Both female castes contribute to colony emigration in the polygynous ant Mystrium oberthueri

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Thermal and hydric implications of diurnal activity by a small tropical frog during the dry season

Amphibians are typically intolerant of high temperatures and dehydrating conditions, and small species are particularly susceptible to desiccation. The rockhole frog, Litoria meiriana (Hylidae), is diurnal and is often observed on rocks in the sun near streams in tropical Australia. These hot, desiccating conditions are avoided by most frog species. We measured the microclimate in the areas used by frogs and the activity, body temperatures and hydric state of free‐ranging individuals of this small frog. We also used plaster models to further explore the dynamic nature of hydric state by combining estimates of water loss and water uptake with behavioural observations of activity and microhabitat selection. Both direct measures and estimates of dynamic hydric state indicated that free‐ranging frogs generally maintained a hydric state above 95% of full hydration, but occasionally, particularly during the afternoon, frogs allowed their hydric state to fall as low as 85%. Body temperatures of frogs remained below the critical thermal maximum (CT_max) even when the frogs were in the sun, because this species has no cutaneous resistance to evaporative water loss and so they cool by evaporation. However, during the hotter part of the day, on dry sunny substrates, the hydric state of the frogs could fall to near lethal hydration states (approximately 70% of full hydration) within a short period (approximately 20 min). Thus, the threat of desiccation appears to be more limiting than the threat of overheating. These diurnal frogs rely on frequent bouts of rehydration to support their ability to venture onto hot, dry rocks during the day.     

Genetic diversity in water frog hybrids (Pelophylax esculentus) varies with population structure and geographic location

Pelophylax esculentus is a hybridogenetic frog originating from matings between P. ridibundus (RR) and P. lessonae (LL). Typically, diploid hybrids (LR) live in sympatry with one of their parental species, upon which they depend for successful reproduction. In parts of their range, however, pure hybrid populations can be found. These hybrid populations have achieved reproductive independence from their parental species by using triploid hybrids (LLR, LRR) rather than LL and RR as their sexual hosts. These different breeding systems also entail differences in reproduction (clonal versus sexual) and hence offer the opportunity to study how genetic diversity is affected by reproductive mode, population structure and geographic location. We investigated 33 populations in the Scania region (South Sweden) and 18 additional populations from Northern and Central Europe. Within both genomes (L, R), genetic variability increases with the potential for recombination and declines from the main species distribution area southeast of the Baltic Sea to the fringe populations northwest of the Baltic Sea. Within the main study area in Scania, genetic diversity is low and decreases from a core area to the periphery. Genetic differentiation between Scania populations is small but significant and best explained by ‘isolation by distance’. Despite the low genetic variability within the discrete genomes, all‐hybrid P. esculentus populations in southern Sweden are apparently not suffering from direct negative fitness effects. This is probably because of its somatic hybrid status, which increases diversity through the combination of genomes from two species.     

Admixture facilitates adaptation from standing variation in the European aspen (Populus tremula L.), a widespread forest tree

Adaptation to new environments can start from new mutations or from standing variation already present in natural populations. Whether admixture constrains or facilitates adaptation from standing variation is largely unknown, especially in ecological keystone or foundation species. We examined patterns of neutral and adaptive population divergence in Populus tremula L., a widespread forest tree, using mapped molecular genetic markers. We detected the genetic signature of postglacial admixture between a Western and an Eastern lineage of P. tremula in Scandinavia, an area suspected to represent a zone of postglacial contact for many species of animals and plants. Stringent divergence‐based neutrality tests provided clear indications for locally varying selection at the European scale. Six of 12 polymorphisms under selection were located less than 1 kb away from the nearest gene predicted by the Populus trichocarpa genome sequence. Few of these loci exhibited a signature of ‘selective sweeps’ in diversity‐based tests, which is to be expected if adaptation occurs primarily from standing variation. In Scandinavia, admixture explained genomic patterns of ancestry and the nature of clinal variation and strength of selection for bud set, a phenological trait of great adaptive significance in temperate trees, measured in a common garden trial. Our data provide a hitherto missing direct link between past range shifts because of climatic oscillations, and levels of standing variation currently available for selection and adaptation in a terrestrial foundation species.     

Sequencing primers and SNPs for rapidly evolving reproductive loci in endangered ibex and their kin (Bovidae,Capra spp.)

Rapidly evolving genes (e.g. candidate selected loci) are of increasing interest to molecular ecologists and conservation geneticists. Here, we report primers for five regions from three independent nuclear reproductive genes that reliably generate polymorphic sequences across the widespread wild goats of the Capra ibex species group and likely many other species of bovids. From three to nine single‐nucleotide polymorphisms (SNPs) were identified in each gene region among C. ibex subspecies. Average numbers of SNPs per 1000 bp across all five gene regions was 15.0, with a high of 25.3 in the ZP3 exons 3 and 4 sequence and a low of 6.1 in the TNP1 sequence.     

Enhancing the Anaerobic Response

Proteome analysis, and more recently DNA chip technology, hasled to the identification of a large number of genes that areimplicated in the anaerobic response of plants. As a result,an increasingly complex picture of the response in terms ofbiochemical and regulatory processes is emerging. A challengeis to find out more about the function of these newly identifiedgene products, and how they contribute to flooding tolerance.Our approach has been to manipulate levels of candidate geneproducts (using sense and antisense constructs) in the modelsystem Arabidopsis thaliana, combined with biochemical and phenotypicanalysis of the resulting transgenic plants.     

THE DEAD DONOR RULE,VOLUNTARY ACTIVE EUTHANASIA,AND CAPITAL PUNISHMENT

We argue that the dead donor rule, which states that multiple vital organs should only be taken from dead patients, is justified neither in principle nor in practice. We use a thought experiment and a guiding assumption in the literature about the justification of moral principles to undermine the theoretical justification for the rule. We then offer two real world analogues to this thought experiment, voluntary active euthanasia and capital punishment, and argue that the moral permissibility of terminating any patient through the removal of vital organs cannot turn on whether or not the practice violates the dead donor rule. Next, we consider practical justifications for the dead donor rule. Specifically, we consider whether there are compelling reasons to promulgate the rule even though its corresponding moral principle is not theoretically justified. We argue that there are no such reasons. In fact, we argue that promulgating the rule may actually decrease public trust in organ procurement procedures and medical institutions generally – even in states that do not permit capital punishment or voluntary active euthanasia. Finally, we examine our case against the dead donor rule in the light of common arguments for it. We find that these arguments are often misplaced – they do not support the dead donor rule. Instead, they support the quite different rule that patients should not be killed for their vital organs.     

Lipid Labeling in Normal and Nitrogen-Deficient Squash (Cucurbita maxima) Leaves

Squash (Cucurbita maxima Duchesne) plants were grown on normal and on nitrogen-deficient nutrients. The degrees of label incorporation into chloroplast lipids as well as non-chloroplast lipids were determined. Nitrogen-deficient tissues contain less chlorophyll, have a decreased chlorophyll a/b ratio, incorporate more label into phosphatidyl choline and phosphatidyl ethanolamine than into the chloroplast lipids such as mono- and digalactosyl diglycerides, have a reduced capacity to incorporate the hexose moieties into the glycolipids but normal capacity to incorporate bases into the phospholipids of non-chloroplast constituents, and have a normal level of total fatty acids even though the level of linolenate is decreased. All of this would suggest that the most evident changes in membrane lipid constituents during nitrogen-deficiency occur as changes in the chloroplast lipid constituents as opposed to the non-chloroplast lipid constituents.