Hybrid Clowns

[deangelr]

In most haremic species there is no choice, by either male or female. That group of females is "stuck" to that harem (and it's dominating male) by a strong social structure, that's how they live. When the male dies, the largest female changes behavior, color and sex (on that order). Female wrasses don't switch harems if the male of the next harem over is prettier, there is no choice.

I dont have any sound evidence on this but I strongly disagree that there is no choice..

Now, don't take me wrong, I am not saying that sexual selection doesn't exist in reef fishes. All I am saying is that it is not what is driving the bright colors, and is much less important in reef fishes than it is in birds. If you want to see some clear examples of sexual selection just look at freshwater fishes or even some blennies. But it is not correct to say that most reef fishes are colorful because of sexual selection, it's the generalization that bothers me.

I I am not comparing birds to reef fishes. It was just to give the reader an idea of how sexual selection works... I can't think of one circumstance where flamboyant colors exhibited in sexual dimporhism are not due to selective mate choice. Reef fishes are no different.

Bright colors themselves (or even sexual dimorphism) are not per se an indication of sexual selection. If they were, how would you explain brightly colored juveniles and relatively drab adults like many damselfishes and angelfishes?

Juveniles may likeley be so brightly colored in certain species of wrasses etc. to help clearly outline the social structure duing intraspecific species interactions.. Again, I see this as a product of sexual selection.. Almost any sort of differences in phenotype based on social structed in the end boils down to sexual social structure and therofore sexual selection

The phenotypes we see exhibited by any fauna are driven by two factors

• survivability
• sexual selection
  

*sexual selection can also be driven by intrasex competition

Reef fishes come in such a wide variety of colors, often within genus. The same genus, same physical shape, can have drastically different color variations. This is likeley due to mate choice..

Tangs, for example... You think one went black, one went yellow, one sailfin colored. etc.. becuase certain morphs had a better chance of survival, and over time those morphs were selected for based on geographical variation? I dont..

I have already asked you this, But if you don't want to buy what im selling that the variation in reef fishes is in large part due to sexual selection.. How do you explain such bright coloration and different patterns? what factor of survivability would you accredit these features to?

 

[deangelr]

It just blows my mind to think that you can argue the flamboyant colors on a male wrasse. The complex social structure of a harem.. are not dependant (evolutionarily derived from) on sexual selection.. This just seems obvious to me. I am not sure of exactly how it factors into play, but clearly these relationships are driven by social structure and mate choice.

Sexual Dimporphism = product of sexual selection every time

 

[Luiz Rocha]

Male Sparisoma cretense:

Female Sparisoma cretense:

So, according to that logic the difference above has been driven by sexual selection (meaning males choosing only colorful females)?

See, I think mutations just happen and sometimes mutations make colorful fish. If there is one habitat where colorful fish would survive and thrive, that's the coral reef. Again, I am not saying there is no sexual selection, just saying that most of the color is a product of other kinds of adaptations, or maybe just accidental, and because it is not detrimental in the reef it survives.

So, we've been talking just about fish. Let's talk about Nudibranchs, very colorful, bright, hundreds of species, just like fish. Are their bright colors caused by sexual selection? Probably all the nudibranch eyes can do is let the slug know whether it is light or dark, or when a shadow is passing over them.

 

[deangelr]

Male Sparisoma cretense:
So, according to that logic the difference above has been driven by sexual selection (meaning males choosing only colorful females)?

Yes, but this is over evolutionary time. It is not as simple as just female chooses X and then X shows up in the next generation. It also isnt always males choosing, or females choosing. Perhaps they are choosing the most colorful, or maybe the most bland.. We dont know exactly what they are choosing for. This idea gets very complex.. Think about differental chromosomal structure of social bees and other social insects.

See, I think mutations just happen and sometimes mutations make colorful fish. If there is one habitat where colorful fish would survive and thrive, that's the coral reef. Again, I am not saying there is no sexual selection, just saying that most of the color is a product of other kinds of adaptations, or maybe just accidental, and because it is not detrimental in the reef it survives.

Mutations do happen, perhaps the greatest driver in evolutionary diversity.. But mutations would be present in both male and females of a given species if sexual selection were not present. Otherwise there would be no reason an advantageous mutation wouldnt be beneficial and therfore appear in both sexes.


So for my tang example.. You think that the reason we have different colors on different species is due to mutation? Well this would require geographical seperation and that is not the case. Sexual selection allows diversification of phentotype independant of geography. A female, or group of femals may have some allele that prefers a certain trait. If an individual female having this preferences has a high fecundity then that preference can be passed on

So, we've been talking just about fish. Let's talk about Nudibranchs, very colorful, bright, hundreds of species, just like fish. Are their bright colors caused by sexual selection? Probably all the nudibranch eyes can do is let the slug know whether it is light or dark, or when a shadow is passing over them.

I am not referring to nudbranchs.. Their coloration is likely a warning "do not eat me" there are toxins inside.. This sort of selection is a survivability factor. Those nudibranchs showing bright coloration were selected for over time. This is not the case with most fishes.

Good banter BTW

 

[Luiz Rocha]

Alright, here we go, of course we are talking about evolutionary time, not generational stuff. Thousands to millions of years. So, with that in mind, a few misconceptions, first mutation and ultimately speciation do not require geographical separation.

You would be surprised at how few species in the reef show some sort of sexual dimorphism. Males and females of most butterflyfish, angelfish, damselfish, groupers, etc are identical. The only major group of reef fishes that shows sexual dimorphism (or dichromatism) is wrasses.

