Cuban Crocodiles Pose Conservation Conundrum Genetic Analyses of Endangered Animals Reveal Widespread Mixing with Another Species
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NATURE DESMOND BOYLAN FOR FOR BOYLAN DESMOND A baby crocodile at a farm in the Zapata Swamp, Cuba, where the animals are bred before being released into the wild. ECOLOGY Cuban crocodiles pose conservation conundrum Genetic analyses of endangered animals reveal widespread mixing with another species. BY SARA REARDON, CIÉNAGA DE ZAPATA genetic purity of the two species? Or should Cuban researchers have been slow to NATIONAL PARK, CUBA they let hybridization take its course, in the abandon the traditional method of classify- hope that an influx of genes from the hardy ing crocodiles by their head shape in favour ozens of spotted baby crocodiles sit American crocodile will help the Cuban species of more precise genomic identification — in as still as garden statues. Only their to survive as its habitat shrinks and the climate part because the country’s research centres swivelling eyes betray their intense changes? So far, science has not provided a clear lack modern genetic-research tools. Yoamel Dinterest in passing visitors. Then, suddenly, the answer. “We need to follow our instincts, our Milián-García, a biologist at the University of animals snap to life, and begin ambling around ideas, our judgement, and hope that future Havana, discovered that Cuban and American the Zapata Swamp Captive Breeding Farm in generations won’t criticize us,” says Pérez. crocodiles were breeding with each other only Cuba’s swampy Matanzas province. Former president Fidel Castro began the after taking tissue samples to Canadian and US “They’re cute as long as their mouths are effort to breed and conserve the island’s rep- labs with next-generation DNA-sequencing closed,” says Etiam Pérez, an exotic-fauna tiles in 1960, not long after the revolution that technology. researcher at the farm whose leg bears scars put him in power. Yet today, just a few thou- His most recent analysis1 showed that half of from an encounter with an adult crocodile. sand Cuban crocodiles remain in the wild. the 227 wild Cuban crocodiles he tested were The facility is the centrepiece of the Cuban Logging and the expansion of agriculture hybrids, compared with just 16% of 137 cap- government’s 56-year effort to save the criti- have eaten away at their habitat, and demand tive animals. This suggests that the animals’ cally endangered Cuban crocodile (Crocodylus for their valuable leather and meat is high. In interbreeding has accelerated, and that genetic rhombifer). In January, the programme Cuba, where the average monthly salary is analyses are now the only reliable way to released its first 100 captive-born animals into about US$20, people run towards — not away distinguish between the species to study their the wild. But that success has been tempered by from — crocodiles, Pérez says, despite the behaviour. genetic analyses that have revealed widespread steep fines for killing them. Such situations are becoming common, as interbreeding between wild Cuban crocodiles The animals are more curious and aggres- improved sequencing technologies reveal the and the more resilient American crocodile sive than other crocodile species, and can leap extent to which species have interbred through (Crocodylus acutus). metres out of the water to catch tree-dwelling history, says Evon Hekkala, a conservation The findings have prompted Cuban conser- rodents called hutias, says George Amato, geneticist at Fordham University in New York vationists to rethink their ultimate goal. Should a conservation biologist at the American City. Her study2 of Egyptian crocodile mummies their breeding programme fight to maintain the Museum of Natural History in New York City. that are nearly 2,000 years old or more showed 596 | NATURE | VOL 537 | 29 SEPTEMBER©2016 Ma c2016millan Publishers Li mited, part of Spri nger Nature. All ri ghts reserved. IN FOCUS NEWS them to be very different from modern Nile NEUROSCIENCE crocodiles (Crocodylus niloticus), which are thought to be the descendants of multiple species that have probably died out. Hekkala is now studying fossilized crocodiles from Global brain project the Caribbean to see what they reveal about the history of the various species there. To Milián-García, the most important sparks concern question is whether humans have played a part in the loss of the Cuban crocodile’s genetic identity. The Cuban and American Worries include how developing countries could participate. species normally occupy different niches: the latter is more tolerant of salt water and BY SARA REARDON human brain scans or animal gene expression nests in holes, whereas the former prefers into standardized formats that would allow fresh water and builds nests on mounds. n recent years, brain-mapping initiatives more people to analyse them. Habitat destruction may be forcing them have been popping up around the world. But many attendees worried about mar- into the same ecological niche, which could They have different goals