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The conservation performance of protected areas (PAs) is typically measured according to whether species are likely to be present within PAs. However, to attain the goal of long-term conservation it is important to consider the performance of PAs in terms of their ability to support the persistence of the species they contain. We used the concept of minimum viable population (MVP) size to examine the potential for PAs within a large national PA network to support mammal species over the long term. By developing habitat models for each species and estimating the area required to support the MVP size for each species, we identified whether each PA had sufficient habitat to meet the species’ requirements. We found that as a whole the PA network is able to support at least one viable population for all species studied. However, the extent of protection offered to species by the PA network varies considerably, with many PAs not able to support viable populations of individual species on their own. By understanding the capacity of PAs to provide long-term protection to species, our findings can guide strategies to increase the resilience of PA networks as a whole, including by improving habitat quality within and connectivity between PAs.

Population viability analyses are useful tools to predict abundance and extinction risk for imperiled species. In southeastern North America, the federally threatened gopher tortoise (Gopherus polyphemus) is a keystone species in the diverse and imperiled longleaf pine (Pinus palustris) ecosystem, and researchers have suggested that tortoise populations are declining and characterized by high extinction risk. We report results from a 30-year demographic study of gopher tortoises in southern Alabama (1991–2020), where 3 populations have been stable and 3 others have declined. To better understand the demographic vital rates associated with stable and declining tortoise populations, we used a multi-state hierarchical markrecapture model to estimate sex- and stage-specific patterns of demographic vital rates at each population. We then built a predictive population model to project population dynamics and evaluate extinction risk in a population viability context. Population structure did not change significantly in stable populations, but juveniles became less abundant in declining populations over 30 years. Apparent survival varied by age, sex, and site; adults had higher survival than juveniles, but female survival was substantially lower in declining populations than in stable ones. Using simulations, we predicted that stable populations with high female survival would persist over the next 100 years but sites with lower female survival would decline, become male-biased, and be at high risk of extirpation. Stable populations were most sensitive to changes in apparent survival of adult females. Because local populations varied greatly in vital rates, our analysis improves upon previous demographic models for northern populations of gopher tortoises by accounting for population-level variation in demographic patterns and, counter to previous model predictions, suggests that small tortoise populations can persist when habitat is managed effectively.

A problem that conservation biologists face is how to monitor species, given both resource limitations and the inherent challenges of assessing long-term demographic processes. We assessed gopher tortoise (Gopherus polyphemus) abundance at a landscape scale and at the scale of 3 local populations within the Conecuh National Forest (CNF).USA between 1991 and 2017. Landscape-level data were collected 26 from line transect distance sampling arranged uniformly across the CNF and collected during a single season (2011); data for local populations were generated from long-term mark-recapture of individuals at three sites selected based on prior knowledge of high density at each. At a landscape scale, we estimated 5,242 (95% CI = 3,538-7,768) tortoises occurred across the approximately 34,000-ha forest, yielding a density of 0.14-0.32 tortoises/ ha. These low densities across the landscape suggest that, on average, management activities across the property have not allowed tortoise populations to retain social structure needed for long-term persistence. The three local populations, however, contained 25-60 individuals and densities of 1.9–6.9 tortoises/ha. Over the study period, populations at two sites were stable and the third experienced significant population growth. Mean annual survival of individuals was 0.89 and invariant across size classes. Altogether, line transect distance sampling is important for assessing landscape-scale abundance of tortoises but may fail to detect local clusters of high-density sites important for population persistence. Our mark-recapture efforts at the local scale revealed that small populations on these high-density sites can exhibit long-term stability or growth even though they do not meet current established criteria for viability. Improved models that incorporate immigration and emigration and better reflect dynamics of peripheral populations would assist in determining how such populations best contribute to species recovery and regional conservation targets.

