The effect of fragment area on site‐level biodiversity

Habitat fragmentation accompanies habitat loss, and drives additional biodiversity change; but few global biodiversity models explicitly analyse the effects of both fragmentation and loss. Here we propose and test the hypothesis that, as fragment area increases, species density (the number of species in a standardised plot) will scale with an exponent given by the difference between the exponents of the species–area relationships for islands (z ~ 0.25) and in contiguous habitat (z ~ 0.15), and test whether scaling varies between land uses. We also investigate the scaling of overall abundance and rarefaction‐based richness, as some mechanisms make different predictions about how fragment area should affect them. The relevant data from the taxonomically and geographically broad PREDICTS database were used to model the three diversity measures, testing their scaling with fragment area and whether the scaling exponent varied among land uses (primary forest, secondary forest, plantation forest, cropland and pasture). In addition, the consistency of the response of species density to fragment area was tested across three well represented taxa (Magnoliopsida, Hymenoptera and ‘herptiles’). Species density and total abundance showed area‐scaling exponents of 0.07 and 0.16, respectively, and these exponents did not vary significantly among land uses; rarefaction‐based richness by contrast did not increase consistently with area. These results suggest that the area‐scaling of species density is driven by the area‐scaling of total abundance, with additive edge effects (species moving into the small fragments from the surroundings) opposing – but not fully overcoming – the effect of fragment area on overall density of individuals. The interaction between fragment area and higher taxon (plants, vertebrates and invertebrates), which remained in the rarefied richness model, indicates that mechanisms may vary among groups.     

Total sleep deprivation does not significantly degrade semantic encoding

ABSTRACT

Sleep deprivation impairs performance on cognitive tasks, but it is unclear which cognitive processes it degrades. We administered a semantic matching task with variable stimulus onset asynchrony (SOA) and both speeded and self-paced trial blocks. The task was administered at the baseline and 24 hours later after 30.8 hours of total sleep deprivation (TSD) or matching well-rested control. After sleep deprivation, the 20% slowest response times (RTs) were significantly increased. However, the semantic encoding time component of the RTs remained at baseline level. Thus, the performance impairment induced by sleep deprivation on this task occurred in cognitive processes downstream of semantic encoding.     

Effect of temperature on seed production in the invasive grass Glyceria maxima (Hartm.) Holmb. (Poaceae) in South Africa

Temperature is one of the main factors that determine sexual reproduction in terrestrial and emergent aquatic plant species. The effect of temperature on sexual reproduction and seed production of Glyceria maxima (Hartm.) Holmb. in the southern hemisphere is unknown. Glyceria maxima collections in February 2010 at three isolated infestations in KwaZulu-Natal failed to yield a single seed, only empty panicles. Laboratory experiments showed that vernalisation had no consistent effect on seed production. Field- and laboratory-grown plants produced seeds in the 2010/2011 season, because of having sufficient time at optimum temperatures required for seed production (1 491 and 1 585 hours, respectively), compared to a shorter period (1 352 hours) of suitable temperatures during the 2009/2010 growing season. An inadequate period of optimum temperatures (15–25°C) during seed production resulted in the lack of seeds in the field in the 2009/2010 growing season. This study showed that temperature and duration of exposure thereto during the seed-production period play vital roles in G. maxima sexual reproduction.     

Evidence for diet partitioning among three coexisting native freshwater fishes in South Africa's Cape Fold Ecoregion

The partitioning of limited resources commonly explains how different species can coexist within the same ecological community. In this 2010 study, the diets of three coexisting freshwater fishes (Cape galaxias Galaxias zebratus, n = 27; Cape kurper Sandelia capensis, n = 60; Breede River redfin Pseudobarbus burchelli, n = 77) were characterised and compared in three headwater streams in South Africa's Cape Fold Ecoregion using gut contents and stable isotope analyses. These data were analysed to ascertain whether the three species exploit distinct trophic niches. Both approaches provided evidence that these species occupy different trophic niches, though with some overlap. However, dietary differences among sites were not consistent and were probably influenced by site-specific factors like resource availability. Pseudobarbus burchelli had a broader niche breadth at Tierkloof Stream than the other two species, but not at Waaihoek or Tierstel Streams. Our results also suggest that P. burchelli consumed a more omnivorous diet than do the other two species, whereas S. capensis occupied a higher trophic position than the other two species and consumed vertebrates. Our findings suggest that these species occupy non-equivalent feeding niches in Cape Fold Ecoregion headwater streams, and that diet partitioning might facilitate their coexistence in these systems.     

Lactate dehydrogenase (LDH) gene duplication during chordate evolution: the cDNA sequence of the LDH of the tunicate Styela plicata

L-Lactate dehydrogenase (L-LDH, E.C. 1.1.1.27) is encoded by two or three loci in all vertebrates examined, with the exception of lampreys, which have a single LDH locus. Biochemical characterizations of LDH proteins have suggested that a gene duplication early in vertebrate evolution gave rise to Ldh-A and Ldh-B and that an additional locus, Ldh-C arose in a number of lineages more recently. Although some phylogenetic studies of LDH protein sequences have supported this pattern of gene duplication, others have contradicted it. In particular, a number of studies have suggested that Ldh-C represents the earliest divergence among vertebrate LDHs and that it may have diverged from the other loci well before the origin of vertebrates. Such hypotheses make explicit statements about the relationship of vertebrate and invertebrate LDHs, but to date, no closely related invertebrate LDH sequences have been available for comparison. We have attempted to provide further data on the timing of gene duplications leading to multiple vertebrate LDHs by determining the cDNA sequence of the LDH of the tunicate Styela plicata. Phylogenetic analyses of this and other LDH sequences provide strong support for the duplications giving rise to multiple vertebrate LDHs having occurred after vertebrates diverged from tunicates. The timing of these LDH duplications is consistent with data from a number of other gene families suggesting widespread gene duplication near the origin of vertebrates. With respect to the relationships among vertebrate LDHs, our data are not consistent with previous claims that Ldh-C represented the earliest divergence. However, the precise relationships among some of the main lineages of vertebrate LDHs were not resolved in our analyses.      

