Morphological adaptations of acariform mites (Acari: Acariformes) to permanent parasitism on mammals

The external morphological adaptations to parasitism in acariform mites (Acari: Acariformes), permanently parasiting mammals, are briefly summated and analyzed. According to several external morphological criteria (structures of gnathosoma, idiosoma, setation, legs and life cycle), the following six morphoecotypes were established: skin mites (i)-- Cheyletidae, Chirorhynchobiidae, Lobalgidae, Myobiidae, Myocoptidae (the most part), Rhyncoptidae, Psoroptidae; fur mites (ii)--Atopomelidae, Clirodiscidae, Listrophoridae, Myocoptidae (Trichoecius only); skin burrowing mites (iii)--Sarcoptidae; intradermal mites (iv) - sorergatidae and Demodicidae; interstitial mites (v) - pimyodicidae; respiratory mites (vi) - reynetidae, Gastronyssidae, Lemurnyssidae, Pneumocoptidae. In the case of prostigmatic mites, the detailed reconstruction of the origin and evolution of "parasitic" morphoecotypes is possible due to the tentative phylogenetic hypotheses, which were proposed for the infraorder Eleutherengon, a, including the most part of the permanent mammalian parasites among prostigmatic mites (Kethley in Norton, 1993; Bochkov, 2002). The parasitism of Speleognathinae (Ereynetidae) in the mammalian respiratory tract arose independently of the other prostigmats. It is quite possible that these mites switched on mammals from birds, because they are more widely represented on these hosts than on mammals. The prostigmatic parasitism on mammalian skin seems to be originated independently in myobiids, in the five cheyletid tribes, Cheyletiellini, Niheliini, and Teinocheylini, Chelonotini, Cheyletini, and, probably, in a cheyletoid ansector of the sister families Psorergatidae-Demodicidae (Bochkov, Fain, 2001; Bochkov, 2002). Demodicids and psorergatids developed adaptations to parasitism in the skin gland ducts and directly in the epithelial level, respectively in the process of the subsequent specialization. Mites of the family Epimyodicidae belong to the phylogenetic line independent of other cheyletoids. These mites possess the separate chelicerae and, therefore, can not be included to the superfamily Cheyletoidea. It is not quite clear whether they were skin parasites initially or they directly switched to parasitism from the predation. The phylogeny of sarcoptoid mites (Psoroptidia: Sarcoptoidea) is not developed, however, some hypotheses about origin and the following evolution of their morphoecotypes can be proposed. We belive that astigmatic mites inhabiting the mammalian respiratory tract transferred to parasitism independently of other sarcoptoids. The idiosoma of these mites is not so much flattened dorso-ventrally and has proportions which are similar to hose of free-living astigmatids. Moreover, in the most archaic species, the legs are not shortened or thickened as in the most parasites. The disappearance of many morphological structures in these mites, probably, happened parallely with some other sarcoptoids due to their parasitic mode of life. The skin inhabiting sarcoptoids belong to the "basic" morphoecotype, and all other sarcoptoid morphoecotypes, excluding respiratory mites, are derived from it. Some mites of this morphoecotype live on the concave surfaces of the widened spine-like hairs of the rodents belonging to the family Echimyidae (mites of the subfamily Echimytricalginae), in the mammalian ears (some Psoroptidae) or partially sink into the hair follicles (Rhynocoptidae). Finally, mites of the family Chirorhynchobiidae live on the bat wing edges attaching to them by their "ixodid-like" gnathosoma. The fur-sarcoptoids, probably, originated from the skin mites. This morphoecotype is divided onto two subtypes: mites with the dorso-ventrally flattened idiosoma (subtype I) and mites with the teretial idiosoma (subtype II). Each "fur-mite" family includes mites of the both subtypes. All mites of the first subtype belong to the early derivative lineages in their families. Among listrophorids such early derivative lineage is represented by the subfamily Aplodontochirinae (Bochkov, OConnor, 2006), and among Chirodiscidae--by mites of the subfamilies Chirodiscinae, Schizocoptinae, and Lemuroeciinae. Among the "fur" astigmatid families, the family Atopomelidae. probably, is the most archaic, and the most part of atopomelids belongs to the first subtype. However there are several more specialized atopomelid genera belonging to the second subtype, Atopomelus, Dasyurochirus, Lemuroptes, Murichirus, Metachiroecius etc. We believe that mites of the first subtype are represented by the "intermediate" forms between skin mites and mites of the second subtype. Some skin sarcoptoids transferred from skin parasitism to burrowing of the host skin (Sarcoptidae). The established morphoecotypes are partially corresponding to some morphoecotypes established by Mironov (1987) for feather mites. Our morphoecotypes of skin and skin burrowing mites perfectly correspond to Mironov's epidermoptoid and knemidocoptoid morphoecotypes, respectively. The proctophylloid morphoecotype (mites living on the wing feathers), which is the most widely represented within feather mites, has an analogy among mammalian mites - the subfamily Echimytricalginae. The analgoid (mites living in the down feathers) and dermoglyphoid (mites living in the feather quills) morphoecotypes have no analogues among mammalian mites for the obvious reasons. It is interesting why some microhabitats on the host body are not still occupied by prostigmatic or astigmatic mites. We believe that the nutrition is the main limitative factor here. The parasitic prostigmates evolved from predators and, therefore, feed on content of the living cells. They need the direct contact with the live tissues of the host and they belong, therefore, to the morphoecotypes represented by the respiratory, skin, gland duct, intradermal, and interstitial mites. Whereas, the most part of the skin inhabiting astigmats feed on the dead epithelial scales. For this reason these mites, so easily colonized fur of their hosts and feed on the hair grease there. On the other hand, some sarcoptoids transferred to the true parasitism and feed on the cambial cells of the skin epithelium. More over we do not know exactly about nutrition of rhyncoptids yet.     

