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I'm attempting to find research on scientific theories surrounding the evolution of certain plants, and am unable to find any footing with respect to a certain genus.

In this case, I am researching Cucurbita (ie: squash, pumpkins, etc), and can't find any basis for how it survives inherently without outside manual intervention. Unlike hot peppers (eg: Capsicum annuum), it is not easily ingested by birds, who do not suffer from the painful effects of capsaicin, and effectively transport the seeds, undigested, to new areas to spread the plant.

Also, unlike fruit growing on a tree, such as apples, it doesn't (seem) to provide a means to transport seeds any meaningful distance.

Finally, it seems most animals; ruminants, scavengers, and insects alike, would consume and digest the seeds.

Are there any generally-accepted (or at this point, plausible) theories with research to back it with respect to how such plants could survive long term without being manually grown and harvested by a species which eats them? While I understand (and acknowledge) the scientific theory of evolution, I'm not sure how the survival of such plants seems to be a special case.

Thanks!

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    $\begingroup$ Interesting question. I wonder if the answer might possibly be similar to the avocado story -- theplate.nationalgeographic.com/2015/01/05/avocado-guacamole $\endgroup$ – David Blomstrom Mar 5 '16 at 4:14
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    $\begingroup$ I don't remember much, had studied botany a long time ago. But isn't cucurbitaceae that genus where the fruit blasts to disperse the seeds?? Then you dont need animals to eat taht stuff.. $\endgroup$ – Polisetty Mar 5 '16 at 6:12
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    $\begingroup$ Many plants that we use for have gone through thousands of generations of intensive artificial selection $\endgroup$ – rg255 Mar 5 '16 at 7:34
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    $\begingroup$ Sorry, should be family cucurbitaceae $\endgroup$ – Polisetty Mar 5 '16 at 10:47
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    $\begingroup$ I would maybe change the title to something like "Seed dispersal in Cucurbitaceae" $\endgroup$ – C_Z_ Mar 5 '16 at 17:23
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You're right that modern species would have a hard time spreading group seeds, though you're not quite right about the reasons. Cucurbita rinds are extremely bitter, so that modern mammals are reluctant to (or unable to) process the rinds to access the seeds.

According to a recent article (Gourds and squashes (Cucurbita spp.) adapted to megafaunal extinction and ecological anachronism through domestication), the explanation is that wild Cucurbita first co-evolved with North American megafauna, like mammoths and mastodons, who could tolerate the toxic/bitter rind. (The authors also suggest that megafauna also produced suitable habitats for their growth.)

Following the extinction of these megafauna, humans picked up the slack, with most wild Cucurbita going extinct and only domesticated versions remaining.

Collectively, these results point to wild-type declines coinciding with widespread domestication. ...megafauna consumed Cucurbita fruits and dispersed their seeds; wild Cucurbita were likely left without mutualistic dispersal partners in the Holocene because they are unpalatable to smaller surviving mammals with more bitter taste receptor genes. ... Thus, anthropogenic landscapes provided favorable growth habitats and willing dispersal partners in the wake of ecological upheaval.

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Some researchers claim wild avocados were dependent on large Ice Age mammals for seed dispersal. See this article, for example. Maybe the Cucurbitaceae are a similar story.

I wish I could think of the term for such severed relationships - "ghost ecology"? Another somewhat similar example is the question about the pronghorn's speed; why is it so fast when there are no North American predators that can keep up with it?

The answer may have been discovered in a cave in the Appalachians that harbored the bones of a Pleistocene cheetah. In other words, the pronghorn's speed may have evolved to help it escape a predator that no longer exists.

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    $\begingroup$ Please could you add some supporting scientific material that reinforces your answer and allows further reading. $\endgroup$ – rg255 Mar 8 '16 at 7:36

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