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137
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Introduction
Current institution
Additional affiliations
September 1989 - December 1995
January 2002 - present
Position
- Flow, Fish & Fishing: Population dynamics and fishery management in the turbulent coastal ocean
January 1999 - present
Position
- Demographic heterogeneity and its effects on population & community dynamics
Education
August 1989 - June 1996
September 1982 - June 1986
Publications
Publications (137)
Patchy landscapes select for invasiveness
Invasive species are ubiquitous in human-dominated landscapes, yet we have only limited understanding of their ecological and evolutionary dynamics. Williams et al. used an experimental system with the model plant species Arabidopsis thaliana to examine how evolution affects the spread of plant populations...
http://dx.doi.org/10.1890/14-2080.1
The role of theory within ecology has changed dramatically in recent decades. Once primarily a source of qualitative conceptual framing, ecological theories and models are now often used to develop quantitative explanations of empirical patterns and to project future dynamics of specific ecological systems. In t...
Systematic conservation planning has a substantial theoretical underpinning that allows optimization of tradeoffs between biodiversity conservation and other socioeconomic goals. However, thistheory assumes perfect spatial information about the locations of biodiversity features (e.g., species distributions). In practice, planners represent well-kn...
Aim Species distribution models (SDMs) have been used to address a wide range of theoretical and applied questions in the terrestrial realm, but marine-based applications remain relatively scarce. In this review, we consider how conceptual and practical issues associated with terrestrial SDMs apply to a range of marine organisms and highlight the...
Demographic heterogeneity--variation among individuals in survival and reproduction--is ubiquitous in natural populations. Structured population models address heterogeneity due to age, size, or major developmental stages. However, other important sources of demographic heterogeneity, such as genetic variation, spatial heterogeneity in the environm...
Interdisciplinary research and teaching is intellectually rewarding and practically challenging for the same reason: integrating disciplinary perspectives and methods requires all involved to study and communicate beyond the bounds of their expertise. Project facilitators may offer crucial support in such situations, anticipating needs before strug...
Interdisciplinary projects can be surprisingly challenging for experienced academic collaborators socially, intellectually, and practically. Within disciplines, common sets of philosophical assumptions, practical knowledge-bases, and professional goals can help groups to wrestle though interpersonal differences in attitudes, ideas, priorities and w...
Ocean acidification is a global issue with particular regional significance in the California Current System, where social, economic, and ecological impacts are already occurring. Although ocean acidification is a concern that unifies the entire West Coast region, managing for this phenomenon at a regional scale is complex and further complicated b...
Species reintroductions involve considerable uncertainty, especially in highly altered landscapes. Historical, geographic, and taxonomic analogies can help reduce this uncertainty by enabling conservationists to better assess habitat suitability in proposed reintroduction sites. We illustrate this approach using the example of the California grizzl...
Organisms need access to particular habitats for their survival and reproduction. However, even if all necessary habitats are available within the broader environment, they may not all be easily reachable from the position of a single individual. Many species distribution models consider populations in environmental (or niche) space, hence overlook...
Matrix population models (MPMs) are powerful tools for translating demographic and life history information into a form that can be used to address a wide range of research topics, such as projecting population dynamics, evaluating stressor impacts on populations, and studying life history evolution. However, the reliability of such studies depends...
FULL TEXT FREELY AVAILABLE AT https://escholarship.org/uc/item/4003f1m8
1: Randomized experiments have long been the gold standard in determining causal effects in ecological control‐impact studies. However, it may be difficult to address many ecologically and policy‐relevant control‐impact questions‐such as the effect of forest fragmentation or...
Predicting whether, how, and to what degree communities recover from disturbance remain major challenges in ecology. To predict recovery of coral communities we applied field survey data of early recovery dynamics to a multi‐species integral projection model that captured key demographic processes driving coral population trajectories, notably dens...
Aim
Understanding the processes driving population declines in migratory species can be challenging. Not only are monitoring data spatially and temporally sparse, but conditions in one location can carry over to indirectly (and disproportionately) affect the population in another location. Here, we explore whether remote factors can sequentially, a...
Predicting whether, how, and to what degree communities recover from disturbance remain major challenges in ecology. To predict recovery of coral communities we applied field survey data of early recovery dynamics to a multi‐species integral projection model that captured key demographic processes driving coral population trajectories, notably dens...
Behavioral syndromes are widely recognized as important for ecology and evolution, but most predictions about ecological impacts are based on conceptual models and are therefore imprecise. Borrowing insights from the theory of demographic heterogeneity, we derived insights about the population-dynamic effects of behavioral syndromes. If some indivi...
