Ultrastructure and evolution of ballistosporic basidiospores

Basidiospores oiCoprinus cinereus were examined before and during spore discharge using light microscopy, and SEM of frozen-hydrated and other preparations. The process of droplet development at the hilar appendix was divided into three stages: pre-droplet, early and late enlargement. The fully expanded droplet was preserved only in frozen-hydrated specimens. Two-step droplet enlargement was also observed with TEM in Boletus rubinellus, and the droplet at the early enlargement stage was enclosed by a trilaminate membrane. The droplet was not observed in Auricularia species, but basidiospore preservation for SEM was optimum in Auricularia auricula with frozen-hydrated preparations. The hilar appendix of Auricularia fuscosuccinea as studied by TEM was simple compared with those of the Homobasidiomycetes. The implications of the data for evolution of the ballistosporic basidiospore and the discharge mechanism are considered.     

MISCONCEPTIONS ABOUT COERCION AND UNDUE INFLUENCE: REFLECTIONS ON THE VIEWS OF IRB MEMBERS

Payment to recruit research subjects is a common practice but raises ethical concerns relating to the potential for coercion or undue influence. We conducted the first national study of IRB members and human subjects protection professionals to explore attitudes as to whether and why payment of research participants constitutes coercion or undue influence. Upon critical evaluation of the cogency of ethical concerns regarding payment, as reflected in our survey results, we found expansive or inconsistent views about coercion and undue influence that may interfere with valuable research. In particular, respondents appear to believe that coercion and undue influence lie on a continuum; by contrast, we argue that they are wholly distinct: whereas undue influence is a cognitive distortion relating to assessment of risks and benefits, coercion is a threat of harm. Because payment is an offer, rather than a threat, payment is never coercive.     

Conservation value of low fire frequency in tropical savannas: Ants in monsoonal northern Australia

The conservation values of ‘old‐growth’ forests in landscapes subject to repeated disturbance by fire or logging have received considerable conservation attention. However, little is known of the conservation values of old‐growth sites in ecosystems with an evolutionary history of highly frequent disturbance. Here we address the value of low fire frequency (<1 fire/10 years) in tropical savannas, the world's most fire‐prone biome, in terms of ant biodiversity. We do this by comparing savanna ant communities within the Territory Wildlife Park (TWP) near Darwin in the Australian monsoonal tropics, which has experienced a low incidence of fire over 25 years due to active fire exclusion, with those of adjacent (outside) sites experiencing the ambient fire regime of burning every 2–5 years. Ants were sampled using terrestrial and arboreal pitfall traps at 16 sites, eight each inside and outside TWP. More than 16 000 ants were recorded during the study, representing a total of 98 ant species from 30 genera. More species in total were recorded outside (90) than inside (74) TWP, but there was no difference in mean site species richness or abundance, and overall species composition was similar. All species recorded inside TWP are common and widespread throughout the savanna landscapes of the broader region, in the absence of active fire exclusion. Low fire frequency at the Territory Wildlife Park therefore does not appear to have enhanced regional ant conservation values. Our findings reinforce the importance of targeting fire regimes that are clearly linked to positive conservation outcomes, rather than assuming a need for maximum ‘pyrodiversity’.     

Multi‐scale ant diversity in savanna woodlands: an intercontinental comparison

Ecological patterns and processes are highly scale‐dependent, but few studies have used standardized methodology to examine how scale dependency varies across continents. This paper examines scale dependency in comparative ant species richness and turnover in savannas of Australia and Brazil, which are well‐matched climatically but whose ant faunas have contrasting biogeographic origins. The study was conducted in savanna woodland near Darwin in northern Australia and Uberlândia in central Brazil. The sampling design consisted of eight 400‐m line transects, four in each continent, with eight pitfall traps located on and around each of 20 trees evenly spaced along each transect. Ant richness and species turnover were compared at three spatial scales: pitfalls associated with a tree, trees within a transect and transects within a savanna. The composition of the Australian and Brazilian savanna ant faunas was broadly similar at the subfamily level, despite the very low proportion of shared genera and species. The ground and arboreal ant faunas were very distinct from each other in both savannas, but especially in Brazil. Overall ant abundance was almost three times higher in Australia than in Brazil, both on the ground and on vegetation, but overall species richness was higher in Brazil (150 species) than in Australia (93). There was no significant difference in the mean number of species per pitfall trap, but the mean species richness was significantly higher in Brazil than in Australia at both the tree and transect scales. We attribute these scale‐dependent intercontinental differences to biogeographical and historical factors in Brazil that have led to a large regional pool of arboreal species of rainforest origin. Our study underlines the importance of biogeographical context when conducting comparative analyses of community structure across biogeographical scales, and highlights the importance of process acting at regional scales in determining species richness in ant communities.     

