Allogeneic interactions in Hydractinia: is the transitory chimera beneficial?

The colonial marine hydroid, Hydractinia, exhibits four possible outcomes to allogeneic contacts: passive rejection, aggressive rejection, stable fusion and transitory fusion. In the special case of transitory fusion, Hydractinia colonies undergo tissue fusion, followed by tissue death at the original contact area, and colony separation. This type of rejection is different in several aspects from the rejection process that accompanies incompatible encounters. It has been suggested that in transitory fusion, the colonies gain immediate benefits from fusion, mainly due to size increase, without succumbing to costs associated with fusion (germ line parasitism). We report a long-term observation of repeated fusion and separation cycles in clones featuring transitory fusion that revealed a slow-down of specific growth rates following fusion, and recovery in growth rates following separation. Very rapid transfer of stained material between partners in transitory chimeras provides suggestive evidence that protection against germ line parasitism is far from being guaranteed by separation. Our data cast doubt as to whether the benefits considered for transitory fusion are sustainable and support the already made suggestion that fusion with self, rather than fusion with kin, has been the major selective force governing the evolution of allorecognition in colonial invertebrates.     

Novel intron markers to study the phylogeny of closely related mammalian species

Background  

Multilocus phylogenies can be used to infer the species tree of a group of closely related species. In species trees, the nodes represent the actual separation between species, thus providing essential information about their evolutionary history. In addition, multilocus phylogenies can help in analyses of species delimitation, gene flow and genetic differentiation within species. However, few adequate markers are available for such studies.     

Craniodental variation in the African macaque, with reference to various Asian species

Based on twenty-seven craniodental measurements and ratios derived from them, the relationship between the African macaque (M. sylvanus) and the others in Asia were examined with principal components analyses (PCA) and Euclidean distance analysis based upon prior discriminant function analyses (DFA). Results based on analyses of raw measurements indicate that the variation between species lies in the first axis of PCA; the species are dispersed according to their differences in size. The variation between sexes (sexual dimorphism) lies in the second axis. In the analyses of ratio variables, though these two patterns of separation remain orthogonal, they lie at approximately forty-five degrees to each axis. Variables relating to anterior teeth were found to play an important role in variation analysis, and this may be related to the special food preferences of these monkeys: more frequent usage of the incisor teeth for processing frugivorous diets than in other primates that are mainly folivorous. The results from Euclidean distance analyses indicate that the average distance of species within the Asian group is shorter than that between Asian and African groups regardless of sex and variable type. In addition the variation between African and Asian groups is larger than that within Asian group. Thus, it is reasonable to suggest that the African macaque has a range of measurements and ratios quite distinct from the species found in Asia (though the greatest separations result from the analyses of ratio data). These results therefore support the view that M. sylvanus may be regarded as an independent species group in the genus Macaca as proposed by Delson [1980].     

Absidia parricida plays a dominant role in biotrophic fusion parasitism among mucoralean fungi (Zygomycetes): Lentamyces, a new genus for A. parricida and A. zychae

Within the order Mucorales (Zygomycetes), the facultative parasites Parasitella parasitica , Chaetocladium brefeldii , Chaetocladium jonesii and Absidia parricida are known to initiate biotrophic fusion parasitic interactions on a wide variety of other mucoralean hosts. Their phylogenetic relationship within the Mucorales and their ability to form parasitic structures with several known host species was examined. Together with interspecific reactions between the mycoparasites, this study found: (i) no evident differences in the spectrum of non-parasitic hosts tested within the study; (ii) A. parricida parasitises all other fusion parasites; (iii) A. parricida is ancestral to all other parasites; (iv) A. parricida is reported for the first time as phylogenetically basal to all other mucoralean fungi except the Umbelopsidaceae and (v) based on phylogenetic analyses and physiological and morphological characteristics, the slow-growing species A. parricida and Absidia zychae are removed from the genus Absidia and reclassified in the newly described genus Lentamyces .     

Coltriciella minuscula sp. nov., a new species of poroid fungus on Pinus merkusii from an Indonesian tropical forest

Coltriciella minuscula sp. nov. is described and illustrated from a specimen collected on Pinus merkusii from Bogor, Indonesia. This species is characterized by the size of its basidiocarp up to 4 mm in diam, with long hair on the stipe and with ornamented spores. Both morphological distinctiveness and phylogenetic separation based upon analyses of nrDNA ITS sequences support the establishment of this new species. Morphological dissimilarities between C. minuscula and closely related species are discussed.     

