And I just imagined ankylosaurids at bat.
You are basically suggesting that natural selection played no part in seed size or number. That’s extremely unlikely, for two reasons.
(1) The analogy with feathers vs membranes is misplaced. It’s hard to evolve feathers from membranes and vice versa, so evolution works with its available starting material to make do. But it’s easy to evolve changes in size and quantity and chemical composition (such as bitterness or pleasant taste).
(2) Reproductive strategy is, for obvious reasons, something where there is strong selection pressure if one phenotype is advantageous.
So, no, I don’t believe that dismissing these seed differences as purely contingent is an appropriate or adequate explanation here. It’s highly implausible that seed characteristics have no effect on fitness; and if (for example) it were advantageous for the mango to have smaller multiple seeds, that change would likely happen rather quickly (in evolutionary time).
It’s certainly true that there may be several possible strategies, and that even in identical environments different, similar species may pursue different strategies. And that’s precisely why this question is interesting - we have a comparison that may help us to understand exactly what’s going on, what subtle differences do lead two species to pursue different strategies. And these ideas may well lead to testable hypotheses - these are living species for which we could gather data and run experiments.
Again, look at the Galapagos finches. Look at the data that has been gathered on them, including changes in beak size correlated with climate cycles. Do you dismiss all that hard work and hard data gathered by evolutionary biologists as “just so” stories?
Well, yeah, they’d be outliers. Most placentals are mouse- or srew-sized with large litters and short generational turnover. Putting a lot of resources in to fewer “baskets”, as it were, rewards more specialized cases, perhaps putting more pressure onto conspecifics. A prematurely born human would be less nutrient taxing on its mother, but it wouldn’t be at an advantage.
Hey! Another thing I have in common with giant ground sloths.
Is the prickly pear related to either one? It seems to taste good but the damn thing has an annoying cache of seeds…
It may be “easy” to change the quantity of seeds, but it doesn’t seem to be the case in the mango’s evolutionary history. The mango is a member of the family Anacardiaceae, which has around 860 species, most of which produce drupes. So it seems that the single large seed is pretty strongly preserved in the case of this family. A papaya, on the other hand, is from a family with only 34 species, but all of those have multiple seeds. The mango has a single very large, hard seed because it had ancestors that had a single somewhat large seed to work with. A papaya has lots of seeds because it came from ancestors that had lots of seeds.
(I’m no botanist, so I’m relying on the University of Google for the specifics of this.)
Cacti are their own family, Cactaceae. So not closely related to either mango or papaya.
If not the number of seeds, then the size of the seed would probably be more adaptable to selective processes. Why did it not remain a smaller fruit with a smaller seed, which would take less energy/resources to produce?
One might hypothesize that megafauna would be more attracted to eating larger fruit. Megafauna might also have a larger roaming range than smaller animals, aiding seed dispersal, and a seed that had passed through the gut of a megafauna animal would be excreted into a large nutrient-rich pile of dung. The seed’s larger size might also be influenced by the need to pass through a large animal’s gut intact.
Growing up in India, mangoes used to be my favorite summertime fruit (many others too). One thing not mentioned in this thread is that most of the mangoes you get in the stores are varieties (cultivars) developed by humans and have been artificially selected to be big fruited while the trees are relatively short (for easy picking).
Wild (or naturally growing) mangoes are much smaller - about the size of a peach and their seed sizes are comparable or maybe slightly bigger. These mango trees get huge; like three storey tall. I have seen cows, baffalos and even hogs eat these mangoes. I have no idea if the seeds survive their digestive track.
The small mangoes known as desi (indi) mangoes have more fiber and are stronger in taste. Kind of like Crabapples and Apples.
On a hot summer day, you can collect and eat ripe fallen mangoes from a wild mango tree, setup a blanket under the cool shade of the tree, enjoy the nice breeze and take a nap while listening to many birds especially the Asian Koel. Oh and wild mango trees are usually home to herds of rose ringed parakeet.. The parakeets leave the tree in the morning in herds looking for food, then come back as huge swarms in the evenings.
I mentioned that the original wild mangoes may have been smaller than those cultivated today. Agriculturally-grown crops can be larger than their wild ancestors - compare modern maize with its antecedent. So I guess its possible that the reason that the mangoes we generally see and eat today are bigger than peaches is purely as a consequence of human cultivation and selection.
When I was a child living in West Africa, we had a large mango tree in the garden. From memory I would say that it was the size of a beech tree.
The fruit were similar to the smaller ones I buy in the supermarket today, but of course they were all out of our reach. My sister and I would tie a weight to a string and throw it up to snag a branch. This would be enough to shake loose a few of the ripe fruit. We would then sit on the back step, clad in our underwear, and eat them, skin and all. We also sneaked them up to our bedrooms and this was evidenced by the small forest of seedlings that grew in the bed under the window.
We had a cashew tree as well, which was quite rare. The nut hangs down underneath the bell shaped fruit, which i remember as being delicious but short-lived. We used to roast the nuts on an open fire and prise them open for the kernels. They were so acidic that they would take a layer of skin off our fingers - we didn’t care because they were so nice. An annual treat.
The mango and other large tree stone fruit may have evolved to attract large herbivores like elephants and bovines of India. The seed is meant to pass through the animals intestines. The large seed ensures that the seedling is larger than a small seed plant that also grows in the same manure pile, that is hopefully in an opening with lots of sun.
The large seed, or large fruit with few seeds, are for arid areas where the trouble is growing in fertile soil, and the seed is large so that the seedling can develop a good root system before the seed’s food supply is consumed. The large seed prevents birds taking it away, as birds won’t produce a fertile soil in a suitably stable place. (fertile soil on the cliff just washes away in the wet season.)
Pappaya evolved in South America forests, where there isn’t any large herbivore to take the seed to a clearing, and there’s no shortage of fertile soil anyway. Its better to have many seeds that birds and monkeys can swallow, and spread everywhere… to improve the number of seeds that find an opening where each can grow to maturity and reproduce.
That’s some great additional info, and brings climate and vegetation canopy cover into the mix!
It’s interesting that Mexico, where the avocado originated, and India, where the mango originated, are the same latitude and have not dissimilar climates.
There’s a list of the world’s largest seeds here on Wikipedia. Not counting the coconut-style fruit/seeds of the palm family, it appears that the three largest fruit seeds are the avocado, mango and peach - all drupe-style fruit. The peach originated in Northwest China, so a more northerly latitude, but fitting with the idea that large seeds do better in arid climates.
Somewhat tangentially, I was intrigued by a plant on the list called the “Idiot Fruit” and clicked through to read about it. It’s an early species of tree found in the Australian rainforests. Its large seeds are poisonous to animals, it grows only in a very few locations and in “groups of 10-100 trees together (rather than scattered individuals)”. While it is clearly a success for surviving so long, one can see how the innovation of fruit would give a plant an advantage in dispersing seeds over a wide area rather than just having them drop nearby (gravity dispersal). The “Idiot Fruit” appears to have survived through time by reserving its particular spot in the landscape over successive generations, rather than by trying to spread itself and colonize new locales, like a fruit tree might do.
Agreed - the ancestor effect is a pretty serious force - and whilst there are probably numerous cases of plants with multiple seeds per fruit only producing one seed - the reverse is less common.
Put another way: if a plant family can produce multiple seeds in a fruit - i.e. one or more, ‘one’ is just a subset of that behaviour.
If a plant family produces one seed per fruit, switching to more than one is a radical change. If you carefully slice a cherry in half, you’ll see that the whole structure of the fruit is built around the stone - it would not be a simple change at all for the cherry to become seedless, or have more than one seed.