Delaying conservation actions for improved knowledge: how long should we wait?Grantham, Hedley S.; Wilson, Kerrie A.; Moilanen, Atte; Rebelo, Tony; Possingham, Hugh P.
doi: 10.1111/j.1461-0248.2009.01287.xpmid: 19243409
Decisions about where conservation actions are implemented are based on incomplete knowledge about biodiversity. The Protea Atlas is a comprehensive database, containing information collated over a decade. Using this data set in a series of retrospective simulations, we compared the outcome from different scenarios of information gain, and habitat protection and loss, over a 20‐year period. We assumed that there was no information on proteas at the beginning of the simulation but knowledge improved each year. Our aim was to find out how much time we should spend collecting data before protecting habitat when there is ongoing loss of habitat. We found that, in this case, surveying for more than 2 years rarely increased the effectiveness of conservation decisions in terms of representation of proteas in protected areas and retention within the landscape. If the delay is too long, it can sometimes be more effective just using a readily available habitat map. These results reveal the opportunity costs of delaying conservation action to improve knowledge.
Plant genetics shapes inquiline community structure across spatial scalesCrutsinger, Gregory M.; Cadotte, Marc W.; Sanders, Nathan J.
doi: 10.1111/j.1461-0248.2009.01288.xpmid: 19243408
Recent research in community genetics has examined the effects of intraspecific genetic variation on species diversity in local communities. However, communities can be structured by a combination of both local and regional processes and to date, few community genetics studies have examined whether the effects of instraspecific genetic variation are consistent across levels of diversity. In this study, we ask whether host‐plant genetic variation structures communities of arthropod inquilines within distinct habitat patches – rosette leaf galls on tall goldenrod (Solidago altissima). We found that genetic variation determined inquiline diversity at both local and regional spatial scales, but that trophic‐level responses varied independently of one another. This result suggests that herbivores and predators likely respond to heritable plant traits at different spatial scales. Together, our results show that incorporating spatial scale is essential for predicting the effects of genetically variable traits on different trophic levels and levels of diversity within the communities that depend on host plants.
Stochastic and deterministic processes jointly structure tropical arthropod communitiesFarnon Ellwood, M. D.; Manica, Andrea; Foster, William A.
doi: 10.1111/j.1461-0248.2009.01284.xpmid: 19220392
The question of whether ecological assemblages are structured by stochastic and deterministic (e.g. interspecific competition) processes is controversial, but it is difficult to design sampling regimes and experiments that can dissect the relative importance of stochastic and deterministic processes in natural assemblages. Using null models, we tested communities of arthropod decomposers in tropical epiphytes for patterns of species co‐occurrence, while controlling for habitat gradients, seasonal variations and ecological succession. When environmental conditions were controlled, our analysis showed that the communities were structured stochastically. However, analysing mixed sets of communities that were deliberately created either from two distinct heights or two successional stages revealed that communities were structured deterministically. These results confirm that habitat gradients and dispersal/competition trade‐offs are capable of generating non‐random patterns within decomposer arthropod communities, but reveal that when such effects are accounted for, species co‐occurrence is fundamentally random.
Resource dynamics influence the strength of non‐consumptive predator effects on preyPreisser, Evan L.; Bolnick, Daniel I.; Grabowski, Jonathan H.
doi: 10.1111/j.1461-0248.2009.01290.xpmid: 19243407
Predators influence prey populations both by consuming individual prey, and by inducing changes in prey behaviour that limit reproduction and survival. Because prey trade‐off predation risk for forageing gains, the magnitude of predators’ non‐consumptive effects should depend on resource availability. Studies of non‐consumptive effects generally adopt either of two strategies: (i) maintaining a static ration of the prey’s resources; and (ii) using resource populations that vary dynamically in response to prey behaviour. Contrasting these experimental designs using meta‐analysis, we evaluated whether resource dynamics influence the magnitude of non‐consumptive effects on prey growth, survival, fecundity, population density, forageing rate and habitat use. Predators had a more negative effect on prey demography in dynamic‐ vs. static‐resource experiments. Our results highlight the importance of resource dynamics in mediating the magnitude of non‐consumptive effects of predators on prey, and illustrate the often‐unintended impacts of experimental design on estimates of effect size in ecological interactions.
A link between the North Atlantic Oscillation and measles dynamics during the vaccination period in England and WalesLima, Mauricio
doi: 10.1111/j.1461-0248.2009.01289.xpmid: 19292792
Ecologists have become aware of the role played by interannual climatic variability on the temporal dynamics of infectious diseases. In this report, I present evidence from data on measles cases in England and Wales showing that during the post‐vaccination period, the interannual variability of winter weather (represented by the North Atlantic Oscillation, NAO) influences the annual dynamics of the disease. Using annual measles data from seven cities and simple logistic models, this study reveals how, after vaccination, NAO increases its effects on measles fluctuations. In addition, this study shows that vaccination may be represented as a simple vertical and lateral perturbation effect (Royama’s classification), by reducing the maximum per capita growth rate and the equilibrium number of infected individuals. The results suggest that vaccination will not lead to outbreaks of measles from regular cyclic to irregular chaotic dynamics. In contrast, because of the reduction in per capita growth rates, the disease dynamics appear to be more stable than during the pre‐vaccination period. The analysis of annual data on infectious diseases may be useful for detecting long‐term effects of climate and complements the classical analyses and modeling based on monthly or seasonal time‐step data.
Mechanistic niche modelling: combining physiological and spatial data to predict species’ rangesKearney, Michael; Porter, Warren
doi: 10.1111/j.1461-0248.2008.01277.xpmid: 19292794
Species distribution models (SDMs) use spatial environmental data to make inferences on species’ range limits and habitat suitability. Conceptually, these models aim to determine and map components of a species’ ecological niche through space and time, and they have become important tools in pure and applied ecology and evolutionary biology. Most approaches are correlative in that they statistically link spatial data to species distribution records. An alternative strategy is to explicitly incorporate the mechanistic links between the functional traits of organisms and their environments into SDMs. Here, we review how the principles of biophysical ecology can be used to link spatial data to the physiological responses and constraints of organisms. This provides a mechanistic view of the fundamental niche which can then be mapped to the landscape to infer range constraints. We show how physiologically based SDMs can be developed for different organisms in different environmental contexts. Mechanistic SDMs have different strengths and weaknesses to correlative approaches, and there are many exciting and unexplored prospects for integrating the two approaches. As physiological knowledge becomes better integrated into SDMs, we will make more robust predictions of range shifts in novel or non‐equilibrium contexts such as invasions, translocations, climate change and evolutionary shifts.