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I started wondering about this. If you take the more-or-less accepted carnivorous genera (ie. what’s on Barry Rice’s website), which country has the most diverse carnivorous flora?

Is it the one with representatives of the most carnivorous lineages? Going off of the idea that there were 9 independent origins of carnivory — once for the Caryophyllales carnivores, once for Lentibulariaceae, once for Sarraceniaceae, then once for each of the other genera (Brocchinia, Byblis, Catopsis, Cephalotus, Philcoxia, and Roridula), I think Brazil wins — with representatives of 6 of those lineages (2/3 of them!). Assuming this, I believe that’d be followed by Venezuela at 5, Australia and the US at 4, and a whole host of countries with 3. Is that right? If you exclude the bromeliads, I believe Brazil would be tied with Australia at 4, with the US and Venezuela dropping to 3.

What if you’re just counting genera? I think Brazil, the US, and Venezuela are at 7, and Australia (and maybe others) are at 6. I don’t think any single country is higher than 7 genera, but I’m not sure.

But what if you’re counting species? In that case, I think it’s probably Australia, but maybe Indonesia or the Philippines, too. I’d guess that South Africa, Brazil, Venezuela, and Mexico might be up there too. Maybe even the US (how many bladderworts are native to the US?).

What do you think is the best way to measure carnivorous plant diversity? It’s pretty clear that looking at this question from different approaches has different answers. I don’t really know if there’s a right way to look at the question.

Am I missing any other countries with significant carnivorous plant diversity at any of the levels I bring up?

The greatest biodiversity will always be found in the harshest environments, since the increased survival pressure drives adaptation and speciation. South Africa and Australia are known to be hotspots of biodiversity because of this, though Australia is a much larger landmass and hence has a far greater number of species.

Tropical regions such as equatorial South America and southeast Asia are also rather harsh environments - the same nutrient poor soil as desert environments, but wet rather than dry. This results in a wide variety of species in both regions, but neither of them can hold a candle to Australia.

Your question is an excellent one indeed and hinges on our very understanding of what a carnivorous plant is. Many consider only plants which produce digestive enzymes, catch and trap, and gain benefit from the action to be carnivorous. While there are others who consider plants which trap but do not necessarily digest the prey through the production of digestive enzymes but rather through commensalistic relationships with bacterium and other detrivorous organisms which convert the insects captured and killed by the plant into usable compounds. Under the first classification many carnivorous plants in cultivation would not be considered carnivorous but rater paracarnivorous. Including Darlintonia, some Heliamphora, and Carnivorous Bromeliads to name a few.
However as to your question of which country has the most diverse group of carnivorous plants the area is a bit more grey as diversity may refer to genotypical diversity or to phenotypical diversity. Due to this many Carnivorous plants are rather closely related as they all come from the family Droseraceae and although many are in the same family the times of divergence from each other is not very well known however I assume you are asking about the country with the largest amount different genuses in that case you would be looking toward Australia and also in families. Since Australia has Byblis, Aldrovanda, Drosera( wooly, pygmy, and "normal" forms), Utricularia, and Cephalotus. Three of which are not a part of the Droseraceae family making this the most diverse in terms of both genetic data and families.
Africa is also very diverse continent having Aldrovanda, Drosera Regia ( should be its own genus but will talk about that another time), Pinguicula, Utricularia, Genlisea, and Drosera.Giving four families aside from Droseraceae. Brazil is also fairly diverse having Drosera, Heliamphora, Brocchinia( considered a paracarnivorous plant by most), Pinguicula, and Utricularia. However note that most are in the droseraceae family.
Also note that the Nepenthes genus is very diverse in its own right with numerous species. So one may also consider the Phillipines very diverse.
The Family with the largest amount of carnivorous plant species is Droseraceae.
There are many species of bladderworts native to the US also.
It is also important to note that all carnivorous plants are dicots begging the question of origins.
Nice Question hope this helps and Good Growing!

nimbulan wrote:The greatest biodiversity will always be found in the harshest environments, since the increased survival pressure drives adaptation and speciation. South Africa and Australia are known to be hotspots of biodiversity because of this, though Australia is a much larger landmass and hence has a far greater number of species.

Tropical regions such as equatorial South America and southeast Asia are also rather harsh environments - the same nutrient poor soil as desert environments, but wet rather than dry. This results in a wide variety of species in both regions, but neither of them can hold a candle to Australia.

What really interests me is that when you’re looking at carnivores, Brazil has representatives of more carnivorous lineages than Australia, but has fewer species. Isolation of the environment from its surroundings does seem to be a big deal — most of the diversity in Brazilian carnivores is in the highlands, which are obviously isolated: Drosera, Heliamphora, Genlisea, Utricularia, and Brocchinia are mostly in the mountains in the north, iirc. Philcoxia is in the central part of the country and Catopsis is everywhere.

I know many biodiversity hotspots seem to have elevation as an isolating factor, but Australia doesn’t seem to have nearly the same relief as other hotspots. Is the biggest isolating factor keeping species apart in Australia simply the harshness of the summer drying?

I read Allen Lowerie's CPs of Austrailia Magnum Opus book, and he said that 1/3 of all CPs are in Austrailia. Think about it. There's Cephs, dews (pygmies, tuberouse, and tropicals), Utrics, and three species of Neps.

Also though, the Tepui (table-top mountians in Brazil) have thirty percent of their plant life carnivorous. They have Heliamphora, Drosera, Utricularia, and carnivorous bromeliads. Heliamphora live no where else besides the Tepui.

bananaman wrote:What really interests me is that when you’re looking at carnivores, Brazil has representatives of more carnivorous lineages than Australia, but has fewer species. Isolation of the environment from its surroundings does seem to be a big deal — most of the diversity in Brazilian carnivores is in the highlands, which are obviously isolated: Drosera, Heliamphora, Genlisea, Utricularia, and Brocchinia are mostly in the mountains in the north, iirc. Philcoxia is in the central part of the country and Catopsis is everywhere.

I know many biodiversity hotspots seem to have elevation as an isolating factor, but Australia doesn’t seem to have nearly the same relief as other hotspots. Is the biggest isolating factor keeping species apart in Australia simply the harshness of the summer drying?

I don't think that elevation is the direct cause, but rather because vegetation is much less dense at higher elevations (due to temperature and moisture differences) which allows these smaller, more unusual plants like carnivores to flourish. The tepuis are also physically isolated by their unusual structure. The extreme dryness of the climate in Australia most certainly is the major isolating factor there, which limits the ability of the plants to spread to new habitat.