Change of Dufour gland contents with age of workers of Formica sanguinea (Hymenoptera: Formicidae)

ABSTRACT The Dufour glands of newly emerged adult workers of F.sanguinea Latr. are almost empty, but the gland fills slowly over several months. The amount and composition of the secretion varies between individuals but the mean values change with age, the composition reaching its final value only in old foraging workers. Undecane is the major component for most of the period, but its proportion decreases with age. The amount of (Z,E)-α-farnesene increases with age and finally becomes the major component. The change in composition may reflect changes in worker function.     

Ciliates as engineers of phototrophic biofilms

1. Phototrophic biofilms consist of a matrix of phototrophs, non‐photosynthetic bacteria and extracellular polymeric substances (EPS) which is spatially structured. Despite widespread exploitation of algae and bacteria within phototrophic biofilms, for example by protozoans, the ‘engineering’ effects of these ciliates on the spatial heterogeneity of phototrophic biofilms are poorly studied. 2. We studied the potential engineering effects of two ciliates, Urostyla sp. and Paramecium bursaria, on the spatial heterogeneity of synthetic multispecies biofilms. Biomass of phototrophic organisms, EPS and bacteria was analysed three dimensionally using confocal laser scanning microscopy. Spatial heterogeneity and cover of the phototrophs, bacteria and EPS were determined at several depths within the biofilm. 3. Ciliate species did not interfere with the overall development of phototrophic microorganisms, because the thickness of the biofilm was equal whether the ciliates were present or not, even though their abundance did affect spatial heterogeneity of biofilm components. When Urostyla was present, it reduced aggregation in EPS and bacteria and increased EPS biovolume. This implies a local facilitating effect of ciliates on photosynthetic activity. Biofilms to which Paramecium was added did not differ from controls in terms of phototrophs, EPS cover and biovolume. Nevertheless, ciliates affected the spatial heterogeneity of these components as phototrophs and EPS became more evenly distributed. 4. This study shows that ecosystem engineering by organisms does not only occur at large spatial scales, as in grasslands and estuaries, but also plays a role at the microscopic scale of biofilms. This effect on spatial heterogeneity was not driven by substantial exploitation of biofilm components, but via the subtle engineering effects of ciliates.     

Colony stage and not facultative policing explains pattern of worker reproduction in the Saxon wasp

Inclusive fitness theory predicts that in colonies of social Hymenoptera headed by a multiple‐mated queen, workers should benefit from policing eggs laid by other workers. Foster & Ratnieks provided evidence that in the vespine wasp Dolichovespula saxonica, workers police other workers’ eggs only in colonies headed by a multiple‐mated queen, but not in those headed by a single‐mated one. This conclusion, however, was based on a relatively small sample size, and the original study did not control for possible confounding variables such as the seasonal colony progression of the nests. Our aim, therefore, was to reinvestigate whether or not facultative worker policing occurs in D. saxonica. Remarkably, our data show that in the studied Danish population, there was no correlation between worker–worker relatedness and the percentage of worker‐derived males. In addition, we show that variability in cuticular hydrocarbon profiles among the workers did not significantly correlate with relatedness and that workers therefore probably did not have sufficient information on queen mating frequency from the workers’ cuticular hydrocarbon profiles. Hence, there was no evidence that workers facultatively policed other workers’ eggs in response to queen mating frequency. Nevertheless, our data do show that the seasonal progression of the nest and the location in which the males were reared both explain the patterns of worker reproduction found. Overall, our results suggest that the earlier evidence for facultative worker policing in D. saxonica may have been caused by accidental correlations with certain confounding variables, or, alternatively, that there are large interpopulation differences in the expression of worker policing.     

Viability of ecological processes in small Afromontane forest patches in South Africa