Phylogenetic position of the Strepsiptera: Review of molecular and morphological evidence

Molecular evidence of the monophyly of the Halteria (Strepsiptera + Diptera) is reviewed. The majority of morphological characters, which have classically been used to establish a Strepsiptera + Coleoptera sister group, are rejected, because they are based on erroneous interpretations of strepsipteran morphology. The scorings of 31 morphological characters, which directly relate to the phylogenetic position of Strepsiptera, are provided, and their distribution and optimization on the molecular + morphological tree is discussed. Of these, 13 characters specifically support the placement of Strepsiptera within the Mecopterida; seven of which are based on the optimization of inapplicable or missing data, and six of which are based on states that can be scored for Strepsiptera. Only a single character (posteromotorism) suggests a sister group relationship with the Coleoptera. The morphological and molecular data are largely congruent, and suggest that the Strepsiptera are sister group to the Diptera.     

Modern conceptions concerning the macrophylogeny of acariform mites (Chelicerata,Acariformes)

Modern conceptions concerning the macrophylogeny of acariform mites assumed during the last thirty years are summarized. Arguments supporting the hypothesis assuming the monophyly of mite taxa of higher taxonomic ranks (above the superfamily level) are discussed. The main unsolved problems of the phylogeny of the order Acariformes are mentioned. A new provisional classification of the order Acariformes for the taxa ranking from the suborder to the superfamily is proposed.     

Phylogenetic position of Acanthobothrium cleofanus (Cestoda: Onchoproteocephalidea) using molecular evidence

Despite the large number of species described to date for the onchoprotepcephalid genus Acanthobothrium (207), only 16 named species have a genetic sequence. With this background, specimens of adult cestodes of the stingray Hypanus longus were collected off San Blas, Nayarit, and onchoproteocephalid larvae in the carangid fish Trachinotus rhodopus from Puerto Ángel, Oaxaca, both located on the Pacific coast of Mexico. The objective of this work is to investigate the phylogenetic position of these adults and larvae using nuclear ribosomal markers (18S rDNA and 28S rDNA). Morphologically, adult specimens were identified as Acanthobothrium cleofanus; larvae were identified only to family level. The phylogenetic position of both taxa was investigated based on the information of two nuclear molecular markers analyzed under Parsimony (PA) and Bayesian Inference (BI) methods. The newly generated sequences of A. cleofanus from Nayarit are identical to the sequences of several samples of Acanthobothrium sp. collected in the Mexican Pacific, which sequence are available in GenBank; DNA sequences obtained from onchoproteocephalid larva clearly place this taxon within Acanthobothrium but representing an independent lineage. In the resulting phylogenetic trees, Uncibilocularis okei was found nested within Acanthobothrium with an unstable position depending on the optimality criteria, indicating the need for more molecular analyzes with a greater number of species of both genera prior to define its phylogenetic relationships.     

