Hybrid Corals?

[Domboski]

Rare corals are hybridising, says study

Acropora by David Excoffier, Creative Commons.

Rare coral species are saving themselves from extinction by hybridising with other coral species, according to research published by Australian scientists in a recent issue of the journal PLoS ONE.

The study by Zoe Richards and coauthors focused on 14 rare and eight common coral species of the genus Acropora in the Indo-Pacific (for the purposes of the study, rare species are defined as those which have been recorded at less than 2.5% of sites for which data are available in the World Wide Acropora Database), for which the authors carried out a phylogenetic analysis using the highly polymorphic single-copy nuclear Pax-C 46/47 intron and the mitochondrial DNA (mtDNA) control region as markers.

The authors found that many of the rare coral species are polyphyletic for both Pax-C and mitochondrial phylogenies, which has been interpreted as evidence for interspecific hybridisation.

The authors conclude, ?[t]he results presented here imply that a number of rare Indo-Pacific Acropora species are the products of recent hybridisation events, and highlight the significance of hybridisation in coral diversification. Whether these species have hybrid origins or have evolved and then hybridised in the absence of conspecific gametes remains to be elucidated.?

?In summary, although it has often been assumed that small populations have a decreased potential for adaptation, our analyses imply that some rare acroporid corals may actually have increased adaptive potential as a consequence of introgressive hybridisation, and therefore may be less vulnerable to extinction than has been assumed.?

For more information, see the paper: Richards ZT, MJH van Oppen, CC Wallace, BL Willis and DJ Miller (2008) Some rare Indo-Pacific coral species are probable hybrids. PLoS ONE 3(9), e3240. doi:10.1371/journal.pone.0003240

This article may not be reproduced without permission.

 

[Killerdrgn]

Sweet when are we going to get frags of that?

 

[ellebelle]

I will get the actual article.

actually, it's open access:
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0003240

 

[Domboski]

I will get the actual article.

actually, it's open access:
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0003240

I had a feeling you would

 

[jhale]

It makes sense, corals like acropora have very similar structures, so to find them cross pollinating (I know plant term) is not far fetched at all.

 

[ellebelle]

Well, cross pollinating is not the same as hybridizing and I think it's a real mistake to think of corals as plants.

"Cross-pollinating" is fertilization between two different plants, not necessarily two different plant SPECIES. Also, in general, plant genomes are far more pliable than animal genomes. Plant gengineering is far more advanced that animals gengineering. We can splice genes into plant genomes and the plant still grows and develops normally - i.e. a famous early-ish experiment showed a corn plan (Zea mays) with the gene for phosphorenscence from fireflies spliced into the genome. The result was a glowing corn plant. You could never do that with an animal species, even one as simple as a coral.

To say that all corals have a similar structure is like saying all primates have a similar structure. We all have five fingers and five toes and nails instead of claws and grasping and hands etc etc etc. But humans and chimpanzees can't hybridize (or at least, it hasn't been documented. ).

What I think is most interesting about all of this is that not all of the Acroporid corals hybridize AND the ones that do seem to be unidirectional. You see unidirectional hybridization in mammals all the time, usually due to behavioral differences in the different species. But there are no behavioral differences in the acroporid corals - so why is hybridization only going one way in some species? That's totally weird and cool.

 

[prattreef]

Very interesting stuff. Can you explain unidirectional hybridization a bit? This is right up your academic alley isn't it ? :wink1:

 

[Domboski]

What about this: http://www.organicconsumers.org/patent/glowingmonkey.cfm

 

[Killerdrgn]

You could never do that with an animal species, even one as simple as a coral.

How about glo-fish? Those are zebrafish that have been spliced with jellyfish genes (the green and yellow ones at least). Red's are spliced with coral genes.

 

[ellebelle]

Ha, the glowing monkey thing is awesome. But did you see at the bottom? Of 126 fertilizations, only ONE glowing monkey is produced. This kind of stuff is just much much harder with animals.

Okay, I shouldn't have said NEVER. But it's a lot more difficult and we were doing things like that with plants a long time ago.

 

[jhale]

Well, cross pollinating is not the same as hybridizing and I think it's a real mistake to think of corals as plants.