So, let's look at your tang example (and many wrasses too). Many wrasses and tangs spawn in large groups, hundreds of males and females get together at the same time, usually during a certain moon phase, outgoing tide, and spawn together, hundreds of millions of gametes in the water, how can there be sexual selection in a system like this?

Take a look at the photo below, it shows how most wrasses reproduce:

Many males and females at the same time, coincidentally that's the only photo I found on Google, but sometimes you see many colorful (terminal) males on those spawning aggregations. This is a small one, but I have seen some aggregations with hundreds, if not thousands of individuals.

Here a group of Convict Tangs spawning:

Even if females (or males) are choosing which aggregation they go to, they cannot choose single males among hundreds with so many gametes in the water at the same time.

 

[deangelr]

Alright, here we go, of course we are talking about evolutionary time, not generational stuff. Thousands to millions of years. So, with that in mind, a few misconceptions, first mutation and ultimately speciation do not require geographical separation.

I never said that they did. Certain kinds of speciation require geographical seperation, others do not.. no point to go through which types do and dont. But of course we rember "Allo" and "Sym" types.

You would be surprised at how few species in the reef show some sort of sexual dimorphism. Males and females of most butterflyfish, angelfish, damselfish, groupers, etc are identical. The only major group of reef fishes that shows sexual dimorphism (or dichromatism) is wrasses.

I said that most reef fishes show the phenotypes they do, due to sexual selection.. I never said anything about sexual dimorphism being a necessity for sexual selection. Just that sexual selection is always the reason behind sexual dimorphism. Traits that are sexually selected for may bebefit both sexes and so no dimorphism would be present

So, let's look at your tang example (and many wrasses too). Many wrasses and tangs spawn in large groups, hundreds of males and females get together at the same time, usually during a certain moon phase, outgoing tide, and spawn together, hundreds of millions of gametes in the water, how can there be sexual selection in a system like this?

Im confused.. how can there not be. Just because it is group sex doesn't mean that the individuals aren't choosing to particicpate. I can't explain exactly how this works but I know it does.. Social insects have diffent chromosamal structures, most being sterile. This is a trait that isnt necessarily "chosen" by the either male or female bees, but it is a product of sexual selection and diversifies the social structure.

Take a look at the photo below, it shows how most wrasses reproduce:

Many males and females at the same time, coincidentally that's the only photo I found on Google, but sometimes you see many colorful (terminal) males on those spawning aggregations. This is a small one, but I have seen some aggregations with hundreds, if not thousands of individuals.

Trust me.. I am quite familiar with the reproductive methods/avenues taken by fishes. Even in these apparently choatic mating rituals there is a great deal of social structure present

Here a group of Convict Tangs spawning:

Even if females (or males) are choosing which aggregation they go to, they cannot choose single males among hundreds with so many gametes in the water at the same time.

Agian, you are taking that arguement that the phentypic diversity we see in reef fishes in particular is not due to sexual selection, do you have any good explanations.. ?

In an evironment where most fitness needs are met, this allocates extra metobolic energy/time for other endeavors. Organisms often go through more selective pressures when procuring a mate in such circumstances. Although the reef is a highly oligotrophic environment, it is still nutrient rich in a way. The availability of these nutrients enables fishes to meet their fitness needs with minimal effort, and so they spend more time being "choosy"

 

[Luiz Rocha]

So, you are saying that in an aggregation with say 200 fish, each releasing 1,000 gametes in the water column, there is sexual selection going on? That's 100,000 eggs and 100,000 sperms in a fluid environment at the same time. Wouldn't any sperm just fertilize the first egg it finds?

My explanation is that there are many processes involved. Sexual selection is one of them, but I don't see it being the major one. Some fish are toxic, some are mimics, some even don't see the same colors as we do, and the colors that we do see are just a byproduct of the UV pattern that they see. Entire groups are colorful simply because their ancestor was colorful (no need for an adaptive reason there if color is neutral). Entire families of fishes (like squirrelfishes) are red because red is harder to see in twilight and darker areas of the reef where they live.

 

[deangelr]

yes red is a good example of a survivability factor for sure.. And red is a color taken out with depth. many fish that appear red at the surface are infact not red at all when viewed in their natural environment.

And to answer your question about the 200 fish and thousands of gamets having sexual selection involved.. Yes..

we can agree to disagree I guess.

The reason we see such great phenotypic diversity in reef fishes is do the sexual selction The reef environment is a great example of what happens when fitness needs are easily met.

The fish in your avatar is colored the way it is because it was selected that way.. There are no randoms in evolution. Everything has a cost.

 

[Luiz Rocha]

Well, agree to disagree it is then, I think there are dozens of reasons for fish to be colorful (mimicry, camouflage, "false eyes" in butterfly and damselfish, "hitchhike" neutral mutations, speciation itself, etc) sexual selection being only one of them, and not the major one.

 

[Sheol]

Dogs may be the ultimate "Victims" of crazy breeding! Some short-nosed toy breeds must be artificially inseminated, since they cannot mate naturally..
Oh, captive breeding is fine. I'm all for it. But the "Frankenstein" syndrome (breeding freakish things because you CAN..) needs to be curtailed IMO.
Personally, I wish all SW fish were captive spawned, as opposed to being wild caught. Just less genetic monkey business, please!

Sincerely,
Matthew