Presence and development of populations of the introduced brown alga Sargassum muticum in the southwest Netherlands

Of the three Brachionus species used in aquaculture, Brachionus rubens, B. calycilorus and B. plicatilis, the latter is most widely used in raising marine fish and shrimp larvae due to its tolerance to the marine environment. In freshwater aquaculture the use of B. rubens and B. calycilorus is limited, probably because inert food products are readily available as feed for freshwater larvae.The rotifer Brachionus plicatilis is used in large numbers as the first food organism in intensive cultures of marine fish and shrimp larvae. An adequate supply of these rotifers relies on mass cultures. The reproductive rate of rotifers in these cultures depends on food quality and quantity, salinity, temperature and pH of the medium. Removal of waste products from culture tanks leads to higher and more efficient production of rotifers over extended periods of time. Rotifers have to be enriched with polyunsaturated fatty acids, which are essential for proper development and survival of marine fish and shrimp larvae.The future use of preserved rotifers and their resting eggs may help to overcome unforeseen failures of live cultures and may lead to more efficient use of these organisms in raising freshwater and marine fish and shrimp larvae.     

The biogeography of AustralianDaphnia: clues of an ancient (>70 m.y.) origin for the genus

The AustralianDaphnia (D. occidentalis, D. jollyi, D. lumholtzi, D. carinata, D. nivalis, andD. cephalata) include representatives from three distinct groups within the genus. The worldwide distribution of species within these three groups is consistent with a Gondwanan or pre-Gondwanan origin for each group. These data suggest an even more ancient origin for the genusDaphnia. The finding thatD. cephalata must have been separated fromD. carinata since Gondwanan times is consistent with recent biochemical data on the phylogenetic relations of AustralianDaphnia, but contrasts with electrophoretic evidence of continuing hybridization between these two taxa. It is suggested that continued gene exchange between otherwise discrete species, or clonal complexes, ofDaphnia may be maintained for millions of years, partly as a result of the varying degrees of cyclical parthenogenesis, and partly as a result of the highly fragmented population structures, found in these taxa.     

Contributions to the knowledge of African rotifers: Rotifers from Mauritania (W.-Africa)

The number of Rotifer taxa known from Mauritania, is raised from 8 to 90. 61% of these are cosmopolitan, 1 is temperate — boreal, 18% are thermophilic and 20% are tropicopolitan. Most of them are widely distributed in Africa, but some species have limited distributions. The presence of Keratella testudo and Wolga spinifera is remarkable and is probably related to the unusual climatic conditions in the SW Sahara. One phenotype or forma is new to science.     

Ecology of bdelloids: how to be successful

Bdelloids inhabit many different environments. The entire taxon is an order belonging to the phylum Rotifera. In spite of its wide distribution, it has a very uniform morphology, suggesting that natural selection has had almost no effect on its morphological characteristics.This paper reviews the geographical and ecological distributions of bdelloids and their ability to tolerate different conditions is discussed. Two characteristics account for the wide distribution of bdelloids, parthenogenetic reproduction and their ability to withstand unfavorable conditions through anhydrobiosis. The former is an apomictic thelytoky which may ensure genetic homogeneity within clones. However, evidence which suggests variability among and within parthenogenetic clones is discussed. Some recent experimental evidence indicates that anhydrobiosis does not affect the life history of the surviving individuals. The effects of anhydrobiosis on bdelloid populations are considered.     

Morphological variation in Kellicottia longispina

The lengths of the body, the posterior spine and the three longest anterior spines were measured for 25 specimens of Kellicottia longispina from each of the eight lakes distributed from Imikpuk at Point Barrow, Alaska (latitude 71° 15) to Lake Washington (latitude 47° 38). Collections were available for more than two dates from six of the lakes. Temperature ranged from 1.2° to 18 °C. Mean lengths and ratios were examined in relation to latitude and temperature. Each population differed from the others in some aspect of absolute size, variability, or shape as expressed by the ratios of the dimensions. The population from Point Barrow is similar but not identical to Olofsson's var. heterospina.     

A classification of the genus Nothofagus (Fagaceae)

PHILIPSON, W. R. & PHILIPSON, M. N., 1988. A classification of the genus Nothofagus (Fagaceae). The genus Nothofagus is subdivided into two subgenera, two sections and three subsections, employing characters of the pollen, cupule and vernation, together with the incidence of leaf-fall. The subdivision into subgenera also agrees with present geographical distribution and with characters of the secondary xylem. One subgeneric and one subsectional name are new. Reasons are given for departures from previous classifications.     

