Rhynchospora alba (L.)Vahl,its distribution,communities and habitat conditions in Czechoslovakia,Part I

The first part of a study on the phytogeography and phytosociology ofRhynchospora alba (L.)Vahl in Czechoslovakia presents the data on the distribution of the plant. Data from literature and from herbaria are subjected to critical evaluation, and a list of localities and distribution maps are appended.     

Rhynchospora alba (L.) Vahl,its distribution,communities and habitat conditions in Czechoslovakia,Part 2

The second part of the study is connected with the first part which comprised all the available data concerning the distribution ofRhynchospora alba in Czechoslovakia. It presents the results of cenological and synecological research, summarizes the cenotic and habitat characteristics of the species and, on the basis of results thus obtained, attempts at evaluating the diagnostic value ofRhynchospora alba and syntaxonomic position of its communities.     

Growth and population structure of Salamandra salamandra (L.) larvae in different limnological conditions

Salamandra salamandra (L.) larvae were studied in three types of aquatic systems, a permanent spring, a rock pool and temporary ponds. Growth was followed throughout ontogenesis until completion of metamorphosis. Growth patterns changed according to the pond type. Temporary ponds were rich in organic matter and subsequently larvae matured more rapidly there than those in a permanent pool or a spring. In the latter, cannibalism appears to be of major ecological importance, enabling survival and metamorphosis of large size tadpoles. The pattern of growth and metamorphosis is compared with European salamanders and the differences are discussed considering adaptations for survival of this species under xeric conditions.     

Ecobiology and distribution ofSagittaria sagittifolia L. in Czechoslovakia

The paper summarizes hitherto known data concerning the biology and ecology ofSagittaria sagittifolia. The distribution of this species in Czechoslovakia was assessed on the basis of literature data, herbarium specimens and the authors’ own data. The occurrence of this species in plant communities is shown in tables from selected phytocoenological relevés. The chemical properties of the substratum in habitats ofSagittaria sagittifolia over all its distribution area in Czechoslovakia were studied and comparisons calculated by means of cluster analysis. Life cycle, seed production, germination and biomass production of this species were studied and compared with conditions in its habitats.     

Genetic variability, population size and reproduction potential in Ligularia sibirica (L.) populations in Estonia

Ligularia sibirica (L.) Cass. (Asteraceae) is a EU Habitats Directive Annex II plant species that has suffered a lot from human-caused major changes in quality and availability of habitats in Estonia. The aim of this study was to find out if the observed decline in population size is reflected in the amount of genetic variation and fertility in remnant populations of this species. AFLP technique was used for that purpose. Genetic diversity within populations was assessed as the percentage of polymorphic loci in a given population and average gene diversity over loci. The degree of genetic differentiation among populations and genetic differentiation between pairs of populations was estimated. The amount of viable seeds per flower stem was compared among populations and between years (2007 and 2008). Average genetic diversity over loci and proportion of polymorphic loci in L. sibirica populations were significantly correlated with population size, suggesting the action of genetic drift and/or inbreeding. No correlation was found between genetic and geographic distances. Natural barriers like forests may have been efficiently preventing seed migration even between geographically closer populations. Results of this study suggest that genetic erosion could be partially responsible for the lower fitness in smaller populations of this species.     

Age,growth and reproduction of a population of spined loach,Cobitis taenia (L.)

751 specimens of spined loach, Cobitis taenia (L.), were collected and studied over the period October 1972–October 1974. The majority of the males were found to die at the end of the 2+ season and the majority of the females at the end of the 3+ season. Back calculations for length at age were carried out from otolith measurements and found to correspond closely to actual measurements. Males and females grew similarly up until the end of their 1+ year of life, with most rapid growth occurring in the first year. Females continued to grow rapidly up to 2+, the rate then being reduced; the males showed an increasingly reduced rate of growth after the 1+ year. Ford Walford plots gave L∞ results which corresponded closely in most cases with the largest observed specimens. Gonad development and maturation of males and females followed different patterns. Males matured during the 1 + year at a length of approximately 40 mm from which point their dry gonad weight remained at a steady 0.02–0.03% of the body weight. Females appeared to mature a year later and their ovary weight and oocyte diameter increased with fish age. A seasonal cycle in gonad development was evident in females. There was a greater proportion of females to males, especially in the older age group. Spawning time was estimated to be between June and July.     

