Lack of detectable nepotism in multiple-queen colonies of the fire ant Solenopsis invicta (Hymenoptera: Formicidae)

Multiple-queen (polygyne) colonies of the introduced fire ant Solenopsis invicta present a paradox for kin selection theory. Egg-laying queens within these societies are, on average, unrelated to one another, and the numbers of queens per colony are high, so that workers appear to raise new sexuals that are no more closely related to them than are random individuals in the population. This paradox could be resolved if workers discriminate between related and unrelated nestmate sexuals in important fitness-related contexts. This study examines the possibility of such nepotism using methods that combine the following features: (1) multiple relevant behavioral assays, (2) colonies with an unmanipulated family structure, (3) multiple genetic markers with no known phenotypic effects, and (4) a statistical technique for distinguishing between nepotism and potentially confounding phenomena. We estimated relatedness between interactants in polygyne S. invicta colonies in two situations, workers tending egg-laying queens and workers feeding maturing winged queens. In neither case did we detect a significant positive value of relatedness that would implicate nepotism. We argue that the non-nepotistic strategies displayed by these ants reflect historical selection pressures experienced by native populations, in which nestmate queens are highly related to one another. The markedly different genetic structure in native populations may favor the operation of stronger higher-level selection that effectively opposes weaker individual-level selection for nepotistic interactions within nests. Received: 28 June 1996 / Accepted after revision: 6 October 1996     

Comparative study of genetic and social structure in two forms of the fire ant Solenopsis invicta (Hymenoptera: Formicidae)

Summary The genetic and social structures of polygyne and monogyne forms of the fire ant, Solenopsis invicta, are investigated in a comparative manner using allozyme data from two polymorphic loci. Foundress queens of the monogyne form are signly inseminated and appear to produce all males present in the colony during the major summer mating flights. The average regression coefficient of relatedness (b) among female nestmates of the monogyne form is 0.714 (Fig. 2), statistically indistinguishable from the pedigree coefficient of relatedness (G) of 0.75. We suggest that the evolution of obligate worker sterility in Solenopsis is associated with this high relatedness between workers and the queens they rear. Functional queens in polygyne nests also are singly inseminated and are no more closely related to nestmate queens than to other queens (within-nest b=0). Within-nest relatedness of workers in the polygyne population is similarly low (Fig. 2). Both the monogyne and polygyne populations from northcentral Georgia are in Hardy-Weinberg equilibrium at both allozyme loci and we found no evidence of significant population subdividion or inbreeding in the polygyne population. These results do not support the view that kin selection has promoted the evolution of polygyny in North American S. invicta. Rather, mutualism appears to be the most likely selective factor mediating queen associations inthis ant.     

Mate choice by female white-crowned sparrows in a mixed-dialect population

Summary It has been argued that the song dialects of white-crowned sparrows, Zonotrichia leucophrys, may function to restrict gene flow between dialect populations, thus promoting adaptation to local environmental conditions. One proposed mechanism whereby this may occur is if a female mates preferentially with males singing her natal dialect, typically the song type of her father. Previous field and laboratory studies of the role played by song differences in mate choice by female white-crowned sparrows have produced equivocal results. These investigations were conducted in populations in which a single song dialect was predominant. We examined mate choice in a population in which two song dialects are equally common. We found that songs of mates of individual females in successive years were no more likely to be of the same dialect than expected by chance. In addition, individual females did not mate preferentially with males whose songs matched those of their fathers. We conclude that, in this population, females choose mates on the basis of characteristics other than song type.     

Grief and mid-trimester fetal loss

Fetal loss through miscarriage or termination of pregnancy for genetic reasons often provokes the grief of bereavement. This is not fully understood, and the extent of the distress is often underestimated by professionals and family alike. We have examined elements of the normal bereavement process and have found that they may occur in specific and accentuated forms in mid-trimester fetal loss. We discuss our findings in the light of the attachment theory—a psychodynamic model for understanding grief reactions.     

Consumer attitudes regarding environmentally sustainable wine: an exploratory study of the New Zealand marketplace

Previous research has suggested that consumers are becoming increasingly concerned by the effects of conventional agricultural food production practices on human health and environmental wellbeing. This study sought to understand whether environmentally sustainable practices in the vineyard would equate to advantages in the wine marketplace. Structured questionnaires were used to ascertain the views of wine consumers in Christchurch, New Zealand. The findings of this study indicate that consumers have a strong demand for wine which is produced using “green” production practices. Consumers believe that the quality of sustainable wine will be equal to or better than conventionally produced wine, and they are prepared to pay a higher price for this wine.     

Ocean acidification and warming alter photosynthesis and calcification of the symbiont-bearing foraminifera Marginopora vertebralis

The impact of elevated CO₂ and temperature on photosynthesis and calcification in the symbiont-bearing benthic foraminifer Marginopora vertebralis was studied. Individual specimens of M. vertebralis were collected from Heron Island on the southern Great Barrier Reef (Australia). They were maintained for 5 weeks at different temperatures (28, 32 °C) and pCO₂ (400, 1,000 µatm) levels spanning a range of current and future climate-change scenarios. The photosynthetic capacity of M. vertebralis was measured with O₂ microsensors and a pulse-amplitude-modulated chlorophyll (Chl) fluorometer, in combination with estimates of Chl a and Chl c ₂ concentrations and calcification rates. After 5 weeks, control specimens remained unaltered for all parameters. Chlorophyll a concentrations significantly decreased in the specimens at 1,000 µatm CO₂ for both temperatures, while no change in Chl c ₂ concentration was observed. Photoinhibition was observed under elevated CO₂ and temperature, with a 70–80 % decrease in the maximum quantum yield of PSII. There was no net O₂ production at elevated temperatures in both CO₂ treatments as compared to the control temperature, supporting that temperature has more impact on photosynthesis and O₂ flux than changes in ambient CO₂. Photosynthetic pigment loss and a decrease in photochemical efficiency are thus likely to occur with increased temperature. The elevated CO₂ and high temperature treatment also lead to a reduction in calcification rate (from +0.1 to >?0.1 % day^?1). Thus, both calcification and photosynthesis of the major sediment-producing foraminifer M. vertebralis appears highly vulnerable to elevated temperature and ocean acidification scenarios predicted in climate-change models.     

Determination of total chlorine and bromine in solid wastes by sintering and inductively coupled plasma-sector field mass spectrometry

A sample preparation method based on sintering, followed by analysis by inductively coupled plasma-sector field mass spectrometry (ICP-SFMS) for the simultaneous determination of chloride and bromide in diverse and mixed solid wastes, has been evaluated. Samples and reference materials of known composition were mixed with a sintering agent containing Na₂CO₃ and ZnO and placed in an oven at 560 °C for 1 h. After cooling, the residues were leached with water prior to a cation-exchange assisted clean-up. Alternatively, a simple microwave-assisted digestion using only nitric acid was applied for comparison. Thereafter the samples were prepared for quantitative analysis by ICP-SFMS. The sintering method was evaluated by analysis of certified reference materials (CRMs) and by comparison with US EPA Method 5050 and ion chromatography with good agreement. Median RSDs for the sintering method were determined to 10% for both chlorine and bromine, and median recovery to 96% and 97%, respectively. Limits of detection (LODs) were 200 mg/kg for chlorine and 20 mg/kg for bromine. It was concluded that the sintering method is suitable for chlorine and bromine determination in several matrices like sewage sludge, plastics, and edible waste, as well as for waste mixtures. The sintering method was also applied for determination of other elements present in anionic forms, such as sulfur, arsenic, selenium and iodine.