共查询到20条相似文献,搜索用时 453 毫秒
1.
Gilles Bena Marie-France Jubier Isabelle Olivieri Bernard Lejeune 《Journal of molecular evolution》1998,46(3):299-306
We have estimated the potential phylogenetic utility of the ribosomal external transcribed spacer (ETS) from the nuclear
ribosomal region. The ETS was sequenced from 13 annual Medicago (Fabaceae) species upstream a highly conserved motive which was found among many different organisms. In the genus Medicago, the ETS was found to evolve 1.5 times faster than the internal transcribed spacer and to be 1.5 times more informative. Reduced
ribosomal maturation process constraints on ETS are proposed to explain the different evolutionary rates between the two spacers.
Maximal phylogenetic resolution and support was obtained when the two spacers were analyzed together. No incongruence between
the two spacers was found and ETS appears to be a valuable source of information for solidifying ITS plant phylogeny. The
phylogeny obtained in Medicago suggests that none of the three subsections included in the study is monophyletic.
Received: 15 April 1997 / Accepted: 29 July 1997 相似文献
2.
J. Hinrich G.v.d. Schulenburg Ulrike Englisch J.-Wolfgang Wägele 《Journal of molecular evolution》1999,48(1):2-12
A comparison of ribosomal internal transcribed spacer 1 (ITS1) elements of digenetic trematodes (Platyhelminthes) including
unidentified digeneans isolated from Cyathura carinata (Crustacea: Isopoda) revealed DNA sequence similarities at more than half of the spacer at its 3′ end. Primary sequence similarity
was shown to be associated with secondary structure conservation, which suggested that similarity is due to identity by descent
and not chance. Using an analysis of apomorphies, the sequence data were shown to produce a distinct phylogenetic signal.
This was confirmed by the consistency of results of different tree reconstruction methods such as distance approaches, maximum
parsimony, and maximum likelihood. Morphological evidence additionally supported the phylogenetic tree based on ITS1 data
and the inferred phylogenetic position of the unidentified digeneans of C. carinata met the expectations from known trematode life-cycle patterns. Although ribosomal ITS1 elements are generally believed to
be too variable for phylogenetic analysis above the species or genus level, the overall consistency of the results of this
study strongly suggests that this is not the case in digenetic trematodes. Here, 3′ end ITS1 sequence data seem to provide
a valuable tool for elucidating phylogenetic relationships of a broad range of phylogenetically distinct taxa.
Received: 20 October 1997 / Accepted: 24 March 1998 相似文献
3.
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
4.
A. Wiese M. Münstermann T. Gutsmann B. Lindner K. Kawahara U. Zähringer U. Seydel 《The Journal of membrane biology》1998,162(2):127-138
We have studied the interaction of the polycationic peptide antibiotic polymyxin B (PMB) with asymmetric planar bilayer membranes
via electrical measurements. The bilayers were of different compositions, including those of the lipid matrices of the outer
membranes of various species of Gram-negative bacteria. One leaflet, representing the bacterial inner leaflet, consisted of
a phospholipid mixture (PL; phosphatidylethanolamine, -glycerol, and diphosphatidylglycerol in a molar ratio of 81:17:2).
The other (outer) leaflet consisted either of lipopolysaccharide (LPS) from deep rough mutants of PMB-sensitive (Escherichia coli F515) or -resistant strains (Proteus mirabilis R45), glycosphingolipid (GSL-1) from Sphingomonas paucimobilis IAM 12576, or phospholipids (phosphatidylglycerol, diphytanoylphosphatidylcholine). In all membrane systems, the addition
of PMB to the outer leaflet led to the induction of current fluctuations due to transient membrane lesions. The minimal PMB
concentration required for the induction of the lesions and their size correlated with the charge of the lipid molecules.
In the membrane system resembling the lipid matrix of a PMB-sensitive strain (F515 LPS/PL), the diameters of the lesions were
large enough (d= 2.4 nm ± 8%) to allow PMB molecules to permeate (self-promoted transport), but in all other systems they were too small.
A comparison of these phenomena with membrane effects induced by detergents (dodecyltriphenylphosphonium bromide, dodecyltrimethylammonium
bromide, sodiumdodecylsulfate) revealed a detergent-like mechanism of the PMB-membrane interaction.
