Lygodium

About: Lygodium is a research topic. Over the lifetime, 89 publications have been published within this topic receiving 1408 citations. The topic is also known as: Hagnaya.

Studies on the Cytology and Phylogeny of the Pteridophytes

Abstract: 1. A critical cytological investigation of nine species of Ophioglossum (including several cytological and geographic races), one species of Botrychium and the monotypic Helminthostachys has been made.2. The lowest haploid number for Ophioglossum is n=120 and for Helminthostachys, n=94.3. Almost all the species of Ophioglossum investigated in the present study (excepting the aneuploid series in O. reticulatum and perhaps O. vulgatum) are found to form a polyploid series based on the haploid number n=120.4. O. reticulatum L. is shown to have the highest chromosome number yet recorded in any species (n=c. 630, 2n=c. 1260).5. The basic chromosome number of the Ophioglossaceae is postulated to be 15.6. Evidences of chromosome numbers obtained from this study show the probability that there is some parallelism in the cytological evolution of the Ophioglossaceae and the Schizaeaceae. Both Ophioglossum and Schizaea exhibit very high chromosome numbers. The basic number 15, characteristic of the Ophioglossaceae, is also shared by Lygodium, the most primitive genus of the Schizaeaceae.7. Cytological evidence is in favour of regarding Botrychium as the most primitive of the three genera while Helminthostachys is intermediate and Ophioglossum the most specialised.8. There is no cytological support for the segregation of species of Botrychium and Ophioglossum into subgenera or for raising these subgenera to generic status.9. It is suggested that the greater percentage of polyploids as well as higher grades of polyploidy encountered in South Indian races of Ophioglossum may be related to the fact that Peninsular India is geologically one of the oldest land masses with a continued vegetation cover for a very long geological period. This suggestion is incidentally supported by evidences of chromosome numbers from ancient genera like Tmesipteris and Phylloglossum from Australia which also represents a very old geological formation.10. The taxonomic delimitation in species like O. reticulatum, O. petiolatum and O. vulgatum is seen to be very artificially drawn.11. Taxonomic revision in the light of cytology is necessary for O. nudicaule.

The Potential of Biological Control to Manage Old World Climbing Fern (Lygodium microphyllum), an Invasive Weed in Florida

Abstract: -Lygodium microphyllum is native to wet tropical and subtropical Africa, Asia, Australia, and the Pacific islands. The genus Lygodium is taxonomically isolated and has only one native species in North America. Specialized natural enemies of L. microphyllum are predicted to exist that can be safely employed to control the fern in Florida, where it is a severe problem. Lygodium microphyllum (Cav.) R. Br., or Old World climbing fern, is a serious weed in southern Florida, as described in the companion to this paper (Pemberton and Ferriter, 1998). In an attempt to reduce populations of this plant and to limit its spread, a biological control research effort is being initiated. The theory of biological control and the suitability of this approach to reduce and manage L. microphyllum are discussed. To help lay the groundwork for the biological control effort, the native range and taxonomic relations of the fern are defined. This information is used to plan and conduct surveys for natural enemies as well as research to define the potential host ranges of candidate biological control agents. The question of whether insects and other natural enemies can be expected to be associated with L. microphyllum is addressed.

Chloroplast genome evolution in early diverged leptosporangiate ferns.

Abstract: In this study, the chloroplast (cp) genome sequences from three early diverged leptosporangiate ferns were completed and analyzed in order to understand the evolution of the genome of the fern lineages. The complete cp genome sequence of Osmunda cinnamomea (Osmundales) was 142,812 base pairs (bp). The cp genome structure was similar to that of eusporangiate ferns. The gene/intron losses that frequently occurred in the cp genome of leptosporangiate ferns were not found in the cp genome of O. cinnamomea. In addition, putative RNA editing sites in the cp genome were rare in O. cinnamomea, even though the sites were frequently predicted to be present in leptosporangiate ferns. The complete cp genome sequence of Diplopterygium glaucum (Gleicheniales) was 151,007 bp and has a 9.7 kb inversion between the trnL-CAA and trnVGCA genes when compared to O. cinnamomea. Several repeated sequences were detected around the inversion break points. The complete cp genome sequence of Lygodium japonicum (Schizaeales) was 157,142 bp and a deletion of the rpoC1 intron was detected. This intron loss was shared by all of the studied species of the genus Lygodium. The GC contents and the effective numbers of codons (ENCs) in ferns varied significantly when compared to seed plants. The ENC values of the early diverged leptosporangiate ferns showed intermediate levels between eusporangiate and core leptosporangiate ferns. However, our phylogenetic tree based on all of the cp gene sequences clearly indicated that the cp genome similarity between O. cinnamomea (Osmundales) and eusporangiate ferns are symplesiomorphies, rather than synapomorphies. Therefore, our data is in agreement with the view that Osmundales is a distinct early diverged lineage in the leptosporangiate ferns.