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The feed­ing habits of mam­mals haven’t always been what they are today, par­tic­u­larly for omni­vores. Some groups of mam­mals almost exclu­sively eat meat, take lions and tigers and other big cats as exam­ples. Other mam­mals such as deer, cows and ante­lope are pre­dom­i­nantly plant-​eaters,

liv­ing on a diet of leaves, shoots, fruits and bark. But par­tic­u­larly for omni­vores that live on plant foods in addi­tion to meat, the sit­u­a­tion wasn’t always that way, finds a new study by researchers work­ing at the National Evo­lu­tion­ary Syn­the­sis Cen­ter in Durham, North Car­olina. The results appear today in the online edi­tion of the jour­nal Pro­ceed­ings of the National Acad­emy of Sci­ences.

“The research links dietary strat­egy, a basic aspect of ani­mal ecol­ogy, with macroevo­lu­tion­ary diver­si­fi­ca­tion of mam­mals,” said George Gilchrist, pro­gram direc­tor in the National Sci­ence Foundation’s (NSF) Divi­sion of Envi­ron­men­tal Biol­ogy, which funded the research.

George Gilchrist, NSF »

Past research shows that ani­mals with sim­i­lar diets tend to share cer­tain char­ac­ter­is­tics. But this study is the first of its kind to look across all mam­mal groups, includ­ing omni­vores, to recon­struct how evo­lu­tion­ary time changed mam­mal diets. To do that, the researchers com­piled pre­vi­ously pub­lished diet data for more than 1,500 species rep­re­sent­ing more than one third of mam­mals alive today, includ­ing pri­mates, ungu­lates, bats, rab­bits and rodents. By map­ping that data onto the mam­mal fam­ily tree, the researchers were able to trace back­ward in time and infer what the ances­tors of each species most likely ate. They found that while some groups of mam­mals main­tained steady diets, oth­ers changed their feed­ing strate­gies over time.

Today’s omni­vores in par­tic­u­lar – a group that includes pri­mates, bears, dogs and foxes – came from ances­tors that pri­mar­ily ate plants, or ani­mals, but not both, said paper co-​author Saman­tha Price of the Uni­ver­sity of Cal­i­for­nia Davis. While omniv­o­rous mam­mals weren’t always that way, plant-​eaters and meat-​eaters have diver­si­fied within a more well-​worn path. Rad­i­cal shifts were unlikely for these ani­mals. Mam­mals that eat meat for a liv­ing, for exam­ple, didn’t give up their taste for flesh with­out tran­si­tion­ing through an omniv­o­rous stage first.

« Louise Roth, study’s co-​author

“It’s an intu­itive result because it takes very dif­fer­ent kinds of equip­ment to have those kinds of diets. Plant– and animal-​based foods require dif­fer­ent diges­tive chemistries and dif­fer­ent pro­cess­ing mech­a­nisms in the mouth and stom­ach,” said co-​author Saman­tha Hop­kins of the Uni­ver­sity of Ore­gon. The kinds of teeth adapted for tear­ing and slic­ing meat are dif­fer­ent than the large, flat-​topped molars adapted for grind­ing nuts and roots. “It makes sense that you couldn’t eas­ily tran­si­tion from one to the other in one step,” Price said.

The researchers also found that diet is linked to how fast mam­mals spawn new species. As new species arise and oth­ers go extinct, the plant-​eaters pro­lif­er­ate faster than their meat-​eating coun­ter­parts, with omni­vores lag­ging behind both groups. “If there was an evo­lu­tion­ary race to evolve 100 species, it would take three times longer for omni­vores com­pared to her­bi­vores, and car­ni­vores would be in the mid­dle,” Price said.

The above news item is reprinted from mate­ri­als avail­able at National Sci­ence Foun­da­tion via Eureka!. Orig­i­nal text may be edited for con­tent and length.

(Source: National Sci­ence Foun­da­tion, 16.04.2012)