Understanding how the natural world will be impacted by environmental change over the coming decades is one of the most pressing challenges facing humanity. Addressing this challenge is difficult because environmental change can generate both population-level plastic and evolutionary responses, with plastic responses being either adaptive or nonada...
Some ecologists suggest that trophy hunting (e.g., harvesting males with a desirable trait above a certain size) can lead to rapid phenotypic change, which has led to an ongoing discussion about evolutionary consequences of trophy hunting. Claims of rapid evolution come from the statistical analyses of data, with no examination of whether these res...
FULL TEXT FREELY AVAILABLE AT http://escholarship.org/uc/item/8r20x7qz There is a great deal of interest in the effects of biotic interactions on geographic distributions. Nature contains many different types of biotic interactions (notably mutualism, commensalism, predation, amensalism, and competition), and it is difficult to compare the effects...
Migratory animals are threatened by human-induced global change. However, little is known about how stopover habitat, essential for refuelling during migration, affects the population dynamics of migratory species. Using 20 years of continent-wide citizen science data, we assess population trends of ten shorebird taxa that refuel on Yellow Sea tida...
Some ecologists suggest that trophy hunting (e.g. harvesting males with a desirable trait above a certain size) can lead to rapid phenotypic change, which has led to an ongoing discussion about evolutionary consequences of trophy hunting. Claims of rapid evolution come from the statistical analyses of data, with no examination of whether these resu...
Migratory animals are threatened by human-induced global change. However, little is known about how stopover habitat, essential for refuelling during migration, affects the population dynamics of migratory species. Using 20 years of continent-wide citizen science data, we assess population trends of ten shorebird taxa that refuel on Yellow Sea tida...
Migratory animals are threatened by human-induced global change. However, little is known about how stopover habitat, essential for refuelling during migration, affects the population dynamics of migratory species. Using 20 years of continent-wide citizen science data, we assess population trends of ten shorebird taxa that refuel on Yellow Sea tida...
Supplementary Figures, Supplementary Tables and Supplementary Note
Understanding how the natural world will be impacted by environmental change over the coming decades is one of the most pressing challenges facing humanity. Addressing this challenge is difficult because environmental change can generate both population level plastic and evolutionary responses, with plastic responses being either adaptive or non-ad...
What did coral reef ecosystems look like before human impacts became pervasive? Early efforts to reconstruct baselines resulted in the controversial suggestion that pristine coral reefs have inverted trophic pyramids, with disproportionally large top predator biomass. The validity of the coral reef inverted trophic pyramid has been questioned, but...
![Residual plots to assess Francis [59] model fit
Francis growth model...](publication/313809614/figure/fig3/AS:11431281256135566@1719507327116/Residual-plots-to-assess-Francis-59-model-fit-Francis-growth-model-residuals_Q320.jpg)
For broadly distributed, often overexploited species such as elasmobranchs (sharks and rays), conservation management would benefit from understanding how life history traits change in response to local environmental and ecological factors. However, fishing obfuscates this objective by causing complex and often mixed effects on the life histories o...
Life history models.
(PDF)
Capture-recapture data for Carcharhinus amblyrhynchos caught at Palmyra Atoll used to estimate the Francis growth model.
(PDF)
Behavioral syndromes are widely recognized as important for ecology and evolution, but most predictions about ecological impacts are based on conceptual models and are therefore imprecise. Borrowing insights from the theory of demographic heterogeneity, we derived insights about the population-dynamic effects of behavioral syndromes. If some indivi...
In this study pollinators visiting highbush blueberry fields set in landscapes with differing land use pattern in south-central Chile were investigated. Effects of spatial buffers from 0.5 to 8 km around each blueberry field on the abundance of the main wild pollinator, Bombus terrestris queens, were tested. Wild B. terrestris abundances were posit...
Baseline population estimates are lacking for most species of reef shark. The grey reef shark (Carcharhinus amblyrhynchos), which is listed as Near Threatened on the IUCN Red List of Threatened Species, is highly mobile and therefore particularly difficult to monitor. At the same time, its mobility is precisely what has stymied its protection in mu...
Local increases in sea level caused by global climate change pose a significant threat to the persistence of many coastal plant species through exacerbating inundation, flooding, and erosion. In addition to sea level rise (SLR), climate changes in the form of air temperature and precipitation regimes will also alter habitats of coastal plant specie...
