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  • [♪ INTRO]

  • Ah, spring. Plants are sprouting, flowers are blooming,

  • and you know what that means: bees and pollination!

  • But bees aren't the only pollinators out there.

  • In fact, we're often so caught up in our love of our stripey friends

  • that we overlook some of the other, more surprising pollinators.

  • And it's not just that they're unconventional, either:

  • Each gives us a unique example of how the relationship

  • between pollinators and plants evolved in the first place.

  • So, here are five pollinators that aren't bees.

  • Pollinators are important for plants because

  • they move pollen from the male flowers to female ones.

  • Basically, they're taking the plant equivalent of sperm

  • and moving it to the part of the plant that contains the ovaries.

  • After that, a plant can make seeds or fruit that grow to become new plants.

  • In some cases, this process can happen by wind or rain.

  • But animal pollination helps make sure pollen gets spread from plant to plant

  • and not accidentally to the same plant, which would lead to inbreeding.

  • And when animals are involved, that's when things get interesting.

  • First, take elephant shrews.

  • They use their long snouts to burrow in soil or leaf litter

  • in search of insects, berries, or plant shoots.

  • Then, they flick their tongues to send that food into their mouths,

  • similar to how anteaters do it.

  • But their distinctive look is also perfect for getting the nectar deep inside flowers.

  • Which they do, thanks to their sweet cravings.

  • When elephant shrews go for the nectar, pollen gets buried in their snout fur,

  • which they then transfer to other flowers during their next meal.

  • Andboom! Pollination.

  • Scientists have confirmed that elephant shrews pollinate a bunch of flowers

  • including the Pagoda lily and Northern vampire cup.

  • And not only have the shrews evolved snouts that are great at getting inside flowers,

  • the flowers have evolved ways to make sure the shrews get a good dusting of pollen.

  • The pagoda lily flower, for example, is long and curved,

  • so the elephant shrew has to wiggle its snout inside to get at the nectar.

  • Meanwhile, other flowers have evolved ways

  • to get mammals like the shrews interested in them in the first place.

  • Like, the northern vampire cup has two chemicals called 3-hexanone

  • and 1-hexen-3-one in its nectar that work together to lure animals in.

  • 3-hexanone gives foods a sweet, rummy smell and taste,

  • so it might signal to mammals that the nectar is full of sugary energy.

  • And while it isn't clear what 1-hexen-3-one does,

  • scientists think it might help repel animals that aren't pollinators,

  • or enhance the nectar's taste somehow.

  • In any case, elephant shrews get a sugary snack, and the plant gets pollinated.

  • And that's the kind of win-win relationship pollination is all about.

  • Sometimes, it's not the sugar, but the water in nectar that pollinators are after.

  • That's the case for the Noronha skink.

  • This spotted lizard is native to a group of Brazilian islands,

  • and it's what you might call an opportunistic eater.

  • It can be found foraging on the ground in search of food, ranging from eggs,

  • to bits of bird and fish carcass, to human leftovers like cookie crumbs.

  • But when it gets bored of these meals,

  • it will venture up trees in search of something juicer and sweeter.

  • On its home islands of Fernando de Noronha,

  • that something is the nectar from mulungu tree flowers.

  • And while it's sidled up to these blooms,

  • the lizard can't help but get bits of pollen stuck in its scales.

  • Then, as the skink wanders from flower to flower, it drags the pollen with them.

  • Part of the reason lizards are so enticed by the nectar is that the mulungu tree flowers

  • during the dry period, when there's not much water on the island.

  • In fact, the nectar is pretty diluted compared to other species of Brazilian trees,

  • making it a great thirst-quencher for the lizards, and other animals, including some birds!

  • Now, you might be thinking it's kind of strange to have lizards pollinating flowers.

  • And for a while, scientists did, too.

  • But now, they believe lizards might play a more important role

  • in pollination on islands than previously thought.

  • That's because, on islands, lizard populations

  • can grow to much higher numbers than on the mainland,

  • thanks to a lower risk of being picked off by predators.

  • That lower predation risk also means lizards can spend more time looking for

  • exotic foods to include in their diet, like nectar, pollen, and fruit.

  • Now, scientists want to know more about the relationship between lizards and flowers,

  • especially things like if they evolved together,

  • or if the flowers have some special way to attract these animals.

  • Cockroaches probably conjure up images of pest control vans, not pollination.

  • But there are at least two species of them that act as pollinators

  • in the tropics of South Malaysia and French Guiana in South America.

  • One is called A. platystylata, and it's a fan of tropical Clusia trees

  • because of a liquid it gets from the base of the petals.

  • The liquid isn't especially appetizing, it's not sweet like nectar,

  • but it might have some resin in it that the roaches can use for making their nests.

  • And when they're rummaging in Clusia flowers, maybe for those building materials,

  • these cockroaches pick up pollen on their rough bodies and transport it between flowers.

  • Kind of like with the northern vampire cup in our first example,

  • Clusia flowers even produce a scent that's appealing to these roaches to lure them in,

  • which shows that the plants could have evolved to attract these insects specifically.

  • Meanwhile, the other roach pollinator, called H. palliata,

  • does seem to get some food reward from the flowers it pollinates.

  • It munches on pollen from a species of woody climber plant in Costa Rican rainforests,

  • which gives the insect the protein it needs to grow and reproduce.

