles
\n<\/b>ZAHER, H. et al.<\/em> Origin and hidden diversity within the poorly known Gal\u00e1pagos snake radiation (Serpentes: Dipsadidae)<\/a>. Systematics and Biodiversity<\/strong>. on-line. 22 ago. 2018.
\nTHOMAS, R. Gal\u00e1pagos terrestrial snakes: biogeography and systematics<\/a>.\u00a0Herpetological Natural History<\/strong>. v. 5, n. 1, p. 19-40. 1979.
\nZAHER, H. Hemipenial morphology of the South American xenodontine snakes, with a proposal for a monophyletic Xenodontinae and a reappraisal of colubroid hemipenes<\/a>.\u00a0Bulletin of the American Museum of Natural History<\/strong>. v.\u00a0<\/em>240, p. 1\u2013168. 1999.
\nZAHER, Hussam\u00a0et al<\/em>.\u00a0Molecular phylogeny of advanced snakes (Serpentes, Caenophidia) with an emphasis on South American Xenodontines: a revised classification and descriptions of new taxa<\/a>.\u00a0<\/em>Pap\u00e9is Avulsos de Zoologia<\/strong>. v. 49, n. 11, p.115-3. 2009.
\nCHRISTIE, D. M.\u00a0et al<\/em>.\u00a0Drowned islands downstream from the Galapagos hotspot imply extended speciation times<\/a>.\u00a0Nature<\/strong>. v. 355, p. 246-8. 16 jan. 1992.<\/p>\n","protected":false},"excerpt":{"rendered":"Brazilian and Ecuadorian researchers trace the routes the reptiles used to colonize the archipelago and identify three new species","protected":false},"author":17,"featured_media":274002,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"categories":[159],"tags":[206,209,231],"coauthors":[5968],"class_list":["post-273994","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-science","tag-biodiversity","tag-biology","tag-evolution"],"acf":[],"_links":{"self":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/273994","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/users\/17"}],"replies":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/comments?post=273994"}],"version-history":[{"count":6,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/273994\/revisions"}],"predecessor-version":[{"id":296982,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/273994\/revisions\/296982"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/media\/274002"}],"wp:attachment":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/media?parent=273994"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/categories?post=273994"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/tags?post=273994"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/coauthors?post=273994"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}