Abstract The conservation of biodiversity is dependent on protecting ecosystem‐level processes. We investigated the effects of fragment size and habitat edge on the relative functioning of three ecological processes – decomposition, predation and regeneration of trees – in small Afromontane forests in KwaZulu‐Natal, South Africa. Ten sampling stations were placed in each of four forest categories: the interior of three large indigenous forest fragments (100 m from the edge), the edges of these large fragments, 10 small indigenous fragments (<1 ha) and 10 small exotic woodlands (<0.5 ha). Fragment size and edge effects did not affect the abundance of the amphipod Talitriator africana, a litter decomposer, and overall dung beetle abundance and species richness significantly. Bird egg predation was marginally greater at large patch edges compared with the other forest categories, while seed predation did not differ among forest categories. Tree seedling assemblage composition did not differ significantly among large patch interiors and edges, and small indigenous fragments. Sapling and canopy assemblage composition each differed significantly among these three indigenous forest categories. Thus, while tree recruitment was not negatively affected by patch size or distance from the edge, conditions in small fragments and at edges appear to affect the composition of advanced tree regeneration. These ecological processes in Afromontane forests appear to be resilient to fragmentation effects. We speculate that this is because the organisms in these forests have evolved under fragmented conditions. Repeated extreme changes in climate and vegetation over the Pleistocene have acted as significant distribution and ecological extinction filters on these southern hemisphere forest biota, resulting in fauna and flora that are potentially resilient to contemporary fragmentation effects. We argue that because small patches and habitat edges appear to be ecologically viable they should be included in future conservation decisions.     

ANACORACID SHARKS FROM THE ALBIAN (LOWER CRETACEOUS) PAWPAW SHALE OF TEXAS

Abstract:  Recent collecting from the Pawpaw Shale in north-east Texas has yielded several hundred teeth of anacoracid sharks. The material allows for a much-needed revision of the Late Albian anacoracids from North America. The previously recognized Squalicorax sp., also referred to as S. volgensis in more recent publications, is a mix of two different species: S. priscoserratus sp. nov. and S. pawpawensis sp. nov. In addition to these two new species, a single tooth is assigned to S . aff. S. baharijensis . Our data indicate that anacoracids were a considerably more diverse group in the North American Cretaceous than previously thought. We attribute much of the underestimation of diversity to vague species concepts, poor preparation techniques and the associated lack of attention to certain dental features, in particular neck morphology, root surface porosity and the root's vascularization.     

Genetic variation and evolution in the genus Apodemus (Muridae: Rodentia)

Genetic variation was studied using protein electrophoresis of 28–38 gene loci in 1347 specimens of Apodemus agrar-ius, A. peninsulae, A. flavicollis, A. sylvaticus, A. alpicola, A. uralensis, A . cf. hyrcanicus, A. hermonensis, A. m. mystacinus and A. m. epimelas , representing 121 populations from Europe, the Middle East, and North Africa. Mean values of heterozygosity per locus for each species ranged from 0.02 to 0.04. Mean values of Nel's genetic distance ( D ) between the taxa ranged from 0.06 (between A. flavicollis and A. alpicola) to 1.34 (between A. uralensis and A. agrarius ). The highest values of D were found between A. agrarius and other Apodemus species (0.62-1.34). These values correspond to those generally observed between genera in small mammals. Our data show that A. agrarius and A. peninsulae are sister species, well-differentiated from other taxa. High genetic distance between A. m. mystacinus and A. m. epimelas leads us to consider them distinct species and sister taxa to other Western Palaearctic species of the subgenus Sylvaemus . The data also suggest a recent separation of members of the latter group from a common ancestor, and subsequent rapid radiation, making it difficult to infer phylogenetic relationships. Some taxonomic implications of the results are discussed further.© 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 75 , 395–419.     

THE NON-HUMAN PRIMATE ENDOCRINE PANCREAS: DEVELOPMENT,REGENERATION POTENTIAL AND METAPLASIA

An investigation into the development of the Vervet monkey endocrine pancreas revealed a sequence of occurrence of pancreatic peptides that differed from previous reports in mice, dog and human with PP and somatostatin occurring before glucagon and insulin. All four pancreatic peptides were identified, immunohistochemically, in only one of the pancreatic primordial buds, before fusion of the two buds to form the pancreas. This questions the hypothesis that the heterogeneous endocrine cell distribution seen in the adult pancreas is due to the contribution of only PP cells by the ventral bud and non-PP cells by the dorsal bud. Co-localization of glucagon and PP was observed extensively in the developing pancreas and the predominant expression of one over the other in an apparently organized non-random manner accounted for the glucagon- and PP-rich areas seen in the developing pancreas. A small number of cells immunoreactive to glucagon and PP were also observed in the adult. Reports of plasticity of differentiation of other pancreatic cells led us to investigate regeneration potential of the adult monkey pancreas. Partial obstruction of the Vervet monkey main pancreatic duct, by cellophane wrapping, resulted in duct cell proliferation and differentiation to form new endocrine tissue in a way that mimics normal organogenesis. Focal areas of hepatocytes were found in the regenerated pancreas of one monkey, illustrating further the latent developmental capabilities of adult pancreas cells. These findings could lead to interesting new therapies for pancreas and liver disease.     