Conservation planning and biodiversity assessments need quantitative targets to optimize planning options and assess the adequacy of current species protection. However, targets aiming at persistence require population-specific data, which limit their use in favor of fixed and nonspecific targets, likely leading to unequal distribution of conservation efforts among species. We devised a method to derive equitable population targets; that is, quantitative targets of population size that ensure equal probabilities of persistence across a set of species and that can be easily inferred from species-specific traits. In our method, we used models of population dynamics across a range of life-history traits related to species' body mass to estimate minimum viable population targets. We applied our method to a range of body masses of mammals, from 2 g to 3825 kg. The minimum viable population targets decreased asymptotically with increasing body mass and were on the same order of magnitude as minimum viable population estimates from species-and context-specific studies. Our approach provides a compromise between pragmatic, nonspecific population targets and detailed contextspecific estimates of population viability for which only limited data are available. It enables a first estimation of species-specific population targets based on a readily available trait and thus allows setting equitable targets for population persistence in large-scale and multispecies conservation assessments and planning. La planificación de la conservación y las evaluaciones de la biodiversidad necesitan objetivos cuantitativos para optimizar las opciones de planificación y para evaluar la idoneidad de la protección actual de las especies. Sin embargo, los objetivos con miras a la persistencia de poblaciones requieren datos específicos de población, lo que limita su uso a favor de objetivos fijos y no específicos, lo que probablemente resulta en una distribución desigual de los esfuerzos de conservación entre las especies. Diseñamos un método para derivar objetivos de equitativos de población; esto es, objetivos cuantitativos del tamaño de la población que aseguren probabilidades iguales de persistencia en un conjunto de especies y que puedan ser inferidos fácilmente a partir de las características específicas de la especie. En nuestro método utilizamos modelos de dinámica poblacional a lo largo de un rango de características de historias de vida relacionadas con la masa corporal de las especies para estimar poblaciónes mínimas viables objetivo. Aplicamos nuestro método a un rango de masas corporales de mamíferos, desde 2 g hasta 3, 285 kg. Los objetivos de población mínima viable disminuyeron asintóticamente con el incremento de la masa corporal y estuvieron en el mismo orden de magnitud que las estimas de población mínima viable publicadas en estudios, según el contexto y la especie. Nuestro método proporciona un mutuo acuerdo entre los objetivos no específicos y pragmáticos de población y las estimas de viabilidad poblacional detalladas y específicas de contexto, para los que sólo hay información limitada disponible. Esto permite una primera estimación de los objetivos de población específicos de especie basados en una característica ya disponible y por lo tanto habilita el establecimiento de objetivos equitativos para la persistencia poblacional en la planeación y evaluación de la conservación a gran escala y de múltiples especies.

Conservation biologists need to effectively monitor species given resource limitations and the inherent challenges of assessing long-term demographic processes. We assessed gopher tortoise (Gopherus polyphemus) abundance at a landscape scale and at the scale of 3 local populations within the Conecuh National Forest (CNF), Alabama, USA, between 1991 and 2017. We collected landscape-level data from line transect distance sampling arranged uniformly across the CNF during a single season (2011); we obtained data for local populations from long-term mark-recapture of individuals at 3 sites selected based on prior knowledge of high density at each. At a landscape scale, we estimated 5,242 (95% CI=3,538–7,768) tortoises occurred across the approximately 34,000-ha forest, yielding a density of 0.14–0.32 tortoises/ha. These low densities across the landscape suggest that, on average, management activities across the property have not allowed tortoise populations to retain the social structure needed for long-term persistence. The 3 local populations, however, contained 25–60 individuals and densities of 1.9–6.9 tortoises/ha. Over the study period, populations at 2 sites were stable and the third experienced significant population growth. Mean annual survival of individuals was 0.89 and invariant across size classes. Overall, line transect distance sampling is important for assessing landscape-scale abundance of tortoises but may fail to detect local clusters of high-density sites important for population persistence. Our mark-recapture efforts at the local scale revealed that small populations on these high-density sites can exhibit long-term stability or growth even though they do not meet current established criteria for viability. Improved models that incorporate immigration and emigration and better reflect the dynamics of peripheral populations would assist in determining how such populations best contribute to species recovery and regional conservation targets.

The Gravettian is known for its technological innovations and artisanal craftwork. At the same time, continued climatic deterioration led to the coldest and driest conditions since the arrival of Homo sapiens sapiens in Europe. This article examines the palaeodemographic development and provides regionally differentiated estimates for both the densities and the absolute numbers of people. A dramatic population decline characterises the later part of the Gravettian, while the following Last Glacial Maximum experienced consolidation and renewed growth. The results suggest that the abandonment of the northern areas was not a result of migration processes, but of local population extinctions, coinciding with a loss of typological and technological complexity. Extensive networks probably assured the maintenance of a viable population.

In this paper, we propose a simplified bidimensional Wolbachia infestation model in a population of Aedes aegypti mosquitoes, preserving the main features associated with the biology of this species that can be found in higher-dimensional models. Namely, our model represents the maternal transmission of the Wolbachia symbiont, expresses the reproductive phenotype of cytoplasmic incompatibility, accounts for different fecundities and mortalities of infected and wild insects, and exhibits the bistable nature leading to the so-called principle of competitive exclusion . Using tools borrowed from monotone dynamical system theory, in the proposed model, we prove the existence of an invariant threshold manifold that allows us to provide practical recommendations for performing single and periodic releases of Wolbachia -carrying mosquitoes, seeking the eventual elimination of wild insects that are capable of transmitting infections to humans. We illustrate these findings with numerical simulations using parameter values corresponding to the wMelPop strain of Wolbachia that is considered the best virus blocker but induces fitness loss in its carriers. In these tests, we considered multiple scenarios contrasting a periodic release strategy against a strategy with a single inundative release, comparing their effectiveness. Our study is presented as an expository and mathematically accessible tool to study the use of Wolbachia-based biocontrol versus more complex models.

