Any Doctor Who fan will tell you that the ability to move through both space and time is a fundamental part of any Time Lord’s lifestyle. Researcher’s from the USA, UK, Canada and Australia applied a similar concept to the analysis of the entire evolutionary history of birds. Not only that, they didn’t carry this out at some distant point in the glorious technologically-competent future, but right here in the year 2012. Patterns of biodiversity around the world were mapped in space and time for 9,993 different bird species currently in existence today.
“Birds in time”
Large increases in bird diversity began to occur 50 million years ago and continued into the near present. Several bird species took enormous leaps in the development of innovative new morphologies or behaviours: hummingbirds developed a specialised beak for feeding on trickily-shaped nectar-rich flowers, parrots developed the skill of vocal imitation and several songbirds developed vocal organs capable of belting out elaborate tunes. Waterfowl (ducks & geese), warblers, woodpeckers, woodcreepers and white-eyes also underwent rapid diversification (see the red areas on the avian circle of evolution, below). These species represent hot spots of evolution across the avian tree of life.
“Birds in space”
Birds in the Eastern hemisphere, especially in Australia, Madagascar, South-East Asia and Africa, don’t show as much diversity as those in the Western hemisphere, perhaps because in these areas, there is only so much ecological space to go around, and it got filled up quickly and early. The highest level of avian diversity is seen in North America, parts of North Asia and southwest South America, which makes sense since these are the main breeding grounds for many of the rapidly radiating species identified. There is no difference in diversity based on latitude (North-to-South). Isolated locations, such as islands, strongly encouraged explosions of diversification: this is perhaps best illustrated with Darwin’s finches, where one ancient ancestor colonised the Galapagos islands and from there evolved into several differently-equipped finches, each optimally suited to filling a narrow ecological niche.
This research implies that the adaptive zone into which modern birds have diversified may not be saturated, and opportunities for further expansion of bird lineages could still exist. So keep your eyes peeled for the next steps in avian evolution: time-travelling pigeons, anyone?
Patterns of species diversification in the avian circle of evolution. Red indicates a high degree of diversity, blue a low degree of diversity.
Jetz W, Thomas GH, Joy JB, Hartmann K, & Mooers AO (2012). The global diversity of birds in space and time. Nature PMID: 23123857