The freshwater and terrestrial diatom composition of the Subantarctic island Ile de la Possession is investigated in detail. The island is part of the Crozet Archipelago, situated in the southern Indian Ocean. A total of 220 diatom taxa, belonging to 44 genera have been identified after surveying more than 500 samples, taken from all over the island. The most diverse genera are Pirmularia (41 taxa), Nitzschia (19 taxa), Psammothidium (13 taxa) and Diadesmis (11 taxa).

Detailed SEM analysis of all observed taxa resulted in the description of several new species and varieties, especially in the genera Diadesmis and Pinnularia, whereas several others need further observations to be described later on as new taxa. In addition, the taxonomy of the so-called Subantarctic taxa has been thoroughly revised based on the most recent insights. All taxa are morphologically and ecologically characterized and elaborately documented with both LM and SEM micrographs.

This further volume of diatom floristic studies in the Series Bibliotheca Diatomologica focuses on the freshwater and terrestrial diatoms of the Subantarctic island Ile de la Possession.

The subantarctic region consists of several islands and archipelagos, situated in the southern part of the Atlantic, Indian and Pacific Ocean. The investigated island is a part of the Crozet Archipelago, situated in the southern Indian Ocean. Diatoms are one of the most abundant algal groups in the freshwater and terrestrial ecosystems of the Antarctic and Subantarctic Regions. They are an important constituent in freshwater, moss and soil habitats. In spite of this fact, the Subantarctic diatom flora remains poorly studied, especially from the ecological point of view. The present study addresses the lack of a well-documented floristic and ecological work on diatoms from Ile de la Possession in particular and the entire Subantarctic Region in general. All taxa found on Ile de la Possession during the last five years of study were illustrated using LM and SEM techniques. New taxa were described according to the botanical rules.
The study consists of two parts. Methods, geographical and environmental characteristics of the studied area are briefly described in the general part. Diatom taxa in alphabetical order are described in the taxonomical part. Species morphology, autecology and distribution, eventually description and Latin diagnosis are supplemented by 132 plates with excellent LM and SEM micrographs.
A total of 220 diatom taxa belonging to 44 genera have been identified after surveying more than 500 samples, taken from all over the island. The most diverse genera are Pinnularia, Nitzschia, Psammothidium, Diadesmis. Detailed SEM analysis of all observed taxa resulted in the description of 57 new taxa or combinations, especially in the genera Diadesmis and Pinnularia. Due to the recent evolutions in the taxonomical classification of the diatoms, the nomenclature was based on several authors and works, depending on the genus discussed.
A. Poulickova

The island Ile de la Possession is part of the Crozet Archipelago, situated in the Subantarctic Region. The environmental conditions of the island are very special in many ways. The climate is oceanic, calm and wet and geographically the island is rather isolated. Until recent times, it was also protected from significant human impacts. as well. This volume of Bibliotheca Diatomologica introduces the diatom flora of the island from a floristical, geobotanical point of view, while giving notes on many years of taxonomic and ecological work on He de la Possession. During the investigations, 2500 samples were taken from soil, moss and freshwaters, the diatom taxa were identified and physico-chemical parameters of the surrounding environment were also determined. 220 diatom taxa have been identified, among them 35 new species (nov. spec.), 20 new combinations (nov.comb.) and 2 new varieties (nov. var.). There are 132 plates with LM and EM photographs of high quality in this band.

It is a well-known fact that species extinction and coupled with it, decrease in genetic diversity are going on the Earth on a huge scale. That is why this kind of surveying, pioneer research of unexplored natural habitats is of particular importance, especially on isolated, special areas, where plenty of endemic, peculiar and rare species possibly occur. So, first of all, we have to gain as much information as possible at undisturbed habitats before human influence expands to these areas as well. Since the extinction rate of species of natural environments is so high we can never know whether it is not our last chance to get acquainted with new and interesting species. Second of all, biological conservation, species and habitat protection are essential, progressive branches among the biological sciences. To succeed in these scopes, we have to get to know the species and environments. which should be protected as profoundly as possible. The mapping of unimpacted areas offers the opportunity to reveal large-scale phenomena and changes like global weather change, for example. The edaphic diatom flora is also investigated which is a rather infrequent topic in diatomology though not unimportant since our knowledge on edaphic algae is fairly incomplete.

It is a scientific commonplace that the development in genetic research and connected to it the new methods in phylogenetic and taxonomic research have brought many dogmas of classical taxonomy in question. Moreover, the rush developing of electron microscopic equipment and the expanding usage of these moved many phycologists to work with taxonomic categories based on tiny electron microscopic features exclusively. Thus, these two tendencies have turned the whole diatom taxonomy topsy-turvy to such an extent that nobody can be sure about the verity of any phylogenetic-taxonomic systems. However, there are some tendencies and baselines, which should be kept to the fore want the expert to work according to the latest trends. Well, in the age of molecular biology, one can not just neglect the fact that diatoms do also have genes, and that genotypic and phenotypic features are not always in accordance. Of course, it is for the moment quite far away to create a new and acceptable taxonomy about diatoms. Still, it is hardly plausible to describe new species on the exclusive categories like "relatively small central area" and "more elliptical-lanceolate outline". It is hard enough for every diatomist to choose a taxonomic system among the lot available. But one should have surely explained why he uses a certain one. The plates are arranged following the traditional, hypothetically phylogenetic order, according to the authors.

It would have been worth to make some classification of the taxa on the basis of ecological preferences in function of the measured physico-chemical parameters. All in all. this volume could be advised to every algologist, particularly to those working in ecology and taxonomy. Besides, it could be very useful for experts of nature conservation, species and environment protection and of course, it is a good starting-point for someone who wants to deal with the algae of these little-studied island and its surroundings.

K. Szabó

Acta Botanica Ungarica 45 (3-4), pp. 422-423