Magazine R35

Features

Race to save species hotspotsA new study has defined precise areas containing threatened specieswhere habitat destruction of their final remaining toehold may lead toimminent extinction. But many might be saved if relatively cheap action istaken quickly. Nigel Williams reports.

A new study that has identifiedthe remaining habitat ofthreatened species finds nearlythree times as many are on thebrink of extinction than have diedout in the past 500 years. Thenew global analysis of the mostthreatened habitats was carriedout by an international alliance ofconservation scientists whospent three years locating the lastremaining sites where specieslabelled endangered or criticallyendangered are known to belocated.

The researchers identified 794species, including mammals,reptiles, amphibians, birds andconifers, in habitats so disrupted— usually by human development

— that they are now confined tojust one region. In total, 595regions were found to be home toat least one threatened species,with large clusters in the Andes,Brazil’s Atlantic forests, theCaribbean, and Madagascar.Only a third of the sites arelegally protected and nearly allare surrounded by intense humanactivity: logging, forest clearingor home building.

The study was carried out topinpoint conservation hotspotswhere emergency measures areneeded to prevent species losingtheir last footholds.

Taylor Ricketts, aconservationist with the WorldWide Fund for Nature and lead

author of the study, said: “Wenow know where theemergencies are, the species thatwill be tomorrow’s dodos unlesswe act quickly.”

Among the threatened animalsare the mangrove finch, one ofthe species known as Darwin’sfinches in the Galapagos.Ricketts, whose study appears inthe Proceedings of the NationalAcademy of Sciences, publishedlast month, said the findingsshow where urgent conservationmeasures are needed. Incalculations based on local costs,the authors conclude that savingall 565 of the threatenedenvironments would costbetween $200 million and $300million. The median cost ofsaving a single site is a little as$220,000, the authors suggest.“We want governments and localorganisations to think about whatthey can do for the sites nearest

Model: The black robin in the Seychelles is one endangered species now subject to conservation measures to help ensure its futureon the islands. (Picture: Photolibrary.com.)

While most individuals in sexualspecies divide into either males orfemales, evolutionists face achallenge in explaining thosespecies that do not conform to thistype: hermaphrodites are the normin some species and others show amore exotic mix of individuals withvarying sexual identities. Howthese came about and what lightthey may throw on the evolution ofseparate sexes has been anintriguing question for both fieldand theoretical biologists.

In a new study led by StephenWeeks at the University of Akron,Ohio, reported in the Proceedingsof the Royal Society (publishedonline), researchers believe thatone sexual system — males andhermaphrodites, thattheoreticians believe to beevolutionary unstable — mayactually be an ancient andenduring lifestyle in one group offreshwater shrimps.

When evolution favours a shiftfrom one reproductive mode toanother, three temporary forms ofreproduction are thought toaccompany the transition: a

mixture of hermaphrodites, malesand females (trioecy),hermaphrodites and females(gynodioecy), or hermaphroditesand males (androdioecy). Ofthese, many researchers believetrioecy to be highly unstable, andthus, gynodioecy or androdioecyare predicted to be the two likelytransitionary reproductive modes.Field researchers have foundgynodioecy to be more commonthan androdioecy, which issuggested by theoretical studiesof breeding system evolution.

Researchers have developedtwo categories of models thatmight lead to the persistence ofandrodioecy in species in whichthis breeding system has beendocumented. But “because theconditions for the stablemaintenance of males withhermaphrodites are stringent inthese models, androdioecy ispredicted to be short-lived,” theresearchers say.

To date, no multi-species,higher-level taxon has beendescribed as being composed ofonly androdioecious species,again suggesting thatandrodioecy is a relatively recentand transient reproductivedevelopment in the various taxa inwhich it occurs.

One well-describedandrodioecious system is found in

Current Biology Vol 16 No 2R36

Sex-shift surprise

Populations of males andhermaphrodites appear to have asurprising evolutionary endurancein one group of freshwatercrustaceans. Nigel Williamsreports.

Game plan: One group of freshwater shrimps appears to comprise ancient populationsof males and hermaphrodites. (Picture: Photolibrary.com.)

them. Some sites can beconserved for as little as$30,000,” Ricketts said.Estimates suggest that, althoughspecies become extinct naturally,the rate of human-induced loss is100 to 1,000 times faster.

Although the species identifiedin the study require immediateattention and may prove difficultto conserve, the authors believetheir recovery is within reach.Indeed, several species thatwould have met all theresearchers’ criteria asendangered are now recoveringas a result of successfulconservation measures. Theseinclude the Seychelles warbler,the Seychelles magpie-robin andthe Rodrigues Fody. “The 794trigger species represent similaropportunities for conservation,”the researchers report.

“Clearly, the primary responseto avoid these impendingextinctions will be to safeguardtheir sites through landpurchase, conservationeasements, communitymanagement, or protected areaenforcement and to monitor theircondition over time,” theresearchers say.

The researchers also point outthat some species with widergeographical diversity, whichwere excluded from this study oflocally distributed species, arealso under serious threat andalso in need of urgentconservation plans. The dramaticdecline of the Asian Gypsvultures, is highlighted.

“The sites we identify are acritical subset of globalconservation priorities,complementing other efforts byfocusing on relatively smallscales and short time horizons:they are known places whereextinctions are imminent unlessimmediate conservation action istaken,” the authors say.

Mike Parr, secretary of theAlliance for Zero Extinction, theconservationist organisation thatcarried out the study, said: “Atstake are the future geneticdiversity of Earth’s ecosystemsand the global ecotourismeconomy worth billions of dollarsper year. We have a moralobligation to act.”