Evolutionary innovation serve animals get over functional barriers and exploit new niches that were inaccessible to their ancestors . These might even elevate rapid diversification or cut down extinction rates in parentage that germinate them . But for some fish populations in easterly Africa ’s Lake Victoria , their adaptive traits were n’t all that beneficial in the end . Researchers studying the extinction of cichlid mintage with innovative jaw find that more and more particularize trait made them less flexile to changes in their surroundings . The findings are published inSciencethis calendar week .
Several lineages of bristled - fin Pisces the Fishes have severally evolved what ’s visit pharyngognathy – jaw modification to help oneself engender high bite force . It ’s quite useful for consume severely - shelled prey items . For decades , the jaw of pharyngognathous fishes have been reckon of as a classical example of innovations opening up novel niche . And while that ’s potential the vitrine , there was also a major tradeoff : These modifications to the back of the throat reduced their pharyngeal gape , limiting the size of prey that can be swallowed easily .
A team led byMatthew McGeefrom the University of California , Davis , looked at the success of species that have evolved pharyngognathy . wrasse , surfperches , damselfish , marine halfbeaks , and flyingfishes have always lived in shallow maritime habitats alongside normal , non - pharyngognathous fish ; cichlids , meanwhile , often occur in tropical fresh water . In lakes Victoria and Malawi , cichlids with pharyngognathous jaws diversified in the complete absence seizure of any non - pharyngognathous competitors . Some even evolve into predatory , fish - eating niches .
The researchers found that pharyngognathous fishes develop into niches favor heavily - shelled quarry at a much higher rate than other spiny - break water fish , but they evolved into Pisces - eat niches more slowly . They all became less adapted to a more general diet , and the modified gape of raiding Pisces - eating cichlids turned out to be fateful when the non - pharyngognathous Nile perch ( Lates niloticus , pictured above right ) was introduced to Lake Victoria in the fifties . After the voracious invader showed up , the preponderance of predatory cichlids declined . Competition for quarry played a Brobdingnagian role in the mass defunctness of many Lake Victoria cichlid species .
When the squad compared run public presentation and working geomorphology of Nile pole with cichlids , they found that the gape of cichlid fish was half that of the Nile perch . cichlid also took many hr to treat a prey detail that a Nile perch could get down in a few minutes . The predatory cichlid were easily outcompeted by invasive Nile perch . The evolutionary innovation of pharyngognathy is n’t a uniformly beneficial trait , the squad writes , but a differentiation that can promote competitive inferiority and extinction depending on the ecological context .
This " two stripe white lip " from the genus Harpagochromis is an undescribed species of Victorian predator cichlid that ’s now extinct in the natural state . Matthew McGee
Image in the textual matter good manners of John Uhrig
