Currently, right now. Not- how many species of plants are known. How many are there?
How do we estimate that? Is there a Fibonacci number fraction of uncertainty that we can predict? Do we actually already know pretty much most of the plant species?
If I can tag a second question onto this- how many plant species have there ever been? What is the formula for the relationship of the number of plant species through time?
Can we estimate the total number of plant species there will ever be? (On Earth, if you have to ask.)
Is there a limit to the number of possible plant species in an infinite universe?
To your last question, there’s probably some maximum limit to the size a genome can have and still be viable. And there are a finite number of nucleic-acid bases. Therefore, there must be a limit to the number of species possible. But it would be an extremely large limit.
One might quibble that there might be (and probably is) life in the Universe that isn’t DNA-based. But even if we allow other basis chemicals for life, even if we allow all other basis chemicals, it’s still finite. Incomprehensibly larger, but finite. Besides which, any life not based on DNA couldn’t possibly be a plant: It might have many traits in common with plants, and it’d probably get called a “plant” by laymen, but it’d belong to some completely different taxonomy.
You’re asking for a number you define as unknown - so the best we can do is coarsely estimate.
Something around 400,000 species are known. It’s probably reasonable to suspect that this includes something like two-thirds of all species. So we can use 600,000 as a rough guess.
Here’s a graphof the estimated number of plant species in existence at any one time. Plant diversity has more than doubled since the early Cretaceous, mainly due to the diversification of the flowering plants (Angiosperms).
To calculate the total number of species ever, one would have to have an estimate of the average lifetime of a species, and in a cursory search I haven’t found such an estimate. It would probably be on the order of magnitude of one million years, although some species such as Ginkgo biloba appear to have persisted for tens of millions of years (and similar forms go back as as long as 270 million years).
That y axis is puzzling. It must be in units of thousands of species, although there’s nothing on the graph to indicate that. I’m pretty sure there are currently more than 800 species of plants.
Of course, it’s very difficult, when looking at different times, to say whether two individuals are the same species or not, or to draw a line on when a lineage becomes a different species. Certainly, no ginkgo from a million years ago would be pollinating a modern ginkgo, in nature or otherwise. I suppose that if two populations are separated, isolated from each other for some span of time, and then brought back together, and that when they come back together, they go back to interbreeding in the wild, then one could say that both remained the same species, but for species with only one independent population, I’m not even sure how one could define “same species”.
Colibri, would it be true to say that the division into different species is a matter of convenient classification rather than scientific fact? I understand it’s fairly arbitrary whether two closely related plants (or animals) are the same species, two different species, or subspecies. And the classification frequently changes. Thus making it impossible to say how many species, or even to get a ballpark estimate.
My understanding is that Fungi used to be classified as plants, but are now regarded as a separate kingdom. Same thing with single-celled organisms that use chlorophyll to gain energy. That would have removed a hell of a lot of species from the total count.
Edit - Chronos’s post wasn’t there when I began to type my message. I got distracted for an hour, browsing Wiki looking for information.
That’s a separate issue. Everything that’s considered a fungus is more closely related to everything that’s considered an animal than any of those organisms are to any plant. So if you’re going to have any category that includes both plants and fungi, it’ll include animals, too, at which point you have to think that “plant” is the wrong name for that category.
But the answer to “How many species of plants?” would at one time have included the numbewr of species of fungi, but now it doesn’t. The difference in number woiuld be very large. That sort o0f thing adds to the problem of counting the species, and giving a meaningful answer to the question.
True to a certain extent. However, in any single place at any single time, it’s generally clear which organisms are behaving as species, that is, maintaining genetic separation. It’s when you look over wider stretches of space and time things get more complicated. And it also depends on which species concept you are applying. For a long time, the Biological Species Concept has been the prevailing one, but others such as Phylogenetic Species and Evolutionary species exist.
But these concepts don’t change the number of species enormously. Birds have gone through a lumping phase, from the 1930s to the 1960s, and now we are in a splitting phase as new criteria for species have been applied. But this has changed the number of species by maybe 20%. Different concepts aren’t usually going to change the number of species by an order of magnitude. (All this goes for multicellular organisms. When you get to microbes, all bets are off, especially since widely different groups can exchange genetic material.)
The separation of Fungi from plants wouldn’t have affected the estimate of the number of Plants at that time all that much since the number of species of Fungi described was much less than the number of green plants. As of 1990, only about 70,000 of species of Fungi had been described, compared to hundreds of thousands of green plants.
Since the kingdoms were separated, however, genetic analysis has greatly increased
the estimate of the number of fungal species to somewhere between 1.5 and 5.1 million species, with a more recent estimate of 2.2 to 3.8 million species.
Genetic analysis has greatly increased estimates of the diversity of microbes in general, but here the issue is how exactly you define species.
