How Hybrid Fish and Corals can Create New Species?
- Feb 14, 2022
- Anshika Mishra
- 282 0 0
Hybrid fish may be rare in the reef tank hobby, but they are not that rare on wild coral reefs. These mixed fish sell for huge amounts of money when they are available.
Hybrids are relatively common on the border where two species meet in the wild. For instance, nearly 50% of large marine-angle fish species are involved in hybridization today, and almost 40% of Butterflyfish are also involved in the process.
It would be useful to know that we organize animals into clades trees. It is the species tree that we can trace back to a common ancestor. As fish, coral, sharks, and sea snakes interbreed, they form a hybrid. Sometimes if conditions are just rights, the combination can form an entirely new species.
How do we Detect Hybrid Fish?
Well, it turns out, it is not particularly easy. We know a lot more about the hybrids of freshwater fish than saltwater.
As we study more of the world's coral reefs, collecting genetic information as we do so, we are finding more hybrids in the ocean.
Sometimes, it is as simple as looking at the fish. Sometimes, it's clear that this individual is a mix of two-parent species. However, it is not always this easy.
Hybrids can interbreed back with their parent species, and they look identical to their parents. In those cases, unless we have studied the genetics of that individual fish, it is hard to know that we are looking at a hybrid. You might have hybrid fish or even coral in your reef tank today and not even know it.
Hybrid fish are most commonly found at the border between two different species. Therefore, hybrids occurring at the border of two other species have a strong effect on the overall evolution of the species.
When hybrids make their way deeper into their parent species ranges, that impact is made even broader, as the genetic information from the other species is spread into the parent genes.
Hybridization is a big driver of the incredible diversity that we see on coral reefs around the world today.
Hybrid Corals
Hybrids do happen in corals as well. Amongst all that we know, 281 species form combinations alone. That is about 15% of the total species in the family.
Corals don't form a hybrid, only where the species range meets. However, combinations are much more widely distributed in corals v/s fish. We think this is just because of how corals reproduce.
Because most coral reef fish and all the corals have a free-swimming larval stage life, ocean currents can transfer far from their birthplaces. Changes in ocean currents can introduce new individuals to places where they might be likely to hybridize with other species.
This means that the prevalence of hybrid animals can change over time as the ocean itself changes. If the density of those hybrids gets to be high enough that they begin to breed amongst themselves, we can even get a new species.
Corals normally have high levels of genetic information, overlapping between species. But we don't see as many hybrid corals as we might expect because of intra-agressive hybridization.
Intra-agressive hybridization is just a big fancy term for what happens when a hybrid animal is born, but then it breeds back with its parent species enough that it can't find a stable mixed population. This is why it is useful to have low densities of both parent species if you don't want a diverse population to establish as a new species.
You want the hybrid to breed rather than mix back into the parent populations. Inter-breeding groups of corals and fish over thousands of years can form species complexes.
Think about the Wrasses and Butterflyfish. As these groups of fish interbreed, new closely related species arise over time because those resulting species are so closely related. They can be grouped into a species complex which makes studying them easier.
As the world's climate changes and ecological niches available to fish and coral change with it, we can expect new hybrids to be created. Take the example of Clownfish. Many species of clownfish are found primarily in one species of Anemone in the wild.
Climate Change and Coral Reefs
As the climate changes decrease the overall number of anemones, eventually forcing two different species of clownfish into the same Anemone. This close contact makes a hybrid clownfish more likely.
It is also possible that instead of creating new hybrid species, the genomes might mix so completely through continued interbreeding that two-parent species merge into just one hybrid species that entirely replaces both parents.
This can be a problem for long-term species diversity. From two species, we end up with only one. The reverse can happen as well, though. For instance, if the hybrid is better suited to a particular ecological niche, it might become established there over time, and instead of two species, we are left with three. This group of species might eventually be considered complex.
Introgression, breeding back with the parent's species, and the mixing of genomes can give genes that make the resulting hybrids more adaptable in some way. For example, perhaps, one of the coral species of the parent coral is better able to produce protective stress proteins. And possibly, the resulting hybrid would gain this ability as well.
Then that hybrid could become its own more hardy species over time, or perhaps it would interbreed back with the parent species and slowly spread those genes that give better stress tolerance to the parent population. So this great tolerance for heat is one of the exciting things that we see in the corals today.
Adapting Corals
As the oceans warm, this ability to pass on traits like this is a hopeful sign that perhaps the coral reefs will survive if given a chance to adapt to changes over many years.
We don't always have multiple decades to let this happen naturally. So we have already interbred corals to explore this ability, and some of those are living in the ocean's beds today.
If all goes well, we can create genetic hybrids in the lab and replant them out on the bleached reef to prevent the overall breakdown of the coral reef ecosystem.
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