Molecular phylogenetic perspective on the evolution of the deep-sea fish genusCyclothone (Stomiiformes: Gonostomatidae) |
| |
Authors: | Masaki Miya Mutsumi Nishida |
| |
Institution: | (1) Department of Zoology, Natural History Museum & Institute, Chiba, 955-2 Aoba-cho, Chuo-ku, 260 Chiba, Japan;(2) Department of Marine Bioscience, Fukui Prefectural University, 1-1 Gakuen-cho, Obama, 917 Fukui, Japan |
| |
Abstract: | A portion of mitochondrially encoded 12S and 16S ribosomal RNA genes were sequenced from 13 currently recognized species of
the midwater deep-sea fish genusCyclothone (Stomiiformes: Gonostomatidae) and three gonostomatid outgroup taxa. Phylogenetic analyses using maximum parsimony and maximum
likelihood methods were performed on unambiguously aligned, combined sequences (803 bp) of the two genes. The resultant tree
topologies from the two methods were congruent, being robust and supported by various tree statistics, enabling the evolutionary
history ofCyclothone to be described in detail. The molecular phylogeny demonstrated striking inconsistencies with previously proposed “natural
groups”, although the latter could be confidently refuted by the molecular data. The most significant characteristic of the
evolutionary history ofCyclothone was the independent acquisition of an apomorphic depth habitat from the relatively ancestral, lower mesopelagic habitat,
by each of three major distinct lineages that had diverged earlier in their evolution. Moreover, such macroevolutionary habitat
shifts had been necessarily accompanied by morphological and ecological novelties, presumably originating from paedomorphosis.
Repeated evolution of such changes strongly suggests ontogenetic plasticity inCyclothone which could enable these fishes to acquire larval-like, simple organization of body structure. Such a body plan could help
them subsist in food-poor surroundings and regulate reproductive variables that take advantage of increasing larval survival
toward shallower depths. Recent speciation events, on the contrary, have produced contemporary sister species of allopatric
(or microallopatric) distributions, but few morphological and ecological differences. Even if remarkable miniaturization has
occurred, such as in the Mediterranean endemicC. pygmaea, it had to have been a simple truncation of ancestral species' ontogeny without attendance of any discernible paedomorphic
features. On the basis of the fossil record, geological history of the Mediterranean region, and ectotherm molecular divergence
rate, it was estimated thatCyclothone radiation had already started in the early-middle Miocene (17–20 million years ago). |
| |
Keywords: | Molecular phylogeny mitochondrial DNA paedomorphosis progenesis protandry |
本文献已被 SpringerLink 等数据库收录! |
|