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1.
Characterization of the Hydra Lamin and Its Gene: A Molecular Phylogeny of Metazoan Lamins 总被引:4,自引:0,他引:4
Andreas Erber Dieter Riemer Helmut Hofemeister Marc Bovenschulte Reimer Stick Georgia Panopoulou Hans Lehrach Klaus Weber 《Journal of molecular evolution》1999,49(2):260-271
We report sequences for nuclear lamins from the teleost fish Danio and six invertebrates. These include two cnidarians (Hydra and Tealia), one priapulid, two echinoderms, and the cephalochordate Branchiostoma. Combining these results with earlier data on Drosophila, Caenorhabditis elegans, and various vertebrates, the following conclusions on lamin evolution can be drawn. First, all invertebrate lamins resemble
in size the vertebrate B-type lamin. Second, all lamins described previously for amphibia, birds and mammals as well as the
first lamin of a fish, characterized here, show a cluster of 7 to 12 acidic residues in the tail domain. Since this acidic
cluster is absent from all invertebrate lamins including that of the cephalochordate Branchiostoma, it was acquired with the vertebrate lineage. The larger A-type lamin of differentiated cells must have arisen subsequently
by gene duplication and insertion of an extra exon. This extra exon of the vertebrate A-lamins is the only major change in
domain organization in metazoan lamin evolution. Third, the three introns of the Hydra and Priapulus genes correspond in position to the last three introns of vertebrate B-type lamin genes. Thus the entirely different gene
organization of the C. elegans and Drosophila Dmo genes seems to reflect evolutionary drift, which probably also accounts for the fact that C. elegans has the most diverse lamin sequence. Finally we discuss the possibility that two lamin types, a constitutively expressed
one and a developmentally regulated one, arose independently on the arthropod and vertebrate lineages.
Received: 4 February 1999 / Accepted: 1 April 1999 相似文献
2.
Conflict Among Individual Mitochondrial Proteins in Resolving the Phylogeny of Eutherian Orders 总被引:19,自引:0,他引:19
Ying Cao Axel Janke Peter J. Waddell Michael Westerman Osamu Takenaka Shigenori Murata Norihiro Okada Svante Pääbo Masami Hasegawa 《Journal of molecular evolution》1998,47(3):307-322
The phylogenetic relationship among primates, ferungulates (artiodactyls + cetaceans + perissodactyls + carnivores), and
rodents was examined using proteins encoded by the H strand of mtDNA, with marsupials and monotremes as the outgroup. Trees
estimated from individual proteins were compared in detail with the tree estimated from all 12 proteins (either concatenated
or summing up log-likelihood scores for each gene). Although the overall evidence strongly suggests ((primates, ferungulates),
rodents), the ND1 data clearly support another tree, ((primates, rodents), ferungulates). To clarify whether this contradiction
is due to (1) a stochastic (sampling) error; (2) minor model-based errors (e.g., ignoring site rate variability), or (3) convergent
and parallel evolution (specifically between either primates and rodents or ferungulates and the outgroup), the ND1 genes
from many additional species of primates, rodents, other eutherian orders, and the outgroup (marsupials + monotremes) were
sequenced. The phylogenetic analyses were extensive and aimed to eliminate the following artifacts as possible causes of the
aberrant result: base composition biases, unequal site substitution rates, or the cumulative effects of both. Neither more
sophisticated evolutionary analyses nor the addition of species changed the previous conclusion. That is, the statistical
support for grouping rodents and primates to the exclusion of all other taxa fluctuates upward or downward in quite a tight
range centered near 95% confidence. These results and a site-by-site examination of the sequences clearly suggest that convergent
or parallel evolution has occurred in ND1 between primates and rodents and/or between ferungulates and the outgroup. While
the primate/rodent grouping is strange, ND1 also throws some interesting light on the relationships of some eutherian orders,
marsupials, and montremes. In these parts of the tree, ND1 shows no apparent tendency for unexplained convergences.
Received: 5 December 1997 / Accepted: 24 February 1998 相似文献
3.
Michael S.Y. Lee 《Journal of molecular evolution》1999,49(3):385-391
It has recently been argued that living metazoans diverged over 800 million years ago, based on evidence from 22 nuclear
genes for such a deep divergence between vertebrates and arthropods (Gu 1998). Two ``internal' calibration points were used.
