Insect-plant mutualism long before flowering plants?

Insect-plant mutualism long before flowering plants?

Insect-plant mutualism long before flowering plants?

The Chekarda site in Russia is a fossil deposit dating back to the lower Permian, about 280 million years (Ma) ago. This locality is an important site compared to other deposits dated to the same period because it provided an important terrestrial fauna in fossil form: 260 species of insects and many groups of plants. From this site, Russian and Polish researchers describe in a study in the journal Current biology ten insects of the protomeropid group, which are among the oldest known holometabola, as these insects are called whose larvae are very different from adults. However, they have a particular morphological trait that distinguishes them from other insects known from the site …

A fun trunk

These insects have a proboscis. This trait, found in many animals, appeared relatively early as insects from the Carboniferous period (325 Ma) already possessed them, some of which were contemporary with those of this study, such as hemiptera (an order of insects within which find cicadas). However, all of these insects have proboscis which allows them to pierce the tissues of plants, their seeds, and even the cuticle of other arthropods. This fauna of the late Paleozoic thus differs radically from the Chekarda protomeropids: their very mouthparts are devoid of elements that allow them to perforate the tissues. They could therefore only absorb fluids on the surface of a substrate. This discovery therefore makes them the oldest insects to have this type of mouth device. The oldest known to date were, for example, neuropterans (such as ants) dated to the Middle Jurassic (170 Ma), i.e. a difference of over 100 Ma.

Photos of Protomeropid insect fossils from the Permian (280 million years) of Russia.  Credit: Khramov et al./ Current Biology

Photo of two proboscis insect fossils that could only feed on fluids. They lived 280 million years ago in present-day Russia. Credit Khramov et al. / Current biology.

Among the first pollinators?

With this type of trunk, “S.The feeding of sugary gymnospermic fluids is the only function imaginable“remember to Science and the future Alexander Khramov, the lead author of the study. By feeding, the protomeropids could have contributed to pollination, and therefore to the reproduction of plants, bringing pollen (the male gametes) to the ovule (the female gamete). This is the case of the peltaspermales, plants that developed in an environment with an arid climate at the same time as the insects in the study. These plants have the particularity of having female reproductive organs, which remain little open to the external environment. Wind pollination has therefore probably had only a limited effect on these plants. Like today, other factors most likely played a more important role, such as flying insects.

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