Correspondence of seed traits with niche position in glacier foreland succession

Changes in species composition during succession are driven by biotic and abiotic factors leading to a multitude of niches occupied by distinct species. Gradient analyses of plant communities provide opportunities to approximate the niche position of species along a successional gradient. Several plant traits have been used to explain mechanisms governing successional sequences, but generalising changes in species traits during primary succession is still controversial. This study examined whether the seed mass and the optimum temperature for germination could explain the niche position of several glacier foreland species along a primary successional gradient in the Austrian Central Alps. We hypothesised that pioneer species should possess lighter seeds and a lower optimum temperature for germination than late successional species. We found significant differences in the seed mass between species, but the seed mass did not correspond with the assigned niche position on the successional gradient. Germination responses to temperature also differed significantly between species. Pioneer species performed better at lower temperatures than late successional species, suggesting that the optimum temperature for germination is a driver of niche separation. We discuss the interactions between seed traits and environmental conditions along the primary successional gradient emphasising the importance of temperature requirements for the germination. Differences in the regeneration characteristics are a major cue governing species turnover in glacier foreland succession.     

Functional aspects of primate pelvic structure: A multivariate approach

This study aims to clarify the relationship of primate bony pelvic structure to locomotor habit. As with most of the postcranial skeleton, the pelvic bones of species within the Ceboidea and the Cercopithecoidea are remarkably similar visually except for variations in size. Yet there are substantial differences in locomotor pattern between the species in these taxa. I performed canonical analyses on a sample of 17 pelvic variables describing 22 primate species of the Ceboidea, the Cercopithecoidea, and the Hominoidea to discover which variables were significant in separating them into groups. In both analyses there was good separation of major taxa and additional separation of groups that differed in locomotor habit. The separation of colobine from cercopithecine monkeys was particularly consistent. In the analysis, including all 22 species, the variables given particular weight by the canonical analysis were the same as those traditionally used by anatomists for the same purpose. Specifically, breadth of the ischial tuberosity (reflecting presence or absence of ischial callosities) separated the Old from the New World monkeys. Breadth of the iliac tuberosity, in which man and to some extent other hominoids differ from other primates, and ilium height, in which man differs from other primates, were significant. Sagittal diameter of the pelvis was also substantially weighted. Having established that the technique would select variables of anatomical significance, the same method was applied to a study of monkeys only where the characteristics that differ between groups are not well established. Breadth of the ischial tuberosity was again important in separating the Ceboidea from the Cercopithecoidea. Discrimination of locomotor groups within these large divisions was brought about mainly by ischial length and the sagittal diameter of the pelvis. In studying these variables and their relationship to size in greater detail, it was found that among cercopithecoid monkeys, the colobines showed relatively lower values than did cercopithecines for both these dimensions. Atelines showed low values for ischial length but high values for the sagittal pelvic diameter. Biomechanical explanations of these observations are suggested.     

Multivariate analysis of the phenotypic relationships of the species of Paragalaxias and Galaxias (Pisces: Galaxiidae) in Tasmania

The 10 species of Galaxias in Tasmania, G. olidus from mainland Australia and the four species of Paragalaxias were studied using principal co-ordinates analysis (PCOA) and cluster analysis of a standardized Euclidean distance matrix based upon variate means, and by canonical variate analysis (CVA) conducted as a stepwise multiple discriminant analysis. Thirty-five variables comprising 30 morphometric and five meristic characters were analysed. The meristic characters were not included in the CVA. Excellent separation of the two genera was achieved in all analyses. The multivariate analyses were repeated on each genus separately to see if relationships suggested by the overall analysis remain stable. When the resultant groupings of species are compared for the different analyses, no consistent, distinct groupings of species within each genus are apparent. Despite the absence of distinct groupings, some trends in the affinities of some species are evident. In particular, species affinities as indicated by the CVA are more consistent with established opinions of species relationships. From the results of the study it is suggested that caution be exercised in the application of multivariate statistical analyses of morphological data to ichthyological systematics and phylogeny.     

Musical chairs during mitophagy

Mitophagy, or the autophagic degradation of mitochondria, is thought to be important in mitochondrial quality control, and hence in cellular physiology. Defects in mitophagy correlate with late onset pathologies and aging. Here, we discuss recent results that shed light on the interrelationship between mitophagy and mitochondrial dynamics, based on proteomic analyses of protein dynamics in wild-type and mutant cells. These studies show that different mitochondrial matrix proteins undergo mitophagy at different rates, and that the rate differences are affected by mitochondrial dynamics. These results are consistent with models in which phase separation within the mitochondrial matrix leads to unequal segregation of proteins during mitochondrial fission. Repeated fusion and fission cycles may thus lead to “distillation” of components that are destined for degradation.     

