Dispersal limitations, rather than bottlenecks or habitat specificity, can restrict the distribution of rare and endemic rainforest trees

Despite their narrow distribution, Australian rainforests still contain considerable levels of diversity and include many ancient, but often rare, lineages. Very little is known about the general biology of rainforest species, yet their long-term management depends on a better understanding of the main factors leading to rarity. For instance, are they highly endemic taxa, at the early stages of expansion, nearing the end of a period of decline, or persisting at low numbers over the long term? In this study we combine molecular, environmental, and ecological data to identify the factors responsible for the narrow distribution of a paleoendemic rainforest tree: Elaeocarpus sedentarius (Elaeocarpaceae). Between-population and between-generation comparisons of genetic diversity across all known populations of E. sedentarius show evidence of mutation-drift equilibrium rather than evidence of a recent bottleneck. Similarly, floristic and environmental data negate the hypothesis of rarity as a consequence of highly specialized habitat requirements. Instead, genetic structure and the available ecological data support the hypothesis of dispersal limitation as the main cause of endemism and that the species may have attained genetic equilibrium without realizing its full niche potential. We suggest that these factors are likely to explain narrow endemism in a broader range of taxa.     

Definition of plant functional groups for informing implementation scenarios in resource-limited multi-species recovery planning

We describe an approach to multi-species recovery planning and bio-regional biodiversity assessment that uses trait-based plant functional groups as the basis for developing threat/risk assessments for rare, threatened and ‘of concern’ species. Multi-variate methods were used to extract and test emergent groups, and additional information fields related to species life history and distributional data were added to develop a species-level information assessment matrix in spreadsheet format. Relating emergent trait-based plant functional groups to habitat was found to be the most informative approach for the subsequent development of management recommendations and landscape scale threat/risk assessment to inform recovery planning. Examples on the use of the identified groups in a management context are provided. These include higher and lower resource and data availability scenarios, and the role of selected traits in adding to or ameliorating threats and risk of extinction.     

Diving physiology of birds: a history of studies on polar species

Our knowledge of avian diving physiology has been based primarily on research with polar species. Since Scholander's 1940 monograph, research has expanded from examination of the 'diving reflex' to studies of free-diving birds, and has included laboratory investigations of oxygen stores, muscle adaptations, pressure effects, and cardiovascular/metabolic responses to swimming exercise. Behavioral and energetic studies at sea have shown that common diving durations of many avian species exceed the calculated aerobic diving limits (ADL). Current physiological research is focused on factors, such as heart rate and temperature, which potentially affect the diving metabolic rate and duration of aerobic diving.     

Core alpha1-->3-fucose is a common modification of N-glycans in parasitic helminths and constitutes an important epitope for IgE from Haemonchus contortus infected sheep

Synthesis of parasite specific IgE plays a critical role in the defence against helminth infections. We report here that IgE from serum from Schistosoma mansoni infected mice and Haemonchus contortus infected sheep recognizes complex-type N-glycans from Arabidopsis thaliana, which contain R-GlcNAcbeta1-->4(Fucalpha1-->3)GlcNAcbeta1-Asn (core alpha1-->3-Fuc) and Xylbeta1-->2Manbeta1-->4GlcNAcbeta1-R (core beta1-->2-Xyl) modifications, and honeybee phospholipase A2, which carries N-glycans that contain the core alpha1-->3-Fuc epitope. Evidence is presented that core alpha1-->3-fucosylated N-glycans bind a substantial part of the parasite specific IgE in serum of H. contortus infected sheep. These results suggest that the core alpha1-->3-Fuc antigen may contribute to induction of a Th2 response leading to the production of IgE. In addition we show here that N-glycans carrying core alpha1-->3-Fuc and beta1-->2-Xyl antigens are synthesized by many parasitic helminths and also by the free living nematode Caenorhabditis elegans. Since N-glycans containing the core alpha1-->3-Fuc have also been implicated in honeybee and plant induced allergies, this conserved glycan might represent an important common IgE epitope.     

Heart rate and plasma lactate responses during submerged swimming and trained diving in California sea lions, Zalophus californianus

California sea lions, Zalophus californianus, were trained to elicit maximum voluntary breath holds during stationary underwater targeting, submerged swimming, and trained diving. Lowest heart rate during rest periods was 57 bpm. The heart rate profiles in all three protocols were dominated by a bradycardia of 20–50 bpm, and demonstrated that otariid diving heart rates were at or below resting heart rate. Venous blood samples were collected after submerged swimming periods of 1–3 min. Plasma lactate began to increase only after 2.3-min submersions. This rise in lactate and our inability to train sea lions to dive or swim submerged for periods longer than 3 min lead us to conclude that an aerobic limit had been reached. Due to the similarity of heart rate responses and swimming velocities recorded during submerged swimming and trained diving, this 2.3-min limit should approximate the aerobic dive limit in these 40-kg sea lions. Total body O₂ stores, based on measurements of blood and muscle O₂ stores in these animals, and prior lung O₂ store analyses, were 37–43 ml O₂ kg⁻¹. The aerobic dive limit, calculated with these O₂ stores and prior measurements of at-sea metabolic rates of sea lions, is 1.8–2 min, similar to that measured by the change in post-submersion lactate concentration. Accepted: 7 July 1996     