However, only one fossil divergence date (the mammal–bird split) was directly used to calibrate the molecular clock. The second
calibration point (the primate–rodent split) was based on molecular estimates that were ultimately also calibrated by the
same mammal–bird split. However, the first tetrapods that can be assigned with confidence to either the mammal (synapsid)
lineage or the bird (diapsid) lineage are approximately 288 million years old, while the first mammals that can be assigned
with confidence to either the primate or the rodent lineages are 65 million years old, or 85 million years old if ferungulates
are part of the primate lineage and zhelestids are accepted as ferungulate relatives. Recalibration of the protein data using
these fossil dates indicates that metazoans diverged between 791 and 528 million years ago, a result broadly consistent with
the palaeontological documentation of the ``Cambrian explosion.' The third, ``external' calibration point (the metazoan–fungal
divergence) was similarly problematic, since it was based on a controversial molecular study (which in turn used fossil dates
including the mammal–bird split); direct use of fossils for this calibration point gives the absurd dating of 455 million
years for metazoan divergences. Similar calibration problems affect another recent study (Wang et al. 1999), which proposes
divergences for metazoans of 1000 million years or more: recalibrations of their clock again yields much more recent dates,
some consistent with a ``Cambrian explosion' scenario. Molecular clock studies have persuasively argued for the imperfection
of the fossil record but have rarely acknowledged that their inferences are also directly based on this same record.
Received: 26 January 1999 / Accepted: 14 April 1999 相似文献
4.
58,000 Dalton Intermediate Filament Proteins of Neuronal and Nonneuronal Origin in the Goldfish Visual Pathway 总被引:2,自引:11,他引:2
A group of proteins in the goldfish optic nerve with a molecular weight of 58K daltons was analyzed by two-dimensional gel electrophoresis. Results show that the proteins are differentially phosphorylated and found exclusively in a cytoskeletal-enriched fraction. The proteins from this fraction can be reconstituted into typical intermediate filament structures, as shown by electron microscopy. Two components which are of neuronal origin are transported within the slow phase of transport. The 58K proteins are the most abundant proteins in the optic nerve, and they are distinct from actin and tubulin. It was concluded that they are intermediate filament proteins. Cytoskeletal preparations of rat spinal cord, rat optic nerve, and goldfish optic nerve were compared by one-dimensional gel electrophoresis. The rat spinal cord contains glial fibrillary acidic protein (GFAP), and the rat optic nerve contains vimentin and GFAP, in addition to the neurofilament triplet. A typical mammalian neurofilament triplet is not detected in the goldfish optic nerve, while the major cytoskeletal constituent is a 58K band which coelectrophoreses with vimentin in the rat optic nerve by one-dimensional gel electrophoresis. 相似文献
5.
Christina M. Hall 《Journal of neurochemistry》1994,63(6):2307-2313
Abstract: The regulation of expression of two different types of neuronal intermediate filament proteins, ON1 /ON2 and plasticin, was studied during optic nerve regeneration in the goldfish. During regenerative growth of optic axons, there is a rapid and dramatically increased expression of plasticin, a recently cloned, novel type III intermediate filament protein, in the retinal ganglion cells. At the time when the growing axons reinnervate the optic tectum, expression of plasticin declines and there is an increased expression of ON1 and ON2 . This time course suggests that the target tissue participates in the regulation of these proteins. The aim of this study was to characterize the regulatory role played by the optic tectum. To address this issue, a repeated-crush paradigm was used whereby growing axons were hindered from reaching their target. It was found that in absence of tectal contact, the increased expression of ON1 and ON2 normally seen during regeneration was not induced. In contrast, expression of plasticin increased both in the presence and in the absence of tectal contact. 相似文献
6.
Joachim Schütze Alexander Skorokhod Isabel M. Müller Werner E.G. Müller 《Journal of molecular evolution》2001,53(4-5):402-415
One crucial event during evolution to multicellularity was the development of either direct cell–cell contact or indirect
interaction via extracellular matrix (ECM) molecules. The identification of those polypeptides provides conclusive data on
the phylogenetic relationship of metazoan phyla and helps us to understand the position of the Metazoa among the other kingdoms.