  • So far, these are the only two confirmed roach pollinators, but in mid-2017,

  • scientists in Chile uncovered evidence of a possible third one, called M. brevipennis,

  • feeding on nectar and pollen from evening primrose and puya trees.

  • This insect may have become an accidental pollinator while looking for

  • a damp place to lay its eggs, but at this point, scientists aren't 100% sure.

  • After all, you have to watch these insects really closely

  • to make sure that they are in fact spreading pollen to other flowers.

  • But it's something researchers are planning to do soon.

  • Usually when we think about animal pollination, we think about it on land.

  • But there's recent evidence that it happens underwater, too.

  • Which came as a surprise to a lot of people, including scientists!

  • The vast majority of underwater plant fertilization and seed-spreading

  • happens through ocean currents, just like wind might carry seeds on the surface.

  • And lots of plants have adaptations for this.

  • For instance, male and female plants are separated,

  • and female plants have parts that look like tentacles

  • to catch pollen from the males as it flows by.

  • But in 2012, researchers found around 65 species of crustaceans,

  • including microscopic plankton and tiny shrimp,

  • visiting seagrass meadows in Puerto Morelos reef lagoon in Mexico.

  • The crustaceans were feeding on seagrass pollen and a jelly-like substance called mucilage.

  • The scientists suggested the crustaceans may be pollinators,

  • because a few individuals had pollen stuck to their bodies, but they had no evidence.

  • Then in 2016, they brought the animals and the plants into the lab.

  • When they did, they saw that the pollen grains from male flowers

  • were getting caught up in the sticky mucilage

  • and clinging to the crustaceans' antennas, mouthparts, and bodies.

  • They also found pollen on female flowers and concluded that

  • it must have come from the crustaceans since there was no water flow in the tanks.

  • And it wasn't just that the pollen was being moved around:

  • The pollinated, female plants also started to sprout thanks to their crustacean friends!

  • So, the system works!

  • The scientists called this new method zoobenthophily,

  • meaningpollination by animals on the seafloor.”

  • And they think it can boost the likelihood that a plant will make plant babies.

  • Also, this method means that plants can reproduce

  • even when there aren't strong water currents around.

  • Plus, crustaceans can carry pollen further than currents can because, well, they swim.

  • That helps mix up the seagrass' genes too,

  • instead of the same plants always breeding with their neighbors.

  • But, it is also worth noting that all this crab-pollination was going on in the lab.

  • No one has seen this underwater in the wild.

  • That's mostly because scientists didn't consider it a possibility before, though!

  • So it's time to really start looking.

  • Finally, without this next group of pollinators,

  • one of our favourite sugary treats might not exist.

  • I'm talking about chocolate.

  • Biting midges from the family Ceratopogonidae are the only known pollinators of cacao trees.

  • These grayish flies, which are only about the size of poppy seeds,

  • are so important for cacao, they're also called chocolate midges.

  • See, even though cacao trees have both male and female flowers,

  • they can't self-fertilize because of a defense called self-incompatibility.

  • Basically, to prevent inbreeding, pollen from male flowers

  • won't form an embryo with ovaries from a female flower of the same tree.

  • Also, other pollinators have a tough time getting at the

  • pollen-making parts of the flower, called anthers, which are hidden under a flower hood.

  • Bigger insects like bees, for instance,

  • wouldn't stand a chance at squeezing into the tight space.

  • That leaves pollination entirely up to the tiny midges.

  • But hey, at least the trees help out:

  • Research suggests the timing of cacao tree flowering

  • syncs up with when the midges are around during the rainy season.

  • After a couple of big downpours, the midges look for a shaded,

  • damp place to lay their eggs, including in rotting cacao husks.

  • And eventually, they find their way to the plant's flowers.

  • At this point, scientists still aren't sure exactly what attracts the midges to the flowers,

  • since they don't make any nectar,

  • and there's no evidence that their smell is attractive, either.

  • But! If the midges aren't attracted to the flowers themselves,

  • just the general area around the trees,

  • that might help explain why pollination rates are so terrible.

  • Only about one in every 20 flowers and as few as one in 25

  • become fruit or the pods that are used to make chocolate.

  • In the wild, that's not such a terrible thing:

  • One in 20 might be enough for a population of trees to survive.

  • But when you're trying to satisfy the worlds' candy cravingsit's not ideal.

  • Humans try and make up for this by hand pollinating the flowers,

  • but making cacao pods takes a lot of energy on the tree's part,

  • so even then, the trees will limit how many pods actually make it to ripening.

  • More than the other examples in this list, midges and cacao trees

  • are a good example of how evolution between plant and pollinator happens,

  • and how things can go wrong if there are sudden, human-made, changes to that relationship.

  • So this year, let's not forget the unsung heroes of the pollinating world.

  • They contribute to the huge diversity of plants we see on this planet.

  • Including the tasty, chocolatey ones.

  • Thanks for watching this episode of SciShow!

  • If you're in the market for more spring- or summer-related content,

  • you can find more of our videos at youtube.com/scishow.

  • And if you're interested in videos for the kids in your life, we've got you covered there, too.

  • SciShow Kids has a bunch of videos about the seasons and

  • everything that goes along with them, and you can find those videos at youtube.com/scishowkids.

  • [♪ OUTRO]

[♪ INTRO]

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螃蟹、蟑螂和其他3種不是蜜蜂的傳粉者。 (Crabs, Cockroaches, and 3 Other Pollinators That Aren't Bees)

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    林宜悉 發佈於 2021 年 01 月 14 日
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