Reticulate Evolution

[o.c.d.]

If what I've read is true than the Identification of coral should be ever changing because morpholigy is always changing ? Also should tank raised species be in a class of their own ,I'm a little lost.

[Malifluous]

i believe corals are identified by the corallites. Morphology of the entire colony is definitely not the way to truly Id any species .

[greenbean36191]

Coral taxonomy is a mess because it's really hard to define what is a species with them. In many genera like Montipora and Montastraea there is almost continuous variation from one area to another. If you looked at a specimen from one side of the ocean and compared it to something from the other side you would say they were two different species, but when you look at all the areas in between you see that it's a gradual change and there is no clear definition of where one species starts and one stops.

Also, like malifluous said, most taxonomy is based on skeletons. That causes problems of its own because different conditions can cause changes in the skeleton even in genetically identical specimens. In the case of Montipora there have even been reports of two different species sharing the same skeleton. How do you classify that?

There is also a lot of hybridization between some species and possibly even between genera.

[SDguy]

I saw a show on PBS or discovery where they talked about acropora being classified into just a few "super" species, each with many varieties... it was an interesting idea.

[o.c.d.]

So if taxonomy technique dosn't change for corals then it will only get more difficult to Id species. Best educated guess is what we have to go by.
I've alway went by my books to Id and many time corals look similar but not the same so I question it. Now from what I'm getting is they are probably the same species and shouldn't sweat it to much.

[RichConley]

Originally posted by SDguy
I saw a show on PBS or discovery where they talked about acropora being classified into just a few "super" species, each with many varieties... it was an interesting idea.

I had a talk with Rob Toonen a while back, and that seemed to be his oppinion. He said that Delbek was on the same side... IE 6 to 7 major species, and everything is just regional variants of those species.


Both of them also said that the only way to identify things into the dozens of acropora species we have now, is to know location, and thats a major no-no.

IE, if you give them a skeleton, and tell them its from Fiji, they tell you its A. Millepora, but if you tell them its from Palau, its A. Prostrata.

Acropora is a relatively new genus evolutionarily speaking, so it makes sense that theres very little speciation at this point.

[Shoreliner11]

Correct me if I'm wrong here...but the process of reticulate evolution although interelated to taxonomy isn't exactly ret. evolution. Although the problems with coral taxonomy which have been already stated exist, ret. evolution is the process of abiotic factors (ie ocean surface currents) driving the course of coral evolution, rather than per say competition or space availability being the driving force. Veron states it very well in Corals of the World, where species are packaged and repackaged in time by both the hybridization of species as well as speciation occurs. Sorry, this isn't exactly where the thread was going, but I also wanted to clear up my perception of ret. evolution. Thanks guys

Aaron

[greenbean36191]

If you were to graphically represent a "typical" lineage you get a tree with simple branches. When there is reticulate evolution, branches of the tree fuse together to form a net-like graph. In reticulation, recombination of genes from different lineages is the driving evolutionary force (ie. hybridization, backcrossing, polyploidy, etc.).

It's hard to tell how much of a role reticulation plays in coral evolution because the phylogeny (which is reflected by the taxonomy) is a huge mess. We can't even figure out what a species is. We know that some corals "hybridize" and at least in the lab many produce fertile offspring. However, if they're just members of one large polymorphic species then they're really not hybrids and there is no reticulation. Even if they are truly separate species we don't know how much that hybridization occurs in the wild.

Probably the best studied case of reticulation in coral evolution is the Caribbean Acropora and people are still arguing over the evolutionary role of reticulation there. A. prolifera is a hybrid of A. palmata and A. cervicornis, but it's infertile. Still, it reproduces asexually, so some argue that it's a valid species since there are plenty of other animals with no sexual reproduction. Some people also think there is evidence that it can backcross with either of the parent species, which ties the two of them together even if it isn't a true species. Still others think there is no more evolutionary significance to it than any other infertile hybrid, so it doesn't represent a fusion of lineages.

[MCsaxmaster]

And just a note, while Charlie Veron is a proponent of reticulate evolution (one of his babies) and while I respect him immensely, not too many folks put that much stock in the idea.

cj

[o.c.d.]

Can anyone tell me if Vernon's book Corals of the world is a good read filled with interesting thoughts on the matter at hand,or is it more of a means of Identification?I have what I think is a large collection of book so maybe a comarision to would also help.
Thank you all for your responses on reticulate evolution I feel smarter now.

[MCsaxmaster]

It is, more or less, what it sounds like: a temporal and geographic history of the development and proliferation of the scleractinia. It doesn't deal with species identification, at least not directly.

cj

[LockeOak]

Is "Corals of the World" a different volume from "Corals in Space and Time"?

[MCsaxmaster]

Yes, Corals of the World is a three volume series while Corals in Space in Time is a single volume. The former is mostly for identification purposes of zooxanthellate scleractinians. The latter is a historic account of the rise and proliferation of the scleractinia.

cj