Received: 16 September 1997/Revised: 25 November 1997 相似文献
5.
Ronald W. DeBry 《Journal of molecular evolution》1998,46(3):355-360
Sequences were obtained from five species of rodents that are orthologous to an H2a histone pseudogene from Mus musculus. The pseudogene is part of the cluster of replication-dependent histone genes found on Mus musculus chromosome 13. Comparative analysis of these five sequences together with the previously published sequence from M. musculus shows that this gene has likely been a pseudogene throughout the evolution of the genus Mus, while the gene from Rattus norvegicus is likely functional. Three large (>20 bp) deletions were found among the Mus pseudogenes, a feature that is very unusual compared to surveys of processed pseudogenes. In addition, there are two single-base
deletions and one 4-bp insertion among the Mus pseudogenes. The species distributions of one of the large deletions and the 4-bp insertion require either independent insertions
of an identical sequence, independent deletions with identical boundaries, or a deletion followed by precise reintegration
of the original sequence. The evidence favors the hypothesis of multiple deletions with identical boundaries. The ``coding'
regions of the Mus pseudogenes show a much reduced level of among-species variability in the 3′ half of the pseudogene, compared both to the
5′ half and to flanking sequences. This supports a hypothesis that the 3′ end of the pseudogene is the target of frequent
gene conversion by functional H2a genes.
Received: 1 April 1997 / Accepted: 12 June 1997 相似文献
6.
Fucus evanescens is a brown alga of arctic origin that has invaded European coasts. The epiphytic community of F. evanescens in southern Sweden was compared with that of the native Fucus vesiculosus, to examine to what extent an invading seaweed can modify local biodiversity. F. evanescens was much less fouled than F. vesiculosus, supporting both less biomass and fewer species of epiphytes. Multivariate analysis of the most common epiphyte taxa showed that the epiphytic community composition of F. evanescens was not entirely separated from that of F. vesiculosus, but host species contributed significantly to explain the variation in community composition. The biomass of free-living invertebrates was also lower on F. evanescens, although the pattern differed between taxonomic groups. While the biomass of amphipods was lower on F. evanescens, there was no significant difference in biomass of isopods or gastropods between the Fucus species. The good correlation between biomass of epiphytes and free-living animals suggests that the epiphytes play an important role in providing a suitable habitat for many species of free-living epifauna. The study shows that the invasion of F. evanescens affects the environmental conditions for many species associated with the Fucus community but that the direct effect on biodiversity is probably low. 相似文献
7.
8.
Southern hybridization data suggest that the male sex-determining locus, Sry, is often duplicated in rodents. Here we explore DNA sequence evolution of orthologous and paralogous copies of Sry isolated from six species of African murines. PCR amplification followed by direct sequencing revealed from two to four copies
of Sry per species. All copies include a long open reading frame, with a stop codon that coincides closely with the stop codon of
the house mouse, Mus musculus, a species known to have a single copy of Sry. A phylogenetic analysis suggests that there are at least seven paralogous copies of Sry in this group of rodents. Putative orthologues are identical; sequence divergence among putative paralogues ranges from 1
to 8% (excluding the CAG repeat), with much lower levels of divergence in the high-mobility group (HMG-box) region than in
the C-terminal region. A high proportion of nucleotide substitutions in both regions result in amino-acid replacement. The
long open reading frame, conserved HMG-box, and pattern of evolution of the putative paralogues suggest that they are functional.
Received: 4 October 1996 / Accepted: 17 January 1997 相似文献
9.