Recently it became evident that the ECM of sponges is amazingly complex; it is composed of fibrous molecules, e.g., collagen,
and their corresponding receptors, which are highly similar to those existing in other metazoan phyla. While these data already
support the view of monophyly of Metazoa, additional studies are required to understand whether these molecules, which are
similar in their primary sequence, also have the same function throughout the metazoan kingdom. In the present study we identified
the ligand for one of the autopomorphic characters of Metazoa, the single-transmembrane receptor protein with the receptor
tyrosine kinase (RTK) from G. cydonium, as an example: the putative mucus-like protein from G. cydonium. This protein was upregulated during autograft fusion in the homologous system with kinetics similar to those of the RTK.
Additionally, a cDNA was isolated from S. domuncula whose deduced polypeptide displays a high sequence similarity to dermatopontin, an ECM molecule found exclusively in Metazoa.
Furthermore, it is documented that expression of the fibrous ECM molecule collagen is regulated by the characteristic metazoan
morphogens myotrophin and endothelial monocyte-activating polypeptide. These data indicate that the ECM of sponges is not
an unstructured ground substance but provides the basis for integrated cell communication.
Received: 26 October 2000 / Accepted: 1 February 2001 相似文献
7.
Michael Kruse Vera Gamulin Helena Cetkovic Zeev Pancer Isabel M. Müller Werner E. G. Müller 《Journal of molecular evolution》1996,43(4):374-383
Protein kinases C (PKCs) comprise closely related Ser/Thr kinases, ubiquitously present in animal tissues; they respond to
second messengers, e.g., Ca2+ and/or diacylglycerol, to express their activities. Two PKCs have been sequenced from Geodia cydonium, a member of the lowest multicellular animals, the sponges (Porifera). One sponge G. cydonium PKC, GCPKC1, belongs to the ``novel' (Ca2+-independent) PKC (nPKC) subfamily while the second one, GCPKC2, has the hallmarks of the ``conventional' (Ca2+-dependent) PKC (cPKC) subfamily. The alignment of the Ser/Thr catalytic kinase domains, of the predicted aa sequences for
these cDNAs with respective segments from previously reported sequences, revealed highest homology to PKCs from animals but
also distant relationships to Ser/Thr kinases from protozoa, plants, and bacteria. However, a comparison of the complete structures
of the sponge PKCs, which are—already—identical to those of nPKCs and cPKCs from higher metazoa, with the structures of protozoan,
plant, and bacterial Ser/Thr kinases indicates that the metazoan PKCs have to be distinguished from the nonmetazoan enzymes.
These data indicate that metazoan PKCs have a universal common ancestor which they share with the nonmetazoan Ser/Thr kinases
with respect to the kinase domain, but they differ from them in overall structural composition.
Received: 10 January 1996 / Accepted: 12 March 1996 相似文献
8.
Analysis and Comparison of In Vitro Synthesized Glial Fibrillary Acidic Protein with Rat CNS Intermediate Filament Proteins 总被引:5,自引:5,他引:0
Intermediate filament (IF) proteins from rat spinal cord were analyzed by two-dimensional gel electrophoresis and compared with the in vitro translation products of a messenger RNA-dependent reticulocyte lysate system stimulated with 16-day-old rat brain polysomes. In two dimensions, the molecular weight 49,000 to 50,000 band of the IF preparation resolved to seven spots, whereas antiserum to glial fibrillary acidic (GFA) protein precipitated only two immediately adjacent radiolabeled in vitro synthesized products, with molecular weights of 49,000 to 50,000. Autoradiographs of two-dimensional gels of extracted IF proteins incubated with iodinated IgG fraction of GFA protein antiserum showed that all seven spots were recognized by the antiserum. These observations suggest that the primary gene product of GFA protein is modified either by post-translational processing or experimental artifact. 相似文献
9.
A heuristic approach to search for the maximum-likelihood (ML) phylogenetic tree based on a genetic algorithm (GA) has been
developed. It outputs the best tree as well as multiple alternative trees that are not significantly worse than the best one
on the basis of the likelihood criterion. These near-optimum trees are subjected to further statistical tests. This approach
enables ones to infer phylogenetic trees of over 20 taxa taking account of the rate heterogeneity among sites on practical
time scales on a PC cluster. Computer simulations were conducted to compare the efficiency of the present approach with that
of several likelihood-based methods and distance-based methods, using amino acid sequence data of relatively large (5–24)
taxa. The superiority of the ML method over distance-based methods increases as the condition of simulations becomes more
realistic (an incorrect model is assumed or many taxa are involved). This approach was applied to the inference of the universal
tree based on the concatenated amino acid sequences of vertically descendent genes that are shared among all genomes whose
complete sequences have been reported. The inferred tree strongly supports that Archaea is paraphyletic and Eukarya is specifically
related to Crenarchaeota. Apart from the paraphyly of Archaea and some minor disagreements, the universal tree based on these
genes is largely consistent with the universal tree based on SSU rRNA.
