Andrew R. Solow

A Simple Test for Change in Community Structure

1. The effect of disturbance on a biological community is commonly measured by a change in an index of community structure. When such an index is calculated from a sample from the community, it is important to assess the statistical significance of an observed change. 2. A simple randomization test is described for testing for change in community structure. The test can be used in conjunction with any measure of community structure based on observed species abundances such as diversity indices. An example is given

Choosing reserve networks with incomplete species information

Existing methods for selecting reserve networks require data on the presence or absence of species at various sites. This information, however, is virtually always incomplete. In this paper, we analyze methods for choosing priority conservation areas when there is incomplete information about species distributions. We formulate a probabilistic model and find the reserve network that represents the greatest expected number of species. We compare the reserve network chosen using this approach with reserve networks chosen when the data is treated as if presence/absence information is known and traditional approaches are used. We find that the selection of sites differs when using probabilistic data to maximize the expected number of species represented versus using the traditional approaches. The broad geographic pattern of which sites are chosen remains similar across these different methods but some significant differences in site selection emerge when probabilities of species occurrences are not near 0 or 1.

Acoustic alarms reduce porpoise mortality

The most serious danger to dolphins and porpoises around the world is the threat from various forms of gill-net fishing. One potential way to reduce the number of deaths of marine mammals is the use of active acoustic alarms to warn animals about the presence of nets. Until now, acoustic alarms have not been tested in field experiments with sufficient statistical power. Here we describe a field experiment showing that acoustic alarms are effective at reducing the number of deaths of harbour porpoises (Phocoena phocoena) in sink gill-nets.

Inferring Extinction from Sighting Data

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A note on optimal algorithms for reserve site selection

A recent note by Underhill (Biol. Conserv., 70, 85-7, 1994) points out the need for the use of optimization models and a closer working relationship with mathematicians for the solution of biological management problems such as the reserve site selection problem. In this note we give the mathematical formulation of what he terms ‘the more realistic’ version of the reserve selection problem, namely, the problem of maximizing the number of species preserved given a fixed budget for reserve sites. We also discuss some straight-forward data reduction schemes which may reduce the solution time for these problems when they are solved using general off-the-shelf optimization code as mentioned by Underhill.

Microaggregations of oceanic plankton observed by towed video microscopy.

Oceanic plankton have been hypothesized to occur in micropatches (<10 meters) that can have a large impact on marine ecosystem dynamics. Towed video microscopy was used to unobtrusively determine distributions of oceanic plankton over a continuum of scales from microns to hundreds of meters. Distinct, taxa-specific aggregations measuring less than 20 centimeters were found for copepods but not for nonmotile (cyanobacterial colonies) or asexual (doliolid phorozooids) forms, which suggests that these small patches are related to mating. Significant patchiness was also found on larger scales and was correlated among taxa, indicating physical control. These video observations provide new insights into basic plankton ecology by allowing quantitative assessment of individual plankton in their natural, undisturbed state.

Measuring biological diversity

The diversity of a set of species refers to the joint dissimilarity of the species in the set. This paper discusses the measurement of diversity from the set of pairwise distances between the species in the set. A measure called the effective number of species is developed from a non-parametric probability inequality and is shown to have a simple interpretation in terms of comparing linear experiments.

Correlation between rate of sea-level change and frequency of explosive volcanism in the Mediterranean

Volcanic activity has frequently been linked to Quaternary environmental change, either by driving climate modification, or in response to environmental changes. Although a link has been established between large explosive eruptions and small (0.5 °C), brief (1–2 years) falls in global temperatures, both the evidence and mechanisms responsible for longer episodes of eruption-induced planetary cooling remain questionable,,,. In contrast, recent research based on ice-core data suggests that rapid climate changes during the past 110,000 years increased explosive volcanic activity. Here we present a statistical analysis relating the frequency of explosive activity of Mediterranean volcanoes — based on dated tephra layers in deep-sea sediment cores — to the rate of late Quaternary sea-level change. The nonlinear correlation between the two is tentatively explained in terms of dynamic responses of the volcanoes to stress-related influences on various spatial scales. The correlation supports a mechanism or mechanisms by which the climate-driven growth and decay of large ice sheets can influence the eruptive chronologies of distant volcanic edifices via changes in global sea level.

THE VALUE OF IMPROVED ENSO PREDICTION TO U.S. AGRICULTURE

The economic value of long-range weather prediction is measured by the increase in social welfare arising from the use of the prediction in economic decisionmaking. This paper describes a study of the economic value of ENSO prediction to U.S. agriculture. The interdisciplinary study involved the analysis of data and models from meteorology, plant science, and economics under a framework based on Bayesian decision analysis. The estimated annual value of perfect ENSO prediction to U.S. agriculture is

High-resolution observations of plankton spatial distributions correlated with hydrography in the Great South Channel, Georges Bank

323 million.