Atto-Foxes and Other Minutiae.

This paper addresses the problem of extinction in continuous models of population dynamics associated with small numbers of individuals. We begin with an extended discussion of extinction in the particular case of a stochastic logistic model, and how it relates to the corresponding continuous model. Two examples of 'small number dynamics' are then considered. The first is what Mollison calls the 'atto-fox' problem (in a model of fox rabies), referring to the problematic theoretical occurrence of a predicted rabid fox density of [Formula: see text] (atto-) per square kilometre. The second is how the production of large numbers of eggs by an individual can reliably lead to the eventual survival of a handful of adults, as it would seem that extinction then becomes a likely possibility. We describe the occurrence of the atto-fox problem in other contexts, such as the microbial 'yocto-cell' problem, and we suggest that the modelling resolution is to allow for the existence of a reservoir for the extinctively challenged individuals. This is functionally similar to the concept of a 'refuge' in predator-prey systems and represents a state for the individuals in which they are immune from destruction. For what I call the 'frogspawn' problem, where only a few individuals survive to adulthood from a large number of eggs, we provide a simple explanation based on a Holling type 3 response and elaborate it by means of a suitable nonlinear age-structured model.

Family Resilience in a Resource-Cursed Community Dependent on the Oil and Gas Industry.

The economic and social well-being of rural, "resource-cursed" communities can depend on the boom-bust cycles of a single industry like oil and gas. This study used a constructivist, inductive approach to identify the challenges placed on families in one such community and the processes that strengthen family resilience. Semi-structured interviews were conducted with 35 adult residents (30-76 years old, 19 women) from a community in Alberta, Canada, that has specialized in oil and gas extraction for 70 years and experienced its worst economic downturn while the study was underway. Results showed that many families have experienced an endless cycle of poor work-life balance and income instability throughout the economic cycle. Family life often lacked social cohesion as a consequence of demanding work schedules and economic pressures. Additional challenges were the perceived negative effects of rigid gender roles, substance abuse, family conflicts, and domestic violence. Crucial strengthening processes for family resilience were fundamental financial and living standard adaptations (e.g., living within or below one's economic means; having both spouses become earners), maintaining regular contact by having a flexible home routine, and mutually agreeing to change roles during busts (former earners take responsibility for caregiving and running of the household and vice versa). Alternatively, accepting economic volatility and its impact on normal family life processes were essential for family resilience. Findings suggest the need for clinicians to help families foster resilience in communities that depend on resource extraction industries with concurrent adaptations required by individuals, families, and socio-political and economic systems.

El bienestar económico y social de las comunidades rurales "malditas por los recursos" puede depender de los ciclos de auge y caída de una industria única como la del petróleo y el gas. En este estudio se usó un método constructivista e inductivo para identificar las dificultades que enfrentan las familias en una comunidad de este tipo y los procesos que fortalecen la resiliencia familiar. Se realizaron entrevistas semiestructuradas con 35 adultos residentes (de entre 30 y 76 años, 19 mujeres) de una comunidad de Alberta, Canadá, que se ha especializado en la extracción de petróleo y gas durante 70 años y sufrió su peor recesión económica mientras el estudio estaba en marcha. Los resultados indicaron que muchas familias han pasado por un ciclo interminable de desequilibrio entre la vida personal y la laboral, y por la inestabilidad de ingresos durante todo el ciclo económico. La vida familiar con frecuencia careció de integración social como consecuencia de horarios de trabajo demandantes y presiones económicas. Otras dificultades fueron los efectos negativos percibidos de los roles de género rígidos, el abuso de sustancias, los conflictos familiares y la violencia doméstica. Los procesos de fortalecimiento esenciales para la resiliencia familiar fueron las adaptaciones fundamentales de los niveles de vida y económicos (p. ej.: vivir dentro o por debajo de los medios económicos propios; hacer que ambos cónyuges sean asalariados), mantener contacto periódico teniendo una rutina flexible en el hogar y acordar mutuamente cambiar de roles durante las recesiones (los exasalariados asumen la responsabilidad del cuidado y el funcionamiento del hogar, y viceversa). Alternativamente, aceptar la volatilidad económica y su efecto en los procesos normales de la vida familiar fue esencial para la resiliencia familiar. Los resultados indican la necesidad de que los profesionales clínicos ayuden a las familias a fomentar la resiliencia en las comunidades que dependen de las industrias de extracción de recursos mediante adaptaciones simultáneas necesarias para las personas, las familias y los sistemas sociopolíticos y económicos.

Dynamics of bird assemblages in response to temporally and spatially variable resources in arid Australia.