Effective monitoring, prevention and impact mitigation of nonindigenous aquatic species relies upon the ability to predict dispersal pathways and receiving habitats with the greatest risk of establishment. To examine mechanisms affecting species establishment within a large lake, we combined observations of recreational boater movements with empiri...
FULL TEXT FREELY AVAILABLE AT www.escholarship.org/uc/item/5v21m05h
Ecologists are increasingly turning to observational datasets to address hypotheses at large spatial and temporal scales. It is well understood (although often observed in the breach) that applying conventional biometric techniques to such data does not provide causally robust con...
SEE FULL TEXT AT http://escholarship.org/uc/item/5zv4z9f6 Invasive aquatic species pose serious ecological and economic threats to lakes, reservoirs and rivers. This study investigates vectors of introduction of aquatic nuisance species in California and Nevada's water bodies. Our findings show that lakes and reservoirs in California and Nevada are...
Effective monitoring, prevention and impact mitigation of nonindigenous aquatic species (NAS) relies upon the ability to predict dispersal pathways and receiving habitats with the greatest risk of establishment. To examine mechanisms affecting species establishment within a large lake, we combined observations of recreational boater movements with...
Effective monitoring, prevention and impact mitigation of nonindigenous aquatic species (NAS) relies upon the ability to predict dispersal pathways and receiving habitats with the greatest risk of establishment. To examine mechanisms affecting species establishment within a large lake, we combined observations of recreational boater movements with...
Local increases in sea level caused by global climate change pose a significant threat to the persistence of many coastal plant species through exacerbating inundation, flooding, and erosion. In addition to sea level rise (SLR), climate changes in the form of air temperature and precipitation regimes will also alter habitats of coastal plant specie...
Local increases in sea level caused by global climate change pose a significant threat to the persistence of many coastal plant species through exacerbating inundation, flooding, and erosion. In addition to sea level rise (SLR), climate changes in the form of air temperature and precipitation regimes will also alter habitats of coastal plant specie...
FULL TEXT FREELY AVAILABLE AT www.escholarship.org/uc/item/7s4995x4 . . .
Dispersal heterogeneity is increasingly being observed in ecological populations and has long been suspected as an explanation for observations of non-Gaussian dispersal. Recent empirical and theoretical studies have begun to confirm this. Using an integro-difference model,...
Background/Question/Methods
Ecologists seek to anticipate how species interactions shift a species’ range margins (the limit of its geographic distribution). There is a great diversity of types of species interactions and at present, we lack a clear understanding of which species’ interactions most influence species’ range margins. To resolve thi...
FULL TEXT FREELY AVAILABLE FROM http://www.escholarship.org/uc/item/8s5395dz.
Fisheries science often uses population models that assume no external recruitment, but nearshore marine populations harvested on small scales of <200 km often exhibit an unknown mix of self-recruitment and recruitment from external sources. Since empirical determination...
Background / Purpose:
Within-population variation in individual behavior is now recognized as important for ecology and evolution. Some such variation can be classified as behavioral syndromes (also known as animal personality), in which suites of behavioral traits are consistently displayed across ecological contexts. For example, some individua...
Background/Question/Methods
Ecologists have long recognized that individuals within stage or age classes phenotypically vary, but this variation has only recently been added to population models. In plant populations, individuals may vary in growth rate. A simple model shows that when all individuals of an annual plant start at the same size and...
FULL TEXT FREELY AVAILABLE AT www.escholarship.org/uc/item/7vw6c5gg . . . Populations of many species display spatially synchronous fluctuations in abundance. Synchrony is most commonly attributed to three processes: factors that influence recruitment (e.g., dispersal, early survival), large-scale environmental variability, and spatially autocorrel...
Background / Purpose:
Demographic heterogeneity – variation (other than that due to age, size, or stage) in the propensities of individuals within a population to survive, reproduce, and grow – has attracted much attention in recent years. Empirical studies have documented substantial heterogeneity in a number of populations. Theoretical studies...
Background/Question/Methods
Natural populations often exhibit leptokurtic dispersal patterns, with a higher probability of long range dispersal events than predicted by Gaussian diffusion. Heterogeneity in individual dispersal behavior is often observed and has long been suspected to cause such leptokurtosis; this has been confirmed by recent the...
Background/Question/Methods
Species reintroductions – the release of captured or captive-bred organisms into areas within their historic range that they no longer occupy – are an increasingly common tool in conservation, growing exponentially in the past century. Despite accompanying growth in reintroduction-related research and scientific guidanc...