"Cross-pollinating" is fertilization between two different plants, not necessarily two different plant SPECIES. Also, in general, plant genomes are far more pliable than animal genomes. Plant gengineering is far more advanced that animals gengineering. We can splice genes into plant genomes and the plant still grows and develops normally - i.e. a famous early-ish experiment showed a corn plan (Zea mays) with the gene for phosphorenscence from fireflies spliced into the genome. The result was a glowing corn plant. You could never do that with an animal species, even one as simple as a coral.

To say that all corals have a similar structure is like saying all primates have a similar structure. We all have five fingers and five toes and nails instead of claws and grasping and hands etc etc etc. But humans and chimpanzees can't hybridize (or at least, it hasn't been documented. ).

What I think is most interesting about all of this is that not all of the Acroporid corals hybridize AND the ones that do seem to be unidirectional. You see unidirectional hybridization in mammals all the time, usually due to behavioral differences in the different species. But there are no behavioral differences in the acroporid corals - so why is hybridization only going one way in some species? That's totally weird and cool.

yes well if you want to get all technical about it...

:lol2:

 

[ellebelle]

Unidirectional hybridization is when only one sex of a specific species mates with the females of the other species. Since I study primates, I'm going to use a monkey example. Hamadryas baboons and Anubis baboons have a hybridization zone in Ethiopia where their two ranges meet. There are some substantial differences between them both behaviorally and physically. Hamadryas baboons have a lot of sexual dimorphism and a strict social organization where each dominant male has a series of females that compose one-male bands. The dominant male copulates only with those females. Anubis baboons live in large multi-male, multi-female groups. They are less sexually dimophic and lack the big furry ruffs that male hamadryas baboons have. Female and males mate somewhat indiscrimnantly (this is an oversimplification, but it will do). In this situation, the vast majority of the hybrids from this species are male hamadryas baboons and female anubis baboons. This is likely because a female hamadryas baboon would simply not find a male anubis baboon "attractive". They look more like less dominant male hamadryas. Also male hamadryas should be more aggressive at acquring mates because of the mate-guarding/one-male band social structure. We know that these hybrids are unidirectional because 99% all of the hybrids sampled have anubis female mtDNA (passed through the female) and mixed nuclear DNA (half from male, half from female).

If you read the whole article, the same thing is seen in the corals that are hybridizing. They don't have mixed mtDNA, which means the hybridization is going unidirectionally. If it were going both directions, we should see a mixed mtDNA.

Some of the older species have mixed mtDNA, but if a species has a long evolutionary history, it's hard to tease apart whether or not the results are due to lineage sorting or a more recent hybridization event.

 

[prattreef]

Thanks, that makes sense, but how does that work with broadcast spawners like corals where fertilization is random amidst clouds of sperm and egg?

 

[ellebelle]

Exactly why I think it is interesting, Randy. Without knowing anything beyond a hobbyist knowledge of coral biology and reproduction, maybe there is some kind of chemical incompatibility going the opposite direction... some kind of post-zygotic isolating mechanism.

Hybrids can "fail" at different stages post-conception. For example (using mammals again), a mule is a horse x donkey. But technically it is a hybrid fail because a donkey is sterile. In mammals, hybrids can fail at three other stages - either sperm and egg aren't compatible, the offspring can't grow and develop normally and ends in spontaneous abortion and the offspring is still born.

 

[Domboski]

Would you mind keeping an eye out for a follow up article? It would be interesting to find the explanation on why unidirectional hybridization happens in corals?

 

[ellebelle]

These are abstracts, but I can download the entire articles on work on Tuesday.

Here is an earlier article by the same group:
http://www.ncbi.nlm.nih.gov/pubmed/...nel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum

Another Acropora hybrid article:
http://www.ncbi.nlm.nih.gov/pubmed/...nel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum

It looks like Zoanthids might hybridize as well.
http://www.ncbi.nlm.nih.gov/pubmed/...nel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum

This article might have the answer to why these guys are only unidirectional hybrids:
http://www.ncbi.nlm.nih.gov/pubmed/...nel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum

And finally, here is an article about wrasse hybrids:
http://www.ncbi.nlm.nih.gov/pubmed/...nel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum
You can see that the article discusses the fact that the hybrids are bidirectional, unlike the coral.