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.