Background/Question/Methods
Demographic heterogeneity -- unmodeled variation in the propensities of individuals in a population to survive, reproduce, and grow -- has attracted much attention in recent years. Empirical studies have documented substantial heterogeneity in a number of populations. Theoretical studies have shown that it can have sub...
The probability of dispersal from one habitat patch to another is a key quantity in our efforts to understand and predict the dynamics of natural populations. Unfortunately, an often overlooked property of this potential connectivity is that it may change with time. In the marine realm, transient landscape features, such as mesoscale eddies and alo...
Among-individual variation in vital parameters such as birth and death rates that is unrelated to age, stage, sex, or environmental fluctuations is referred to as demo-graphic heterogeneity. This kind of heterogeneity is preva-lent in ecological populations, but is almost always left out of models. Demographic heterogeneity has been shown to affect...
Ecology Letters (2012)
Coordinating decisions and actions among interacting sectors is a critical component of ecosystem-based management, but uncertainty about coordinated management’s effects is compromising its perceived value and use. We constructed an analytical framework for explicitly calculating how coordination affects management decisions...
Shorebirds are one of the most well-monitored taxa in Australia. In this paper, we review the spatial and temporal coverage of the Australian shorebird monitoring count data currently administered by Bird Life Australia, and comment on the subset of those data likely to be of immediate use for comprehensive trend analysis. Of the 253 shorebird area...
The precarious state of many nearshore marine ecosystems has prompted the use of marine protected areas as a tool for management and conservation. However, there remains substantial debate over their design and, in particular, how to best account for the spatial dynamics of nearshore marine species. Many commercially important nearshore marine spec...
Estimating the abundance of migratory species is difficult because sources of variability differ substantially among species and populations. Recently developed state-space models address this variability issue by directly modeling both environmental and measurement error, although their efficacy in detecting declines is relatively untested for emp...
Classifying species according to their risk of extinction is a common practice and underpins much conservation activity. The reliability of such classifications rests on the accuracy of threat categorizations, but very little is known about the magnitude and types of errors that might be expected. The process of risk classification involves combini...
Background/Question/Methods
Habitat conversion is a primary threat to terrestrial biodiversity, and fishing is a primary threat to marine biodiversity; both threats can be ameliorated by establishing reserves, if we know where the biodiversity can be found. However, scientists have catalogued only a fraction of the 5-10 million species on Earth....
Ecology Letters (2010) 13: 360–371
Several recent advances in coexistence theory emphasize the importance of space and dispersal, but focus on average dispersal rates and require spatial heterogeneity, spatio-temporal variability or dispersal-competition tradeoffs to allow coexistence. We analyse a model with stochastic juvenile dispersal (driven b...
Demographic stochasticity can have large effects on the dynamics of small populations as well as on the persistence of rare genotypes and lineages. Survival is sensibly modeled as a binomial process, but annual reproductive success (ARS) is more complex and general models for demographic stochasticity do not exist. Here we introduce a stochastic mo...
Simple population models are increasingly being used to predict extinction risk using historical abundance estimates. A very simple model, the stochastic exponential growth (SEG) model, is surprisingly robust. Extinction risk is commonly computed for this model using a mathematical approximation (the “diffusion approximation”) that assumes continuo...
Background/Question/Methods
Demographic heterogeneity – variation in propensities to survive and reproduce – is ubiquitous in natural populations. Most population models disregard heterogeneity other than those reflecting differences in age, size, or major developmental stages. In a series of earlier papers, we showed that this heterogeneity can h...
The objective of grassland management is to maintain keystone species, as well as species diversity, to promote a particular community structure, or to preserve specific ecosystem processes. Studies of grassland management rarely ascertain the effects on rare plant species, although conservation plans for rare herbaceous plants often recommend habi...
Many nearshore fish and invertebrate populations are overexploited even when apparently coherent management structures are in place. One potential cause of mismanagement may be a poor understanding and accounting of stochasticity, particularly for stock recruitment. Many of the fishes and invertebrates that comprise nearshore fisheries are relative...
The establishment of marine protected areas is often viewed as a conflict between conservation and fishing. We considered consumptive and nonconsumptive interests of multiple stakeholders (i.e., fishers, scuba divers, conservationists, managers, scientists) in the systematic design of a network of marine protected areas along California's central c...
Some studies suggest that fishery yields can be higher with reserves than under conventional management. However, the economic performance of fisheries depends on economic profit, not fish yield. The predictions of higher yields with reserves rely on intensive fishing pressures between reserves; the exorbitant costs of harvesting low-density popula...
Effect of reserve configuration on yield and profit.
Change in profit to fisheries operating under suboptimal reserve-based versus optimal conventional management policies.