Bird assemblages in arid Australia are often characterized as being highly variable through time in response to boom and bust dynamics, although the importance of habitat in structuring assemblages at a local-scale is also recognized. We use a novel approach to investigate the importance of rainfall variability in structuring bird assemblages in a resource-limited environment. Monthly bird surveys were conducted at ten plots for 8 years at a botanical and zoological park in central Australia, including five irrigated plots within a fenced area and five natural plots outside. Irrigation-used to promote growth, flowering, and fruiting of plants-created an artificial resource-enhanced environment against which the response of birds to natural fluctuations in season and rainfall were compared. Species richness was generally maintained at a higher level in resource-enhanced plots during dry times but was higher in natural plots when rainfall was high, mainly due to increases in granivores and insectivores. Honeyeaters were consistently more abundant at irrigated plots. Rainfall was important in structuring bird assemblages at all plots; however, assemblages were more stable in irrigated plots and did not respond as dramatically to a period of very high rainfall. The comparative smoothing of fluctuations in the composition and abundance of birds in irrigated areas highlights the importance of primary productivity, normally tied to rainfall, in driving temporal change in arid-zone bird communities. There was also evidence that different plots in differing habitats supported distinct bird assemblages and that this spatial distinctiveness persisted irrespective of rainfall and determined, to some extent, the response to rainfall. Our study is one of few long-term studies of arid bird assemblages and highlights the importance of both long-term cycles of productivity driven by rain and season as well as site differences in the dynamics of arid-zone bird communities. These insights are particularly valuable as climate change further exacerbates rainfall variability worldwide and initiatives to conserve avifauna in increasingly extreme environments may be required.

Latitudinal influence on gametogenesis and host-parasite ecology in a marine bivalve model.

Reproduction and parasites have significant impacts on marine animal populations globally. This study aimed to investigate the associative effects of host reproduction and a host-parasite interplay on a marine bivalve, along a geographic gradient of latitude. Cockles Cerastoderma edule were sampled from five European sites (54°N to 40°N), between April 2018 and October 2019. A histological survey provided data on trematode (metacercaria and sporocyst life stages), prevalence, and cockle stage of gametogenesis to assess the influence of a latitudinal gradient on both interplays. Sex ratios at the northernmost sites were skewed toward females, and spawning size was reduced at the lower latitudes. Trematode infection did not follow a latitudinal gradient. Localized site-related drivers, namely seawater temperature, varied spatially, having an impact on cockle-trematode interactions. Spawning was related to elevated temperatures at all sites. Prolonged spawning occurred at southern latitudes, where seawater temperatures were warmer. Trematode prevalence and the impact of trematodes on gametogenesis were found to be spatially variable, but not latitudinally. Therefore, it is not possible to determine the likelihood of boom and bust events in cockles, based on the latitudinal location of a population. In terms of sublethal impacts, it appeared that energy was allocated to reproduction rather than somatic growth in southern populations, with less energy allocated to reproduction in the larger, northern cockles. The demonstrated spatial trend of energy allocation indicates the potential of a temporal trend of reduced cockle growth at northern sites, as a result of warming sea temperatures. This awareness of the spatially varying drivers of populations is crucial considering the potential for these drivers/inhibitors to be exacerbated in a changing marine environment.

Resilience in Times of Economic Boom and Bust: A Narrative Study of a Rural Population Dependent upon the Oil and Gas Industry.

How do residents of small towns that depend on oil and gas extraction or processing industries withstand economic boom and bust cycles? To answer this question, this article reports on a narrative analysis of residents' life stories gathered from 37 adults of a small town on the Canadian prairies dependent on the oil and gas industry, employing the theories of narrative inquiry and narrative identity. Participants aged 30 to 76 were interviewed and their experiences of living in an unstable economy that is dependent mostly on a single resource extraction industry were explored. Specifically, we asked participants about the effect of economic change on factors related to resilience like family interactions, work choices, educational pathways, and the quality of their social lives. Our analysis of adult narratives looked for patterns in the relationship between risk exposure, promotive and protective factors at multiple systemic levels (individual, relational, cultural), and functional outcomes such as individual coping, community cohesion, and social and economic sustainability. Results show that a strong identity, in particular expressions of personal agency, communion, and engagement in meaning making are contributing factors to adult resilience in a context of economic change. Our results also highlight how positive attitudes towards a better future may inadvertently undermine the need for residents of oil and gas-dependent towns to commit to economic diversification and other potential resilience-promoting strategies.

Formulating spread of species with habitat dependent growth and dispersal in heterogeneous landscapes.

Habitat heterogeneity can have profound effects on the spreading dynamics of invasive species. Using integro-difference equations, we investigate the spreading dynamics in a one-dimensional heterogeneous landscape comprising alternating favourable and unfavourable habitat patches or randomly generated habitat patches with given spatial autocorrelation. We assume that population growth and dispersal (including emigration probability and dispersal distance) are dependent on habitat quality. We derived an approximation of the rate of spread in such heterogeneous landscapes, suggesting the sensitivity of spread to the periodic length of the alternating favourable and unfavourable patches, as well as their spatial autocorrelation. A dispersal-limited population tends to spread faster in landscapes with shorter periodic length. The spreading dynamics in a heterogeneous landscape was found to be not only dependent on the availability of favourable habitats, but also the dispersal strategy. Estimates of time lag before detection and the condition for boom-and-bust spreading dynamics were explained. Furthermore, rates of spread in heterogeneous landscapes and corresponding homogeneous landscapes were compared, using weighted sums of vital rates.