Modelling epiphytic bryophyte vegetation in an urban landscape

Abstract

Air pollution in the urban environment of Halle, Germany, has significantly decreased over the last decade. We investigated the distribution and recolonization of the epiphytic bryoflora. We tested the hypothesis that after a period of nearly complete absence of epiphytic mosses and liverworts, recolonization would occur first in the most favourable habitats and proceed from there. The aims of the study were to analyse these habitat conditions, to generate habitat models for the most abundant species and to identity favourability of habitats. At the community level, mixed linear models revealed the factors aspect of plots, inclination of trees and landscape features to be of particular relevance to bryophyte diversity and coverage. At the species level, generalized linear mixed models with logit link functions identified aspect, tree inclination and landscape type to be the key habitat factors for most taxa, while identity of the host tree species and stand structure were of minor importance. In general, epiphytic bryophyte vegetation did not attain high coverage and many species occurred only rarely. Thus, significant habitat models were obtained only for frequent species (e.g. Orthotrichum diaphanum) and only with low coefficients of determination. Nevertheless, the results clearly show that species-sorting is an effective mechanism of community assembly even in this early stage of recolonization.     

Fatty acid composition of muscle and heart tissue of Nile perch,Lates niloticus,and Nile tilapia,Oreochromis niloticus,from various populations in Lakes Victoria and Kioga,Uganda

The fatty acid composition in the heart tissue and muscle tissue of the Nile perch, Lates niloticus, and Nile tilapia, Oreochromis niloticus populations from Lakes Kioga and Victoria was determined by methanolysis and gas chromatography of the resulting fatty acid methyl esters. The analytical data were treated by multivariate principal component analysis. The most abundant individual fatty acids were palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1n9), vaccenic acid (18:1n7), arachidonic acid (20:4n6) and docosahexaenoic acid (22:6n3). Due to high levels of both n6 and n3 fatty acids, the ratios of n3 to n6 were between 1 and 2, typical for freshwater fish species. Two Lake Victoria and one Lake Kioga populations of Nile tilapia and Nile perch were distinguished by the fatty acid profiles in their heart and muscle tissue. The heart tissue showed better separation than muscle tissue, due to dominance of polar phospholipids. It is rationalised that genetics are more important than diet in determining the fatty acid composition of the tissues.     

Notes on African Mosses. I. Andreaea camerunensis sp.nov. and other Mosses mostly from Nigeria and the British Cameroons

Abstract

Reproductive ecological traits such as success of fertilization, partitioning of sexes, the relative success of sexual versus asexual reproduction and dispersal distances are likely to considerably influence genetic structure within and among plant populations. In the liverwort Mannia fragrans both sexual and asexual reproduction can be frequently observed: sporophytes are produced abundantly every year and asexual propagation by fragmentation of thalli is also common. The aim of this study was to use ecological and molecular methods (ISSR markers) to separate the role of sexual and asexual components in shaping the partitioning of genetic variability within and among populations. In addition to genetic analyses conducted seasonally, sex expression and fertilization rates, sex ratios, regeneration from vegetative fragments and outcrossing was estimated in 3 populations of the species. Sex expression rates were high and, in spite of strongly female biased sex ratios, high fertilization rates were detected. However, capacity for regeneration from fragments was also high. Despite frequent spore production genetic diversity was low within populations. This is probably the result of the predominance of asexual reproduction s. 1. including crossing between genetically identical plants. Although recombination and mutation occasionally generates new haplotypes, these have little chance to spread because of the large spores mainly falling into their own patch, where chances for germination are low. Due to small size and isolation of the populations, genetic drift is likely to eliminate these haplotypes. Remote populations differed significantly, each being dominated by a few clones, reflecting negligible gene flow among them. Differences among individual populations can partly be related to differences in their reproductive behaviour and degree of isolation.     

The macroinvertebrates of the Cunene River from the Ruacana Falls to the river mouth and assessment of the conservation status of the river