Received: 4 January 2001 / Accepted: 16 May 2001 相似文献
10.
We have investigated the phylogenetic relationships of monotremes and marsupials using nucleotide sequence data from the
neurotrophins; nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3). The study included
species representing monotremes, Australasian marsupials and placentals, as well as species representing birds, reptiles,
and fish. PCR was used to amplify fragments encoding parts of the neurotrophin genes from echidna, platypus, and eight marsupials
from four different orders. Phylogenetic trees were generated using parsimony analysis, and support for the different tree
structures was evaluated by bootstrapping. The analysis was performed with NGF, BDNF, or NT-3 sequence data used individually
as well as with the three neurotrophins in a combined matrix, thereby simultaneously considering phylogenetic information
from three separate genes. The results showed that the monotreme neurotrophin sequences associate to either therian or bird
neurotrophin sequences and suggests that the monotremes are not necessarily related closer to therians than to birds. Furthermore,
the results confirmed the present classification of four Australasian marsupial orders based on morphological characters,
and suggested a phylogenetic relationship where Dasyuromorphia is related closest to Peramelemorphia followed by Notoryctemorphia
and Diprotodontia. These studies show that sequence data from neurotrophins are well suited for phylogenetic analysis of mammals
and that neurotrophins can resolve basal relationships in the evolutionary tree.
Received: 27 January 1997 / Accepted: 20 March 1997 相似文献
11.
Jih-Shiou Liu Yau-Heiu Hsu Tzu-Yu Huang Na-Sheng Lin 《Journal of molecular evolution》1997,44(2):207-213
Satellite RNA of bamboo mosaic potexvirus (satBaMV) is a linear RNA molecule which encodes a 20-kDa nonstructural protein.
Sequences of seven different satBaMV isolates from bamboo hosts in three genera showed 0.7% to 7.5% base variation which spanned
the whole RNA molecule. However, the putative 20-kDa open reading frame was all preserved in these isolates. The phylogenetic
relationship based on the nucleotide sequence did not show particular grouping of satBaMV from the host in one genus; neither
was the grouping of satBaMV evident by location of sampling. Putative secondary structures of the 3′ untranslated regions
showed a basic pattern with conserved hexanucleotides (ACCUAA) and polyadenylation signal (AAUAAA) located in the loop regions.
Although the satBaMV-encoded 20-kDa protein is a nonstructural protein, its predicted secondary structure contains eight-stranded
β-sheets which may form ``jelly-roll' structure similar to that found in capsid protein encoded by satellite virus of panicum
mosaic virus.
Received: 26 June 1996 / Accepted: 9 September 1996 相似文献
12.
13.
We document the phylogenetic behavior of the 18S rRNA molecule in 67 taxa from 28 metazoan phyla and assess the effects of
among-site rate variation on reconstructing phylogenies of the animal kingdom. This empirical assessment was undertaken to
clarify further the limits of resolution of the 18S rRNA gene as a phylogenetic marker and to address the question of whether
18S rRNA phylogenies can be used as a source of evidence to infer the reality of a Cambrian explosion. A notable degree of
among-site rate variation exists between different regions of the 18S rRNA molecule, as well as within all classes of secondary
structure. There is a significant negative correlation between inferred number of nucleotide substitutions and phylogenetic
information, as well as with the degree of substitutional saturation within the molecule. Base compositional differences both
within and between taxa exist and, in certain lineages, may be associated with long branches and phylogenetic position. Importantly,
excluding sites with different degrees of nucleotide substitution significantly influences the topology and degree of resolution
of maximum-parsimony phylogenies as well as neighbor-joining phylogenies (corrected and uncorrected for among-site rate variation)
reconstructed at the metazoan scale. Together, these data indicate that the 18S rRNA molecule is an unsuitable candidate for
reconstructing the evolutionary history of all metazoan phyla, and that the polytomies, i.e., unresolved nodes within 18S
rRNA phylogenies, cannot be used as a single or reliable source of evidence to support the hypothesis of a Cambrian explosion.
Received: 9 December 1997 / Accepted: 23 March 1998 相似文献
14.
