Search results for "Isoetes"
showing 10 items of 21 documents
Clarifying the nomenclature of some Euro-Mediterranean quillworts ( Isoetes , Isoetaceae): Indicator species and species of conservation concern
2018
International audience; To stabilize the application of some names in the genus Isoetes in the Mediterranean biodiversity hotspot, we studied herbarium specimens and imaged spores with scanning electron microscopy, with special reference to those taxa in the I. lon‐gissima and I. histrix groups that were described from France, Algeria and Turkey, and are in need of a taxonomic revision. The following names are lectotypified: I. adspersa, I. boryana, I. delalandei, and I. viollaei. Holotypes of I. perralderiana and I. olympica were ascertained. We conclude that I. boryana (listed in the “Bern Convention” and in the European Union “Habitats” Directive) justifies consideration at species rank,…
Dispersal and colonization in heterosporous lycophytes: palynological and biogeographical notes on the genus Isoetes in the Mediterranean region
2016
After a short review of the available information on dispersal in the heterosporous genus Isoetes, which has been the subject of some mainly anecdotal or occasional observations, a case study in the Mediterranean area is presented. In the geographical context given by the island of Sicily with its satellite islets and archipelagos, the distribution of terrestrial and amphibian Isoetes species was analysed to verify if any of them occurred in the oceanic (‘thalassogenous’) islets, never connected to the mainland. The only species revealed to be able to cross the geographical and ecological barrier represented by the sea and colonize some volcanic islands was Isoetes durieui Bory, a terrestri…
The genus isoetes (Isoetaceae): A provisional checklist of the accepted and unresolved taxa
2016
Isoetes is a widely distributed lycophyte genus of at least 200 species occurring in diverse habitats. The species can be difficult to identify because Isoetes, with its apparent simplicity of form and conserved morphology, provides few diagnostic features to reliably distinguish its species. The last worldwide monograph, published nearly a century ago, listed 77 taxa. The first step in producing a flora or monograph of all known species of a genus is to compile a list of the acceptable species names. The list presented here is a compilation of 192 accepted names representing taxa from regions around the world: chromosome numbers were assigned to 101 of them, with polyploidy settled on 46.7…
Different spore structures in sympatric Isoetes histrix populations and their relationship with gross morphology, chromosome number, and ribosomal nu…
2011
Abstract Traditionally, megaspores have supplied the most relevant character for the taxonomy of Isoetes at several systematic levels, including discriminant features usually used in species identification and diagnosis. Isoetes histrix Bory is a terrestrial circum-Mediterranean quillwort characterized by dark, shiny, and persistent phyllopodia with megaspore sporangia completely covered by a velum and tuberculate megaspores. Specimens of this species from Sardinian temporary wetlands showed the sympatric presence of two kinds of individuals with correlated variation in size, ornamentation, and radial ridges of megaspores, and in ornamentation of microspores. However, they showed the same d…
Isoëtes sabatina (Isoëtaceae, Lycopodiopsida). Taxonomic distinctness and preliminary ecological insights
2021
1) Isoëtes sabatina is the rarest aquatic quillwort in Europe. Although recently found (2013) in Lake Bracciano (central Italy), the species is just one step away from extinction with an estimated population not exceeding 400 individuals and a spatial range of a few hundred square metres. 2) Lake Bracciano is a deep, oligo-mesotrophic Mediterranean volcanic lake that has been subjected to human activities. From January to October 2017, the lake experienced a dramatic water level decrease (up to −1.50 m), which significantly affected the littoral zone and the habitat of I. sabatina. 3) To improve the chances of survival of I. sabatina, the first eco-taxonomic investigation on this species wa…
The genus Isoëtes L. (Lycophyta, Isoëtaceae): Synthesis of karyological data
2001
Summary A synthesis of relevant karyological data regarding the genus Isoetes is given, with an up-to-date check list of chromosome numbers including 152 records referring to 67 taxa (62 species and 5 infraspecific taxa) and 16 hybrids. Total of different chromosome counts (considering two or more cytotypes for certain taxa, excluding hybrids) is 80. Probable base number is x = 11, even though x = 10 and x = 12 have been proposed for certain species. On the basis of data here summarized, the mean percentage of polyploidy is 61.2%; 31 taxa are diploids (38.8%), 28 are tetraploids (35.0%), 8 are hexaploids (10.0%), with a few species each which are tri-, penta-, octo-, deca- and dodeca-ploids…
Disentangling Isoetes setacea and removing threats to Isoetes echinospora
2015
The name Isoetes setacea has been applied to two different species, causing nomenclatural and taxonomic confusion. Some authors have rejected it on that account, yet it is currently used in a sense that is incompatible with its type. That type represents one of two similar species, I. echinospora and I. lacustris, which still today grow together at the type locality. An epitype is designated here, ensuring that I. setacea is sunk in synonymy under I. lacustris. A second name potentially threatening I. echinospora is I. tenella. It is currently regarded as a synonym of I. lacustris, but its type, a plate in Flora Danica, cannot be confidently identified, nor are there any specimens associate…
A conspectus of and key to GreekIsoetes(Isoetaceae), based on a reassessment of Haussknecht's gatherings of 1885
2015
The three Isoetes species recorded from Thessalia (Thessaly) in N Greece by Haussknecht, in 1899, under the names I. setacea, I. heldreichii, and I. phrygia, were reassessed using megaspore and microspore ornamentation in addition to macromorphological features. “Isoetes setacea” is not the SW European I. delilei to which the name I. setacea was generally misapplied, nor “I. echinospora” as it has been called due to a misunderstanding, but a so far undescribed species here named I. haussknechtii; it has not been found again in Haussknecht’s locality but has recently turned up in Peloponnisos and the E Aegean Islands. I. heldreichii, described from Haussknecht’s gathering, is apparently exti…
Global review of recent taxonomic research into Isoetes (Isoetaceae), with implications for biogeography and conservation
2018
With the advent of cytological analysis, Scanning Electron Microscopy, the recognition of sterile hybrids, improved access to wild populations and increasingly comprehensive molecular investigations, there has been a revolution in Isoetes taxonomy in recent times. The last 40 years have seen an almost 100% increase in the diversity documented during the previous two centuries. Four geographic areas account for over 90% of this diversity: northern-central South America, eastern North America, western Eurasia (including the northern Mediterranean) and South to Tropical Africa. There is a significant global conservation concern for Isoetes, with many taxa being rare (known from one to a handfu…
A critical conspectus of ItalianIsoetes(Isoetaceae)
2014
The work on the Isoetaceae account for the Critical Flora of Italy has resulted in a new, synonymic inventory of Italian Isoetes taxa, based on herbarium studies, observation by scanning electron microscopy and critical re-examination of the previously published works. Ten species are listed. The names I. longissima and I. gymnocarpa are restored as correct, to replace I. velata and I. subinermis, respectively. Eighteen lectotypes, one epitype and one neotype are designated. A dichotomous key to Italian taxa is provided.