Score averaging for alien species risk assessment: a probabilistic alternative

In many biological risk assessment problems and specifically those involving invasive alien species and quarantine pests, ordinal scoring systems are used as a basis for risk quantification. Frequently, the problem is disaggregated into a series of components to allow a more structured and systematic evaluation. Each component is then scored and an overall measure of risk calculated from the set of scores. No satisfactory method exists to compute an overall measure of risk and most practitioners have resorted to score-averaging. Here we describe an approach involving the linear mapping of scores to notional probabilities to allow the use of conditional probability to derive an overall measure. Initial results give better discrimination between high and low risk cases and closer correspondence with independent expert judgement than does score-averaging.     

1971～200O年间安大略省基拉尼公园里的甲壳类浮游动物群落从酸化水体中得到恢复:pH6作为恢复的目标

尽管大气中SO2- 4的沉降减少,地表水的酸度也因此降低,但尚未记录到广泛的生物从酸化中恢复过来.本文通过考察1971～2000年间加拿大安大略省基拉尼公园的46个湖泊甲壳类浮游动物种的丰富度(物种数目)和组成的时间变化趋势,来估计由于水质有了重大改善即pH现在＞6后湖泊中生物的恢复程度,并与其他两组(从未酸化的湖泊和仍然酸化的湖泊[pH＜6])作比较.在这三组湖泊中,物种丰富度的时间趋势无法加以区别,物种丰富度的变化也不能说明恢复的程度.对比之下,在pH值增加到6以上的湖泊中,其浮游动物群落的组成(以物种多度的多变量指数表征)则有所变化,从"损害"状态返回到了中性湖泊的典型状态.在酸性湖泊也记录到浮游动物组成有某些恢复.虽然仍为酸性,这些湖泊的pH水平已经升高.基拉尼省公园里甲壳类浮游动物恢复的程度和速度为北美和欧洲其他酸化地区的将来预示了光明的前景.     

Iterating Masuyama’s method to reduce sampling variation

Masuyama in Sankhya 14(3):181–186, 1954 gave a method for addressing the boundary overlap problem that arises when sampling in a delineated study region. Here we propose a general sampling framework that allows one to iterate Masuyama’s method in a way that provides a smaller sampling variance. Results of simulations comparing the proposed method to existing approaches for addressing the boundary overlap problem are given. Variations, including systematic sampling, are also discussed.     

Climate justice,adaptation and the Paris Agreement: a recipe for disasters?

A Capability Approach is adopted to critically analyse, in the interests of Climate Justice, whether the Paris Agreement is likely to adequately protect human and non-human Capabilities from the worst impacts of climate disasters. The mitigation, adaptation, and loss and damage provisions of the Paris Agreement are not convincing. Adaptation offers only a modest response to climate change, compared with mitigation, and current financial commitments to fund adaptation in developing countries are far too low. Consequently, the Parties to the United Nations Framework Convention on Climate Change have a long way to go in their negotiations before they have any hope of meeting their agreed temperature goals, and protecting human and non-human Capabilities from climate disasters.     

Alternative prey and the dynamics of intraguild predation: theoretical perspectives

A rich body of theoretical literature now exists focused on the three-species module of intraguild predation (IGP), in which a top predator both attacks and competes with an intermediate predator. Simple models of intraguild predation are often unstable, either because one consumer is excluded, or because sustained oscillations emerge from long feedback loops. Yet, many natural IGP systems robustly persist. Standard models of intraguild predation simplify natural systems in crucial ways that could influence persistence; in particular, many empirical IGP systems are embedded in communities with alternative prey species. We briefly review the key conclusions of standard three-species IGP theory, and then present results of theoretical explorations of how alternative prey can influence the persistence and stability of a focal intraguild predation interaction.     

The Rarest of Darwin's Finches

The Mangrove Finch (Cactospiza heliobates) is unique among Darwin's finches in its specialized habits and naturally fragmented distribution on individual islands. It has been reported to occupy six patches of mangroves separated to varying degrees on two of the Galápagos islands, Isabela and Fernandina. We present the results of a field study in three of the patches. The species appears to have become extinct on Fernandina and to be restricted now to a maximum of four habitat islands on Isabela. In one of them, Playa Tortuga Negra, we estimate the population of breeding adults to be 10–20 pairs. At another, west of Villamil, the population size is probably now small due to the cutting of mangroves. The other two populations, close to each other east of Punta Moreno, probably hold the largest demes. Their status is unknown. We estimate that the genetically effective size of the combined populations is 30–380 individuals. Because the populations are so small and restricted, they are vulnerable to any disturbance of the environment. This has probably been so throughout their history because they inhabit a fragmented habitat in a tectonically active region. New anthropogenic threats this century are an introduced wasp (Polistes versicolor), which may be a predator on a major food item (insect larvae) of the finches, and destruction of the habitat. Protection of the occupied habitat against human exploitation is required for the preservation of the species because no alternative habitat is known.     

The use of polymerase chain reaction for the identification of sciaenid eggs

Traditionally, sciaenid eggs have been identified based on morphological characteristics such as size, number of oil globules and/or pigmentation patterns. Identification of sciaenid eggs by these procedures is time consuming and often inaccurate due to considerable egg size overlap among species. The utilization of molecular techniques for the identification of economically important species has become a fundamental component in ecological studies involving fish eggs and larvae. This study reports the development of a series of both multiplex and individual polymerase chain reactions to identify the eggs of 11 sciaenid species commonly found in the Gulf of Mexico and estuaries near Port Aransas and Corpus Christi, TX, USA. Following method development, the discriminatory power of the assay was first determined with samples from adult fish collected from Aransas and Corpus Christi Bays, Galveston Bay and the lower Laguna Madre in northern Mexico. Most (97%) of these fishes were correctly identified to the level of species. To demonstrate the applicability of the assay, wild fish eggs were collected and analyzed from the Aransas Pass tidal inlet from September through December 2005. During this period, the eggs of four target species were positively identified which was in keeping with current knowledge regarding the spawning areas and seasons of these sciaenids based on the presence of mature females, eggs and/or larvae. Future use of this method can provide valuable information to better discriminate spawning sites and seasons of these species.