Delineation Of Genera Research Articles

A revised classification of Dryopteridaceae based on plastome phylogenomics and morphological evidence, with the description of a new genus, Pseudarachniodes

Dryopteridaceae are the largest fern family and include nearly 20% of extant fern diversity, with 24 currently recognized genera. Recognition and delineation of genera within this family have varied greatly. The three-subfamily classification of Dryopteridaceae was based primarily on molecular phylogenetic relationships but lacked morphological evidence, and the phylogenetic relationships of the subfamilies and genera of Dryopteridaceae are only partially resolved. A comprehensive and robust phylogeny is urgently needed. The heterogeneous morphology of the current members of Dryopteridaceae makes the family and its subfamilies difficult to define by single morphological characteristics or even character combinations. We carried out phylogenetic analyses to reconstruct a highly supported phylogeny of Dryopteridaceae. Our analyses recovered 24 strongly supported clades grouped into seven major clades of Dryopteridaceae. Seven morphological characters including habit, rhizome shape, frond morphology, rachis-costae architecture, appendages on stipe base and lamina, and soral arrangement were found to be informative for identifying different major clades and clades in Dryopteridaceae. Based on phylogenetic reconstruction and morphological analysis, we presented an updated infra-familial classification of Dryopteridaceae with seven subfamilies and 24 genera including four newly proposed subfamilies (Ctenitoideae, Lastreopsidoideae, Pleocnemioideae, and Polystichopsidoideae). Morphological character combinations of each subfamily are summarized, and a key is provided. Most genera sensu PPG I are recognized, with Stigmatopetris reclassified into Dryopteridoideae and Arthrobotrya considered a synonym of Teratophyllum. A new genus Pseudarachniodes is introduced. This revised classification will serve as a foundational framework for future investigations on taxonomy, biogeography, and diversification of the most species-rich Dryopteridaceae in ferns.

Taxonomic revision of the Peyssonneliales (Rhodophyta): Circumscribing the authentic Peyssonnelia clade and proposing four new genera and seven new species.

The Peyssonneliaceae represents the only family in the order Peyssonneliales, a clade of red encrusting algae distributed worldwide, including 136 species in eleven currently accepted genera. Delineation of genera in the Peyssonneliaceae has mostly been based on vegetative characteristics. Previous molecular phylogenies have shown that some traditionally circumscribed genera are not monophyletic and relationships among them are uncertain. We contribute to the knowledge of the evolutionary history of this clade, presenting a robust rbcL phylogeny that provides new insights on the origin and diversification of the Peyssonneliales. Based on a broad dataset and morphological analyses, we propose a revised taxonomic scheme for the Peyssonneliales resolved as monophyletic with well-supported main lineages. Our results show that Peyssonnelia is polyphyletic, and, therefore, we propose three new genera, Agissea, Olokunia, and Rhodowynnea to accommodate species currently assigned to Peyssonnelia, but distantly related to the clade with the type species of the genus. Additionally, barcoding techniques and analyzed criteria for specific delimitation supported the establishment of one new genus, Brasilophycus, and seven new species, from northeastern Brazil: Agissea amadoi, A. densissima, A. taberniforma, A. villatlantica, A. yemonjasagbae, Brasilophycus similis, and B. roseomarginatus. Our integrative taxonomic approach reveals underestimated diversity of Brazilian Peyssonneliales. Investment in broader sampling along the Brazilian coast and other tropical areas may reveal that its marine biodiversity can be expanded, enlightening our knowledge about this ecologically important group of red algae.

