Reproduction and the central project of evolutionary theory

In much of the discourse of evolutionary theory, reproduction is treated as an autonomous function of the individual organism — even in discussions of sexually reproducing organisms. In this paper, I examine some of the functions and consequences of such manifestly peculiar language. In particular, I suggest that it provides crucial support for the central project of evolutionary theory — namely that of locating causal efficacy in intrinsic properties of the individual organism. Furthermore, I argue that the language of individual reproduction is maintained by certain methodological conventions that both obscure many of the problems it generates and serve to actively impede attempts to redress those difficulties that can be identified. Finally, I suggest that inclusion of the complexities introduced by sexual reproduction — in both language and methodology — may radically undermine the individualist focus of evolutionary theory.I am indepted to the Rockefeller Foundation for a Humanities Fellowship that supported this research during the spring of 1986. I am also grateful to Richard Lewontin, Diane Paul, and Lisa Lloyd for many extremely helpful conversations.     

Effect of incubation temperature on the hatching of rotifer resting eggs collected from sediments

Sediment samples from Loch Leven, Scotland, were incubated at 5°C, 10°C and 15°C to induce hatching of rotifer resting eggs. The emergent animals were identified and counted. The temperature which induced hatching varied among the nine species studied. These results are discussed in relation to seasonality and temperature preferences previously recorded for the most abundant species. Resting egg densities of 2.2–13.9 eggs cm^–3 were recorded in the upper 5 cm of sediment.     

The organic content of the surficial sediment: a method for the study of ecosystems development in abandoned river channels

To characterise different abandoned river channels, a simple index of the surface sediment was developed i.e. the content of organic matter (expressed as C × N) plotted in relation to that of CaCO₃. The age of the channels studied ranges from 20 to 300 years. Some of them still contain water; others are silted up. Two types are distinguished. The ecosystems of the first one are closed and show a slow rate of development governed by autogenous processes. Those of the second type are more open and show a fast rate of development mainly controlled by allogenous processes. These distinctions are used in a diagrammatic model of the dynamics of Rhône River alluvial plain to be used in fundamental or applied future research.     

Microbial communities colonising nutrient-enriched marine sediment

Sediment cores were set up to study microbial colonisation and interactions on marine sand grains under enrichment conditions. Cores were enriched with photosynthetic media in the light and dark (PL, PD) and heterotrophic media in the light and dark (HL, HD), and were incubated for 25 days. Sediment chlorophylls were then measured by acetone extraction, viable heterotrophic bacteria by plate counts, and numbers of cells mm^–2 sand grain surface by s.e.m. Chlorophyll a occurred in all sediments but was highest in the PL sediment. Bacteriochlorophyll a was only observed in the HL sediment. Heterotrophic viable counts were high in the HL and HD sediments. Dense growth of diatoms and blue-green algae, and a marine fungal Thraustochytrid sp. occurred on PL grains. The blue-green alga Schizothrix was often associated with the diatom Amphora on PL grains. Many different bacteria grew on HL and HD grains and some unusual colony and cell morphologies were recorded (Caulobacter, Flexibacter, polymer strands). Characteristic flakey material sometimes occurred in hollows on grains. The results are discussed in relation to microbial communities in low energy sedimentary environments.     

On the degree of genetic divergence in Drosophila ananassae populations transferred to laboratory conditions

Twelve natural populations of Drosophila ananassae were sampled and laboratory populations were derived. All the populations were maintained in food bottles in the laboratory for ten generations by transferring fifty flies (females and males in equal number) in each generation. After ten generations they were analysed chromosomally to determine the frequency of different chromosome arrangements. The results show that there is significant variation in the frequencies of chromosome arrangements and in the level of inversion heterozygosity. Although some of the populations became mo-nomorphic for certain inversions, in general all populations remained polymorphic even after ten generations. The degree of genetic differentiation in the populations after they were transferred to laboratory conditions has been estimated by calculating genetic identity and distance between the initial and final populations based on the differences in chromosome arrangement frequencies. The estimates of I and D suggest that there is considerable variation in the degree of genetic divergence in D. ananassae populations. Some populations have remained unchanged while others have diverged to a considerable extent.     

Obligation and the new naturalism

Although it has become increasingly evident that an adequate theory of obligation must rest on evolutionary biology and human ethology, attempts toward this end need to explore the full range of personal, cultural, and political obligations observed in our species. The new naturalism reveals the complexity of social behavior and the defects of reductionist models that oversimplify the foundations of human duties and rights. Ultimately, this approach suggest a return to the Aristotelian concept of natural justice.     

