Primary Succession on a Hawaiian Dryland Chronosequence

We used measurements from airborne imaging spectroscopy and LiDAR to quantify the biophysical structure and composition of vegetation on a dryland substrate age gradient in Hawaii. Both vertical stature and species composition changed during primary succession, and reveal a progressive increase in vertical stature on younger substrates followed by a collapse on Pleistocene-aged flows. Tall-stature Metrosideros polymorpha woodlands dominated on the youngest substrates (hundreds of years), and were replaced by the tall-stature endemic tree species Myoporum sandwicense and Sophora chrysophylla on intermediate-aged flows (thousands of years). The oldest substrates (tens of thousands of years) were dominated by the short-stature native shrub Dodonaea viscosa and endemic grass Eragrostis atropioides. We excavated 18 macroscopic charcoal fragments from Pleistocene-aged substrates. Mean radiocarbon age was 2,002 years and ranged from < 200 to 7,730. Genus identities from four fragments indicate that Osteomeles spp. or M. polymorpha once occupied the Pleistocene-aged substrates, but neither of these species is found there today. These findings indicate the existence of fires before humans are known to have occupied the Hawaiian archipelago, and demonstrate that a collapse in vertical stature is prevalent on the oldest substrates. This work contributes to our understanding of prehistoric fires in shaping the trajectory of primary succession in Hawaiian drylands.     

An apoptosis-inducing genotoxin differentiates heterozygotic carriers for Werner helicase mutations from wild-type and homozygous mutants

Immortalized B lymphocytes from Werner syndrome subjects are shown to be hypersensitive to 4-nitroquinoline-1-oxide (4NQO), supporting earlier work on T lymphocytes. We also show that B cell lines from clinically normal heterozygous carriers exhibit sensitivities to this genotoxic agent, which are intermediate to those of wild-type and homozygous mutants. 4NQO is shown to induce an apoptotic response. These data encourage research on DNA repair with such cell lines and raise the question of an enhanced sensitivity of the relatively prevalent heterozygous carriers to certain environmental genotoxic agents. Received: 21 April 1997 / Accepted: 25 July 1997     

Constructing more informative plant–pollinator networks: visitation and pollen deposition networks in a heathland plant community

Interaction networks are widely used as tools to understand plant–pollinator communities, and to examine potential threats to plant diversity and food security if the ecosystem service provided by pollinating animals declines. However, most networks to date are based on recording visits to flowers, rather than recording clearly defined effective pollination events. Here we provide the first networks that explicitly incorporate measures of pollinator effectiveness (PE) from pollen deposition on stigmas per visit, and pollinator importance (PI) as the product of PE and visit frequency. These more informative networks, here produced for a low diversity heathland habitat, reveal that plant–pollinator interactions are more specialized than shown in most previous studies. At the studied site, the specialization index was lower for the visitation network than the PE network, which was in turn lower than for the PI network. Our study shows that collecting PE data is feasible for community-level studies in low diversity communities and that including information about PE can change the structure of interaction networks. This could have important consequences for our understanding of threats to pollination systems.     

Promoter regions of the ExtA extensin gene from Brassica napus control activation in response to wounding and tensile stress

Plant Molecular Biology -     

Intensive Care Ethics in Evolution

The ethics of treating the seriously and critically ill have not been static throughout the ages. Twentieth century medicine has inherited from the nineteenth century a science which places an inappropriate weight on diagnosis over prognosis and management, combined with a seventeenth century duty to prolong life. However other earlier ethical traditions, both Hippocratic and Christian, respected both the limitations of medicine and emphasised the importance of prognosis. This paper outlines some of the historical precedents for the treatment of the critically ill, and also how the current paradigm limits clinical practice and causes ethical tensions. An understanding that other paradigms have been ethically acceptable in the past allows wider consideration and acceptance of alternatives for the future. However future alternatives will also have to address the role of technology, given its importance in this area of medicine.     

The Nuffield Council’s green light for genome editing human embryos defies fundamental human rights law

In July 2018, the Nuffield Council on Bioethics released the report Genome editing and human reproduction: Social and ethical issues, concluding that human germline modification of human embryos for implantation is not ‘morally unacceptable in itself’ and could be ethically permissible in certain circumstances once the risks of adverse outcomes have been assessed and the procedure appears ‘reasonably safe’. The Nuffield Council set forth two main principles governing anticipated uses and envisions applications that may include health enhancements as a public health measure. This essay provides a critique of three aspects in the Nuffield Council’s Report: its presumption of therapeutic efficacy, its inflation of parental rights to create a certain type of child, and its reliance on a specially commissioned report that appears to distort key definitions in international law.     

Strength and physical fitness predict the perception of looming sounds

Listeners consistently perceive approaching sounds to be closer than they actually are and perceptually underestimate the time to arrival of looming sound sources. In a natural environment, this underestimation results in more time than expected to evade or engage the source and affords a “margin of safety” that may provide a selective advantage. However, a key component in the proposed evolutionary origins of the perceptual bias is the appropriate timing of anticipatory motor behaviors. Here we show that listeners with poorer physical fitness respond sooner to looming sounds and with a larger margin of safety than listeners with better physical fitness. The anticipatory perceptual bias for looming sounds is negatively correlated with physical strength and positively correlated with recovery heart rate (a measure of aerobic fitness). The results suggest that the auditory perception of looming sounds may be modulated by the response capacity of the motor system.