Maximum likelihood (ML) phylogenies based on 9,957 amino acid (AA) sites of 45 proteins encoded in the plastid genomes of
Cyanophora, a diatom, a rhodophyte (red algae), a euglenophyte, and five land plants are compared with respect to several properties
of the data, including between-site rate variation and aberrant amino acid composition in individual species. Neighbor-joining
trees from AA LogDet distances and ML analyses are seen to be congruent when site rate variability was taken into account.
Four feasible trees are identified in these analyses, one of which is preferred, and one of which is almost excluded by statistical
criteria. A transition probability matrix for the general reversible Markov model of amino acid substitutions is estimated
from the data, assuming each of these four trees. In all cases, the tree with diatom and rhodophyte as sister taxa was clearly
favored. The new transition matrix based on the best tree, called cpREV, takes into account distinct substitution patterns
in plastid-encoded proteins and should be useful in future ML inferences using such data. A second rate matrix, called cpREV*,
based on a weighted sum of rate matrices from different trees, is also considered.
Received: 3 June 1999 / Accepted: 26 November 1999 相似文献
15.
A Molecular Phylogeny of Lilium in the Internal Transcribed Spacer Region of Nuclear Ribosomal DNA 总被引:4,自引:0,他引:4
Tomotaro Nishikawa Keiichi Okazaki Tae Uchino Katsuro Arakawa Tsukasa Nagamine 《Journal of molecular evolution》1999,49(2):238-249
Phylogenetic relationships among 55 species of Lilium, Cardiocrinum giganteum, and Nomocharis saluenensis were inferred from nucleotide sequence variations in the internal transcribed spacer (ITS) regions of 18S–25S nuclear ribosomal
DNA. The phylogeny derived from ITS sequences estimated using maximum-likelihood methods indicated that (1) most of the species
construct their own clade according to the classification based on morphological features at the section level; (2) section
Daurolirion is not independent of Sinomartagon, and it is appropriate to integrate two sections as Sinomartagon; (3) it is appropriate that L. henryi and L. bulbiferum are classified into subsection 6a and Sinomartagon–Daurolirion, respectively; (4) subsection 6b is much closer to Sinomartagon than subsection 6a and Archelirion, and it arose directly from Sinomartagon; and (5) Lilium is much closer to Nomocharis than Cardiocrinum. Phylogenetic estimation using sequences of the ITS region is suitable at the levels of genus, section, and most of subsection.
Received: 18 December 1998 / Accepted: 14 March 1999 相似文献
16.
The chaetognaths are an extraordinarily homogeneous phylum of animals at the morphological level, with a bauplan that can
be traced back to the Cambrian. Despite the attention of zoologists for over two centuries, there is little agreement on classification
within the phylum. We have used a molecular biological approach to investigate the phylogeny of extant chaetognaths. A rapidly
evolving expansion segment toward the 5′ end of 28S ribosomal DNA (rDNA) was amplified using the polymerase chain reaction
(PCR), cloned, and sequenced from 26 chaetognath samples representing 18 species. An unusual finding was the presence of two
distinct classes of 28S rDNA gene in chaetognaths; our analyses suggest these arose by a gene (or gene cluster) duplication
in a common ancestor of extant chaetognaths. The two classes of chaetognath 28S rDNA have been subject to different rates
of molecular evolution; we present evidence that both are expressed and functional. In phylogenetic reconstructions, the two
classes of 28S rDNA yield trees that root each other; these clearly demonstrate that the Aphragmophora and Phragmophora are
natural groups. Within the Aphragmophora, we find good support for the groupings denoted Solidosagitta, Parasagitta, and Pseudosagitta. The relationships between several well-supported groups within the Aphragmophora are uncertain; we suggest this reflects
rapid, recent radiation during chaetognath evolution.
Received: 19 March 1996 / Accepted: 5 August 1996 相似文献
17.
Juan Ausiö Manfred L. J. Van Veghel Raquel Gomez Daniel Barreda 《Journal of molecular evolution》1997,45(1):91-96
We have isolated and characterized for the first time, the SNBPs from an organism (Neofibularia nolitangere) of the phylum Porifera (Sponges). We have shown that these proteins consist of histones which, as expected, exhibit an amino
acid composition very similar to that of other eukaryotic histones. The finding of histones in the sperm of these primitive
organisms provides support to the notion that histones (SNBPs of the histone, H, type) were the proteins present at the onset
of SNBP evolution. In contrast, a discrete number of alternative SNBP types (protamine-like, PL; protamine, P, types) seem
to have appeared later on in the course of evolution and are found in both protostomes and deuterostomes, most likely as a
result of processes of parallel evolution.
