Regressive progression,progressive regression or neither? Phylogeny and evolution of the Percopsiformes (Teleostei,Paracanthopterygii)

Dillman, C.B., Bergstrom, D.E., Noltie, D.B., Holtsford, T.P. & Mayden, R.L. (2010). Regressive progression, progressive regression or neither? Phylogeny and evolution of the Percopsiformes (Teleostei, Paracanthopterygii). —Zoologica Scripta, 40, 45–60. Cave animals have fascinated scientists for centuries, and clades consisting primarily of cave‐adapted species are even more intriguing. The percopsiforms are an enigmatic group of fishes comprised of nine species in seven genera, with four species in three genera exhibiting characteristic troglomorphic features, such as a lack of pigmentation and eyes. Nucleotide characters presented here provide the first test of monophyly for both the Percopsiformes and Amblyopsidae with this character type and taxonomic completeness. Characters of ND2 support a monophyletic Percopsiformes and Amblyopsidae and further document phylogeographic subdivision in two stygobitic genera, Amblyopsis and Typhlichthys, in Amblyopsidae. Age estimates from time‐calibrated branch lengths utilizing two independent intra‐lineage fossils indicate that the ancestor to amblyopsids is Eocene in age, and that phylogeographic subdivision in both Amblyopsis and Typhlichthys occurred primarily in the Miocene. Interestingly, ancestral character state reconstruction for the amblyopsids strongly supports the re‐evolution of eyes and body pigment. While certainly unconventional, but supported with this character set, the hypothesis provides continued challenge to Dollo’s Law.