A NEW species of baleen whale has been discovered. The stunning find, made after researchers studied the body shape and genetics of a few leviathan skeletons gathering dust for the past 25 years in a museum in Japan, reinforces just how little we still know about the world鈥檚 fauna, including its greatest mammals.
The announcement, which comes in the week that the IUCN, the World Conservation Union, released its latest list of the world鈥檚 endangered species (see 鈥淩ed alert鈥�), also highlights a growing problem in conservation science. We are in the midst of a major rethink about what constitutes a species, and where the boundaries between them lie. Most people were taught there are two species of elephant. Now we are unsure if there are three, or even six. Another icon, the gorilla, may actually be two closely related species of great ape. And some scientists say that uncertainty is making it increasingly difficult to know what populations most need to be conserved.
鈥淚f you don鈥檛 know who the players are, it鈥檚 hard to keep track of the game,鈥� says Scott Miller, an animal classification expert at the US National Museum of Natural History in Washington DC.
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Marine biologists have puzzled over the identity of the new whale species since eight specimens were caught by Japanese research whalers in the 1970s. That mystery now appears to be solved. The whales differ from known fin and sei whales in the shape of their skull and in the comb-like baleen plates they use to filter food from the water, reports a team of researchers led by Shiro Wada at the Japanese National Research Institute of Fisheries Science in Yokohama. The whales鈥� mitochondrial DNA also differs from that of related species, confirming that they belong in a separate, new species called Balaenoptera omurai (Nature, vol 426, p 278). The DNA evidence also backs taxonomists who have argued that Eden鈥檚 whale (B. edeni), is really two species: Eden鈥檚 whale, B. edeni, and Bryde鈥檚 whale, B. brydei. At a stroke, Wada鈥檚 team has ballooned the number of Balaenoptera species from six to eight.
Such events are by no means rare. Toothed whale species have been redefined several times in the past few decades, and biologists now suspect there may be as many as seven species of killer whale, and even more species of bottlenose dolphin. The landscape is so confused that the US government is sponsoring a meeting next April to figure out how to put things in better order.
The confusion runs much deeper than just whales. No one would expect experts to have a good handle on the number of species in any given group of beetles or worms, but molecular analyses are turning up new species even in groups of animals that are easy to see and have been studied in great detail for years. For instance, researchers published molecular evidence in 2001 that there are actually three species of modern elephant, the Indian, and the savannah and forest elephant in Africa. Then subsequent research last year suggested that elephants in Africa could even belong to five separate lineages (快猫短视频, 21 September 2002, p 24). And biologists cannot agree whether gorillas should be redefined into separate western and mountain species.
On other occasions, genetic comparisons have done away with species. The most notorious example is the red wolf, Canis rufus, which has been the focus of intense conservation effort in the US. Genetic studies now show that it is probably a simple hybrid of the grey wolf and the coyote.
No one knows just how much rethinking needs to be done, but Paul Hebert, an evolutionary biologist at the University of Guelph, Canada, has begun an ambitious programme that may turn up an answer. Hebert and his team are sequencing a single gene 鈥� cytochrome C oxidase I 鈥� in organisms and using this 鈥渕olecular barcode鈥� to identify species and tell them apart (快猫短视频, 13 March, p 14). Already, Hebert has read the barcodes for 200 species of North American birds and found three new species. Marine fishes show a similar rate of hidden species, and the rate for groups such as Asian bats and butterflies is around 5 per cent. 鈥淚 think we鈥檙e going to completely revise our understanding of these groups,鈥� he says.
Not everyone agrees there are enough hidden species to cause a conservation problem. 鈥淥ne or two per cent is a small deviation from what we have,鈥� says Michael Novacek, a mammal evolution expert at the US Museum of Natural History in New York. 鈥淭he barcode work substantiates a lot of traditional ornithology.鈥�
But to conserve some groups of animals, it is crucial to have a clear understanding of the species involved, says Novacek. 鈥淥bviously we need to save the whales in general,鈥� he notes, 鈥渂ut our knowledge of which populations are unique and most threatened can only be sustained if we know what those entities are.鈥�
Botanist Bruce Stein of US conservation body NatureServe warns that subdividing species too finely can dilute conservation efforts. 鈥淲e want to try to protect the full array of diversity, but we don鈥檛 want to have things so finely split that it is diverting our attention from those things that are very distinctive.鈥�
The sticking point is that no one can agree on exactly what makes a species. The traditional test 鈥� whether two populations can produce fertile offspring 鈥� is not practical for most species, so taxonomists go on appearance, bolstered in recent years by comparing DNA sequences. But at some point, people have to judge how much genetic divergence between two groups constitutes separate species. 鈥淭here aren鈥檛 completely objective ways to identify species,鈥� says James Mead, curator of marine mammals at the US National Museum of Natural History. In bottlenose dolphins, for example, DNA studies have identified 150 recognisable genetic lineages, but how many deserve to be species? 鈥淚t boils down to subjectivity,鈥� he says.
A new trend is to delineate species as evolutionarily separate lineages, including separated populations that are evolving in divergent ways. This has already happened for albatrosses. There are 13 recognised species, but the IUCN lists 21 threatened lineages, says Les Christidis of Museum Victoria in Melbourne. Extending that to all birds could double or triple the number of recognised species, says Mark Burgman of the University of Melbourne.
The issue is about more than semantics. As the red wolf shows, mistaken identity can lead to wasted conservation efforts. It can also muddy conservationists鈥� view of which animals should be given the highest priority. For example, now Wada鈥檚 group has identified three species of baleen whale instead of one, researchers will need to investigate how the behaviour of each differs, and which is rarer, says team member Tadasu Yamada, who researches marine mammals at the National Science Museum, Tokyo. Only then can conservationists design management plans to prevent such species going extinct.
Red alert
THIS week the World Conservation Union (IUCN) released its latest Red List of threatened species. The list contains 12,259 species from around the world, up 1092 from last year. But those numbers depend on definitions of species that are more than a century old for the best-known groups, and often inconsistent. Also, the new species have been added largely because data on their status has become available for the first time.
The biggest changes are in plants and invertebrates, where data on conservation conditions is poor and many species are unknown to science. New information highlights the dangers to island species, with 125 Hawaiian plants and 35 snails from the Galapagos Islands added to the threatened list.
Birds and mammals are much better known, but problems remain with inaccurate data. This year, the conservation status of only 6 of 4763 mammals in the database changed because they had become more or less threatened. The golden lion tamarin improved from critically endangered to endangered, and five other species were reclassified to reflect the discovery that they are more at risk than last year.
Yet the status of 33 mammal species changed simply to reflect new data on their numbers, correct errors in the status assigned, or in one case to account for one species being split into two, says Craig Hilton-Taylor, IUCN Red List Programme Officer in Cambridge.
The IUCN plans a major update next year, including a compete reassessment of all 9942 bird species on the list.