Phylogenetic interrelationships of the barbets (Aves: Capitonidae) and toucans (Aves: Ramphastidae) based on morphology with comparisons to DNA-DNA hybridization

A phylogenetic analysis of the interrelationships of the barbets (Capitonidae) and the toucans (Aves: Ramphastidae, Superfamily Ramphastoidea) is presented. Thirty-two morphological characters from the literature and independent osteological observations were analysed. Character polarity was determined by outgroup comparison to the Picidae, Indicatoridae, Galbulidae, Bucconidae and Coraciiformes. Four alternative phylogenetic hypotheses were compared: (1) the overall most parsimonious morphological phylogeny, (2) the most parsimonious morphological phylogeny in which the capitonids and ramphastids were hypothesized as monophyletic sister groups, and (3) and (4) the most parsimonious hypotheses for the evolution of the morphological characters within two proposed DNA-DNA hybridization phylogenies of the ramphastoids. The analysis focused on the higher level relationships of ramphastids and capitonids and interrelationships among capitonid genera. Two cladistic analyses were performed using 26 phylogenetically informative characters, and the PAUP and CONTREE computer alogorithms. The most parsimonious morphological phylogeny required fewer character changes and had a lower consistency index than any of the alternative hypotheses but congruence between the most parsimonious phylogeny and the second, revised DNA-DNA hybridization hypothesis was very high. Based on these results the monophyly of the Capitonidae is rejected. The ramphastids and the Neotropical capitonids form a well corroborated clade within the pantropical ramphastoid radiation. Neither the African, Asian nor New World capitonids is monophyletic. The genus Trachyphonus is the sister group to all other capitonids and ramphastids. The sister group to the ramphastids is the genus Semnornis. The interrelationships of the Old World capitonids excluding Trachyphonus are not completely resolved by these morphological data but one of the alternative phylogenetic resolutions is presented as a preliminary hypothesis. The clades in this resolved phylogeny are diagnosed and the palaeontology and biogeography of the ramphastoids arc-reviewed in light of this new evidence. A phylogenetic classification is proposed in which the Capitonidae is rejected and the capitonids and ramphastids are placed in seven subfamilies of the Ramphastidae.     

The convergent trajectories of bird communities along ecological successions in european forests

Summary There is much more variation in the composition of bird communities in the earlier open and semi-open seral stages of ecological successions in forested landscapes of Europe than later on in preforested and forested climactic stages. The demonstration of this trend is achieved from the study of four habitat gradients, two in the mediterranean region (Provence and Corsica) and two in central Europe (Burgundy, France and Poland). A multivariate analysis has been used to illustrate the dynamics of communities along these succession. Displays of the results in bivariate space as well as an illustration of the distributional profiles of some of the most characteristic species show that: i) there is a discrimination between the two mediterranean gradients and the two medioeuropean ones and ii) each succession starts with a very distinct set of species and then the four gradients regularly converge in the last climactic stage where there is almost no discrimination between communities. These results are discussed in the light of the history of European biotas during the Pleistocene. The reason why there is more variation in species composition in the earlier seral stages than in the later forested stages are discussed according to current theories on the role of habitat selection on speciation processes.     

When is an island not an island? Insular effects and their causes in fynbos shrublands

Summary According to the equilibrium theory of island biogeography, insularisation will lead to species loss from habitat remnants. Extinctions will continue untill species number equilibrates at a level appropriate for the size and isolation of the island remnants. We tested whether insularisation leads to species loss by comparing plant species numbers on islands of fynbos shrublands surrounded by Afrotemperate evergreen forest with extensive mainland tracts of fynbos. Species area curves for islands and subsamples of mainland had significantly different slopes (z _island=0.43, z _mainland=0.16). Small islands had the fewest species (less than one fifth) relative to mainland samples of similar size. The species area curves intersect at 590 ha so that reserve sizes of this order of magnitude are needed to avoid species losses relative to extensive areas of fynbos.We compared traits of species on islands and mainlands to determine processes most affected by insularisation. Island floras did not differ from the mainland in the mix of dispersal types, pollinator syndromes or proportion of dioecious species. Islands did have significantly fewer species of low stature and significantly more species that survive fire only as seed and not by resprouting. We infer that the main cause of species loss is change in disturbance frequency. Islands have fewer fires and lose species dependent on frequent fires. We predict that island effects could be reduced by judicious fire management of small reserves.