Producer: Popular Science China
Production: Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Sheng Jie Chen Xiaozheng
Producer: Computer Network Information Center, Chinese Academy of Sciences
In this world, there is always a existence that "feels sorry for you" or "smells the same". Iron Tree, no exception.
The "iron tree" mentioned here is the iron tree in the idiom "iron tree blossoming".
The flowering iron tree, the female flower of the iron tree on the left and the male flower of the iron tree on the right
△(Image source: Wikipedia)
After the living iron tree blooms, its flowers will emit a strange "smell". A small beetle called the Australian mushroom, attracted by the "stench" and the heat emitted by the iron tree flower, in its lifetime, it only feeds on the pollen of the iron tree, which can be said to be the "die-hard powder" of the iron tree flower!
Recently, Chinese and foreign researchers have found that a small beetle belonging to the Australian mushroom beetle, from 100 million years ago, was attracted by the "smell" of the iron tree flower, feeding on the pollen of the iron tree and pollinating the iron tree. The results were published online on August 16, 2018 in the journal Current Biology.
So, what does love look like across a hundred million years?
Who helps Iron Tree pollen?
The iron tree, its big name: cycads, is an ancient and unique class of gymnosperms. Although cycads currently have few species (mostly living in the tropics), their origins can be traced back to the Permian period and flourished in the Mesozoic Era (especially the Jurassic and Cretaceous periods). Therefore, the Jurassic period is also called the "cycad and dinosaur age".
Thorny Tuojiang Dragon (model) and Iron Tree (real) in the courtyard of Nanjing Paleontological Institute
△(Source: Institute of Ancient Studies, Chinese Academy of Sciences)
Iron trees are strictly insect-borne gymnosperms. It is currently believed that in its natural state, the pollination and reproduction of iron trees requires the assistance of insects, and its pollinators mainly include a variety of beetles (Coleoptera) and some thrips (Taproids, one of the important economic pests). Live pine cypresses, ginkgo biloba, etc. are wind-mediated gymnosperms.
Although cycad fossils are common in Mesozoic strata, direct fossil evidence related to the early evolution of cycad pollination has long been missing.
This time, Cai Chenyang, an associate researcher of the "Research Team on the Origin and Early Evolution of Modern Terrestrial Ecosystems" at the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences, and Researcher Huang Diying, systematically collected and studied a large number of Burmese amber insect fossils, and cooperated with Chinese and foreign counterparts to discover a morphologically specialized Beetle of the Australian mushroom family (Boganiidae), which is a new genus. The researchers named it: Cycad Chalky Flat Nail (Cretoparacucujus cycadophilus Cai and Escalona, 2018). At the same time, in this amber specimen, many cycad pollens gathered in clusters were also found.
Under the microscope, the chalky cycads preserved in Burmese amber resemble flat nails and cycad pollen
△（图片来源Beetle pollination of cycads in the Mesozoic）
A stable relationship of 167 million years
Researchers conducted comprehensive research on this specimen from multiple disciplines such as functional morphology, branch sequence systematics, and biogeography.
From a functional point of view, in this middle Cretaceous (about 100 million years ago) Burmese amber, there is a well-preserved Australian mushroom, this insect body length of about 2 mm, mouth features are very specialized, compared to the general beetle, the jaw whisker is very long, accounting for nearly one-third of the body. Researchers speculate that this feature may be related to the sense of smell, which has a small fove at the base of the upper jaw, and these morphological features are very similar to the beetles that eat pollen live (such as Australian mushrooms, some tailless nails, etc.).
The mid-Cretaceous cycad chalk resembles a flattened chalk with enlarged heads
From the branch sequence systematic analysis, based on all known genera and fossil genera of the living Australian fungus, the chalky flathead and the modern living in southwestern Australia constitute a sister group.
From a biogeographic point of view, the relationship between The Australian mushroom and the iron tree on the two continents of the modern southern hemisphere (Australia, Africa) is very close. The discovery of cycad-like flat nails has verified that the pollination relationship between Australian mushrooms and some cycads has long been established.
Biogeographic distribution of pollinators of cycads and mushrooms, and systematic relationships between pollinators
Tip: There is a Zemico cycad in southwestern Australia, and the living beetle of the genus Oblongata eats its pollen and assists in pollination.
The main pollinator of the genus Cycads far away on the African continent (southeastern South Africa) is the Australian mushroom of another genus.
Macrozamia riedlei and Australian mushroom in southwestern Australia
Through close observation, the researchers also found many tiny oval pollen next to the body and mouthparts of the beetle specimen.
It is preserved with the cycad chalky flat nails and forms a "clumps" of cycad pollen
Dr. Li Liqin of the Nanjing Institute of Paleontology conducted a detailed study of this pollen morphology and believed that most of the pollen in the amber was "hugged" and formed large or small pollen clusters, most likely from cycads. The formation of pollen clusters suggests that it may be a class of insect-borne plants. The pollen of wind-borne plants is spread in the form of a single grain, and it is almost impossible to "cling".
This again confirms that chalky flattened nails were likely to be a class of early cycad pollinators. Therefore, the discovery of these pollens also proves for the first time that cycads once lived in the forests of ancient Myanmar.
Ecological restoration map of cycad chalky in the middle Cretaceous period
The results of the study proved that the pollination relationship between beetles and cycads originated very early, no later than the early Jurassic period, and their relationship was established much earlier than the well-known relationship between pollinators such as bees and butterflies and angiosperms. Moreover, the pollination relationship between this beetle and cycad is relatively stable, at least from the early Jurassic period (167 million years ago) to the present.
△ Image source: Baidu Pictures
This study was jointly funded by the Chinese Academy of Sciences, the Ministry of Science and Technology of China, the National Natural Science Foundation of China and the Natural Science Foundation of Jiangsu Province.
Thesis Information:
Chenyang Cai*, Hermes E. Escalona, Liqin Li, Ziwei Yin, Diying Huang, Michael S. Engel (2018) Beetle pollination of cycads in the Mesozoic. Current Biology, DOI: 10.1016/j.cub.2018.06.036
(The images indicated in this article are authorized)