Phylogenetic Relationships of the Glycolytic Enzyme, Glyceraldehyde-3-Phosphate Dehydrogenase, from Parabasalid Flagellates 总被引:4,自引:0,他引:4
Over 90% of the open reading frame of gap genes for glycolytic glyceraldehyde-3-phosphate dehydrogenase (GAPDH; EC 1.2.1.12) was obtained with PCR from five species
of Parabasala. With gap1 from Trichomonas vaginalis obtained earlier, the data include two sequences each for three species. All sequences were colinear with T. vaginalis gap1 and shared with it as a synapomorphy a 10- to 11-residue insertion not found in any other gap and an S-loop with characteristic features of eubacterial GAPDH. All residues known to be highly conserved in this enzyme
were present. The parabasalid sequences formed a robust monophyletic group in phylogenetic reconstructions with distance-based,
maximum-parsimony, and maximum-likelihood methods. The two genes of the amphibian commensal, Trichomitus batrachorum, shared a common ancestor with the rest, which separate into two well-supported lineages. T. vaginalis and Tetratrichomonas gallinarum (both representatives of Trichomonadinae) formed one, while Monocercomonas sp. and Tritrichomonas foetus formed the other. These data agreed with and/or were close to published reconstructions based on other macromolecules. They
did not support the ancestral position of Monocercomonas sp. proposed on the basis of morphological characteristics but confirmed an early emergence of Trichomitus batrachorum. The sequence pairs obtained from three species indicated either gene duplications subsequent to the divergence of the corresponding
lineages or a strong gene conversion later in these lineages. The parabasalid clade was a robust part of the eubacterial radiation
of GAPDH and showed no relationships to the clade that contained all other eukaryotic gap genes. The data clearly reveal that the members of this lineage use in their glycolytic pathway a GAPDH species with properties
and an evolutionary history that are unique among all eukaryotes studied so far.
Received: 28 April 1997 / Accepted: 14 October 1997 相似文献
10.
Cristina Torti Ludvik M. Gomulski Anna R. Malacrida Pierre Capy Giuliano Gasperi 《Journal of molecular evolution》1998,46(3):288-298
Mariner elements were amplified using the polymerase chain reaction from two species of tephritid flies, Ceratitis rosa and Trirhithrum coffeae. The sequences were ∼1.3 kb in length. None of these elements appeared to be functional, as in every case the open reading
frame (ORF) was disrupted by the presence of frameshifts or stop codons. These elements, Crmar1 and Tcmar1, are very similar to the Ccmar1 element previously amplified from the closely related tephritid species C. capitata and are members of the mellifera subfamily of mariner elements. The phylogeny and pattern of divergence of these elements were examined in relation to the phylogeny of the host
species. It is highly probable that the elements were present in the ancestral lineage prior to the divergence of the three
species. The copy numbers of the elements within each species are very different, ranging from about 10 in T. coffeae to 5,000 in C. rosa. The possible mechanisms which determine the copy number of an element in the host genome are discussed.
Received: 25 April 1997 / Accepted: 31 July 1997 相似文献
11.
Héctor Musto Héctor Romero Helena Rodríguez-Maseda 《Journal of molecular evolution》1998,46(2):159-167
Synonymous codon choices vary considerably among Schistosoma mansoni genes. Principal components analysis detects a single major trend among genes, which highly correlates with GC content in
third codon positions and exons, but does not discriminate among putatively highly and lowly expressed genes. The effective
number of codons used in each gene, and its distribution when plotted against GC3, suggests that codon usage is shaped mainly by mutational biases. The GC content of exons, GC3, 5′, 3′, and flanking (5′+ 3′+ introns) regions are all correlated among them, suggesting that variations in GC content may
exist among different regions of the S. mansoni genome. We propose that this genome structure might be among the most important factors shaping codon usage in this species,
although the action of selection on certain sequences cannot be excluded.
Received: 10 March 1997 / Accepted: 27 June 1997 相似文献
12.