Phylogenetic position of turtles among amniotes: evidence from mitochondrial and nuclear genes

Maximum likelihood analysis, accounting for site-heterogeneity in evolutionary rate with the Gamma-distribution model, was carried out with amino acid sequences of 12 mitochondrial proteins and nucleotide sequences of mitochondrial 12S and 16S rRNAs from three turtles, one squamate, one crocodile, and eight birds. The analysis strongly suggests that turtles are closely related to archosaurs (birds+crocodilians), and it supports both Tree-2: (((birds, crocodilians), turtles), squamates) and Tree-3: ((birds, (crocodilians, turtles)), squamates). A more traditional Tree-1: (((birds, crocodilians), squamates), turtles) and a tree in which turtles are basal to other amniotes were rejected with high statistical significance. Tree-3 has recently been proposed by Hedges and Poling [Science 283 (1999) 998-1001] based mainly on nuclear genes. Therefore, we re-analyzed their data using the maximum likelihood method, and evaluated the total evidence of the analyses of mitochondrial and nuclear data sets. Tree-1 was again rejected strongly. The most likely hypothesis was Tree-3, though Tree-2 remained a plausible candidate.     

The phenomenon of phylogenetic synhospitality in acariform mites (acari: acariformes)--the permanent parasites of vertebrates

The term synhospitality means the association of two or more closely related parasite species with one host species (Eichler, 1966). The cases of two or three synhospitalic species are known from the same host species, and especially ones where parasites were recorded from different parts of the host range, are quite common. The most ordinary reason causing synhospitality in permanent parasites is the host switching. Nevertheless, there are a number of synhospitality cases, where the parasite complex is monophyletic because evolved on a single host species. The special term--"phylogenetic synhospitality" (FS) is proposed for these cases of synhospitality. Most known cases of FS in acariform mites, permanent parasites of vertebrates, are analysed. It is found out that both astigmatan and prostigmatan parasite mites demonstrate a numbers of FS. The majority of these examples represent parasitism of two or three synhospitalic parasite species. Impressive examples of FS involving a number of synhospitalic species is shown by only astigmatan mites inhabiting the fur of mammals or plumage of birds. Most known examples involving four or more mite species are discussed: 51 mite species of the genus Schizocarpus (Chirodiscidae) parasitizing Castor fiber and C. canadensis (Castoridae); 6 species of Listrophorus spp. (Listrophoridae) from Ondatra zibethicus (Cricetidae); 23 species of Listrophoroides s. 1. (Atopomelidae) from Maxomys surifer (Muridae); 21 species of Cytostethum (Atomelidae) from Potorous tridactylus (Potoridae); 4 species of Listrophoroides (Afrolistrophoroides) from Malacomys longipes (Muridae); 7 species of Fainalges (Xolalgidae) from Aratinga holochlora (Psittacidae); 4 species of Zygepigynia (Pteronyssidae) from Chrysocolaptes lucidus (Picidae). The main reason of FS is that, in spite of the Fahrenholz's rule, the speciation of many parasites proceeds much more intensively than in their hosts because of the more rapid replacement of the parasitic generations. The first factor causing FS is the mite speciation it temporary segregated populations of the host (allopatric speciation). In this case, the "multispecies complexes" appeared after the subsequent reintegration of the host populations formerly isolated. The second factor is the speciation due to the specialization of mites to local microhabitats in the fur or plumage of host (sympatric or synxenic speciation). The second way of speciation is most characteristic for mites with highly specialized attaching structures. The phenomenon of FS more resides in ectoparasites of mammals rather than in feather mites in spite of much more structural complicacy of plumage rather than the fur. The high mobility of birds and wide dispersion of their new generations probably embarrass the process of sympatric speciation in their parasites. As a rule, only really significant geographical barriers play role for population isolation in birds. Thus, it could be concluded that two independent factors or their combination lead to FS. (i) The complex and/or disjunctive host range giving a possibility for allopatric speciation in parasites. (ii) The deep mite specialization to local microhabitats on the host body causing sympatric (synxenic) speciation. Fur of mammals and plumage of birds are very complicated in structure and microconditions and provide a considerable number of different microhabitats for mites inhabiting them. The prevalence of one of these two factors depends on the biological peculiarities of both parasites and their hosts. In mites with lesser specialized attaching organs, for example in atopomelids, allopatric speciation dominates. In mites with strongly specialized attaching organs, for example in listrophorids or chirodiscids, both pathways of speciation may take place. In feather mites, sympatric speciation should be more probable due to quite complicate and various structure of feathers in avian hosts. In fur mites, sympatric speciation is more likely in mites parasitizing hosts with peculiar ecology, for example in semiaquatic rodents possessing quite different fur structure in different parts of the body.     