In situ bioassessment of dredging and disposal activities in a contaminated ecosystem: Toronto Harbour

The contamination of Toronto Harbour is a very serious problem. The major sources of pollution are the Don River and sewer outflows, as well as industrial, and municipal effluents. The problem is further compounded by perturbations of the toxic sediment caused by dredging, dredge-disposal, navigation, and recreational activities. The impact of contamination and nutrient enrichment was reflected in the size-fractionated primary productivity experiments. Generally, microplankton/netplankton (> 20 µm) productivity was enhanced whereas ultraplankton (< 20 µm) productivity was inhibited. These observations are attributable to interactions between ameliorating nutrients and toxic contaminants as well as to the differential sensitivity of natural phytoplankton size assemblages to the bioavailable chemical regime. In situ environmental techniques applied in Toronto Harbour were effective, sensitive, and rapid, and provided a better understanding of the impact of dredging/disposal activities under natural conditions. These techniques have great potential in the assessment of the ecotoxicology of harbours and other stressed environments.     

Nutrient release rates from the sediments of Saginaw Bay,Lake Huron

Direct measurements of net production rates and pore water profiles of solutes in the fine-grained sediments of Saginaw Bay, imply corresponding steady-state fluxes to the overlying water of 1.1–1.3 (I), 450–1010 (NH₄ ⁺), 1250–2650 (Si(OH)₄), 3000–3400 (Ca²⁺), 440–1330 (Mg²⁺), 1.5–728 (Fe²⁺), and 179–281 (Mn²⁺) moles/m²/day and 11.0–11.8 (alkalinity) meq/m²/day at 17.5 °C. Silica production rates in sediments apparently follow first order kinetics with a rate coefficient of 0.09/day and a steady-state silica concentration of 1.2 mM at 23.5°C. The remaining solutes follow kinetics approximately independent of solute concentration over the range of concentrations observed. Measured solute production rates are consistent with observed solute profiles only if lateral diffusion gradients are maintained in the sediments by the burrowing and irrigation activity of benthic organisms such asChironomous, the dominant burrower in Saginaw Bay. Assuming that solute fluxes from Saginaw Bay are representative of all of the post-glacial sediments of Lake Huron, the iodine flux from sediments is comparable to the total fluvial input of iodine. The extrapolated silica fluxes from Lake Huron sediments balance the estimated biogenic silica flux to the sediments.     

Early warning assays: an overview of toxicity testing with phytoplankton in the North American Great Lakes

The use of phytoplankton as test organisms in bioassays has recently gained momentum due to their simplicity, availability, sensitivity, rapidity of analysis, and cost-effectiveness. Increasing emphasis is currently being given to field and in situ experiments using indigenous populations, particularly ultraplankton/picoplankton (2–20 m) which play a key role in the microbial loop and food chain dynamics. Impact evaluation can be determined at the structural, ultra-structural, and functional level. An array of techniques is available for toxicity testing including the use of either algal cultures or natural assemblages in laboratory or in situ experiments, the selection of which depends on the objectives, precision required, and project budget of the particular study. An overview is presented of the various procedures using algae in toxicity testing with a focus on the Great Lakes and an emphasis on field techniques. The effective use and application of such sensitive technology has tremendous potential for early warning detection of ecosystem perturbations in concert with a multi-trophic battery of tests.     

Characteristics of settling matter and its role in nutrient cycles in a deep oligotrophic lake

The settling flux of seston (dry weight, DW), chlorophyll a (Chl a), particulate organic carbon (POC), particulate organic nitrogen (PON), and particulate phosphorus (PP) was measured monthly in 1981–1983 at 10 different depths in Lake Chuzenji, Japan; an oligotrophic lake with a maximum depth of 163 m. The Ti concentration in entrapped matter was used to separate the sedimentation flux into allochthonous and autochthonous components. Inflow loads of dissolved nutrients (DN: 4.5, DP: 0.48 g m^-2a^-1) were almost sufficient to supply the autochthonous fluxes at 30 m (PON: 2.9, PP: 0.51 g m^-2a^-1 ), and this flux of POC (26.6 g m^-2a ^-1) was about one-third of primary production (84 g C M^-2a^-1). Sedimentation of particulate matter was the main path of losing nutrients from lake water, explaining more than 80% removal of inflow loads (TN, TP). Decomposition rates during sedimentation which were calculated from the vertical difference in the autochthonous flux agreed very closely with the results obtained by laboratory experiments of a 100-day incubation (content ratios from field observations were: POC 0.67, PON 0.65, PP 0.85; and from laboratory experiments they were: POC 0.68, PON 0.70, PP 0.94). These decomposition rates and those near the sediment interface were used to explain dissolved oxygen depletion and nitrate increase in the hypolimnion during stratification. The average sinking velocities were 1.82m d^-1 for seston and 1.16 m d^-1 for Chl a at 30m, they were influenced by Chl a content of seston.