Phylogenetic analysis in the Festuca-Lolium complex using molecular markers and ITS rDNA 总被引:1,自引:0,他引:1
G. Charmet C. Ravel F. Balfourier 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(8):1038-1046
Molecular markers were used to investigate phylogenetic relationships among the eight species of ryegrass (Lolium) and 11 species of fescue (Festuca). RAPD and RFLP analyses were carried out on total bulked DNA from each population. Factorial analysis of a phenetic distance
matrix yielded three major groups: (1) fine-leaved fescues, (2) broad-leaved fescues and (3) ryegrasses. Six non-coding regions
of chloroplastic DNA were PCR-amplified, then digested by 20 restriction enzymes. Nuclear rDNA sequences, including internal
transcribed spacers (ITSs) were used to estimate the average proportion of nucleotide substitutions. The correlation between
substitution rate estimated from ITS sequences and that estimated from organelle DNA restriction sites was very high (0.94),
and the corresponding UPGMA trees were very similar, with a slightly better resolution of the ITS tree in the Lolium genus. The time-scale inferred from substitution rates indicated that the period since divergence of the broad-leaved fescues
from the fine-leaved fescues was four times as long as that since divergence of the genus Lolium from the former. Among the broad-leaved fescues, meadow fescue was closer to the Lolium group, while F. glaucescens and tall fescue were very closely related. North-African fescues were clustered together and giant fescue was the most differentiated
species in this group. Our dataset was merged with ITS sequences recovered from the EMBL database, and the neighbor-joining
method was used to draw a phylogenetic tree. In this tree, the tribe Poeae was clearly monophyletic, and more closely related
to the Aveneae than to the Triticeae or Bromoideae. The genus Festuca appeared somewhat artificial, since Vulpia myuros and Dactylis glomerata were placed between fine-leaved and broad-leaved fescues.
Received: 10 January 1997/Accepted: 21 February 1997 相似文献
13.
A PstI DNA family was isolated from the genome of a lacertid, Lacerta graeca. The 185-bp monomeric unit (pGPS) was cloned and hybridized to DNAs and chromosomes of several lacertid species. The data
showed that pGPS hybridizes to the (1) centromeric or pericentromeric heterochromatin of almost all the chromosomes of L. graeca and (2) genomic DNA of species phylogenetically related and unrelated to L. graeca. The presence of pGPS even in species immunologically apart more than 30 million years suggests that this repeated family
might be either very ancient or have been conserved during evolution due to its functional role. The latter hypothesis might
be supported by the results of sequence analysis which showed some homology with both several alphoid sequences of primates
and the CDEIII centromeric sequence of yeast. Segments of the satellite sequence are similar to the mammalian CENP-B box.
These observations suggest that pGPS might have a role in determining the centromeric function in lacertid lizards.
Received: 6 February 1997 / Accepted: 14 May 1997 相似文献
14.
The Peperomia polybotrya coxI gene intron is the only currently reported group I intron in a vascular plant mitochondrial genome and it likely originated
by horizontal transfer from a fungal donor. We provide a clearer picture of the horizontal transfer and a portrayal of the
evolution of the group I intron since it was gained by the Peperomia mitochondrial genome. The intron was transferred recently in terms of plant evolution, being restricted to the single genus
Peperomia among the order Piperales. Additional support is presented for the suggestion that a recombination/repair mechanism was used
by the intron for integration into the Peperomia mitochondrial genome, as a perfect 1:1 correspondence exists between the intron's presence in a species and the presence
of divergent nucleotide markers flanking the intron insertion site. Sequencing of coxI introns from additional Peperomia species revealed that several mutations have occurred in the intron since the horizontal transfer, but sequence alterations
have not caused frameshifts or created stop codons in the intronic open reading frame. In addition, two coxI pseudogenes in Peperomia cubensis were discovered that lack a large region of coxI exon 2 and contain a truncated version of the group I intron that likely cannot be spliced out.
Received: 29 May 1997 / Accepted: 1 November 1997 相似文献
15.
Frédérique Viard Pierre Franck Marie-Pierre Dubois Arnaud Estoup Philippe Jarne 《Journal of molecular evolution》1998,47(1):42-51
Size homoplasy was analyzed at microsatellite loci by sequencing electromorphs, that is, variants of the same size (base
pairs). This study was conducted using five interrupted and/or compound loci in three invertebrate species, the honey bee
Apis mellifera, the bumble bee Bombus terrestris, and the freshwater snail Bulinus truncatus. The 15 electromorphs sequenced turned out to hide 31 alleles (i.e., variants identical in sequence). Variation in the amount
of size homoplasy was detected among electromorphs and loci. From one to seven alleles were detected per electromorph, and
one locus did not show any size homoplasy in both bee species. The amount of size homoplasy was related to the sequencing
effort, since the number of alleles was correlated with the number of copies of electromorphs sequenced, but also with the
molecular structure of the core sequence at each locus. Size homoplasy within populations was detected only three times, meaning
that size homoplasy was detected mostly among populations. We analyzed population structure, estimating F
st and a genetic distance, based on either electromorphs or alleles. Whereas little difference was found in A. mellifera, uncovering size homoplasy led to a more marked population structure in B. terrestris and B. truncatus. We also showed in A. mellifera that the detection of size homoplasy may alter phylogenetic reconstructions.
