"No Hummingbirds in Asia" is a blow to those of us who know the world's best from elementary school textbooks and become interested in it. To compensate for this regret, people call the sunbird, which is very similar in appearance and feeding behavior to hummingbirds, but almost unrelated to the "Asian hummingbird", and even mistakes a moth for a hummingbird, and finally named it "Macroglossum stellatarum".
Hummingbird hawk moth
Almost all of the 338 known species of hummingbirds are concentrated in Latin America, with most of these species distributed in tropical and subtropical Central and South America, but some species live in temperate regions. As the bird is named, hummingbirds mainly rely on nectar for food, and of course, like other birds, they prey on some small insects.
However, in 2004, German ornithologist Gerald Mayr discovered 30 million-year-old hummingbird fossils in baden-Würtberg, Germany, thus changing the idea that hummingbirds have long been considered Native Americans, and also taking an important step in the study of hummingbird evolution.
These hummingbird fossils are preserved in a museum in Stuttgart, Germany. Unlike other larger vertebrates, hummingbirds do not leave many fossils. Prior to this, scientists had found fossils of hummingbirds in soil formations in Brazil and the Bahamas. These fossils were formed during the Pleistocene period of geological epoch, dating from about 2.6 million to 10,000 years ago.
Meier's newly discovered hummingbird fossils are not very complete, and some of the features exhibited are more like swifts than modern hummingbirds. Coupled with the fact that hummingbirds have long been considered to be unique to the Americas, Meier observed and studied them more closely, and finally confirmed that this was an early hummingbird fossil and named it "European Hummingbird".
How similar in habits, we all have to admit the fact that they are not particularly related, but it seems that the swifts and hummingbirds that cannot be beaten by eight rods have deep roots.
Hummingbirds (left) can suck nectar in the air, while sunbirds (right) cannot
Hummingbirds, Swifts and Swifts belong to the order Swifts, and their common ancestors lived on Eurasia 42 million years ago. To further explore the evolution of hummingbirds, Jimmy McGuire of the University of California, Berkeley, and his colleague Robert Dudley spent a decade collecting DNA data from 451 individuals in 284 species of hummingbirds and mapping out the phylogenetic trees of hummingbirds, showing the evolution of hummingbirds in full.
Phylogenous tree of hummingbirds
Existing fossils suggest that hummingbirds began to differentiate from swift species on Eurasia about 42 million years ago and then set out on their way to the Americas. Hummingbirds could not have flown over the ocean, and McGuire speculated that they might have entered North America via the land bridge of the Bering Strait at the time, and then headed south to South America. During the Pleistocene period, the Bering Land Bridge played an important role in the migration of animals such as mammoths into the Americas.
Selective exchange of fauna between Eurasia and North America
About 22 million years ago, the ancestors of modern hummingbirds all arrived in South America. South America provided excellent conditions for the explosive evolution of hummingbirds, especially along the Andes. For example, in cold high-altitude areas, pollinators are relatively rare, which makes room for hummingbirds to survive and develop.
Hummingbirds' ability to use niches is also reflected in their adaptation to isolated valleys and steep slopes with rapidly changing climates, and the Andes also provide habitat for hummingbirds, from which hummingbirds evolve nine different species, including the South American hummingbird.
Subsequently, some species of hummingbirds re-entered North America in search of habitat. About 5 million years ago, hummingbirds entered the Caribbean region six times before and after. One of the beebirds, which originated in North America, bee hummingbirds, was also involved in the invasion of the Caribbean Sea, but later settled in South America along with the existing lineage.
This evolution of hummingbirds is quite interesting and seems to be quite perfect. But with the development of genetic technology, scientists sequenced the genomes of birds and found that birds generally lack the genes that code for the sweetness receptors needed by vertebrates to sense sweetness.
There are five main kinds of tastes in biology: "sour, sweet, bitter, salty, and fresh", and we can perceive that these tastes benefit from the corresponding receptors of taste receptor cell species, and the sweetness and umami taste of vertebrates are mediated by a G protein-coupled receptor called T1Rs. There are three types of T1Rs in vertebrates, with the T1R1-T1R3 dimer responsible for feeling the umami, while the T1R2-T1R3 dimer can sense sweetness.
Of course, these receptors are not necessary for vertebrates, such as cats and other carnivorous vertebrates do not exist in the body of the sweet receptor, they do not feel sweet. The lack of a gene sequence encoding T1R2 in the bird genome will not theoretically feel sweet, but how can hummingbirds, birds that mainly feed on nectar, forage without a sweetener receptor?
