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Species hiding in plain sight

July 19, 2007
Courtesy BioMed Central
and World Science staff

New spe­cies are evad­ing de­tec­tion us­ing an al­most fool­proof dis­guise—their ident­ical ap­pear­ance to other, known spe­cies

A new study sug­gests it’s com­mon for dif­fer­ent an­i­mal spe­cies to look alike de­spite oth­er sig­nif­i­cant ge­net­ic dif­fer­ences. This in­tro­duces un­cer­tain­ty to bio­di­vers­ity es­ti­mates glob­al­ly, re­searchers say.

A new spe­cies of ham­mer­head shark re­port­ed by Uni­ver­si­ty of South Car­o­li­na re­search­ers last year. It was ge­net­i­cal­ly dis­tinct from, but vi­s­ual­ly iden­ti­cal to, the scal­loped ham­mer­head Sphyrna lewini.


The on­ly way to iden­ti­fy these ev­o­lu­tion­ary splin­ter groups from their look-alike cousins is through DNA pro­files and by check­ing for dis­tinct mat­ing groups, the sci­en­tists add. A spe­cies is us­ual­ly de­fined as a group of or­gan­isms whose mem­bers share a com­mon gene pool and can in­ter­breed.

Markus Pfen­ninger and Klaus Schwenk of J.W. Goe­the Un­ivers­ity in Frank­furt, Ger­ma­ny, scanned the Zo­o­log­i­cal Rec­ord da­ta­base, a com­pila­t­ion of pub­lished zo­o­log­i­cal lit­er­a­ture, for the past three dec­ades for re­ports of hid­den or “cryp­tic” spe­cies. 

They found 2,207 ex­am­ples of these, even­ly spread among all ma­jor branches of the an­i­mal king­dom and all geo­graph­i­cal ar­eas.

The find­ings go against re­ceived wis­dom that the in­sect or rep­tile branches of the an­i­mal king­dom are more like­ly to har­bour cryp­tic spe­cies, and that these are more like­ly to be found in the trop­ics than in tem­per­ate re­gions, the re­search­ers said. Thus, they added, zo­ol­o­gists should con­sid­er fac­tor­ing in some “cryp­tic di­vers­ity” as a ran­dom er­ror in all bio­di­vers­ity as­sess­ments.

There also exist whole “com­plexes” of cryp­tic spe­cies—whole groups of spe­cies that are re­pro­duc­tive­ly iso­lat­ed from each oth­er but that look alike. 

The find­ings have im­plica­t­ions for con­serva­t­ion ef­forts, ac­cord­ing to Pfen­ninger and Klaus. Anoth­er pos­si­bil­ity is that pathogens, par­a­sites and in­va­sive spe­cies dis­guised as their rel­a­tives may yet re­main un­de­tected, rep­re­sent­ing a po­ten­tial hu­man health threat. The research appears in the July 19 issue of the on­line sci­en­tif­ic jour­nal BMC Ev­o­lu­tion­ary Bi­ol­o­gy.


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New species are evading detection using a foolproof disguise – their own un changed appearance. Research published in the online scientific journal BMC Evolutionary Biology, suggests it’s common for different animal species to look alike despite other significant genetic differences. This introduces un certainty to biodiversity estimates globally. The on ly way to identify these evolutionary splinter group from their look-alike cousins is through DNA profiles and the existence of distinct mating groups, scientists say. Markus Pfenninger and Klaus Schwenk of J.W. Goethe University in Frankfurt, Germany searched the Zoological Record database, a compilation of published zoological literature, for the past three decades to pinpoint reports of hidden or “cryptic” species. They found 2207 examples even ly spread among all major branches of the animal kingdom and all geographical areas. The findings go against received wisdom that the insect or reptile branches of the animal kingdom are more like ly to harbour cryptic species, and that these are more like ly to be found in the tropics than in temperate regions, the researchers said. Thus, they added, Zoologists should consider factoring in some “cryptic diversity” as a random error in all biodiversity assessments. A so-called “complex” of cryptic species is a whole group of species that is reproductive ly isolated from each other but that look alike—but lacking conspicuous differences in appearance. The findings also have implications for conservation efforts, according to Pfenninger and Klaus. Another possibility is that pathogens, parasites and invasive species disguised as their relatives may yet remain un detected, representing a potential human health