Received: 21 July 1997 / Accepted: 29 January 1998 相似文献
16.
Detailed nucleotide diversity studies revealed that the fil1 gene of Antirrhinum, which has been reported to be single copy, is a member of a gene family composed of at least five genes. In four Antirrhinum majus populations with different mating systems and one A. graniticum population, diversity within populations is very low. Divergence among Antirrhinum species and between Antirrhinum and Digitalis is also low. For three of these genes we also obtained sequences from a more divergent member of the Scrophulariaceae, Verbascum nigrum. Compared with Antirrhinum, little divergence is again observed. These results, together with similar data obtained previously for five cycloidea genes,
suggest either that these gene families (or the Antirrhinum genome) are unusually constrained or that there is a low rate of substitution in these lineages. Using a sample of 52 genes,
based on two measures of codon usage (ENC and GC3 content), we show that cyc and fil1 are among the least biased Antirrhinum genes, so that their low diversity is not due to extreme codon bias.
Received: 20 June 2000 / Accepted: 25 October 2000 相似文献
17.
Ana I. Antón Antonio J. Martínez-Murcia Francisco Rodríguez-Valera 《Journal of molecular evolution》1998,47(1):62-72
The ribosomal RNA multigene family in Escherichia coli comprises seven rrn operons of similar, but not identical, sequence. Four operons (rrnC, B, G, and E) contain genes in the 16S–23S intergenic spacer region (ISR) for tRNAGlu-2 and three (rrnA, D, and H) contain genes for tRNAIle-1 and tRNAAla-1B. To increase our understanding of their molecular evolution, we have determined the ISR sequence of the seven operons in
a set of 12 strains from the ECOR collection. Each operon was specifically amplified using polymerase chain reaction primers
designed from genes or open reading frames located upstream of the 16S rRNA genes in E. coli K12. With a single exception (ECOR 40), ISRs containing one or two tRNA genes were found at the same respective loci as those
of strain K12. Intercistronic heterogeneity already found in K12 was representative of most variation among the strains studied
and the location of polymorphic sites was the same. Dispersed nucleotide substitutions were very few but 21 variable sites
were found grouped in a stem-loop, although the secondary structure was conserved. Some regions were found in which a stretch
of nucleotides was substituted in block by one alternative, apparently unrelated, sequence (as illustrated by the known putative
insertion of rsl in K12). Except for substitutions of different sizes and insertions/deletions found in the ISR, the pattern of nucleotide
variation is very similar to that found for the 16S rRNA gene in E. coli. Strains K12 and ECOR 40 showed the highest intercistronic heterogeneity. Most strains showed a strong tendency to homogenization.
Concerted evolution could explain the notorious conservation of this region that is supposed to have low functional restrictions.
Received: 31 July 1997 / Accepted: 17 October 1997 相似文献
18.
Henna Rinne Ulrika Björkman Conny Sjöqvist Sonja Salovius-Laurén Johanna Mattila 《欧洲藻类学杂志》2018,53(3):369-380
Fucus vesiculosus and F. radicans (Phaeophyceae) are important habitat-formers on rocky shores in the Bothnian Sea. While both species occur sympatrically along the entire western Bothnian Sea coast, F. radicans has been found only in the northern part of the eastern coast. According to previous studies, the two species can be distinguished based on morphology, F. radicans having narrower thalli and a bushier appearance. However, marine mapping in the eastern Bothnian Sea has revealed that high morphological variation in Fucus, partly caused by gradients in salinity and exposure, makes differentiation between the two species difficult. We studied morphological and genetic variation to find out whether the two Fucus species can be differentiated in the south-eastern Bothnian Sea, and if F. radicans occurs in the area. The study was carried out in six subareas including 350 km of coast, with a salinity gradient of 3.5–6.5 PSU, and varying wave exposure. We found a gradual change towards smaller and narrower thalli and a higher number of holdfasts in Fucus populations when moving northwards to lower salinities. Distinct Fucus morphs were often found within the study sites but the morphs were genetically differentiated only at one study site in the Skaftung subarea, suggesting the occurrence of both species. However, in the Vasa subarea the sample size for analysing genetic differentiation was low due to high clonality. In the Luvia subarea south of Skaftung, Fucus morphology corresponded to that of F. radicans in earlier studies but the population was genetically more similar to F. vesiculosus in the southern subareas. We conclude that by using only morphological characteristics it is not possible to differentiate between the two species in central and northern parts of the eastern Bothnian Sea. Based on genetic analyses, the southernmost known occurrence of F. radicans in the eastern Bothnian Sea is in Skaftung. 相似文献
19.