Phylogenetic relationships within the Alcidae (Charadriiformes: Aves) inferred from total molecular evidence

The Alcidae is a unique assemblage of Northern Hemisphere seabirds that forage by "flying" underwater. Despite obvious affinities among the species, their evolutionary relationships are unclear. We analyzed nucleotide sequences of 1,045 base pairs of the mitochondrial cytochrome b gene and allelic profiles for 37 allozyme loci in all 22 extant species. Trees were constructed on independent and combined data sets using maximum parsimony and distance methods that correct for superimposed changes. Alternative methods of analysis produced only minor differences in relationships that were supported strongly by bootstrapping or standard error tests. Combining sequence and allozyme data into a single analysis provided the greatest number of relationships receiving strong support. Addition of published morphological and ecological data did not improve support for any additional relationship. All analyses grouped species into six distinct lineages: (1) the dovekie (Alle alle) and auks, (2) guillemots, (3) brachyramphine murrelets, (4) synthliboramphine murrelets, (5) true auklets, and (6) the rhinoceros auklet (Cerorhinca monocerata) and puffins. The two murres (genus Uria) were sister taxa, and the black guillemot (Cepphus grylle) was basal to the other guillemots. The Asian subspecies of the marbled murrelet (Brachyramphus marmoratus perdix) was the most divergent brachyramphine murrelet, and two distinct lineages occurred within the synthliboramphine murrelets. Cassin's auklet (Ptychoramphus aleuticus) and the rhinoceros auklet were basal to the other auklets and puffins, respectively, and the Atlantic (Fratercula arctica) and horned (Fratercula corniculata) puffins were sister taxa. Several relationships among tribes, among the dovekie and auks, and among the auklets could not be resolved but resembled "star" phylogenies indicative of adaptive radiations at different depths within the trees.      

Phylogenetic analysis of the formin homology 2 domain

Formin proteins are key regulators of eukaryotic actin filament assembly and elongation, and many species possess multiple formin isoforms. A nomenclature system based on fundamental features would be desirable, to aid the rapid identification and characterization of novel formins. In this article, we attempt to systematize the formin family by performing phylogenetic analyses of the formin homology 2 (FH2) domain, an independently folding region common to all formins, which alone can influence actin dynamics. Through database searches, we identify 101 FH2 domains from 26 eukaryotic species, including 15 in mice. Sequence alignments reveal a highly conserved yeast-specific insert in the "knob loop" region of the FH2 domain, with unknown functional consequences. Phylogenetic analysis using minimum evolution (ME), maximum parsimony (MP), and maximum likelihood (ML) algorithms strongly supports the existence of seven metazoan groups. Yeast FH2 domains segregate from all other eukaryotes, including metazoans, other fungi, plants, and protists. Sequence comparisons of non-FH2 regions support relationships between three metazoan groups (Dia, DAAM, and FRL) and examine previously identified coiled-coil and Diaphanous auto-regulatory domain sequences. This analysis allows for a formin nomenclature system based on sequence relationships, as well as suggesting strategies for the determination of biochemical and cellular activities of these proteins.     

Phylogenetic position of the mite family Myobiidae within the infraorder Eleutherengona (Acariformes) and origins of parasitism in eleutherengone mites

The position of the family Myobiidae in the infraorder Eleutherengona (Prostigmata) was analyzed with a cladistic parsimony approach for the first time. Species of the genera Anystis von Heyden (Anystidae), Pomerantzia Baker (Pomerantziidae), and Walytydeus Kuznetzov (Paratydeidae) were selected as outgroups. Among Eleutherengona, species of the following genera were selected as ingroup taxa: Hirstiella Berlese (Pterygosomatidae), Eucheyletia Baker, Cheyletiella Canestrini (Cheyletidae), Syringophilus Heller (Syringophilidae), Tarsocheylus Berlese (Tarsocheylidae), Heterocheylus Lombardini (Heterocheylidae), Pygmephorus Kramer (Pygmephoridae), Raphignathus Dugès (Raphignathidae), Neognathus Willmann (Caligonellidae), Storchia Oudemans (Stigmaeidae), and Tuckerella Womersley (Tuckerellidae). Three most parsimonious trees with similar topology were obtained. In all these trees, the family Myobiidae is situated outside of the clade joining the higher Raphignathae (Raphignathoidea and Cheyletoidea) and represents a branch within the earlier derivative Raphignathae. This result is based primarily on characters from leg setation and postembryonic development. The conclusion from this topology is that myobiid mites have developed some gnathosomal structures convergently with Cheyletoidea, including the stylet-like chelicerae and stylophore fused with the subcapitulum. The evolution of animal eleutherengone parasitism is discussed. Parasitism arisen independently in numerous phyletic lineages or superfamilies of Eleutherengona. The representatives of some phylogenetically distant eleutherengone lineages developed similar adaptations to predation and parasitism. However, in spite of some similarities in these adaptations, the evolutionary trends and pathways for switching to a parasitic mode of life are quite different in particular eleutherengone lineages.     

