Using species abundance models as indicators of habitat disturbance in tropical forests

1. In temperate communities, species abundance distributions have been used to detect ecosystem disturbance: in undisturbed habitats, distributions are claimed to generally fit log-normal models, whereas in disturbed habitats, distributions fit log-series models.
2. There is a growing literature on the effects of habitat disturbance in tropical ecosystems and several studies suggest that species abundance models may be useful in detecting disturbance, although data are lacking.
3. Nummelin (1998) claims that these models are not universal indicators of forest disturbance, but we highlight a number of problems with the data presented in Nummelin's study and conclude that it is too soon to dismiss these models. We discuss several important points arising from Nummelin's study which need to be considered if species abundance models are to be used appropriately.     

Identification and Characterization of Aspergillus Nidulans Mutants Defective in Cytokinesis

Filamentous fungi undergo cytokinesis by forming crosswalls termed septa. Here, we describe the genetic and physiological controls governing septation in Aspergillus nidulans. Germinating conidia do not form septa until the completion of their third nuclear division. The first septum is invariantly positioned at the basal end of the germ tube. Block-and-release experiments of nuclear division with benomyl or hydroxyurea, and analysis of various nuclear division mutants demonstrated that septum formation is dependent upon the third mitotic division. Block-and-release experiments with cytochalasin A and the localization of actin in germlings by indirect immunofluorescence showed that actin participated in septum formation. In addition to being concentrated at the growing hyphal tips, a band of actin was also apparent at the site of septum formation. Previous genetic analysis in A. nidulans identified four genes involved in septation (sepA-D). We have screened a new collection of temperature sensitive (ts) mutants of A. nidulans for strains that failed to form septa at the restrictive temperature but were able to complete early nuclear divisions. We identified five new genes designated sepE, G, H, I and J, along with one additional allele of a previously identified septation gene. On the basis of temperature shift experiments, nuclear counts and cell morphology, we sorted these cytokinesis mutants into three phenotypic classes. Interestingly, one class of mutants fails to form septa and fails to progress past the third nuclear division. This class of mutants suggests the existence of a regulatory mechanism in A. nidulans that ensures the continuation of nuclear division following the initiation of cytokinesis.     

Wading through the swamp: what does tropical peatland restoration mean to national‐level stakeholders in Indonesia?

Ecological restoration is considered to play an important role in mitigating climate change, protecting biodiversity, and preventing environmental degradation. Yet, there are often multiple perspectives on what outcomes restoration should be aiming to achieve, and how we should get to that point. In this study we interview a range of policymakers, academics, and non‐governmental organization (NGO) representatives to explore the range of perspectives on the restoration of Indonesia's tropical peatlands—key global ecosystems that have undergone large‐scale degradation. Thematic analysis suggests that participants agreed about the importance of restoration, but had differing opinions on how effective restoration activities to date have been and what a restored peatland landscape should look like. These results exemplify how ecological restoration can mean different things to different people, but also highlight important areas of consensus for moving forward with peatland restoration strategies.     

Lipid reserves,fasting capability and the evolution of nestling obesity in procellariiform seabirds

Several alternative explanations have been proposed to account for the evolution of nestling obesity in a variety of avian groups. These predict quite different patterns of fat accumulation, storage and use by chicks of different ages. Yet surprisingly few studies have measured changes in body composition during chick development. We tested the applicability of these hypotheses for fulmars, Fulmarus glacialis, by direct measurement of changes in water, lipid and lean dry mass in growing chicks. Lipid and lean dry mass increased until ca. 70% of the way through chick rearing, but then levelled off. Total body water also increased until the same stage, but gradually declined thereafter, and it was this change rather than fat metabolism that resulted in mass recession. The observed pattern of a continued increase in stored lipid, and most importantly, its maintenance all the way through the mass-recession phase until chicks reach fledging, is incompatible with many of the proposed hypotheses. We suggest that the most likely ultimate explanation for large fat deposits is to fuel chicks during the initial critical period away from the nest site while they learn to forage     

Anthropogenically-Mediated Density Dependence in a Declining Farmland Bird

Land management intrinsically influences the distribution of animals and can consequently alter the potential for density-dependent processes to act within populations. For declining species, high densities of breeding territories are typically considered to represent productive populations. However, as density-dependent effects of food limitation or predator pressure may occur (especially when species are dependent upon separate nesting and foraging habitats), high territory density may limit per-capita productivity. Here, we use a declining but widespread European farmland bird, the yellowhammer Emberiza citrinella L., as a model system to test whether higher territory densities result in lower fledging success, parental provisioning rates or nestling growth rates compared to lower densities. Organic landscapes held higher territory densities, but nests on organic farms fledged fewer nestlings, translating to a 5 times higher rate of population shrinkage on organic farms compared to conventional. In addition, when parental provisioning behaviour was not restricted by predation risk (i.e., at times of low corvid activity), nestling provisioning rates were higher at lower territory densities, resulting in a much greater increase in nestling mass in low density areas, suggesting that food limitation occurred at high densities. These findings in turn suggest an ecological trap, whereby preferred nesting habitat does not provide sufficient food for rearing nestlings at high population density, creating a population sink. Habitat management for farmland birds should focus not simply on creating a high nesting density, but also on ensuring heterogeneous habitats to provide food resources in close proximity to nesting birds, even if this occurs through potentially restricting overall nest density but increasing population-level breeding success.