Received: 5 March 1997 / Accepted: 6 March 1997 相似文献
18.
Hughes AL 《Journal of molecular evolution》1999,48(5):565-576
It has been proposed that two rounds of duplication of the entire genome (polyploidization) occurred early in vertebrate
history (the 2R hypothesis); and the observation that certain gene families important in regulating development have four
members in vertebrates, as opposed to one in Drosophila, has been adduced as evidence in support of this hypothesis. However, such a pattern of relationship can be taken as support
of the 2R hypothesis only if (1) the four vertebrate genes can be shown to have diverged after the origin of vertebrates,
and (2) the phylogeny of the four vertebrate genes (A–D) exhibits a topology of the form (AB) (CD), rather than (A) (BCD).
In order to test the 2R hypothesis, I constructed phylogenies for nine protein families important in development. Only one
showed a topology of the form (AB) (CD), and that received weak statistical support. In contrast, four phylogenies showed
topologies of the form (A) (BCD) with statistically significant support. Furthermore, in two cases there was significant support
for duplication of the vertebrate genes prior to the divergence of deuterostomes and protostomes: in one case there was significant
support for duplication of the vertebrate genes at least prior to the divergence of vertebrates and urochordates, and in one
case there was weak support for duplication of the vertebrate genes prior to the divergence of deuterostomes and protostomes.
Taken together with other recently published phylogenies of developmentally important genes, these results provide strong
evidence against the 2R hypothesis.
Received: 22 December 1997 / Accepted: 5 October 1998 相似文献
19.
Molecular Evolution of the Myeloperoxidase Family 总被引:4,自引:0,他引:4
Animal myeloperoxidase and its relatives constitute a diverse protein family, which includes myeloperoxidase, eosinophil
peroxidase, thyroid peroxidase, salivary peroxidase, lactoperoxidase, ovoperoxidase, peroxidasin, peroxinectin, cyclooxygenase,
and others. The members of this protein family share a catalytic domain of about 500 amino acid residues in length, although
some members have distinctive mosaic structures. To investigate the evolution of the protein family, we performed a comparative
analysis of its members, using the amino acid sequences and the coordinate data available today. The results obtained in this
study are as follows: (1) 60 amino acid sequences belonging to this family were collected by database searching. We found
a new member of the myeloperoxidase family derived from a bacterium. This is the first report of a bacterial member of this
family. (2) An unrooted phylogenetic tree of the family was constructed according to the alignment. Considering the branching
pattern in the obtained phylogenetic tree, together with the mosaic features in the primary structures, 60 members of the
myeloperoxidase family were classified into 16 subfamilies. (3) We found two molecular features that distinguish cyclooxygenase
from the other members of the protein family. (4) Several structurally deviated segments were identified by a structural comparison
between cyclooxygenase and myeloperoxidase. Some of the segments seemed to be associated with the functional and/or structural
differences between the enzymes.
Received: 25 January 2000 / Accepted: 19 July 2000 相似文献
20.
A mitochondrial DNA (mtDNA) phylogeny of cichlid fish is presented for the most taxonomically inclusive data set compiled
to date (64 taxa). 16S rDNA data establish with confidence relationships among major lineages of cichlids, with a general
pattern congruent with previous morphological studies and less inclusive molecular phylogenies based on nuclear genes. Cichlids
from Madagascar and India are the most basal groups of the family Cichlidae and sister to African–Neotropical cichlids. The
cichlid phylogeny suggests drift-vicariance events, consistent with the fragmentation of Gondwana, to explain current biogeographic
distributions. Important phylogenetic findings include the placement of the controversial genus Heterochromis basal among African cichlids, the South American genus Retroculus as the most basal taxon of the Neotropical cichlid assemblage, and the close relationship of the Neotropical genera Cichla with Astronotus rather than with the crenicichlines. Based on a large number of South American genera, the Neotropical cichlids are defined
as a monophyletic assemblage and shown to harbor significantly higher levels of genetic variation than their African counterparts.
Relative rate tests suggest that Neotropical cichlids have experienced accelerated rates of molecular evolution. But these
high evolutionary rates were significantly higher among geophagine cichlids.
Received: 18 September 1998 / Accepted: 16 December 1998 相似文献