Phylogenetic position of the spirochetal genus Cristispira.

Comparative sequence analysis of 16S rRNA genes was used to determine the phylogenetic relationship of the genus Cristispira to other spirochetes. Since Cristispira organisms cannot presently be grown in vitro, 16S rRNA genes were amplified directly from bacterial DNA isolated from Cristispira cell-laden crystalline styles of the oyster Crassostrea virginica. The amplified products were then cloned into Escherichia coli plasmids. Sequence comparisons of the gene coding for 16S rRNA (rDNA) insert of one clone, designated CP1, indicated that it was spirochetal. The sequence of the 16S rDNA insert of another clone was mycoplasmal. The CP1 sequence possessed most of the individual base signatures that are unique to 16S rRNA (or rDNA) sequences of known spirochetes. CP1 branched deeply among other spirochetal genera within the family Spirochaetaceae, and accordingly, it represents a separate genus within this family. A fluorescently labeled DNA probe designed from the CP1 sequence was used for in situ hybridization experiments to verify that the sequence obtained was derived from the observed Cristispira cells.     

Phylogenetic position of the Sphaeropleaceae (Chlorophyta)

 The complete 18S rRNA gene sequences of four Sphaeroplea C.A. Agardh strains (Sphaeropleales, Sphaeropleaceae), two Atractomorpha Hoffman strains (Sphaeropleales, Sphaeropleaceae) and two Ankyra Fott strains (Chlorococcales, Characiaceae) were determined and subjected to phylogenetic analyses. The analyses indicated that all these taxa belong to a monophyletic lineage (Sphaeropleaceae) and are related to a group of chlorophycean algae comprising autosporic taxa and taxa that reproduce by zoospores which are characterized by directly opposed basal bodies. The taxonomic assignment of the Sphaeropleaceae as a family within the Sphaeropleales (Chlorophyta, Chlorophyceae) is discussed. Received December 22, 2000 Accepted September 25, 2001     

Phylogenetic position of phylum Nemertini, inferred from 18S rRNA sequences: molecular data as a test of morphological character homology.

Partial 18S rRNA sequence of the nemertine Cerebratulus lacteus was obtained and compared with those of coelomate metazoans and acoelomate platyhelminths to test whether nemertines share a most recent common ancestor with the platyhelminths, as traditionally has been implied, or whether nemertines lie within a protostome coelomate clade, as suggested by more recent morphological analyses. Maximum-parsimony analysis supports the inclusion of the nemertine within a protostome-coelomate clade that falls within a more inclusive coelomate clade. Bootstrap analysis indicates strong support for a monophyletic Coelomata composed of a deuterostome and protostome-coelomate clade. Support for a monophyletic protostome Coelomata is weak. Inference by distance analysis is consistent with that of maximum parsimony. Analysis of down-weighted paired sites by maximum parsimony reveals variation in topology only within the protostome-coelomate clade. The relationships among the protostome coelomates cannot be reliably inferred from the partial sequences, suggesting that coelomate protostomes diversified rapidly. Results with evolutionary parsimony are consistent with the inclusion of the nemertine in a coelomate clade. The molecular inference corroborates recent morphological character analyses that reveal no synapomorphies of nemertines and flatworms but instead suggest that the circulatory system and rhynchocoel of nemertines are homologous to coelomic cavities of protostome coelomates, thus supporting the corresponding hypothesis that nemertines belong within a protostome-coelomate clade. The sequence data provide an independent test of morphological character homology.     