A PCR-based method to distinguish the sibling species Stylonychia mytilus and Stylonychia lemnae (Ciliophora, Spirotrichea) using isocitrate dehydrogenase gene sequences

A differentiation, based on morphological characters, between Stylonychia mytilus and Stylonychia lemnae is very difficult, especially for non-specialists. These two sibling species were considered as one species, S. mytilus, until detailed cytological and genetic studies could show the existence of two genetically isolated varieties. Further morphological and biochemical analyses verified the separation and finally in 1983 a new species S. lemnae was described. The examination of several isoenzymes revealed unambiguous differences in the banding pattern of isocitrate dehydrogenase (IDH) between these two species. Therefore, the IDH gene of 30 isolates of S. lemnae and S. mytilus coming from various regions all over the world were amplified and sequenced. The sequence analyses revealed intraspecific as well as interspecific substitutions, which were used for the development of species-specific PCR primers for both species. Application of these species-specific primer pairs now allows a very easy and clear identification of both sibling species.     

Cell-cell fusion

Cell-cell fusion is a highly regulated and dramatic cellular event that is required for development and homeostasis. Fusion may also play a role in the development of cancer and in tissue repair by stem cells. While virus-cell fusion and the fusion of intracellular membranes have been the subject of intense investigation during the past decade, cell-cell fusion remains poorly understood. Given the importance of this cell-biological phenomenon, a number of investigators have begun analyses of the molecular mechanisms that mediate the specialized fusion events of a variety of cell types and species. We discuss recent genetic and biochemical studies that are beginning to yield exciting insights into the fusion mechanisms of Saccharomyces cerevisiae mating pairs, Caenorhabditis elegans epithelial cells and gametes, Drosophila melanogaster and mammalian myoblasts, and mammalian macrophages.     

Small mammal abundance in relation to microhabitat in a dry sub-humid grassland in Kenya

Six species of rodents and two species of insectivores, live-trapped on a 1 ha grid over a 27 month period, were studied in relation to microhabitat factors in a dry sub-humid grassland in Kenya. Wet season peaks of small mammal species were followed by low numbers trapped during the dry seasons. Species distributions were correlated with different microhabitat parameters, and the separation of species with apparently similar environmental requirements could be explained largely in terms of current knowledge of the biology of the species. Correlation analyses indicated an ecological separation of two closely-related Mus species and of two Crocidura shrews. Overlap indices were extremely high, ranging from 0.556 to 0.877 for all combinations of pairs of species. It seems likely that neither food nor micro-habitat partitioning completely explains the coexistence of the small mammal species and it is suggested that populations are highly transient, moving from refuge areas into temporarily favourable areas during the wet season.     

The unusual gynoecium structure and extragynoecial pollen-tube pathway in <Emphasis Type="Italic">Phytolacca</Emphasis> (Phytolaccaceae)

The fusion of carpels into a unified compound gynoecium is considered a dominant feature of angiosperm evolution and it also occurs by postgenital fusion during the gynoecium development in some apocarpous species. However, we found the reverse process, the separation of carpels from combined carpel primordia, during the development of the gynoecium in Phytolacca. Semithin sectioning and scanning electron microscopy were utilised to observe the structure and development of the gynoecia in Phytolacca acinosa and Phytolacca americana, fluorescence microscopy was utilised to observe the pollen tube growth in the gynoecia of the two species, and the topology method was applied to analyze the relationship between the gynoecium structure and pollen tube pathway. Although the gynoecia of P. acinosa and P. americana are both syncarpous, the degree of carpel fusion in the mature gynoecia of the two syncarpous species is different as a result of variant developmental processes. However, change in the degree of carpel fusion during the development of gynoecia in Phytolacca does not affect pollen tube growth because of the existence of the extragynoecial pollen-tube pathway. Thus, the change in the degree of carpel fusion in Phytolacca is primarily the result of diversification of developmental processes related to selection pressure.     

Evolutionary relationships between Saccharomyces cerevisiae and other fungal species as determined from genome comparisons

The increasing number of fungal genomes whose sequence has been completed permits their comparison both at the nucleotide and protein levels. The information thus obtained improves our knowledge on evolutionary relationships between fungi. Comparison of the Saccharomyces cerevisiae genome with other Hemiascomycetes genomes confirms that a whole-genome duplication occurred before the diversification between Candida glabrata and the Saccharomyces sensu stricto species and after separation from the branch leading to the other Hemiascomycetes. Duplication was followed by individual gene losses and rearrangements affecting extensive DNA regions. Although S. cerevisiae and C. glabrata are two closely related yeast species at an evolutionary scale, their different habitats and life styles correlate with specific gene differences and with more extensive gene loses having occurred in the parasitic C. glabrata. At a closer evolutive scale, diversification among the sensu stricto species began with nucleotide changes at the intergenic regions affecting sequences that are not relevant for gene regulation, together with more extensive genome rearrangements involving transposons and telomeric regions. One important characteristic of fungal genomes that is shared with other eukaryotes is the fusion of gene sequences coding for separate protein modules into a single open reading frame. This allows diversification of protein functions while saving gene information.     

