Which seeds have the hardest coats?

Which seeds can be spread by endozoochory?

• Spread by birds and mammals eating the fruit and seeds then depositing the seed. http://en.wikipedia.org/wiki/Seed_dispersal#Dispersal_by_animals Would it work with all angiosperms ("enclosed seed")? Does it matter what kind of animal eats it? I would like to use my dogs to distribute such seeds. I tried it with tomato seeds but there was no result.

• Answer:

  Not all seeds of angiosperms will germinate after gut-passage. Other means of animal dependent seed dispersal (biotic dispersal) include epizoochory and dyszoochory [1]. Epizoochory--dispersal on the exterior of animals is the result of seeds with highly developed seed coats (with burrs, hooks, etc.), and dyszoochory--dispersal through animal behavior (burying, hoarding, etc.) is made possible through the evolution of seeds that have longer germination periods and that possibly require freeze and thaw cycles. That said, it does seem that there are certain "types" of seeds that are able to withstand gut-passage (endozoochory) for germination [2], but there is not a concise "list" of seeds. Generally, though, "fleshy, often brightly colored berries, arillate seeds, drupes, and big fruits... that are evidently eaten by vertebrates and pass through the gut before the seeds enter the soil elsewhere" [3]. Additionally, small seeds that are able to fit in the pits of molars, that have hard seed coats that can withstand gastric acids, and that are in "seed banks" (the horn of grains) are able to pass through the gut and germinate [4]. Weed seeds thrive despite gut passage, but then they have seeds that are very tenacious. Re: your experiment with your dogs, are you certain you had viable tomato seeds before they passed through the dogs' guts? (i.e. did you plant seeds from the same tomato that you fed your dog?). I've seen septic leach fields with tomato sprouts, so viable tomato seeds do sprout after gut passage. [1] There are many other means of dispersal including: achory, agochory, ahemerob, agrochory, allochory, anemoballochory, anemochory, anthropochory, atelochory, autoballochory, autochory, ballistichory, ballochory, barochory, blastochory, boleochory, bristle contraction, bythisochory, chamaeochory, dysochory, endochory, endozoochory, epichory, epizoochory, ethelochory, hermerochory, herpochory, hydroballochory, hydrochory, meteochory, myrmacachory, nautochory, ombrochory, ornithochory, speirochory, stomatochory, synchory, unassisted dispersal, zooballochory, and zoochory. Schulze, Ernst-Detlef, Erwin Beck, Kaus Muller-Hohenstein (2005) Plant Ecology. New York: Springer Publishing. [2] I should hesitate before saying they require gut-passage because I've not seen data that indicates that it is a requirement. The fleshy attractive fruit or bountiful seed heads certainly encourage ingestion of the fruit, seed and animal locomotion ensures dispersal beyond the parent plant's range, and there are studies that indicate that there is a higher rate of germination after gut-passage, but plants will still germinate even without gut passage. [3]http://www.publish.csiro.au/?act=view_file&file_id=BT02124.pdf [4]"Why are small seeds dispersed through animal guts" http://onlinelibrary.wiley.com/doi/10.1111/j.2006.0030-1299.14114.x/abstract?systemMessage=Wiley+Online+Library+will+be+disrupted+on+26+May+from+10%3A00-12%3A00+BST+(05%3A00-07%3A00+EDT)+for+essential+maintenance&userIsAuthenticated=false&deniedAccessCustomisedMessage= "Ecological correlates of endozoochory by herbivores" http://onlinelibrary.wiley.com/doi/10.1046/j.1365-2435.2002.00625.x/full