The scientists conducted an experiment on hummingbirds with an aqueous solution of sucrose and purified water, and the results proved that hummingbirds preferred sucrose solutions. This shows that hummingbirds are able to feel "sweet". They then mixed the same volume of artificial sweetener solutions such as aspartame in several identical sucrose solutions to form a new mixed solution, while taking another set of sucrose solutions and mixing them with sucrose solutions as a control group. Experiments have shown that hummingbirds have a certain rejection of artificial sweeteners.
Hummingbirds show sensitivity to sucrose, fructose, and glucose, which are rich in nectar, suggesting that they can specifically identify nectar. Further research found that hummingbirds recognizing "sweet" receptors may be related to their umami receptors T1R1-T1R3 dimer. The umami receptor of a branch of the common ancestor of early hummingbirds and swifts mutated to allow them to feel the taste of nectar, and instead fed on nectar that was less competitive and easier to obtain, and gradually developed into what is now hummingbird.
So we can't tell whether the nectar in hummingbird's eyes is sweet, umami or something else, only it knows. However, it has to be said that this mutation opened the door to a new world for the evolution of hummingbirds.
Hummingbirds have a single food source, all of which are nectar, but they are extremely diverse, and can evolve hundreds of species. It is also worth mentioning that in some places, up to 25 species of hummingbirds can coexist, and the competition will not be fierce?
Take a closer look at the various hummingbirds and you'll notice that the shape of the hummingbird's beak perfectly matches the shape of the corolla they feed on the flowers. Hummingbirds need nectar for food and survival, and flowers can also use hummingbirds to achieve the purpose of pollination, and the two adapt to each other and co-evolve in the long-term evolutionary process.
This specific evolution is even more pronounced in the long-beaked hummingbird. For example, the knife-billed hummingbird, which takes the nectar of the Climbing Plant Passionflower in the Americas as its main food source, in order to adapt to the 11.4 cm long corolla structure of passionflower, the beak of the Knife-billed Hummingbird is the longest of all birds in terms of body proportions. This has led to their specific and specialized resource selection, with relatively short-beaked and straight-beaked species being more random in terms of feeding.
Knife-billed hummingbird
Many hummingbird-pollinated plants have red, orange, and bright pink flowers because hummingbirds are more sensitive to these colors, while insects are not, thus avoiding competition between hummingbirds and insects. On Santa Cruz Island off the southern coast of California, the yellow-flowered shrub monkey face flowers rely only on bees to pollinate, while the red island monkey face flowers attract hummingbirds.
In addition, the flowers pollinated by hummingbirds have a low sugar content in their nectar and a high sucrose content; because birds have an underdeveloped sense of smell, hummingbird pollinated flowers are usually tasteless. The nectar of the flowers, which are mainly pollinated by insects, is more concentrated, and is usually dominated by glucose and fructose.
Among different species of hummingbirds, competition is also reduced due to differences in the shape of the feeding flower and the shape of the beak, and the dwarfing of the world's smallest hummingbirds is an excellent example. If passionflower is used as a food source, it obviously has no advantage over the knife-billed hummingbird. After the size is reduced, it is more advantageous to compete with insects for nectar.
It can be seen that hummingbirds will use the resources that match themselves to maximize the efficiency of feeding, and they are also good at using different resources. So it's not hard to see why these nectar-fed birds can be so diverse.
Hummingbirds seem to behave in extremes: the smallest size, the longest beak relative to the body, and the wings can flap a dozen or even dozens of times per second when flying; because extremely high metabolism requires a lot of food consumption, some species of hummingbirds are territorially aware and will protect food sources from other hummingbirds to ensure their future food supply. In addition, hummingbirds have an enlarged hippocampus that gives them a certain memory of the spatial location of the flowers they have eaten, facilitating the next feeding.
For 22 million years, hummingbirds have been reshaping and developing themselves at a rapid pace as the environment changes, and have evolved species that can adapt to different environments in the same ecological niche. It's no wonder that reptilian McGuire is so interested in hummingbirds outside of his specialty.
Hummingbirds are still in a process of dynamic diversification, migrating to the Americas to fill ecological niches and spatial niches in North America, South America and the Caribbean, and profoundly affecting continental flora. In some places, hummingbird populations have reached saturation, while hummingbirds adapted to new environments are constantly emerging.
Bactrian and dromedaries
Hummingbirds originated in Eurasia but became extinct in Eurasia, and this phenomenon of evolving on one continent and migrating to another and then becoming extinct in its original homeland is not unique, and the camel we are more familiar with is also an example of this. 45 million years ago, camels lived in North America, about 3 to 7 million years ago, when one of the branches migrated south to South America and evolved into llamas or alpacas; while the other branch reached Asia and Africa via the Bering Land Bridge, evolving into Bactrian and Dromeranes. About 2.58 million years ago, camels in North America were completely extinct.
It can be seen that the evolution of organisms is not always limited to a closed space, and there are many possibilities for biological evolution that are worth exploring.
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