Phylogenetic position of cetaceans relative to artiodactyls: reanalysis of mitochondrial and nuclear sequences

By a maximum likelihood analysis of mitochondrial DNA sequences, we examine Graur and Higgins' hypothesis of the Ruminantia/Cetacea clade with Suiformes as an outgroup. Graur and Higgins analyzed these sequences by the neighbor-joining and parsimony methods, as well as by the maximum likelihood method under the assumption that the substitution rate is the same for all sites. The Ruminantia/Suiformes clade assumed by the traditional taxonomy was rejected strongly by this analysis and the Ruminantia/Cetacea clade was supported. Adoption of a more realistic model distinguishing among rates at different codon positions in the maximum likelihood analysis of the same data, however, grossly reduces the significance level on the Graur-Higgins hypothesis. Thus, although the Ruminantia/Suiformes grouping is indeed least likely from Graur and Higgins' data set of mitochondrial DNA, this traditional tree cannot be rejected with statistical significance under the new analysis, and more data are needed to settle the issue. In the same way, we examine Irwin and Arnason's suggestion of the Hippopotamus/Cetacea clade by using cytochrome b and hemoglobins alpha and beta, and it turn out that their suggestion is also fragile. This analysis demonstrates the importance of selecting an appropriate model among the alternatives in the maximum likelihood analysis and of using many different genes from many relevant species in order to make reliable phylogenetic inferences.      

Phylogenetic position of Cyperus clandestinus (Cypereae,Cyperaceae) clarified by morphological and molecular evidence

Extreme morphological reduction and convergent evolution can obscure taxonomic relationships. This phenomenon is frequently encountered in Cyperaceae, where characters traditionally used to diagnose genera have been shown to have evolved independently multiple times. The Ethiopian high‐altitude perennial first described as Cyperus clandestinus was subsequently moved to Ficinia because it has spiral glume arrangement, unlike typical Cyperus species, which have distichous glume arrangement. However, this position has remained uncertain as no nutlets have previously been studied to establish the presence or absence of the gynophore – the synapomorphy for Ficinia. We resolve this 140‐year‐old puzzle by describing the morphology of the nutlet, which lacks a gynophore, and use DNA sequence data to resolve the taxon within Cyperus. Cyperus clandestinus was found to be closely related to Remirea maritima and Cyperus cyperoides in the C₄Cyperus clade, whose members predominantly have distichously arranged glumes. This provides further evidence for the unreliability of glume arrangement as a character to distinguish between members of the Cyperus and Ficinia clades, whereas gynophore presence is more congruent with molecular data.     

用叶绿体rbcL和rps4-trnS区序列确定亚洲特有单型属——篦齿蕨属的系统位置

篦齿蕨属Metapolypodium Ching是亚洲大陆特有植物, 仅含篦齿蕨Metapolypodium manmeiense (Christ) Ching 1种, 分布于中国西南及其邻近地区, 其系统位置一直是一个有待解决的问题。本文用叶绿体rbcL和rps4-trnS区序列探讨篦齿蕨属的系统位置。我们对篦齿蕨及其近缘类群的叶绿体rbcL和rps4-trnS区进行PCR扩增和序列测定。用最大简约法、邻接法和贝叶斯推断法对自测序列结合由GenBank下载的rbcL和rps4-trnS区序列进行独立和联合的系统发育分析, 所构建的系统发生树的拓扑结构基本一致。结果显示: 篦齿蕨属与多足蕨属Polypodium L. emend. Ching的关系较疏远, 而与水龙骨属Polypodiodes Ching和拟水龙骨属Polypodiastrum Ching的成员聚成一个支系, 与栗柄水龙骨Polypodiodes microrhizoma (C. B. Clarke ex Baker) Ching的关系最近。根据本文的研究结果, 我们赞成秦仁昌1978年的分类系统, 即分别承认多足蕨属、篦齿蕨属、水龙骨属、拟水龙骨属和棱脉蕨属Schellolepis J. Sm.为独立的类群。根据分子系统学证据, 宜将栗柄水龙骨转移到篦齿蕨属中。     

Phylogenetic position and physiology of Cerinosterus cyanescens

Partial 25S rRNA sequencing of Cerinosterus cyanescens showed it to be a close relative of Microstroma juglandis, a member of the basidiomycetous order Microstromatales. It is unrelated to the generic type species, C. luteoalba, which is a member of the order Dacrymycetales. The clinical occurrence of C. cyanescens is possibly explained by its thermotolerance and lipolytic activity. The species' nutritional profile is established. Growth on n-hexadecane is rapid; it grows well on typical plant constituents like gallic, tannic, vanillic, quinic and p-coumaric acids, but not on 3-hydroxybenzoic acid, phenol and hydroquinone. The failure to assimilate D-galactose, L-sorbose and ethylamine, the presence of urease and sensitivity to cycloheximide are diagnostic for the species.