Zdenek Kaplan

Phenotypic plasticity inPotamogeton (Potamogetonaceae)

Sources of the extensive morphological variation of the species and hybrids ofPotamogeton were studied, especially from the viewpoint of the stability of the morphological characters used inPotamogeton taxonomy. Transplant experiments, the cultivation of clones under different values of environmental factors, and the cultivation of different clones under uniform conditions were performed to assess the proportion of phenotypic plasticity in the total morphological variation. Samples from 184 populations of 41Potamogeton taxa were grown. The immense range of phenotypic plasticity, which is possible for a single clone, is documented in detail in 14 well-described examples. The differences among distinct populations of a single species observed in the field were mostly not maintained when grown together under the same environmental conditions. Clonal material cultivated under different values of environmental factors produced distinct phenotypes, and in a few cases a single genotype was able to demonstrate almost the entire range of morphological variation in an observed trait known for that species. Several characters by recent literature claimed to be suitable for distinguishing varieties or even species were proven to be dependent on environmental conditions and to be highly unreliable markers for the delimiation of taxa. The unsatisfactory taxonomy that results when such classification of phenotypes is adopted is illustrated by three examples from recent literature. Phenotypic plasticity was found to be the main source of morphological variation within the species ofPotamogeton, having much more influence than morphological differences caused by different genotypes.

Genetic variation within and between populations of Potamogeton pusillus agg.

AbstractPatterns of isozyme variation were examined in 17 populations of P. pusillus and P. berchtoldii, together with one population of P. trichoides taken for comparison. Both P. pusillus and P. berchtoldii displayed low levels of variation within populations associated with high levels of interpopulation differentiation. This pattern of partitioning of genetic variation within and between populations is attributed to the founder effect, frequent vegetative propagation by turions, dominant self-fertilization and limited seedling recruitment. The mechanism of pollen transfer was investigated in cultivation. Effective pollination takes place in air above the water surface (autogamy, geitonogamy, anemogamy), on the water surface (epihydrogamy) or below water surface (hydroautogamy). The species are self-compatible. The low level of infra-population variation together with rare occurrence of heterozygotes suggest that selfing is the most frequent mode of pollination, although the protogynous flowers may occasionally permit some cross-pollination. Unique enzyme markers were found for P. pusillus and P. berchtoldii, and also for the single population of P. trichoides. All multienzyme phenotypes were species-specific. Isozyme data support the separate position of P. pusillus and P. berchtoldii. UPGMA dendogram based on enzyme data of 133 plant samples revealed three distinct main enzymatic entities perfectly corresponding to the three morphologically defined species.

Neotypification of Potamogeton ×fluitans Roth and the distribution of this hybrid

The identity of the name Potamogeton fluitans Roth has for a long time been uncertain. An analysis of the history of the name and its use is presented and the identity of the extant material ascribed to Roth discussed. The name P. fluitans is neotypified with a specimen from a population of the hybrid P. lucens L. × P. natans L. recently studied morphologically, anatomically and electrophoretically. Nomenclature of the hybrid is summarized and lectotypes for a further four names designated. Distribution of the hybrid is described and a list of representative specimens given.

1638) Proposal to Conserve the Name Potamogeton schweinfurthii A. Benn. (Potamogetonaceae) with a Conserved Type

Potamogeton schweinfurthii A. Benn. is the name generally applied to a rather common and widely distributed species in Africa and on several surrounding islands. Soon after it was first proposed by Bennett (1.c.), the name was adopted in the world-wide revision of the genus by Graebner (in Engler, Pflanzenr. 31 (IV.11): 79. 1907). Since then, it has been adopted in all relevant literature (e.g., Dandy, J. Linn. Soc., Bot. 50: 526. 1937; Berhaut, Fl. Senegal 81. 1954; Andrews Flow. Pl. Sudan 3: 234. 1956; Ozenda, Fl. Sahara Sept. Centr. 126. 1958; Obermayer in Codd et al., Fl. South. Afr. 1: 66. 1966; Berhaut, Fl. Senegal ed. 2: 180. 1967; Hepper, Fl. West Trop. Afr., ed. 2, 3: 16 1968; Denny et Lye, Kew Bull. 28: 117-120. 1973; Lisowski et al., Fl. Afr. Centr., Potamogetonaceae 6. 1978; Symoens, Fl. Cameroun 26: 60. 1984; Jafri in Jafri et El-Gadi, Fl. Libya 5. 1984; Wiegleb, Feddes Repert. 99: 259. 1988; Lye in Thulin, Fl. Somalia 4: 14. 1995; Wiegleb, Willdenowia 25: 55. 1995; Lye in Edwards et al., Fl. Ethiopia Eritrea 6: 23. 1997; Wiegleb et Kaplan, Folia Geobot. 33: 273. 1998). This species is closely related to the Eurasian P lucens L. with which it shares many important morphological and anatomical characters. Potamogeton schweinfurthii has submerged leaves sessile to shortly petiolate (mostly 0-3 cm), with acute to mucronate apex, and floating leaves sometimes developed but mostly not present in adult fertile plants. The stem anatomy pattern of this species shows the endodermis of U-type, interlacunar bundles present and subepidermal bundles absent or scattered ones present (see Wiegleb in Flora 184: 198-200. 1990 and Wiegleb et Kaplan in Folia Geobot. 33: 248. 1998 for a detailed explanation of anatomical structures and terminology). Potamogeton schweinfurthii is in Africa sometimes confused with P nodosus Poir. Even though this latter species is in some of its phenotypes very similar to P schweinfurthii, it is actually not closely related but occupies within the genus a rather isolated position together with the East-Asian P distinctus A. Benn. In contrast to

Taxonomic and nomenclatural notes on Luzula and Juncus (Juncaceae)

Summary Kirschner, J. & Kaplan, Z.: Taxonomic and nomenclatural notes on Luzula and Juncus (Juncaceae). - Taxon 50: 1107-1113. 2001. - ISSN 0040-0262. New taxa and combinations are presented to be included in the prepared treatment of Juncaceae in the Flora of the World. A new section, Luzula sect. Atlanticae, and a new species, Luzula indica, are described, and three new combinations are made: Luzula nipponica (Satake) Kirschner & Miyamoto, L. lutescens (Koidzumi) Kirschner & Miyamoto, and Luzula alpino-pilosa subsp. deflexa (Kozuharov) Kirschner. A new name, Juncus meianthus K. Wilson is proposed for a later homonym, J. gracilis R. Br. The name Luzula acuminata Raf. is neotypified in order to retain its current usage.

Taxonomic identity and typification of selected names of North American Potamogetonaceae

Most names in North American Potamogetonaceae have not been typified. Details of typifications are given for 72 names based on North American material published in the genus Potamogeton mainly by North American botanists. All names are reviewed for their nomenclatural validity and legitimacy, and interpreted taxonomically. Holotypes are indicated for 31 names and previously declared lectotypes or neotypes are listed for eight names. Lectotypes are designated for 24 previously untypified names and step-2 lectotypifications are proposed for three names that were based on heterogeneous material. Type material for three Rafinesque names and one proposed by Wood have not been located. An annotated list provides collection data, type status, homotypic synonyms, and currently accepted names. Two names are excluded from Potamogeton, being based on species of Myriophyllum (Haloragaceae).