Floating mats: their occurrence and influence on shoreline distribution of emergent vegetation

1. A study was conducted on the northern shore of Lake Victoria (Uganda) to determine the factors controlling the occurrence of floating root mats and the influence of the floating mats on the distribution of emergent vegetation. 2. Environmental conditions within 78 bays in the study area were characterised using bay size, wave exposure, water depth, littoral slope, sediment characteristics and water level fluctuations. Emergent plants that form floating root mats occur along the shores of these bays. The way in which commonly occurring shoreline vegetation was distributed across a wave‐exposure gradient was compared with their distribution across a water level fluctuation gradient. 3. Results suggested that wind–wave action and water level fluctuations are important factors determining the occurrence of floating mats. Mat‐forming plants occur in the most sheltered locations along the shore and in waterbodies with modest water level fluctuations. 4. The ability to form mats facilitated the lakeward expansion of emergent plants. Plants forming floating root mats had a larger depth range than non‐mat forming plants. 5. The initiation mechanisms for the floating mats of emergent vegetation in Lake Victoria appear to be: (i) invasion of mats of free‐floating plants by emergent vegetation; and (ii) detachment of emergent plants from the lake bed following flooding. 6. The formation of floating mats comes with a cost and benefit to emergent plants. The cost is increased vulnerability to damage by water level fluctuations or wind–wave action, leading to reduced horizontal distribution. The benefit is that deep flooding is avoided, thus increasing vertical distribution. The net effect may be to lead to dominance of mat‐forming plants in low‐energy environments and non‐mat‐forming plants in high‐energy environments.     

Total soil C and N sequestration in a grassland following 10 years of free air CO2 enrichment

Soil C sequestration may mitigate rising levels of atmospheric CO_2. However, it has yet to be determined whether net soil C sequestration occurs in N‐rich grasslands exposed to long‐term elevated CO₂. This study examined whether N‐fertilized grasslands exposed to elevated CO₂ sequestered additional C. For 10 years, Lolium perenne, Trifolium repens, and the mixture of L. perenne/T. repens grasslands were exposed to ambient and elevated CO₂ concentrations (35 and 60 Pa pCO₂). The applied CO₂ was depleted in δ¹³C and the grasslands received low (140 kg ha^?1) and high (560 kg ha^?1) rates of ¹⁵N‐labeled fertilizer. Annually collected soil samples from the top 10 cm of the grassland soils allowed us to follow the sequestration of new C in the surface soil layer. For the first time, we were able to collect dual‐labeled soil samples to a depth of 75 cm after 10 years of elevated CO₂ and determine the total amount of new soil C and N sequestered in the whole soil profile. Elevated CO₂, N‐fertilization rate, and species had no significant effect on total soil C. On average 9.4 Mg new C ha^?1 was sequestered, which corresponds to 26.5% of the total C. The mean residence time of the C present in the 0–10 cm soil depth was calculated at 4.6±1.5 and 3.1±1.1 years for L. perenne and T. repens soil, respectively. After 10 years, total soil N and C in the 0–75 cm soil depth was unaffected by CO₂ concentration, N‐fertilization rate and plant species. The total amount of ¹⁵N‐fertilizer sequestered in the 0–75 cm soil depth was also unaffected by CO₂ concentration, but significantly more ¹⁵N was sequestered in the L. perenne compared with the T. repens swards: 620 vs. 452 kg ha^?1 at the high rate and 234 vs. 133 kg ha^?1 at the low rate of N fertilization. Intermediate values of ¹⁵N recovery were found in the mixture. The fertilizer derived N amounted to 2.8% of total N for the low rate and increased to 8.6% for the high rate of N application. On average, 13.9% of the applied ¹⁵N‐fertilizer was recovered in the 0–75 cm soil depth in soil organic matter in the L. perenne sward, whereas 8.8% was recovered under the T. repens swards, indicating that the N₂‐fixing T. repens system was less effective in sequestering applied N than the non‐N₂‐fixing L. perenne system. Prolonged elevated CO₂ did not lead to an increase in whole soil profile C and N in these fertilized pastures. The potential use of fertilized and regular cut pastures as a net soil C sink under long‐term elevated CO₂ appears to be limited and will likely not significantly contribute to the mitigation of anthropogenic C emissions.