Philcoxia

Eric

Carnivore
This genus was presented in CPN in 2012. Since then there was not much new in the CP world, but some progress in the science. There are now at least 7 species, all of them are probaly carnivorous, but specialised in catching nematodes:
P.bahiensis , P.goiasensis, P.minensis, P.tuberosa, P.rhizomatosa, P.courensis, and P.maranhensis.
The first three were described by Taylor and Souza in 2000 (Souza mentioned it already in his thesis in 1996). The most recent two were described in 2017. They are not related to any other CPs, but to plants like waterhyssop (Plantaginaceae, Tribus Gratioleae). Probably all are very rare, certainly they are inconspicious and it is difficult to find them unless they are flowering. Sand and diamond mining endanger these species.
 

Apoplast

Carnivorous Plant Addict
I'm on a science tear today. I don't yet buy that it is indeed carnivorous. This hinges on broad botanical sampling of how plants can take nutrients up (ever hear of foliar fertilizer?), how we define "carnivory" in plants, and the intersection of the previous two with the techniques used to suggest carnivory in these plants. I won't bore everyone with all of this now. But I wanted to weigh in since this has come up again.
 

jeff

Carnivorous Plant Addict
A real carnivorous plant is a plant capable of attracting and capturing prey (mainly insects, mites and other small invertebrates) and then assimilating them by their enzyme, in whole or in part, in order to meet (partially) its own needs.

some exceptions like the heliamphora which digests its prey only thanks to the bacteria contained in its water reservoir or or roridula that needs a pushpin
 

Apoplast

Carnivorous Plant Addict
Agreed. However does incidental consumption count?


I would argue, we need to tweak the working definition of carnivory in plants. It needs to include an evolutionary component to exclude the myriad "non-standard" ways plants take up nutrients besides from labile minerals in soil water through roots hairs, which are not primarily selected to capture nutrients from animals. I've been thinking this through as examples like Philcoxia and teasel have come out in the literature. If we continue to use the same standards, we will find that many plants are "carnivorous", which I suspect from the stand point of natural selection is not true.

I believe we need to move toward a working definition of carnivory that is more like this one:
Carnivory in plants is occurs when plants have significant and costly adaptations which are primarily under selection to capture nutrients directly from non soil mineral sources in the kingdom Animalia.

Even this I argue needs work. It leaves out the old clade of protists which might be actively captured, but I think it is a start. It would exclude things like teasel, and Philcoxia (which may well be coating its leaves primarily as a form of protection from light in its environment, with "prey" capture being incidental), but include Heliamphora, Darlingtonia, and the Nepenthes which are, shall we say, directly manured. It also ends what I believe to be a tiresome debate about whether or not to include Roridula, which this definition includes. It does not include the autonomy in carnivory, but I have been thinking about those as well. I've not yet though about to present them in a way that avoids the pitfalls of the scala naturae in the non-directional nature of evolution. Plus, most people probably think I'm off my rocker thinking about the definition this much, let alone how to create catagories within the new definition.
 
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jeff

Carnivorous Plant Addict
in my opinion apart from the attraction, the capture ,2 point are very important for carnivores the production of enzymes by the plant itself to dissolve the prey, and the circulation of nitrogenous substances of the prey in the plants from the traps.

However does incidental consumption count? yes and no , yes for the carnivorous and the protocarnivorous , no for the rest
 

Apoplast

Carnivorous Plant Addict
Jeff, I absolutely appreciate your input here and I hope that by having a discussion with you about this I am not discouraging you in any way shape of form.

I do see your response as illustrating my critique well though. We shouldn't need definitions that include "in my opinion". We should have a single, accepted, and scientifically sound definition. The definition also needs to include widely accepted carnivores like Heliamphora, so we no longer need to list several exceptions from the definition. Needing to list so many exceptions, and so often, is the strongest argument that the current definition is insufficient. Additionally, having conditional considerations such as whether incidental consumption would qualify further suggests we need a new and better definition.

Your description of the attributes that are necessary and sufficient to qualify as carnivorous; I fully agree are important considerations. However, I would argue these are considerations of degree, and what I was referring to degree of autonomy of carnivory in plants. But they should not act as the primary definition.

Please know, my objections to the definition are general, and my argument not with you personally. Again, I find your contributions to be wonderful and valuable! I am simply expressing my concerns with how the carnivorous plant community approaches the fundamental definition that defines the group. The scientists who study these plants are often just as guilty of this.

In fact, this entire thought stems from my discussion with another evolutionary biologist at a conference several years back. He was beginning to study hormone control in VFT as a side project and was shocked at the poor definition of plant carnivory that is accepted. He indicated that it suggested many of the people studying this group are not as familiar as they should perhaps be with the wider plant nutrient literature. We know a lot about how plants take up and use nutrients, and being a variant on this spectrum is the fundamental uniting factor for carnivorous plants. But it is not clean, as nutrient uptake in plants falls along many axes - much like succulence. Succulence is a common evolutionary response to uneven water availability, by creating capacitance in the system, but how much storage is needed before it crosses the threshold to being a "succulent"?

The crux of my point is that we can't consider carnivory in isolation as our current definition does. It needs to be placed within the context of the much wider world of plant nutrient uptake and use. Which is why I am arguing for a new definition.
 
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