The influences of habitat, landscape structure and climate on local distribution patterns of the nuthatch (Sitta europaea L.)

The nuthatch, Sitta europaea L., is a small (23 g), cavity-nesting woodland bird which, since the 1970s, has been expanding its range in Britain. However, within this range, the species is notably scarce in an area of eastern England. This gap in the species distribution could arise for several reasons including habitat quality, local landscape structure, regional landscape structure and climate. Field surveys and logistic models of breeding nuthatch presence/absence were used to investigate the relative influences of habitat quality, landscape structure and climate on the prevalence of nuthatches in eastern England. Field surveys of woods in the study area indicated that habitat quality was sufficient to support a nuthatch population. A model of habitat occupancy in relation to local landscape structure, developed in the Netherlands, was applied to the study area. The number of breeding pairs predicted for the study area by the model was lower than expected from habitat area alone, suggesting an additional effect of isolation. However, observed numbers were even lower than those predicted by the model. To evaluate the possible roles of climate and large-scale landscape structure on distribution, presence/absence data of breeding nuthatches at the 10-km grid square scale were related to variables describing climate and the amount and dispersion of broadleaved woodland. While climate in the study area appeared suitable, models including landscape variables suggested that the study area as a whole was unlikely to support nuthatches. Although suitable habitat was available, woodland in the study area appeared to be too isolated from surrounding nuthatch populations for colonisation to be successful. This situation may change if current increases in both national and regional populations continue, thus increasing the number of potential colonists reaching the study area. Received: 3 November 1997 / 22 January 1998     

Sexual reproduction in the phyllodioicous bryophyte Homalothecium lutescens (Hedw.) H.Rob. in relation to habitat age,growth conditions and genetic variation

Sporophyte production and female fertility were investigated in seventeen calcareous grassland demes of the moss Homalothecium lutescens (Hedw.) H.Rob. on the Baltic island of Öland, with the aim of understanding the relationships between sexual reproduction, habitat age, genetic variation and factors related to growth conditions. The overall proportion of fertile female shoots (with perichaetia) was 35%. Fertility status at the level of individual shoots was positively associated with shoot length and density, while within deme fertility was positively associated with bush cover. There was no association between female fertility and habitat age, genetic diversity (H_S) or allelic richness. Out of 1344 investigated shoots, only two were normal-sized fertile males. Dwarf males were also extremely rare, and found almost exclusively on shoots with sporophytes. Few sporophytes were observed (in the two demes with highest fertility and bush cover). No relationship between genetic variation and the frequency of sporophytes and males was found. The lack of a relationship between sexual reproduction and genetic variation suggests that sexual reproduction may not occur in the same grassland fragments as the recruitment of new clones (from spores or vegetative fragments). The majority of the dry, open grassland habitats, where H. lutescens is typically found in the study area, appear to be suboptimal for both dwarf males and fertilization. Sexual reproduction is more likely to occur in shaded (although grazed) grassland patches, where moisture levels are likely to be higher and the moss colonies are generally more vigorous.     

External morphology of a Slovenian population of pumpkinseed Lepomis gibbosus (L.) from a habitat with extreme thermal conditions

The external morphology and growth variability of morphometric characters of pumpkinseed (n = 141) from an oxbow (River Sava, Slovenia) that receives thermal effluent were examined using triple regression analysis. Differences in external morphology between pumpkinseed from the oxbow and both native North American (River Otonabee, Looncall Lake, Canada) and non‐native Central European populations (side arms of the River Danube, Slovakia) were evaluated. Two possible morphotypes among adults were observed, whereas the morphology of juveniles appears rather uniform across geographical location (i.e. Otonabee, Looncall, Danube). This suggests that environmental conditions, i.e. epigenetical information, seem to be responsible for most of variability in pumpkinseed morphology, which represents a function of epigenetical mechanisms. However, further investigation into epigenetical interactions, especially early development, fecundity, number of spawning acts per season, parental care, egg size and age at maturation are necessary to test this hypothesis.     