Flux Analysis of Glucose Metabolism in Rhizopus oryzae for the Purpose of Increasing Lactate Yields

A flux analysis of glucose metabolism in the filamentous fungus Rhizopus oryzae was achieved using a specific radioactivity curve-matching program, TFLUX. Glycolytic and tricarboxylic acid cycle intermediates labeled through the addition of extracellular [U-14C]glucose were isolated and purified for specific radioactivity determinations. This information, together with pool sizes and the rates of glucose utilization and end product production, provided input for flux maps of the metabolic network under two different experimental conditions. Based upon the flux analysis of this system, a mutant of R. oryzae with higher lactate and lower ethanol yields than the parent was sought for and found.     

Flowering phenology of Campanula on Mt Olynipos, Greece

We studied the fowering phenology of the genus Campanula (represented by nine species) along the elevation gradient of Mt Olympos (Greece) in order to assess whether there are elevation patterns at the genus level and whether these relate to patterns previously observed along such gradients at the community level. The traits examined were time and duration of the flowering period, flower life span, and duration of male and female flower phases. Floral attributes, such as number of flowers per plant, flower biomass, flower size, were also studied in order to examine whether they change with elevation or influence flower phenology. Flowering of Campanula species started in mid-May and ended in late September. The average duration of flowering of the genus was ca 27 d and the average floral longevity 4 d. In all but one species, the female phase lasted longer than the male. Campanula versicolor differed remarkably from all others in flower phenology and other floral trails. Nearly all Campanula populations studied had right or positively skewed flowering distributions indicating that flowering begins more abruptly than it ends. At the genus level, the time of flowering increased with elevation by 2 3d for every 100 m. Floral longevity also increased with elevation, by 0,2 d for every 100 m. Neither duration of flowering nor duration of the flower phases showed any consistent change with elevation. The same is true of the non–phenological floral traits examined. No trade–off between duration of flowering and flower life span or between structure and maintenance of flowers was apparent. The pattern of increasing floral longevity along the elevation gradient suggests a mechanism of compensation for reduecd pollinator availability.     

Treatment of Patients with Systemic Lupus Erythematosus including Nephritis with Chlorambucil

Six female patients with systemic lupus erythematosus (S.L.E.) have been treated with chlorambucil. In five the decision was taken after failure by corticosteroids to control progressive renal disease in the face of unacceptable corticosteroid toxicity. After the introduction of chlorambucil renal function improved and all patients remain well six, six, five, three, and two-and-a-half years later, respectively. On renal biopsy five had focal proliferative glomerulonephritis. Repeat biopsy in two cases showed quantitative improvement. The sixth patient was treated with chlorambucil because of failure by corticosteroids to control peripheral vascular lesions and haemolysis and she remains well four years later. In four patients is it probable that amenorrhoea was related to chlorambucil treatment, but there were no other important side effects although one patient developed a degree of marrow depression during treatment. Chlorambucil may hold advantages over the immunosuppressive drugs normally recommended in this condition, azathioprine and cyclophosphamide, as it appears less liable to cause important marrow suppression and, unlike cyclophosphamide is not associated with alopecia and haemorrhagic cystitis.     

Excavation and architecture of Argentine ant nests

We used x-ray computed tomography to study the elaboration of nest structures in small sand-filled nest boxes by Argentine ant (Linepithema humile) colonies composed of 10, 100, and 1000 workers. The pattern of nest growth was consistent with a process of density-dependent stimulation of excavation, which subsided as nests grew and the density of digging stimuli declined. Thus, nest excavation would be auto-regulating, and final nest size should be adjusted to colony size. We found that excavation rates and final nest sizes increased with colony size, but were not tenfold greater in 1000-worker colonies than in 100-worker colonies. In the largest colonies, the internal surface area scaled allometrically with volume, so that more surface was obtained relative to volume excavated as the nest grew. Although the gross features of Argentine ant nests, such as total size, seem explicable by a simple, self-organized regulatory process, other features of the nest architecture will require further investigation. Received 3 March 2005; revised 26 April 2005; accepted 3 May 2005.     

The scale of analysis determines the spatial pattern of woody species diversity in the Mediterranean environment

We examine the spatial pattern of woody species diversity at different scales, in two sites of Mt. Holomontas in northern Greece, which falls within the transitional zone between temperate forests and Mediterranean-type ecosystems. We investigate how diversity is distributed in space and whether the perceived pattern changes with the scale of observation. We use two different metrics of diversity: species richness and species turnover. Our main finding is that the spatial pattern of diversity changes with the scale of observation or analysis. For a given scale, the pattern of species richness (alpha diversity) is negatively correlated with the pattern of species turnover (beta diversity). Species-rich areas have more species in common with their neighbors than species-poor areas. The between-scale disparity of the spatial pattern of diversity may be a general feature of ecological systems. For this to be validated, studies with different groups of species in different biomes and in different biogeographical areas are required; our study contributes to this direction providing evidence that this holds true for woody species in Mediterranean communities. Finally, we discuss how these findings might affect important issues in theoretical and applied ecology, such as identifying the environmental factors driving biodiversity.