Hybrid Chaetodon tinkeri x Chaetodon miliaris
In October 2011, Robert Whitton and Richard Pyle found a small juvenile hybrid butterflyfish while conducting a rebreather dive in deep water in the Hawaiian Islands. It was the first hybrid Chaetodn tinkeri x C. miliaris reported since the early 1970’s. Interestingly, it was paired with a juvenile C.
Interspecies hybridization is an inherently fascinating biological phenomenon that can potentially offer us insight into the process of evolution and speciation on coral reefs. Aquarists have always admired such aberrant fishes for their unique aesthetic qualities, spending lavishly on these peculiar piscines, but we don’t often stop to ponder why it is that such genetic intermixing is possible in the first place. What ultimately limits the ability of two distinct species to form viable offspring? It’s beyond the scope of this humble blog post to attempt to answer that question with any real clarity, as even the brightest minds in evolutionary biology struggle with understanding the variables involved. But one obvious limitation can be seen by observing the general relatedness between the parent species in such hybridization events. Consider the many known mixes that occur with the Ocellaris Clownfish (Amphiprion ocellaris), which has been known to form crosses with its allopatric sister species, A. percula, and with virtually every other species group that occurs within its West Pacific Range: A. clarkii, A. frenatus, A.sandaracinos and even the Maroon Clownfish Premnas biaculeatus!
Clownfish hybrid pairing
Hybrid clownfish pair. Maroon clown and snow onyx percula.
This last mix is one I wish to highlight, as it helps to show how hybridization can elucidate evolutionary relationships that traditional morphology-based classifications have gotten incorrect. Despite the larger size and strongly spined operculum of the Maroon Clownfish, genetic studies have consistently shown that it is a close relative of the ocellaris/percula species group, and, in all likelihood, it will eventually be merged into that genus when the group is taxonomically revised next. On the other hand, there has never been a documented hybrid of a clownfish with another type of damselfish, despite the fact that clownfish are members of this diverse family. Is this a behavioral limitation? Is this a genetic limitation?

C. ornatissimus X C. reticulatus. This hybrid supports the close relationship of these two species revealed in genetic studies. Credit Yusuke

激レア海水魚 Rare Marine Fish Aquarium
Paracentropyge multifasciata Centropyge venusta hybrid.I am Japanese Aqualist.My Private Blog. http://aquariumzone.jp/archives/9763 Copyright (C) Namamugi Marin Fish Center All Rights Reserved. http://namamugi-fish.com/ 2013年6月10日に生麦海水魚センターに入荷したシマヤッコとスミレヤッコのハイブリッド個体です。
It’s interesting to note how hybridization can vary in extent across different groups. We already saw how the different subgenera/species groups of clownfishes can interbreed, but the same seems untrue for butterflyfishes and the closely related angelfishes of the Family Pomacanthidae. While the classification has been slow to catch up with recent molecular research, it seems that the major evolutionary lineages of angelfishes stick to themselves. Of the many known hybrid “Centropyge”, the parentage appears to, without exception, involve close relatives. For instance, there are known crosses of the Flame Angelfish with Potter’s Angelfish, but never has there been an example of a Flame Angelfish interbreeding with the more distantly related Lemonpeel Angelfish or Multibar Angelfish or Colin’s Angelfish, though all of these are found together across the Central Pacific. The reason for this might have to do with some insurmountable barrier present in their DNA or some nuance of their behavioral ecology which limits interactions, but, whatever the cause, it helps to prove the utility of applying hybrid incompatibility towards our understanding of past evolution.
That’s one of my next fish! Beautiful