Evidence for a functional membrane barrier in the transition zone between the flagellum and cell body of Chlamydomonas eugametos gametes

Evidence is presented which supports the concept of a functional membrane barrier in the transition zone at the base of each flagellum of Chlamydomonas eugametos gametes. This makes it unlikely that agglutination factors present on the surface of the cell body can diffuse or be transported to the flagellar membrane. The evidence is as follows: 1) The glycoprotein composition of the flagellar membrane is very different to that of the cell-body plasma membrane. 2) The flagella of gametes treated with cycloheximide, tunicamycin or , -dipyridyl become non-agglutinable but the source of agglutination factors on the cell body is not affected. 3) Even under natural conditions when the flagella are non-agglutinable, for example in vis-à-vis pairs or in appropriate cell strains that are non-agglutinable in the dark, the cell bodies maintain the normal complement of active agglutinins. 4) When flagella of living cells are labeled with antibodies bound to fluorescein, the label does not diffuse onto the cell-body surface. 5) When gametes fuse to form vis-à-vis pairs, the original mating-type-specific antigenicity of each cell body is slowly lost (probably due to the antigens diffusing over both cell bodies), while the specific antigenicity of the flagellar surface is maintained. Even when the flagella of vis-à-vis pairs are regenerated from cell bodies with mixed antigenicity, the antigenicity of the flagella remains matingtype-specific. 6) Evidence is presented for the existence of a pool of agglutination factors within the cell bodies but not on the outer surface of the cells.Abbreviations and symbols CHI cycloheximide - GTC guaniline thiocyanate - mt ⁺/mt ^- mating type plus or minus - PAS Periodic-acid-Schiff reagent - SDS sodium dodecyl sulphate     

The influence of 400 r x-irradiation on the number and the localization of mature and immature goblet cells and Paneth cells in intestinal crypt and villus.

The influence of 400 R X-irradiation on the localization and the number of mature and immature goblet cells and Paneth cells in rat duodenal epithelium has been studied. At short times after irradiation, when the total proliferative activity in the crypts of Lieberkuhn is reduced, the proportion of mature and immature goblet cells of the total number of crypt cells was increased; also an absolute increase in the number of goblet cells in the crypts was found. The immature goblet cells were localized in the lower half of the crypt as in control animals, whereas the number of the mature cells increased over the whole crypt length. When the proliferative activity of the crypt cells increases again from 12 to 48 hr after irradiation the number of both types of goblet cells decreases. Between 48 and 72 hr, when the whole crypt is involved in proliferation, a second increase of both types of goblet cells was found. However, the localization of the immature goblet cells is no longer restricted to the lower half of the crypt but they also appear at the higher cell positions. On the villus no immature goblet cells were found and the changes in the numbers of mature goblet cells do reflect the changes induced by irradiation in the goblet cell population in the crypt. The absolute number and localization of Paneth cells did not change under the experimental conditions. The findings are discussed in relation to cell proliferation and differentiation processes in intestinal crypts.     

The effect of increased crypt cell proliferation on the activity and subcellular localization of esterases and alkaline phosphatase in the rat small intestine

Synopsis The activity and ultrastructural localization of alkaline phosphatase and esterase has been studied in normal rat intestine and after the increased crypt cell proliferation that occurs during recovery after 400 rad X-irradiation. Alkaline phosphatase activity is not present in crypt cells of normal intestine, but becomes apparent after the cell has migrated on to the villus. The enzyme is localized in the microvilli, along the lateral cell membranes and in dense bodies. Its activity increases 10 to 15-fold from the base to the tip of the villus. Morphometric analysis of the cell structureswhere this enzyme is localized reveals no marked changes in their relative proportions during crypt cell development.The expansion of the proliferative cell compartment along the whole length of the crypt which occurs during recovery after irradiation (72 hr after 400 rad X-irradiation) results in a marked reduction of alkaline phosphatase activity in the lower 10–15 cell positions at the base of the villus. During subsequent migration of these cells, the activity increases with cell age but normal values are not attained. From a morphometric analysis it was found that the ultrastructural development is similar to that in controls. These results suggest that during cell maturation, normal values for alkaline phosphatase activity are only attained after a 10–12 hr period of maturation in a non-proliferative state and only after the cell has migrated on to the functional villus compartment.In normal intestine, esterase activity shows a 3-fold increase from the bottom to the tip of the crypt and a 3 to 4-fold increase during migration up to the middle of the villus. Enzyme activity is localized in the endoplasmic reticulum, the dense bodies and the perinuclear space. Morphometric analyses reveal a 2 to 3-fold increase in the absolute size of these subcellular compartments during crypt cell differentiation and a 2-fold increase at the crypt-villus junction. The relative sizes increase 1.5-fold during crypt cell differentiation and at the time of transition of the cells on to the villus.Increased crypt cell proliferation after irradiation leads to a marked decrease in esterase activity both in crypts and villi. Morphometric analyses of electron micrographs indicate that these changes in activity are not related to any changes in the subcellular structures in which the enzyme is localized. It appears that the normal development of esterase activity depends both on the functional state of the cell and its localization in the crypt or villus.