The development and shell microstructure of the pseudodeltidium and interarea in thecideide brachiopods

Abstract: This study examines the development of the delthyrium, pseudodeltidium and interarea, their growth during the early juvenile stages of ontogeny and the extrapolation of morphology from adult shells to the probable juvenile state. Examination of the development and shell microstructure of the cardinalia of early juvenile thecideide brachiopod ventral valves from Jurassic, Cretaceous and Holocene specimens suggests that the delthyrium develops early in ontogeny and that the initial development of the pseudodeltidium precedes that of the interarea. Also, until the interarea is formed, the postero‐lateral flanks of the ventral umbo are palintropic. The development of the interarea can be seen to be a consequence of the lateral extension of the early juvenile hinge line. Initially, the pseudodeltidium consists solely of a thin plate of primary shell material. Comparison of the morphology of the pseudodeltidium of early juveniles with that of adults suggests that the initially curved lateral profile of the pseudodeltidium is retained, or even accentuated, in the ontogeny of lacazellines, but in all thecidellinines, with the exception of Pachymoorellina and Minutella, following the appearance of the interarea, the pseudodeltidium becomes flattened and often appears continuous with the interarea. However, we do not support any proposal that suggests that, in thecideides, only those forms in which the delthyrium is closed by a dorsally convex plate should be considered to possess a pseudodeltidium sensu stricto, mainly because of physiological differences and the prospect of possible taxonomic confusion in the future. Instead, we propose the term planodeltidium for a flat pseudodeltidium, typically developed in the thecidellinines, and rugideltidium for a convex pseudodeltidium, typically developed in the lacazellines, but also in Pachymoorellina and Minutella. Despite the presence of a rugideltidium, we believe the affinities of Minutella are more strongly with the thecidellinines and have included it in the new subfamily Minutellinae of the family Thecidellinidae.     

Assortative mating among Anastrepha fraterculus (Diptera: Tephritidae) hybrids as a possible route to radiation of the fraterculus cryptic species complex

Reproductive isolation among populations of Anastrepha fraterculus has been found acting at the pre‐ and post‐zygotic levels. Differences in timing of sexual activity and male sexual pheromone composition among populations could partially account for prezygotic isolation. Hybrid males were found to produce a novel pheromone, which is a mix of parental pheromones. In the present study, we found that the hybrid females showed a significant preference to mate with hybrid males than with parental males. Male location during pheromone emission is associated with its reproductive success and, thus, differences in the location of males during courtship could also play a role in isolation. We found evidence that reproductive isolation is also related to the location of males during courtship. Hybrid male behaviour regarding location during pheromone release was found to be influenced by the maternal lineage. If these populations hybridized in the field, the hybrid females would tend to mate with hybrid males probably leading to the formation of a new entity within the A. fraterculus complex. This simple and fast process could be one reason explaining the high number of taxonomic entities within this complex. Further studies on other members of the fraterculus species group may reveal whether this can be considered as an example of homoploid hybrid speciation. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 346–354.     

Scales of spatiotemporal variability in macroinvertebrate abundance and diversity in monsoonal streams: detecting environmental change

1. We quantified spatial and temporal variability in benthic macroinvertebrate species richness, diversity and abundance in six unpolluted streams in monsoonal Hong Kong at different scales using a nested sampling design. The spatial scales were regions, stream sites and stream sections within sites; temporal scales were years (1997–99), seasons (dry versus wet seasons) and days within seasons. 2. Spatiotemporal variability in total abundance and species richness was greater during the wet season, especially at small scales, and tended to obscure site‐ and region‐scale differences, which were more conspicuous during the dry season. Total abundance and richness were greater in the dry season, reflecting the effects of spate‐induced disturbance during the wet season. Species diversity showed little variation at the seasonal scale, but variability at the site scale was apparent during both seasons. 3. Despite marked variations in monsoonal rainfall, inter‐year differences in macroinvertebrate richness and abundance at the site scale during the wet season were minor. Inter‐year differences were only evident during the dry season when streams were at base flow and biotic interactions may structure assemblages. 4. Small‐scale patchiness within riffles was the dominant spatial scale of variation in macroinvertebrate richness, total abundance and densities of common species, although site or region was important for some species. The proportion of total variance contributed by small‐scale spatial variability increased during the dry season, whereas temporal variability associated with days was greater during the wet season. 5. The observed patterns of spatiotemporal variation have implications for detection of environmental change or biomonitoring using macroinvertebrate indicators in streams in monsoonal regions. Sampling should be confined to the dry season or, in cases where more resources are available, make use of data from both dry and wet seasons. Sampling in more than one dry season is required to avoid the potentially confounding effects of inter‐year variation, although variability at that scale was relatively small.     

Effect of Nitrogen Supply on the Kinetics and Regulation of Nitrate Assimilation in Chlamydomonas reinhardtii Dangeard

Concentration-dependent NO