The proposed construction of a second hydroelectric power-generating dam on the Cunene (Kunene) River on the Namibia-Angola border, more than 100km downstream of the Ruacana hydroelectric power plant, will have a major influence on the aquatic biota of this river. In order to assess the potential impact of this impoundment a more detailed inventory of the biota in the river prior to this development was needed. Unfortunately the river presently does not represent an entirely undisturbed system as the operation of the Ruacana hydroelectric power station since 1970 has had a long-term effect on its biota. In the low-flow mid-summer season in particular, large areas of the river become irregularly inundated and exposed, sometimes on a daily basis, making them unsuitable for macroinvertebrate colonisation. There are six impoundments along the Cunene River upstream of the Ruacana Falls in Angola. These, however, do not have any major disruptive effects on daily flow variation in the Cunene River in Namibia although whole system biological consequences could be considerable but are unstudied. The Cunene River has a diverse freshwater fish fauna but, prior to the surveys reported here, the aquatic macroinvertebrates had been poorly studied. Surveys conducted by staff of the Department of Water Affairs (DWA) of Namibia and the Albany Museum, Grahamstown, in 1997 and 1998 have resulted in 216 aquatic macroinvertebrate species being recorded from Ruacana to the river mouth. The lower Cunene River, flowing through a very arid region, is biogeographically isolated and therefore highly vulnerable to change. The biota recorded reflects a fauna of widespread species and several elements of tropical origin. Several undescribed species may reflect some endemics but because of limited knowledge of the tropical rivers, this cannot be ascertained with certainty. From the aspect of conservation, the river contains a diversity of species with an abundance of filter-feeding species. Further surveys conducted during different seasons will undoubtedly record more taxa.     

Aerial and underground biomasses of three Sphagnum-dwelling liverworts

Abstract

The few studies that have investigated levels of genetic variation in liverworts have found very little polymorphism. Our electrophoretic data show, however, that the leafy liverwort Porella platyphylla maintains high levels of genetic variation in at least some natural populations from the southeastern United States. Within a single population from southwestern North Carolina, we detected 26 distinct multilocus genotypes and more than 80% of the enzyme loci we surveyed were polymorphic. It seems likely that earlier studies of mostly thalloid species from glaciated regions of Europe have presented a biased picture of levels of variation in liverwort populations.     

Extensive Genetic Polymorphism of Peptidases A, B, C, and D, in Wild Rabbit (Oryctolagus cuniculus) Populations from the Iberian Peninsula

Genetic polymorphism of peptidases A, B, C, andD in the wild rabbit (Oryctolagus cuniculus)was assessed by horizontal starch gel electrophoresis,in a total of 1003 individuals comprising 16 Iberian and 2 French populations and 1 domestic stock.Twenty-five different alleles were detected: 6 in PEPA,4 in PEPB, 8 in PEPC, and 7 in PEPD. The highest valuesof observed heterozygosity averaged over the four loci were obtained for the southwestern Iberianpopulations and a clinal loss of variability in anortheastern direction was detected. A clear separationbetween the two putative subspecies O. c.cuniculus and O. c. algirus was notobtained.     

Genetic Diversity of Chinese Native Pigs Inferred from Protein Electrophoresis

We examined protein polymorphism of 20 nativepig breeds in China and 3 introduced pig breeds. Thirtyloci have been investigated, among which six loci werefound to be polymorphic. Especially, the polymorphismof malate dehydrogenase (MDH), adenylate kinase(AK), and two new alleles of adenosine deaminase (ADA)had not been reported in domestic pigs and wild pigs.The percentage of polymorphic loci (P), the meanheterozygosity (H), and the mean number ofalleles (A) are 0.200, 0.065, and 1.300, respectively.The degree of genetic variability of Chinese pigs as awhole was higher than that of goats, lower than thatof cattle and horses, and similar to that ofsheep. Using the gene frequencies of the 30 loci, Nei'sgenetic distance among the 20 native breeds in China and3 introduced pig breeds was calculated by theformula of Nei. The program NEIGHBOR in PHYLIP3.5c was chosen to construct an UPGMA tree and a NJtree. Our results show that, of the total geneticvariation found in the native pig breeds in China, 31%(0.31) is ascribable to genetic differencesamong breeds. About 69% of the total genetic variationis found within breeds. Most breeds are in linkagedisequilibrium. The patterns of genetic similaritiesbetween the Chinese native pig breeds were notin agreement with the proposed pig type classification.     

Genetic diversity in populations of Sphagnum capillifolium from the mountains of Bulgaria,and their possible refugial role

Abstract

Genetic diversity in eight populations of Sphagnum capillifolium from different Bulgarian mountains was investigated by means of isozyme electrophoresis. High levels of allelic diversity were found (H_S = 0.119), comparable to earlier estimates for northern European populations (H_S = 0.116). Strong differentiation among populations and a low number of widespread genotypes suggest a high degree of isolation and restricted gene flow between populations, which is consistent with generally small and scattered populations. The large proportion of distinguishable genotypes (mean 0.498) suggests high levels of out-crossing either currently or in the past. Introgression between S. capillifolium and S. rubellum, a species not found in Bulgaria, was suggested by the occurrence of rubellum-alleles in five populations from different mountains. This could be explained by an ancient hybridization event in a sympatric population. Based on (1) the high genetic diversity, (2) the fairly wide distribution of alien alleles, and (3) the isolated distribution of populations even within one mountain, a possible survival of S. capillifolium in the Balkan area during the Quaternary ice periods is hypothesized.