mod birds originated around 95 million years ago in South America , consort to researchers who created a " clip tree " using both fossils and genomic data from 100 of birdie . Their findings , published inScience Advancesthis hebdomad , show that scale plate tectonics and globular climate change left an imprint on the phylogenesis of modern hoot .
When it comes to species richness and dispersion , our feathered friends are the most divers group of mundane vertebrate , yet many view of their evolutionary account are still being heatedly debate . For instance , while most researchers agree that modern birds originated some time in the Cretaceous period , their estimates diverge from 72 million to 170 million year ago .
To well interpret how birds arose , Santiago ClaramuntandJoel Cracraftfrom the American Museum of Natural History combined datum on 130 dodo dame with DNA sequences from 230 species spanning all avian orders and hundreds of avian families . This allowed them to generate a time tree – an evolutionary tree with temporal information – that illustrates the ramification ( or variegation ) of modern shuttlecock . fogey are used to put particular date on some parts of the Sir Herbert Beerbohm Tree , and DNA sequences combined with statistical methods are used to extrapolate the timing information to the rest of the tree .
They discovered that the most late common root of all of today ’s Bronx cheer lived in what is now South America on West Gondwana around 95 million long time ago in the early Late Cretaceous . But it was n’t until rough 66 million years ago during the Cretaceous - Paleogene ( K - Pg ) transition that the ancestors of modern snort began to broaden chop-chop around the human race , the duo ’s biogeographical models show . The K - Pg extinction was when all non - avian dinosaur were wiped out .
Using land bridges , the birdie expanded to various continents through two primary scattering routes : They reached the Old World ( Africa , Europe , and Asia ) through North America , and they made their way to Australia and what is now New Zealand through Antarctica . Their diversification was heavily influenced by continental shifts and the change configuration of landmasses , from seafloor spreading to the uplift of mountain scope .
When the team looked for patterns linking bird evolution with global clime , they find that variegation rate increased during periods of cooling and decreased during period of thaw . Cooler temperatures belike do the far-flung retraction and fragmentation of tropical forests . Isolating populations puts them at risk of infection of experimental extinction , but it also sets the stage for the evolution of new species .
For speciation rate to be higher than extinction pace , the fragmentation should be moderate . " tropic biomes are fragmented but those shard should be large slab of habitat , in which populations can persist , " Claramunt explicate to IFLScience . But if the fragments are too diminished , " experimental extinction rate may go by speciation rate , and the normal would be the opposite . " Warming , on the other hand , increase connectivity . " Speciation need a point of closing off ; if population remain machine-accessible , speciation can not happen , " he adds . " At the same clip , quenching may also be low because population are large and co-ordinated , foreclose local extinction . " So while warming may aid metal money survive , it does n’t stimulate speciation .