The role of sexual and clonal reproduction in maintaining population in Fritillaria camtschatcensis (L.) Ker-Gawl. (Liliaceae)

Fritillaria camtschatcensis can reproduce by means of both sexual reproduction and clonal multiplication. Despite prolific seed production, no seedlings have been found for several years in natural populations on Mt Hakusan. The purposes of this paper are to clarify: (i) whether population size is maintained mainly by clonal multiplication; and (ii) if this is the case, to what extent occasional seedling establishment affects population growth rate and population structure. Two permanent quadrats were placed in subalpine meadows in 1992 on Mt Hakusan. Plant size, location and reproductive states for all ramets in the quadrats were recorded every year. Projection matrices were created based on field census, and computer simulation experiments were performed. Fritillaria camtschatcensis had two types of flower, male flower and cosexual flower, and they were changeable. This is the first report on sex lability in Fritillaria. Clonal growth was more closely correlated with life-history stages, especially with sexual states than with plant size. The population growth rate, , was 1.006 for the Mizuyajiri population and 1.047 for the Nanryu population, respectively. Seedlings were found in 1996 for the first time. These facts indicate that populations of F. camtschatcensis on Mt Hakusan can usually be maintained by clonal multiplication. However, it is not yet certain whether seeds germinate every year or whether a flush of seedling emergence occurs once in every few years in natural populations. Computer simulation revealed that: (i) there was a critical germination rate above which population growth rate suddenly increased; and (ii) occasional seedling establishment could provide almost the same contribution to population growth rate as that of annual seedling establishment. These results suggest that population size can be maintained mainly by clonal multiplication, and the role of sexual reproduction lies beyond maintaining the population size in F. camtschatcensis.     

Root distribution and the cause of its spatial variability inPseudotsuga taxifolia (Poir.) Britt.

Summary The roots of 36-year-old Douglas firs were sampled in a stratified random fashion with a Veihmeyer-type auger. The lengths of root were very variable as was the proportion of fine roots which were dead. From consideration of the possible causes of spatial variability, it was concluded that it was not due primarily to environmental variation; nor to position relative to the tree trunks and crowns except for concentrations adjacent to the trunks where stem flow is considerable. Cyclical initiation, extension and death of fine roots in a spatial pattern with cells perhaps as small as 30 cm diameter could explain the observations. A drought period might have caused more extensive death of fine roots on one of the three plots examined.     

Biotopic distribution, population structure, and some features of small mammal reproduction in Chisinau City

Comparative analysis of species composition, biotopic distribution, population structure, and reproduction of rodents and insectivores in Chisinau City was performed in October?CNovember 2008 (3029 traps days, 715 animals). Sylvaemus sylvaticus appeared to be the most numerous and widely distributed species, the reproductive strategy of which consisted of intense reproduction in the summer. The second most abundant species was Microtus rossiaemeridionalis, which had a different reproductive strategy, with part of its population continuing to reproduce actively in the autumn. Urban woodlands are the most close to natural biotopes by the species composition. The highest number of animals was defined for meadows and gardens. No rodents and insectivores are found on lawns and waste grounds.     

Growth, sex determination and reproduction of Dryopteris filix-mas (L.) Schott gametophytes under varying nutritional conditions

KORPELAINEN, H., 1994. Growth, sex determination and reproduction of Dryopteris filix-mas (L.) Schott gametophytes under varying nutritional conditions. Gametophyte isolates originating from two populations of Dryopteris filix-mas (L.) Schott were grown in culture media containing different amounts of nutrients. Both nutrition and source population significantly affected gametophyte growth, sex, reproduction and mortality. Taking into account the most optimal nutritional condition for the selfing of gametophytes originating from individual source sporophytes, the proportions of hermaphrodites reproducing by intragametophytic selfing in the two populations varied from 33 to 96% and from 54 to 100%, respectively. It is emphasized that when examining the amount of genetic load only hermaphrodites, not all individuals, should be included, and genetic load should be estimated from the growth experiments where the intensity of reproduction is at the maximum. It was detected that hermaphroditic gametophytes are considerably larger than males or asexuals. It follows that gametophyte size is decisive in sex determination. It is suggested that the effect of antheridiogen hormones, which is considered to be an important factor in gametophyte sex determination, is indirect. Antheridiogens would actually affect size, and size would influence sex expression. The ecology of fern mating systems, and the different genetic and nongenetic factors which promote intergametophytic matings are discussed.