Both means and year-to-year variances of climate variables such as temperature and precipitation are predicted to change. However, the potential impact of changing climatic variability on the fate of populations has been largely unexamined. We analyzed multiyear demographic data for 36 plant and animal species with a broad range of life histories a...
Lively debate continues over whether marine reserves can lead to increased fishery yields when compared to conventional, quota-based management, apparently driven by differences in the complexity and biological richness of the models being used. In an influential article, Hastings and Botsford used an analytically tractable, spatially implicit, non...
Question: How can we link genotypic, phenotypic, individual, population, and community levels of organization so as to illuminate general ecological and evolutionary processes and provide a framework for a quantitative, integrative evolutionary biology? Framework: We introduce an evolutionary framework that maps different levels of biological diver...
Plant invaders have been suggested to change soil microbial communities and biogeochemical cycling in ways that can feedback to benefit themselves. In this paper, we ask when do these feedbacks influence the spread of exotic plants. Because answering this question is empirically challenging, we show how ecological theory on 'pushed' and 'pulled' in...
Using data on breeding birds from a 35‐year study of Florida scrub‐jays Aphelocoma coerulescens (Bosc 1795), we show that survival probabilities are structured by age, birth cohort, and maternal family, but not by sex. Using both accelerated failure time (AFT) and Cox proportional hazard models, the data are best described by models incorporating v...
Recent advances in stochastic demography provide unique insights into the probable effects of increasing environmental variability on population dynamics, and these insights can be substantially different compared with those from deterministic models. Stochastic variation in structured population models influences estimates of population growth rat...
Ecological and evolutionary change is generated by variation in individual performance. Biologists have consequently long been interested in decomposing change measured at the population level into contributions from individuals, the traits they express and the alleles they carry. We present a novel method of estimating individual contributions to...
Increased temporal variance in life-history traits is generally predicted to decrease individual fitness and population growth. We show that a widely used result of stochastic sensitivity analysis that bolsters this generality is flawed because it ignores the effects of correlations between vital rates. Considering the effects of these correlations...
Individual growth rate of animals is increasingly used as an indicator of ecological stressors. Environmental contaminants often affect physiological processes within individuals, which in turn affect the animal's growth rate. Consequently, there is an increasing need to estimate parameters in physiologically based individual growth models. Here, w...
The forest insect pest Bupalus piniarius (pine looper moth) is a classic example of a natural population cycle. As is typical for populations that exhibit regular oscillations in density, there are several biological mechanisms that are hypothesized to be responsible for the cycles; but despite several decades of detailed study there has been no de...
Invasions by non-native taxa can have severe consequences for native species. In the heavily invaded serpentine grasslands of central California, many native species appear to be restricted to isolated outcrops of shallow serpentine soil, or “hummocks,” although the extent to which these hummocks function as refuges for native vegetation has never...
It has long been recognized that variability in animal size is affected by how individual growth rate is autocorrelated in time. Earlier studies have attributed the mechanism generating the autocorrelation primarily to size-dependent growth rate and autocorre- lation in resource abundance. All of these studies have shown that positive autocorrelati...
Biodiversity is a valuable, but poorly understood, natural resource, which is being lost at an accelerating rate as a result of human actions. We present a broad, introductory review of biodiversity concepts. Biodiversity is first defined at the species and community levels. Available methods and approaches for quantifying biodiversity are discusse...
Demographic stochasticity increases the variance in the growth rate of small populations, and is an important factor to consider when predicting the fates of such populations. Unfortunately, the concept has been treated inconsistently. It is often defined verbally as representing chance variation among individuals in both traits (such as survival p...
Questions
Question (1)
Simple branching process models allow us to explore the effects of demographic stochasticity on extinction risk of a population (absent density dependence or temporal environmental variability). In theory it can be calculated exactly, but in work I am doing it is helpful to use an approximation attributed to Bartlett, in which extinction probability of a branching process with mean m>1 and variance v is exp[-2(m-1)/v].
In his 2001 book, Caswell calls this "Bartlett's approximation" (section on Extinction-effective population size, p. 477 in the 1st edition), citing Bartlett's 1955 book. In Bartlett's book ("An Introduction to Stochastic Processes"), the derivation of this term appears on pp. 40-41. However, it is unclear whether Bartlett was describing something that was already well known, or whether this really is the first appearance of the expression. The application Bartlett gives is to the extinction of a slightly advantageous mutation.
Does anyone know of an earlier occurrence of this approximation, either in the genetics literature or the probability theory literature?