Use of population viability analyses (PVAs) in endangered species recovery planning has been met with both support and criticism. Previous reviews promote use of PVA for setting scientifically based, measurable, and objective recovery criteria and recommend improvements to increase the framework's utility. However, others have questioned the value of PVA models for setting recovery criteria and assert that PVAs are more appropriate for understanding relative trade‐offs between alternative management actions. We reviewed 258 final recovery plans for 642 plants listed under the U.S. Endangered Species Act to determine the number of plans that used or recommended PVA in recovery planning. We also reviewed 223 publications that describe plant PVAs to assess how these models were designed and whether those designs reflected previous recommendations for improvement of PVAs. Twenty‐four percent of listed species had recovery plans that used or recommended PVA. In publications, the typical model was a matrix population model parameterized with ≤5 years of demographic data that did not consider stochasticity, genetics, density dependence, seed banks, vegetative reproduction, dormancy, threats, or management strategies. Population growth rates for different populations of the same species or for the same population at different points in time were often statistically different or varied by >10%. Therefore, PVAs parameterized with underlying vital rates that vary to this degree may not accurately predict recovery objectives across a species’ entire distribution or over longer time scales. We assert that PVA, although an important tool as part of an adaptive‐management program, can help to determine quantitative recovery criteria only if more long‐term data sets that capture spatiotemporal variability in vital rates become available. Lacking this, there is a strong need for viable and comprehensive methods for determining quantitative, science‐based recovery criteria for endangered species with minimal data availability. Uso Actual y Potencial del Análisis de Viabilidad Poblacional para la Recuperación de Especies de Plantas Enlistadas en el Acta de Especies En Peligro de E.U.A

The sand-dune lizard Liolaemus multimaculatus is an Endangered species endemic to the Pampean coastal dunes of Argentina. To inform the development of a future Action Plan for this species, we investigated the demography and conservation status of all remaining populations, and we suggest management actions appropriate to local needs. We used population viability analysis to assess extinction risk in three inbreeding scenarios and estimate the minimum viable population and the minimum area requirement. To assess the current status of each local population, we used information related to population size, human pressure and connectivity. The results were then used to set and prioritize conservation management actions at local level. Our models indicated that populations of > 2,400 individuals would be viable in the long term and that inbreeding depression has a strong effect on extinction risk. The southern patches of coastal dune contain the largest populations of sand-dune lizards, and they are also better connected and less threatened. We suggest land protection as the priority management action for populations larger than the minimum viable population, whereas habitat recovery, when possible, should be the priority for patches of coastal dune smaller than the minimum area requirement. Supplementation with a small number of individuals could stabilize unviable populations but should be considered only in certain situations. The long-term conservation of the sand-dune lizard will be feasible only if a conservation action plan is developed and implemented.

For decades conservation biologists have proposed general rules of thumb for minimum viable population size (MVP); typically, they range from hundreds to thousands of individuals. These rules have shifted conservation resources away from small and fragmented populations. We examined whether iteroparous, long-lived species might constitute an exception to general MVP guidelines. On the basis of results from a 10-year capture-recapture study in eastern New York (U.S.A.), we developed a comprehensive demographic model for the globally threatened bog turtle (Glyptemys muhlenbergii), which is designated as endangered by the IUCN in 2011. We assessed population viability across a wide range of initial abundances and carrying capacities. Not accounting for inbreeding, our results suggest that bog turtle colonies with as few as 15 breeding females have > 90% probability of persisting for > 100 years, provided vital rates and environmental variance remain at currently estimated levels. On the basis of our results, we suggest that MVP thresholds may be 1-2 orders of magnitude too high for many long-lived organisms. Consequently, protection of small and fragmented populations may constitute a viable conservation option for such species, especially in a regional or metapopulation context. Durante décadas, los biólogos de la conservación han propuesto reglas generales básicas para el tamaño poblacional mínimo viable (TMV); típicamente, fluctúan entre cientos y miles de individuos. Estas reglas han desplazado recursos para poblaciones pequeñas y fragmentadas. Examinamos si especies iteróparas, longevas pueden constituir una excepción a las reglas generales del TMV. Con base en los resultados de un estudio de captura-recaptura durante 10 años en el este de Nueva York (E.U.A.), desarrollamos un modelo demográfico integral para la tortuga Glyptemis muhlenbergii amenazada globalmente, considerada en peligro por la UICN (2011). Evaluamos la viabilidad poblacional de un amplio rango de abundancias iniciales y capacidades de carga. Sin considerar la endogamia, nuestros resultados sugieren que colonias de G. muhlenbergiicon tan solo 15 hembras reproductoras tiene >90% de probabilidad de persistir por >100 años, suponiendo que las tasas vitales y la variación ambiental permanecen en los niveles estimados actuales. Con base en nuestros resultados, sugerimos que los umbrales del TMV pueden ser 1-2 órdenes de magnitud más altos para muchos organismos longevos. Consecuentemente, la protección de poblaciones pequeñas y fragmentadas pueden constituir una opción de conservación para tales especies, especialmente en un contexto regional o metapoblacional.