Entrainment of Geotropic Oscillations in Hypocotyls of Heliunthus annuus– An Experimental and Theoretical Investigation

A theory for the geotropic movements of the Heliunthus unnuus hypocotyl has been given earlier by Johnsson et ul. In the present paper this theory is tested by extensive experiments. The magnitude as well as the rate of geotropic curvature are found to be in agreement with the theoretical predictions. Further, the geotropic reaction time, defined as the time between the start of geotropic stimulation and the start of the geotropic reaction is determined as a function of the stimulation angle with respect to the plumb line. A slight variation found in the reaction time is included in the theory.     

OBSERVATIONS ON NOCTULE BATS (NYCTALUS NOCTULA) CAPTURED WHILE FEEDING

In the summer and early autumn of 1960, 1961 and 1962, noctule bats flying low, taking house crickets as these flew from a municipal rubbish tip, were captured in mist nets, ringed, released and in many cases recaptured a number of times. The flying bats showed no fear of human beings or predatory birds and did not learn to avoid the net. In June and July of each year the majority of bats caught were adult females, the flying young of the year first appearing in August though some did not fly until September and October. Young males did not reach sexual maturity in the year of their birth, though five out of fourteen females recaptured at a year old did. There was a considerable movement of adult males in the late summer, adult bats being captured in approximately equal numbers of both sexes during August and September. In October the females seemed to disappear, the majority of the bats caught during that month being males: by November the crickets had ceased to fly and no more bats could be captured though a few wero still flying on warm nights. There was a marked difference in feeding behaviour over these three years, the bats concentrating more on crickets in 1960 than in 1961 and 1962. Though the differences are not statistically significant there were indications of an increase in body weight between July and October in the years when less cricket feeding was occurring. About 50 per cent of the females captured in each of the years 1960 and 1961 were recaptured feeding on the same site in the following year: the recovery rate of males was about 30 per cent in 1961, 60 per cent in 1962.     

Complex phylogeographic patterns in the freshwater alga Synura provide new insights into ubiquity vs. endemism in microbial eukaryotes

The global distribution, abundance, and diversity of microscopic freshwater algae demonstrate an ability to overcome significant barriers such as dry land and oceans by exploiting a range of biotic and abiotic colonization vectors. If these vectors are considered unlimited and colonization occurs in proportion to population size, then globally ubiquitous distributions are predicted to arise. This model contrasts with observations that many freshwater microalgal taxa possess true biogeographies. Here, using a concatenated multigene data set, we study the phylogeography of the freshwater heterokont alga Synura petersenii sensu lato. Our results suggest that this Synura morphotaxon contains both cosmopolitan and regionally endemic cryptic species, co‐occurring in some cases, and masked by a common ultrastructural morphology. Phylogenies based on both proteins (seven protein‐coding plastid and mitochondrial genes) and DNA (nine genes including ITS and 18S rDNA) reveal pronounced biogeographic delineations within phylotypes of this cryptic species complex while retaining one clade that is globally distributed. Relaxed molecular clock calculations, constrained by fossil records, suggest that the genus Synura is considerably older than currently proposed. The availability of tectonically relevant geological time (10⁷–10⁸ years) has enabled the development of the observed, complex biogeographic patterns. Our comprehensive analysis of freshwater algal biogeography suggests that neither ubiquity nor endemism wholly explains global patterns of microbial eukaryote distribution and that processes of dispersal remain poorly understood.     

Not enough niches: non‐equilibrial processes promoting species coexistence in diverse ant communities

Abstract Explanations for species coexistence in ant communities have traditionally focused on niche partitioning, particularly relating to differences in diet, foraging times and nesting requirements. Although niche separation is undoubtedly important, it seems insufficient to account for the high levels of local species richness that are commonly observed. This paper explores alternative explanations for ant species coexistence, focusing on factors that prevent competitive exclusion in diverse ant communities experiencing high levels of behavioural dominance, such as characteristically occurs in Australia. Very high species densities require two conditions to be met: first, a large number of species must successfully establish; and second, there must be a high rate of species persistence once established. In this context I advance five propositions based around three sets of arguments. First, ant sociality and modularity confers a high level of persistence once colonies are established, so that species coexistence is determined to a significant extent by processes operating at the establishment phase, rather than just by interactions between established colonies. Second, competitive outcomes are highly conditioned by environmental variation, which severely limits competitive exclusion. Finally, dominant species are highly patchy in space, and cannot comprehensively monopolize resources, such that there will usually be room for low densities of subordinate species. These propositions have relevance to neutral theories of community ecology, and to understanding intercontinental differences in local species richness.     

HIV risk behaviors among outpatients with severe mental illness in Rio de Janeiro,Brazil

We conducted the first study to examine rates of sexual activity, sexual risk behaviors, sexual protective behaviors, injection drug use (IDU), needle sharing, and knowledge about HIV/AIDS among outpatients with severe mental illness (SMI) in Rio de Janeiro, Brazil. Using a measure with demonstrated reliability, we found that 42% of 98 patients engaged in vaginal or anal sex within the past three months. Comorbid substance use disorder was significantly associated with sexual activity. Only 22% of sexually active patients used condoms consistently, despite having better HIV knowledge than those who were sexually abstinent. Overall, 45% of patients reported not engaging in any HIV protective behaviors. There were no reports of drug injection. Adults with SMI in Brazil are in need of efficacious HIV prevention programs and policies that can sustain these programs within mental health treatment settings.