Until recently, sticklebacks were thought to be pretty closely related to seahorses and pipefish. At first glance, it seems reasonable: both groups of fish have bony armor plates, male parental care, and species with elongated bodies and snouts. Many of the species also share a mode of swimming called “labriform” that I’ll be talking about more in a later entry.
So, the pipefishes and sticklebacks share parental care, bony armor, elongation, swimming mode – seems like a slam dunk, right? Wrong.
Things are rarely that simple when you’re dealing with the incredible diversity of teleost fishes, particularly within the Percomorpha, often referred to as the “bush at the top of the tree of life”. Fish are just too diverse for simple morphology-based relationships – you need genetic data to really see what’s going on, and you need a lot of it, because there are so many groups.
In a paper published early last year, Kawahara et al used 75 sequenced mitogenomes to generate a phylogeny of the Gasterosteiformes and related species, and…bam, there goes the neighborhood!
Gasterosteiformes(bolded in the figure above) was split into three pieces: seahorses, pipefishes and their relatives ended as sister to the gurnards, the weird indostomids were sister to the weird synbranchiformes, and finally, the closest relatives of the Gasterosteidei(sticklebacks) were eelpouts and pholids.
A pholid (from Wikimedia Commons)
Obviously, there’s still a lot of work to be done with these fishes – nuclear genes need to be sequenced to back up the mitochondrial genome data, and given the number of species in the presumed stickleback sister group, it’s conceivable that there could be a paraphyly issue as well.
Either way, it looks like the sticklebacks are in for a wild ride!
KAWAHARA, R., MIYA, M., MABUCHI, K., LAVOUE, S., INOUE, J., SATOH, T., KAWAGUCHI, A., & NISHIDA, M. (2008). Interrelationships of the 11 gasterosteiform families (sticklebacks, pipefishes, and their relatives): A new perspective based on whole mitogenome sequences from 75 higher teleosts Molecular Phylogenetics and Evolution, 46 (1), 224-236 DOI: 10.1016/j.ympev.2007.07.009