and areas of exper- shalling the numerous proposals under one produce hybrids ill-equipped to prosper in Itise, but now researchers will attempt to apply umbrella. Existing brain-research programmes a changing ecosystem. their collective knowledge in a global push to have different priorities: Japan and China, for But an influx of genes from the saltwater- more fully understand the brain. instance, are investing heavily in primate tolerant American crocodile could also Thomas Shannon, the US under secretary research, which the United States tends to avoid help Cuban crocodiles to survive as Cuba’s of state for political affairs, announced the for ethical reasons. The European Union’s flag- rising seas encroach on freshwater rivers launch of the International Brain Initiative on ship Human Brain Project (HBP) is attempting and lakes. “Do you want to be judgemen- 19 September at a meeting that accompanied to understand the basic science of how the brain tal about a species getting by by accessing the United Nations’ General Assembly in New works, whereas Canada is focusing on creating the genomic resources available to it by York City. The United States, Argentina, Japan technologies that can be applied to medicine. hybridization?” Hekkala asks. and Germany are collaborating on the initiative. Others expressed concerns that some meet- While they grapple with such questions, Details — including who will pay for it — ing attendees were ignoring existing resources. Cuban researchers are using in-depth are still up in the air. However, researchers at For instance, Canada’s nine-year-old CBRAIN genetic studies to optimize their breeding a separate, but concurrent, meeting hosted by programme serves as a clearing house for data programme. Last month, Milián-García, the US National Science Foundation at the and methods, and is already used by neurosci- Pérez and their colleagues reported3 that Rockefeller University in New York City dis- entists in 22 countries and the HBP. female Cuban crocodiles can produce cussed which aspects of programmes already single clutches of eggs that contain DNA in existence could be aligned under the global LEFT OUT from multiple fathers. To maximize the initiative. The reaction was a mixture of con- And some worry that the global initiative would amount of genetic diversity in the captive cerns over the fact that the initiative could exclude developing countries. “If the only way population, he says, the crocodile-breeding siphon resources and attention from existing to do international is for each country to put in farm should allow each female to mate with projects, and anticipation over the possibilities US$300 million, that will not be international,” several males. for advancing our knowl- says Sandhya Koushika of the Tata Institute of Yet conservation research in Cuba edge about the brain. “We’re Fundamental Research in Mumbai, India. remains challenging. Everything from One of several goals still in the Valeria Della-Maggiore, a physiologist at the buying fuel to sending samples to other for the initiative is the neuroscience University of Buenos Aires in Argentina and countries requires a US government per- creation of universal craft era. chair of the Latin American Brain Mapping mit, a consequence of the decades-old US brain-mapping tools. Labs Everyone has Network, says that she knew nothing about economic embargo against Cuba. “It’s the tend to make their own their secret the International Brain Initiative and was sur- only place you can’t solve a problem with variations of experimental sauce.” prised to see Argentina among its sponsors. The money,” Amato says. tools and often run experi- Rockefeller programme did not include speak- Despite these difficulties, Cuba’s per- ments in their own ways. This makes it hard ers from developing countries, and she is con- ennially underfunded scientists make do for different teams to collaborate or exchange cerned that they are not being consulted in the by forging international collaborations information. At the Rockefeller meeting, development of international initiatives. and dreaming up homemade solutions to physicist Michael Roukes of the California The point of the Rockefeller gathering, says equipment shortages. Institute of Technology in Pasadena noted that co-organizer Cori Bargmann, a neuroscientist And the Cuban government continues the Industrial Revolution took off only when at the Rockefeller University, was to get a sense to make conservation a priority. In 2014, factories with interchangeable components of existing programmes, and future meetings it closed off 500 hectares of the Zapata began replacing companies that had one-off will be more focused once organizers know who Swamp to future development, protect- machines. “We’re still in the neuroscience craft is to participate in the joint project. ing land that had previously produced era,” he says. “Everyone has their secret sauce.” Overall, scientists are hopeful that the 15,000 cubic metres of milled lumber per Another idea proposed at the meeting was the new global initiative will enable them to take year.