[ad_1]
When Charles Darwin created modern biology with his theory of evolution, he used the term “tree of life”.
For many years after, scientists speculated on how species were related and evolved looking for similarities in appearance and lifestyle.
Now, however, the guesswork is over as we can now read and follow the changes in the DNA between living things. It supported some past speculation, but there were some big surprises.
Botany once included algae and fungi with higher plants, but now we know from DNA that fungi share a common ancestor with animals and are not related to plants, while “algae” are photosynthesizers. related to plants with other unrelated ones, including some bacteria. DNA even showed a surprising relationship between hippos, dolphins and whales.
Complete trees of life for large groups are now possible and we finally have one. A new book, “The Largest Avian Radiation” by Fjeldsa, Christidis and Ericson, provides just that for the 6,200 species of roosting birds, which make up 60% of all birds.
Perching birds are tiny descendants of dinosaurs that survived the disaster that killed their older parents, and their tree of life tells how it happened.
The large dinosaurs were wiped out 66 million years ago when an asteroid hit what is now Yucatan in the northern hemisphere.
Therefore, the southern hemisphere was where its devastation was least intense and where there was much more good habitat than there is today because we know from fossils that many large parts of Antarctica were then forested rather than covered with ice.
No perching birds live there today, but the most ancestral are in a suborder now confined to New Zealand, where the genus of southern hemisphere forests once found in Antarctica survive today.
Such forests are also present at the southern tip of South America, and it is here that the evolution of the next most advanced suborder of perching birds exploded into 1,350 species. Its two largest groups have clearly evolved in South America, and while one of them extends only north to tropical Mexico, the other reaches Alaska and includes our flycatchers. and our kingbirds.
The third and smallest group of the suborder is the most diverse in Southeast Asia, but its most ancestral species is confined to the wettest rainforest of South America, and some intermediate species in Africa suggest that this group may have reached Asia there by crossing a then narrower South Atlantic.
This suborder is known as the sub-oscins because it lacks the anatomy to produce complex songs. All other perching birds belong to a more advanced suborder called Oscines or Songbirds, and its most ancestral members are 322 species found in and around Australia, which can proudly be called the “continent where the song began” . Probably the most familiar families of these basal oscines to non-Australians are lyrebirds, arbor birds, and honeyeater.
New Guinea, a land mass in northern Australia created when that continent collided with volcanic islands as it drifted north from Antarctica, gave birth to the first group of songbirds that have invaded the rest of the world.
It included around 800 species and even included three families that reached the Americas: the shrikes, vireos, and the crows and jays family, which includes the crows, the largest perching birds. One family of this group remained in New Guinea, however, the spectacular Birds of Paradise.
By far the largest group of roosting birds are the 3,900 species of upper oscines that also spread from New Guinea to the Old World and then to the Americas. The older groups among them are less diverse and widely dispersed around the world, but some are familiar here: wrens, waxwings, and phainopeplas.
The more recent upper oscines belong to several superfamilies, the smallest of which has only 2 families. The largest of them consists of chickadees and chickadees, and the smallest has only one American species, the verdin of our deserts.
A much larger superfamily, the Old World Warblers, has few families that reach the Americas, but the exceptions are larks, swallows, wild tits, and wrentits.
A smaller, better developed superfamily in the Americas includes nuthatches, lianas, flycatchers, and wren, but another large, Old World warblers, includes starlings and 3 families that naturally reach the Americas: ladles, mockers / mockers and thrushes.
The last of these superfamilies is the largest, with 1,500 species. It started in the Old World but has reached some of its greatest diversity in the Americas.
One innovation that enabled him to achieve this success was a conical beak for breaking and eating grass seeds, acquired 10 million years ago, just as climate change caused the replacement of many forests. by the grass. Its first members devoid of this bill were all from the Old World, with the exception of the olive warbler, a family of a species living from Arizona to Nicaragua.
The first cone-billed families began in the Old World and included our familiar introduced house sparrow, but two of these naturally spread to the Americas: pipits and finches.
Seven groups of these provide our finches, crossbills and many of our grosbeaks and one that has reached Hawaii provides its various lianas.
This superfamily has an advanced group of 16 families which includes 5 families providing much of our diversity of perching birds: 142 species are our American sparrows; 111 are our wood warblers, which have returned to the insects of the grass; 108 are our blackbirds, orioles and skylarks; 52 are our cardinals; and, most important of all, 327 are our tangaras.
Reading the DNA finally sorted out this complex pattern and provided a few surprises: Yellow-breasted cats are with orioles, not wood warblers, and our tangaras, like westerns, are actually cardinals.
The enormous diversity of tangaras is mainly found in South America, and a surprise inclusion are the Galapagos finches made famous by Darwin. The only true Tanager reaching the United States and barely is the White Collar Seminary.
In addition to 10 chapters building in detail the tree of life of perched birds, the book contains range maps of their many families, beautiful and precisely colored paintings, and ten more chapters and two appendices on topics explaining the evolution of these birds and often useful for other species.
The first appendix, for example, summarizes ecological information that is very relevant to California as well as the rest of the world.
This is by far the best and most useful one-volume biology book I have ever seen.
Dr Holstein is a retired consultant environmentalist who has worked across much of California, a longtime conservation activist with the California Native Plant Society and a board member of Tuleyome, a conservation organization nonprofit based in Woodland, California.
[ad_2]
Source link