3
Mitochondrial Molecular Clocks
and the Origin of Euteleostean
Biodiversity: Familial Radiation of
Perciforms May Have Predated
the Cretaceous/Tertiary Boundary
YOSHINORI KUMAZAWA I, MOTOOMI YAMAGUCHI 2.\ AND MUTSUMI NISIIlDA 2.3
1 Department of Earth and Planetary Sciences, Nagoya University, Furo-cho, Chikusa-ku,
Nagoya 464-8602, Japan
2 Department of Marine Bioscience, Fukui Prefectural University, 1-1 Gakuen-machi, Obama
917-0003, Japan
3 Current Address: Ocean Research Institute, University of Tokyo, 1-15-1 Minamidai, Nakanoku, Tokyo 164-8639, Japan; e-mail: mnishida@orLu-tokyo.ac.jp
Abstract
Euteleostean fishes, especially those in the order Perciformes, can represent vertebrate biodiversity. Fossil evidence suggests an apparently explosive radiation of
perciform families in the early Cenozoic, raising the question of how freshwateradapted perciforms like cichlids could distribute over the well-separated landmasses
of Gondwanaland origin. In order to gain insights into the time and mode of the
perciform radiation by molecular methods, complete mitochondrial genes for NADH
dehydrogenase subunit 2 and cytochrome b were sequenced for 13 perciforms, a
characiform and a basal neopterygian Amia. Phylogenetic trees constructed from
concatenated amino acid sequences of these genes together with published sequences
for other taxa were mostly in agreement with current views on ichthyological classification. The relative rate tests indicated approximate homogeneity of molecular
evolutionary rates among many of the diverse fish groups. Gamma-corrected distances based on the mitochondrial protein sequences were shown to provide a good
estimate of pairwise distances even for divergences of a few hundred million years
ago in time or 0.5-1.0 substitutions per site in pairwise distance. The molecular
evolutionary rate for the fishes could be calibrated consistently using the diverKey words. Teleostei, Perciformes, Cichlidae, freshwater fishes, mitochondrial DNA, cytochrome b, phylogenetic tree, fossil records, molecular clock, vertebrate evolution, biodiversity,
adaptive radiation, biogeography, divergence time, Cretaceousffertiary boundary
35
Mitochondrial Molecular Clocks
and the Origin of Euteleostean
Biodiversity: Familial Radiation of
Perciforms May Have Predated
the Cretaceous/Tertiary Boundary
YOSHINORI KUMAZAWA I, MOTOOMI YAMAGUCHI 2.\ AND MUTSUMI NISIIlDA 2.3
1 Department of Earth and Planetary Sciences, Nagoya University, Furo-cho, Chikusa-ku,
Nagoya 464-8602, Japan
2 Department of Marine Bioscience, Fukui Prefectural University, 1-1 Gakuen-machi, Obama
917-0003, Japan
3 Current Address: Ocean Research Institute, University of Tokyo, 1-15-1 Minamidai, Nakanoku, Tokyo 164-8639, Japan; e-mail: mnishida@orLu-tokyo.ac.jp
Abstract
Euteleostean fishes, especially those in the order Perciformes, can represent vertebrate biodiversity. Fossil evidence suggests an apparently explosive radiation of
perciform families in the early Cenozoic, raising the question of how freshwateradapted perciforms like cichlids could distribute over the well-separated landmasses
of Gondwanaland origin. In order to gain insights into the time and mode of the
perciform radiation by molecular methods, complete mitochondrial genes for NADH
dehydrogenase subunit 2 and cytochrome b were sequenced for 13 perciforms, a
characiform and a basal neopterygian Amia. Phylogenetic trees constructed from
concatenated amino acid sequences of these genes together with published sequences
for other taxa were mostly in agreement with current views on ichthyological classification. The relative rate tests indicated approximate homogeneity of molecular
evolutionary rates among many of the diverse fish groups. Gamma-corrected distances based on the mitochondrial protein sequences were shown to provide a good
estimate of pairwise distances even for divergences of a few hundred million years
ago in time or 0.5-1.0 substitutions per site in pairwise distance. The molecular
evolutionary rate for the fishes could be calibrated consistently using the diverKey words. Teleostei, Perciformes, Cichlidae, freshwater fishes, mitochondrial DNA, cytochrome b, phylogenetic tree, fossil records, molecular clock, vertebrate evolution, biodiversity,
adaptive radiation, biogeography, divergence time, Cretaceousffertiary boundary
35