Composition,spatial and temporal variability of the soil seed pool in a Eucalyptus populnea shrub woodland in central New South Wales

Three sites in a Eucalyptus populnea woodland in central New South Wales were sampled for the number and composition of seed in the surface cm of soil. There was a total of 3200 seeds/m² beneath eucalypt canopy, 13800 seeds/m² in grassy inter-tree areas and 4000 seeds/m² in bare inter-tree areas in April, 1975. These numbers were reduced by 23, 73 and 66% respectively during the subsequent 10 months, when there was no addition of seed. This decline was thought to be mainly due to predation, with germination as a secondary factor. Species composition of the seed pool differed between the three sites with seed of some species being only found beneath the eucalypt canopy or in the inter-tree areas. There were no seeds that were not present as plants in the community. Any attempts to restore this woodland to its former grassy nature should take into account the low seed population of many of the formerly common grass species and the high number of shrub seeds (>200/m²). Species distribution of seed was highly heterogeneous making adequate sampling very difficult. Extracting and identifying the seed took 8 to 12 man-h per 100 g sample.     

Ionotropic Nucleation of Calcium Carbonate by Molluscan Matrix

The hydrophilic, sulfated fraction of the organic matrix foundin molluscan shells appears to be involved in crystal nucleation.It is located primarily at the sites of initial nucleation.The hydrophilic fraction favors in vitro formation of calcifieddeposits, when it is fixed in place on the hydrophobic fraction.Calcium is bound by the hydrophillic fraction with high affinityand selectivity. Enzymatic desulfation reduces the calcium binding.However, the binding stoichiometry of one calcium for everytwo ester sulfates is not altered. The calcium binding induceslocal anion binding, which induces secondary calcium binding.This coordinated ion binding is known as ionotropy. The resultantlocal high concentration of ions is thought to bring about nucleation.     

Eubrachythoracid arthrodires from Gogo, Western Australia

Two monotypic genera of coccosteoid eubrachythoracid arthrodires are described from the Upper Devonian Gogo Formation of Western Australia as Compagopiscis gen. nov. and Gogopiscis gen. nov. They are most closely related to Torosteus Gardiner & Miles, also from the Gogo Formation, and all three are placed in the family Plourdosteidae Vezina, 1990; Compagopiscis and Gogopiscis are jointly the sister-group of Torosteus.     

Population Differentiation in Locomotor Performance and the Potential Response of a Terrestrial Organism to Global Environmental Change

SYNOPSIS. Models of global climate change predict an increasein the mean surface temperature between 1.5° and 4.5°Cby the middle of the next century. Even a moderate increaseof 3°C is likely to result in a shift in the distributionof North American habitat types and vegetational associations,either in latitude or elevation or both. The challenge to ConservationBiology is to predict the responses of terrestrial organismsto the expected alteration in habitats and ecosystems. Recentbiophysical models have been expanded to demonstrate the intimateassociations between the thermal environment, organismal physiologyand ecology. Thus, the expected turnover in habitats may havea profound influence on the distribution of organisms. I describeone possible approach that couples temporal and spatial variationin an ecologically relevant physiological trait, locomotoryperformance, in a widespread species of lizard, Urosaurus ornatus,to predict the expected response of species to global change. Estimates of maximum velocity and endurance capacity were obtainedfrom 16 populations throughout the range of U. ornatus. Informationon spatial variation was supplemented with data on temporalvariation spanning an eight year period from a single referencepopulation. I used thesedata to address two questions: 1) isthere an association between locomotory performance and theexpected habitat changes predicted from global climate modelsand 2) is there sufficient variation within a population torespond to habitat modification. Populations of U. ornatus varied significantly in sprint speedand stamina. Several environmental factors expected to correlatewith global climatechange were evaluated using the patternsof variation in locomotor performance. Results from this studysuggest that high elevation populations found in ponderosa pineforests should be most susceptible to changes in climate. Within-populationvariation was found to span the range of variation seen amongpopulations and was sensitive to temporal variation in climaticconditions. Given the expected and rapid change in environments,small, ectothermic, terrestrial species may not have the abilityto modify their geographic distribution. However, the resultspresented here suggest that only certain populations are atrisk; yet the evolutionary response of the population may belong relative to the rate of environment change.