Some aspects on the morphology and ecology of Rhodomonas minuta var. nannoplanctica and R. lens (Cryptophyceae) in two Greek lakes

Significant morphological and ecological differences between Rhodomonas minuta var. nannoplanctica and R. lens were observed during the study of phytoplankton in two Greek lakes. The shape and size characteristics support the validity of these species, so the fusion of closely related species of Rhodomonas proposed by Javornicky is not accepted in this study. Apart from the morphological differences between Rhodomonas minuta var. nannoplanctica and R. lens contrasting ecological requirements were noticed. A broader distribution of Rhodomonas minuta var. nannoplanctica in relation to temperature and pH and a preference for lower nutrient concentrations than R. lens were found. The two taxa may coexist by shifting their niches at different times in Lake Volvi and by vertical niche separation in Lake Vegoritis.     

Musical chairs during mitophagy

Mitophagy, or the autophagic degradation of mitochondria, is thought to be important in mitochondrial quality control, and hence in cellular physiology. Defects in mitophagy correlate with late onset pathologies and aging. Here, we discuss recent results that shed light on the interrelationship between mitophagy and mitochondrial dynamics, based on proteomic analyses of protein dynamics in wild-type and mutant cells. These studies show that different mitochondrial matrix proteins undergo mitophagy at different rates, and that the rate differences are affected by mitochondrial dynamics. These results are consistent with models in which phase separation within the mitochondrial matrix leads to unequal segregation of proteins during mitochondrial fission. Repeated fusion and fission cycles may thus lead to “distillation” of components that are destined for degradation.     

Distribution of cave-dwelling bats and conservation status of underground habitats in the Istanbul area

Populations of cave-dwelling bat species were investigated in the transitory region between the Eastern Thrace and the Western Pontus. Data were collected during 30 surveys in 13 underground sites, 10 of which had not been surveyed previously by bat researchers, between March 1999 and March 2000. Approximately 20 000 bats representing eight species were recorded. Grouping the sites according to their ecological resemblance, by means of cluster and correspondence analyses, yielded different results for the summer and winter data. In summer, there was a partial separation of the sites by their location in biogeographic regions. In winter, no regional grouping was observed. It was concluded that in the transitory region, species distribution does not differ considerably between the Eastern Thracian and Western Pontic ecosystems. In addition, a conservation scoring system is proposed for those sites investigated, their status is evaluated, and the most important local roosts are identified.     

Comparative Morphometrics and Associated Growth Trends of Two Benthophagous Cichlid Species from Lake Malawi (Pisces, Perciformes)

Body shape differences between two benthophagous, sympatric cichlid species, Ctenopharynx pictus and Otopharynx sp. “heterodon nankhumba” were examined for 14 morphometric characters using measurements obtained from 11 morphological landmarks and additional 6 characters from the head region using principal component and regression analyses. The two species, though not closely related, superficially resemble each other and, being benthic feeders, directly compete for food resources unless morphological differences lead to trophic specialization. Hence, the present study explores the presence of such morphological variations. Principal component analysis (PCA), revealed that only four characters loaded highly on PC II and, therefore, account for most of the variations in the external morphology between the two species. C. pictus has longer lower jaws reflecting longer gape, and a shorter abdominal cavity than O. sp. “heterodon nakhumba”. The regression analyses showed significant differences in the allometric coefficients of the lower jaw and abdominal cavity, which might have contributed to differences in overall shape detected between the two species. The difference in gape size between the two species may be related to different feeding habits employed by each species, and such specializations are suggested to reduce interspecific competition for food resources. We suggest that the ensuing ecological separation promotes sympatry of these two species.     

Phytosociological and conservational study of the arable weed communities in western Hungary

Abstract

The present study surveyed the weed vegetation on extensively managed arable fields and unsprayed field edges in western Hungary, based on 1698 phytosociological relevés collected between 1995 and 2005. The separation of the 15 vegetation units was conducted with the traditional comparative tabular method, and the diagnostic species were determined with statistical fidelity measures. The numerical analyses show that the most important factor in the separation of weed communities is the fluctuating proportions of winter and summer annuals and cosmopolitan elements throughout the year. Soil chemical properties are the second most important whereas soil texture and climatic factors also contribute to the development of weed communities. The surveyed vegetation units support 41 red list weed species. Across all associations, the average proportion of insect-pollinated plant species is 68%, and the average proportion providing weed seed food sources for farmland birds is 47%. These factors illustrate the importance of weed communities in agro-ecosystem function and the need for their conservation.