Ena Urbach David J. Scanlan Daniel L. Distel John B. Waterbury Sallie W. Chisholm 《Journal of molecular evolution》1998,46(2):188-201
Cultured isolates of the unicellular planktonic cyanobacteria Prochlorococcus and marine Synechococcus belong to a single marine picophytoplankton clade. Within this clade, two deeply branching lineages of Prochlorococcus, two lineages of marine A Synechococcus and one lineage of marine B Synechococcus exhibit closely spaced divergence points with low bootstrap support. This pattern is consistent with a near-simultaneous
diversification of marine lineages with divinyl chlorophyll b and phycobilisomes as photosynthetic antennae. Inferences from 16S ribosomal RNA sequences including data for 18 marine picophytoplankton
clade members were congruent with results of psbB and petB and D sequence analyses focusing on five strains of Prochlorococcus and one strain of marine A Synechococcus. Third codon position and intergenic region nucleotide frequencies vary widely among members of the marine picophytoplankton
group, suggesting that substitution biases differ among the lineages. Nonetheless, standard phylogenetic methods and newer
algorithms insensitive to such biases did not recover different branching patterns within the group, and failed to cluster
Prochlorococcus with chloroplasts or other chlorophyll b-containing prokaryotes. Prochlorococcus isolated from surface waters of stratified, oligotrophic ocean provinces predominate in a lineage exhibiting low G + C nucleotide
frequencies at highly variable positions.
Received: 18 January 1997 / Accepted: 18 May 1997 相似文献
20.
Phylogeny and Rates of Molecular Evolution of Planktonic Foraminifera: SSU rDNA Sequences Compared to the Fossil Record 总被引:5,自引:0,他引:5
Colomban de Vargas Louisette Zaninetti Heinz Hilbrecht Jan Pawlowski 《Journal of molecular evolution》1997,45(3):285-294
Planktonic foraminifera are marine protists, whose calcareous shells form oceanic sediments and are widely used for stratigraphic
and paleoenvironmental analyses. The fossil record of planktonic foraminifera is compared here to their molecular phylogeny
inferred from ribosomal DNA sequences. Eighteen partial SSU rDNA sequences from species representing all modern planktonic
families (Globigerinidae, Hastigerinidae, Globorotaliidae, Candeinidae) were obtained and compared to seven sequences representing
the major groups of benthic foraminifera. The phylogenetic analyses indicate a polyphyletic origin for the planktonic foraminifera.
The Candeinidae, the Globorotaliidae, and the clade Globigerinidae + Hastigerinidae seem to have originated independently,
at different epochs in the evolution of foraminifera. Inference of their relationships, however, is limited by substitution
rates of heterogeneity. Rates of SSU rDNA evolution vary from 4.0 × 10−9 substitutions/site/year in the Globigerinidae to less than 1.0 × 10−9 substitutions/site/year in the Globorotaliidae. These variations may be related to different levels of adaptation to the
planktonic mode of life. A clock-like evolution is observed among the Globigerinidae, for which molecular and paleontological
data are congruent. Phylogeny of the Globorotaliidae is clearly biased by rapid rates of substitution in two species (G. truncatulinoides and G. menardii). Our study reveals differences in absolute rates of evolution at all taxonomic levels in planktonic foraminifera and demonstrates
their effect on phylogenetic reconstructions.
Received: 21 January 1997 / Accepted: 17 April 1997 相似文献