[ad_1]
Under the eyes of a researcher, a lemur takes the long smell of a fruit growing in a tree of a tropical rainforest in eastern Madagascar. He passes the test of the animal. The lemur takes a bite.
Seconds later, he sniffs another fruit from the same tree. This time, it's not interested.
A group of researchers has been trying to determine the type of information that animals are able to discern if a fruit is ripe. In an article published in Science Advances, they say that fruit plants can evolve to tell animals that their scent is ripe.
This helps some fruits that depend on the animals to distribute their seeds.
Omer Nevo is one of the authors of the study. An ecologist of evolution at the University of Ulm, Germany, he has long claimed that it is assumed that fruits have evolved to attract animals that disperse their seeds. This could mean a scent – for those who depend on animals such as lemurs that are partially color blind and have a relatively poor vision.
There are other types of fruits that appear to have evolved to become colorful at maturity – more likely to attract animals that are more dependent on sight, such as birds.
Other scientists have already explained that the smell was simply a byproduct of the ripening of some fruits.
Nevo explains that the characteristics of the fruits, such as their size or color, have been studied in more detail than their smell, as they are easily measurable with the help of a tape measure or a small tape. a simple instrument. He says it takes several hours to get a perfume sample, and then a long, extra process to identify "often dozens, if not hundreds, of different chemicals" in a lab. "It's a lot more work, and I think it's one of the main reasons it's falling behind," Nevo adds.
In the Ranomafana National Park in Madagascar, where there is an incredible diversity of fruits of all shapes and sizes, some plants depend on only on the lemurs to spread their seeds. There are other plants that depend on birds and other animals.
The researchers collected hundreds of mature and immature fruit samples from 30 plant species. They split them into two groups – those that depend on lemurs and those that depend on other animals – and tested the emitted chemicals to determine if odors differed between mature and immature samples.
"And the idea was that birds probably rely less on their sense of smell and that they really have very good color vision, so they tend to focus on visual cues such as food color, "says Nevo. in these fruits, one would see less pressure on the plants to indicate their maturity through the smell of the fruit. "
On the other hand, for plants that depend on lemurs, "the idea was that if the scent of the fruit was a signal to the animals, one would expect the scent of the ripe fruit to be very different from the fragrance of the immature fruit. , "Nevo said.
"And that's exactly what we found."
Bird-dependent fruits have very little odor difference between immature pieces and ripe pieces.
"This has shown us that this change in the amount and in the chemical emitted by the fruits in the species dispersed by the lemurs is not an inevitable byproduct of the process of ripening of the fruits, which does not occur. is not something that characterizes all fruits, but something that is unique to fruits for whom it would be useful, "says Nevo. "Because animals use perfume."
The researchers also observed nine red-bellied lemurs in the park and clearly saw them sniffing fruit and deciding to eat them based on their scent.
"If a species tries to convey information about maturity through a scent, if it changes a lot of scent when it becomes ripe, lemurs would be more motivated when they would feed on that fruit to sniff the fruit." before deciding to ingest or consume it, reject it, "says Nevo.
He adds that the more we know that a fruit changes smell at maturity, the more lemurs seemed to smell it.
The situation of fruit scents in Madagascar can be particularly dramatic, he says, because of the many plant species that depend only on lemurs – and their poor vision – for distributing seeds.
"It may be that in other systems, it is first weak, and then a little masked by other changes, by other characteristics of the fruit," he says.
For example, if a plant relies on many different animals, including some with better vision, it may be less likely to have a very different smell at maturity.
9(MDA2Mjc5MzcwMDEyODc3ODU1ODgyZGI5MA001))
Source link
