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I have come across this video which put forth the hypothesis that bramble actually qualifies as a carnivorous plant. The observations that have led to the hypothesis are:
1. Sheep getting caught frequently in bramble
2. Sheep will die without human intervention.
3. The rotting corpse of the sheep will nourish the plant for many days.
4. The thorns angle inward -- supposedly evidence for adaptation that helps trap prey animal.

I agree , on the surface it looks plain silly but that is a reflexive reaction, not an argument. Is this a plausible hypothesis? If not , please give reasons.

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    $\begingroup$ Could you provide more information about why this plant may be carnivorous? $\endgroup$ – hamilthj Apr 18 '17 at 15:41
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    $\begingroup$ Are you using the word 'carnivorous' as meaning "meat eating"? What is the (unstated) hypothesis that the plant is carnivorous? ("The plant is carnivorous" is not a hypothesis. It is a conclusion.) Please do not simply link to a video; summarizing the relevant content is more likely to get you a good answer. Thanks. $\endgroup$ – anongoodnurse Apr 18 '17 at 17:51
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    $\begingroup$ @anongoodnurse: There are also some of us for whom video is not a good way of conveying information. Even if I chose to spend my time watching, the amount of information I'd retain would be significantly less than if it was presented as text. $\endgroup$ – jamesqf Apr 18 '17 at 19:23
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    $\begingroup$ @jamesqf I understand your point, but in that case we would have to present information always in many different ways to provide for all types of learners. For me, a mp3 file with spoken word, please. $\endgroup$ – skymningen Apr 19 '17 at 9:07
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    $\begingroup$ Voted to reopen and flagged. Thanks for the edit! $\endgroup$ – anongoodnurse Apr 19 '17 at 14:14
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Even if the adaptations to tangle were well supported, brambles would still not be carnivorous.

Carnivorous plants release digestive enzymes to digest their prey or have other adaptations specifically to pull nutrients from the things they kill. Brambles would have to rely on something else to rot the carcass and pick up whatever trace nutrients that get released into the soil like any other plant. Brambles tendency to tangle could just as easily be a defensive adaptation meant to encourage herbivores to avoid it. Without any specific adaptations to uptake the nutrients from killed animals, classifying them as carnivorous would be premature.

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This is really more of a comment than an answer, but I'd challenge most of those premises.

1) Sheep getting caught. But (AFAIK) wooly sheep are the (recent, in evolutionary terms) product of human breeding. Blackberries &c wouldn't have had time to evolve specific mechanisms to trap them. Most animals have relatively slick hair (or none, as with humans), and don't get trapped.

2) Domestic sheep don't really exist in the wild, do they? So there almost always will be human intervention.

3) Does rotting meat provide needed nutrition to the plant? I grow blackberries & raspberries, and they seem to do just fine without dead critters.

4) But if you spend time in places where blackberries or other brambles grow wild in some profusion (western Oregon, for instance), you do not notice (or at least I never have) an abundance of dead critters in the bushes. (Addendum: and dead critters of significant size, say larger than a rabbit, tend to be noticable, especially when you hike with dogs :-))

So I have to conclude that there's something wrong with this claim.

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    $\begingroup$ I had a farm so cluttered by brambles that I considered calling it Bramble Hill. My goats loved to eat brambles (I think they're well known for it), and, as you said, slick hair means no problem. Never lost a goat to brambles nor found any dead animals amongst them. $\endgroup$ – anongoodnurse Apr 22 '17 at 1:21
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I saw the same video and thought it was interesting. While others who didn't bother to watch the video might miss a few interesting points.

Video link https://youtu.be/RuzLXxbGc4c

It was pointed out that the thorns didn't stick straight out defensively as many thorns do, but rather raked back, thus grabbing and making it difficult to pull away.

Based on this article, it appears it would be more appropriate to call bramble "Protocarnivorous". https://en.m.wikipedia.org/wiki/Protocarnivorous_plant

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Maybe thorns originally evolved to deter mammals but not birds for the sake of successful seed dispersal by birds.

An analog is spicy pepper plants having seeds with a greater tendency to survive and germinate into new plants after having passed through bird digestive systems than if those same seeds had passed through a mammalian digestive system. It is also observed that birds are less sensitive to capsaicin than mammals. Thus, it is concluded that spicy pepper plants were selected due to both the presence of birds and mammals in their evolutionary past.

Maybe the bramble/berry-bush whose selected traits originally were a result of selection due to a particular outcome, now finds itself interacting differently with its environment due to changes in the environment. i.e. the presence of wooly sheep, but it just so happens that this change in environment favors those previously and separately developed traits, just in a different way.

An analog for selection favoring an existing platform: the tetrapod forelimb was a good base for: flight (bats), swimming (whales and seals), strength (bears), and manipulation of the environment (apes.), But these all started off as a tetrapod forelimb, selection just happened to modify each forelimb to its own environment.

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  • $\begingroup$ Your post does not really answer the question. The question is about whether the present adaptation of the plant qualify it as a carnivore. Can you please focus on that aspect? $\endgroup$ – WYSIWYG Apr 8 at 14:11
  • $\begingroup$ My bad, thanks for bringing me closer to correctness. To answer "whether the present adaptation of the plant qualify it as a carnivore." I respond with: No, but only because using the current definition of "carnivore" developed through the ontological analyses of existing carnivores is inadequate for defining evolving contemporaries. I argue we are observing a carnivorous plant in the making, we just happen to observe it at a time and stage when it fits the conventional lexical definition of "protocarnivorous." $\endgroup$ – Isaac Park Apr 11 at 6:38

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