Genetic diversity in chrysophytes: Comparison of different gene markers

Chrysophytes are a diverse group of protists belonging to the Stramenopiles. They encompass a broad range of nutrition strategies (phototrophy, mixotrophy and heterotrophy) and morphological forms (unicellular, colonial, branched, non-scaled to silica-scaled). However, taxonomy, identification and delineation of genera and species are hampered by the polyphyletic origin of several morphotypes and the low resolution of morphological features; moreover, description of these features requires in many cases special equipment like TEM or SEM. To test the congruent phylogeny, genetic resolution and to reveal the genetic diversity of chrysophytes, we evaluated in this study different gene markers, in particular SSU and LSU rRNA genes, ITS, and COI in terms of phylogenetic clustering, separation of phylogenetic lineages and genetic distances within and between clades. Our results showed that the general topology of the SSU rRNA gene phylogeny is similar to that of the LSU rRNA gene phylogeny, with a higher genetic divergence for the latter. The topology of the COI phylogeny differed from the ribosomal data, and showed the highest genetic divergence within groups and between groups for all compared markers. The 5.8S rRNA gene offered only a limited phylogenetic resolution with low genetic divergence. ITS showed a high genetic divergence, but phylogenetic analyses were hampered by high variance in sequence lengths between clades.

Revision of Stylarioides delle Chiaje, 1831 (Annelida: Flabelligeridae)

There has been confusion regarding the delineation of genera in the Flabelligeridae. Thus, it is not surprising that some genera like Pherusa Oken, 1807 currently include different body patterns with differing branchial and chaetal features. A revision of all materials available has allowed a standardized approach; one of its results has been the restriction of Pherusa to encompass species provided with eight branchial filaments and anchylosed neurochaetae. At the same time, Stylarioides delle Chiaje, 1831, with Stylarioides monilifer delle Chiaje, 1831, as its type species, which has been wrongly regarded as a junior synonym of other flabelligerid genera, is reinstated, restricted and revised. It includes species whose members have cylindrical bodies, often tapering into a distinct, thinner cauda, and their tunic includes a variable amount of sediment grains on their papillae. The branchiae are arranged in two lateral spirals, often transformed into a serpuloid branchia by having two lateral branchial peduncles, each with filaments arranged in spiral; the body papillae are short, and their chaetae include fine, short, multiarticulate notochaetae, and short, anchylosed neurohooks. Coppingeria Haswell, 1892, a monotypic genus defined by the presence of two branchial peduncles with spiral filaments, is regarded as a junior synonym of Stylarioides. The species included are S. monilifer from the Mediterranean Sea, S. bengalensis Fauvel, 1932, from India, S. granulosus Caullery, 1944, from the Java Sea, S. grubei n. sp. from the Red Sea, S. hirsutus Lo Bianco, 1893, from the Mediterranean Sea, S. longisetosa (Haswell, 1892) n. comb., from Australia, S. muiri n. sp. from Tristan da Cunha, S. plantei n. sp. from Madagascar, S. saldanha (Day, 1961) n. comb., from South Africa, S. swakopianus Augener, 1918, from Western Africa, and S. tropicus Augener, 1918, from Western Africa. Other species provided with lateral pedunculate branchiae differ from Stylarioides by having a racket-shaped peduncle, where the thin branchial filaments are separated into two lateral groups, each with filaments arranged in parallel lines. Further, their body has a truncate posterior end, larger cephalic cage chaetae, and larger notochaetae and neurohooks. For these species, Treadwellius n. gen. is proposed, with Stylarioides atentacula Hoagland, 1920, as the type species. The species included are T. atentacula (Hoagland, 1920) n. comb, from the Philippine Islands, T. bifidus (Fauvel, 1932), from the Arabian Sea, and T. gilleti n. sp. from Western Africa.

Systematics of two deep-water species from the Indo-West Pacific: Struvea gardineri A.Gepp & E.Gepp and Phyllodictyon orientale (A.Gepp & E.Gepp) Kraft & M.J.Wynne (Siphonocladales, Chlorophyta)

Two rare and ill-known subtidal species of stalked, net-forming green algae, Struvea gardineri A.Gepp & E.Gepp and Phyllodictyon orientale (A.Gepp & E.Gepp) Kraft & M.J.Wynne, are re-described on the basis of the examination of type material and recent collections from the Maldives, Seychelles, and Socotra Island in the tropical Indian Ocean. The taxonomic position of both species is re-appraised on the basis of morphological data (cell division, branching pattern, tenacular cells, crystalline cell inclusions, cell shape, and cell dimensions) and molecular phylogenetic evidence (partial large subunit nuclear ribosomal DNA sequences). On the basis of the occurrence of segregative cell division in young plants of S. gardineri, this species is returned to its original genus, Struvea. Cell division in P. orientale takes place exclusively by centripetal wall ingrowths, confirming its placement in the genus Phyllodictyon as currently defined. However, morphological observations and molecular phylogenetic studies indicate that the delineation of genera on the basis of modes of cell division is problematic, and that the genera Struvea and Phyllodictyon, as presently conceived, almost certainly do not represent natural groups. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 153, 115–132.

Ultrastructural Studies of Massarina ingoldiana and M. purpurascens

Ascus and ascospore appendage structures can be important characters in delineation of genera. We have therefore examined the ascus and ascospore ultrastructure of Massarina ingoldiana and M. purpurascens, as Massarina is thought to be a heterogeneous genus. The ascus wall of M. ingoldiana is two layered and comparable to M. thalassiae. Ascospores of both species comprise an electron-transparent mesosporium, an electron-dense episporium and an exosporial mucilaginous sheath. In this respect they are similar to the ultrastructure of other Massarina species, and should be maintained in Massarina.

Ultrastructural studies of Massarina ingoldiana and M. purpurascens

Ascus and ascospore appendage structures can be important characters in delineation of genera. We have therefore examined the ascus and ascospore ultrastructure of Massarina ingoldiana and M. purpurascens, as Massarina is thought to be a heterogeneous genus. The ascus wall of M. ingoldiana is two layered and comparable to M. thalassiae. Ascospores of both species comprise an electron-transparent mesosporium, an electron-dense episporium and an exosporial mucilaginous sheath. In this respect they are similar to the ultrastructure of other Massarina species, and should be maintained in Massarina.

DNA restriction fragment length polymorphisms in the rDNA repeat unit of Entomophaga

A heterologous rDNA probe was used to detect restriction fragment length polymorphisms in Entomophaga rDNA sequences. Six Canadian strains of Entomophaga aulicae, isolated from the spruce bud worm or hemlock looper in Ontario or Newfoundland, showed no detectable rDNA variation at 10 different restriction enzyme loci: BamHI, DraI, EcoRI, EcoRV, HindIII, HinfI, MspI, PstI, RsaI, or TaqI. A total of 14 isolates of E. aulicae representative of several different geographic and host origins were compared at the DraI and HindIII rDNA loci and two different banding patterns were detected. Of these, 12 showed the same patterns and were designated E. aulicae type 1. The two members which differed were designated E. aulicae type 2. The variations in rDNA restriction sites did not appear to be geographically dependent. Entomophaga maimaiga, a recently reclassified species from the E. aulicae complex, displayed an rDNA banding pattern clearly distinguishable from the E. aulicae patterns with DraI, EcoRI, EcoRV, or HindIII. Members of the E. grylli species complex exhibited patterns which clearly differed from the patterns seen with either E. aulicae or E. maimaiga isolates. However, members of the E. grylli species complex appeared to be more heterogeneous than those in the E. aulicae complex. Among four E. grylli members, three different rDNA banding patterns were detected with either HindIII or DraI. These were designated as E. grylli type 1, type 2, and type 3. An undesignated Entomophaga isolate from a dipteran host displayed rDNA polymorphisms not previously noted in either the lepidopteran or orthopteran isolates. Our results suggest that RFLPs in rDNA are useful in the delineation of genera and species within the Entomophthorales, but may not be as useful at lower taxonomic levels. These and other RFLPs can however provide useful information regarding the epidemiology of Entomophaga epizootics.

Phylogenetic relationships vs. phenotypic diversity: how to achieve a phylogenetic classification system of the eubacteria.

To establish a hierarchic classification system, ranks cannot be defined by the exclusive and inflexible application of phylogenetic parameters. Because both stability and practicality are prerequisites for a successful system, decisions about the delineation of genera must be made by combining phylogenetic coherency with unifying phenotypic properties of taxonomic value consistent with the needs of a hierarchic system. The phylogenetic depth (age) of a genus has no influence on the decision as long as the members of the genus can be reliably identified as such. The description of those higher taxa that are not easily definable today because of the lack of common phenotypic properties must be postponed until new insights are available. In the end this approach will be both phylogenetic and practical, thus avoiding the use of two classification systems.