Extinction Of Local Populations Research Articles

Climate change may shift metapopulations towards unstable source-sink dynamics in a fire-killed, serotinous shrub.

Climate change, with warming and drying weather conditions, is reducing the growth, seed production, and survival of fire-adapted plants in fire-prone regions such as Mediterranean-type ecosystems. These effects of climate change on local plant demographics have recently been shown to reduce the persistence time of local populations of the fire-killed shrub Banksia hookeriana dramatically. In principle, extinctions of local populations may be partly compensated by recolonization events through long-distance dispersal mechanisms of seeds, such as post-fire wind and bird-mediated dispersal, facilitating persistence in spatially structured metapopulations. However, to what degree and under which assumptions metapopulation dynamics might compensate for the drastically increased local extinction risk remains to be explored. Given the long timespans involved and the complexity of interwoven local and regional processes, mechanistic, process-based models are one of the most suitable approaches to systematically explore the potential role of metapopulation dynamics and its underlying ecological assumptions for fire-prone ecosystems. Here we extend a recent mechanistic, process-based, spatially implicit population model for the well-studied fire-killed and serotinous shrub species B. hookeriana to a spatially explicit metapopulation model. We systematically tested the effects of different ecological processes and assumptions on metapopulation dynamics under past (1988-2002) and current (2003-2017) climatic conditions, including (i) effects of different spatio-temporal fires, (ii) effects of (likely) reduced intraspecific plant competition under current conditions and (iii) effects of variation in plant performance among and within patches. In general, metapopulation dynamics had the potential to increase the overall regional persistence of B. hookeriana. However, increased population persistence only occurred under specific optimistic assumptions. In both climate scenarios, the highest persistence occurred with larger fires and intermediate to long inter-fire intervals. The assumption of lower intraspecific plant competition caused by lower densities under current conditions alone was not sufficient to increase persistence significantly. To achieve long-term persistence (defined as >400 years) it was necessary to additionally consider empirically observed variation in plant performance among and within patches, that is, improved habitat quality in some large habitat patches (≥7) that could function as source patches and a higher survival rate and seed production for a subset of plants, specifically the top 25% of flower producers based on current climate conditions monitoring data. Our model results demonstrate that the impacts of ongoing climate change on plant demographics are so severe that even under optimistic assumptions, the existing metapopulation dynamics shift to an unstable source-sink dynamic state. Based on our findings, we recommend increased research efforts to understand the consequences of intraspecific trait variation on plant demographics, emphasizing the variation of individual traits both among and within populations. From a conservation perspective, we encourage fire and land managers to revise their prescribed fire plans, which are typically short interval, small fires, as they conflict with the ecologically appropriate spatio-temporal fire regime for B. hookeriana, and likely as well for many other fire-killed species.

No recruits for an ageing population: First signs of probable population extinction in one of the last reservoirs of the Critically Endangered species Pinna nobilis

Monitoring threatened species is essential for setting conservation priorities and measures to prevent species extinction. The endemic species Pinna nobilis is now classified on the IUCN Red List as a critically endangered species, with the only possibility to observe entire populations in very specific coastal areas, and a few resistant individuals in open waters. Thus, monitoring and management of these populations are crucial to avoid global species extinction. The present study aims to monitor P. nobilis Mar Menor's coastal lagoon population and to evaluate its possible resilience to recuperate from several environmental catastrophes and human mediated impacts that drastically decimated the population between 2016 and 2019. To do so, between 2019 and 2022, we assessed its population maintenance and its reproductive success. First, we monitored changes in overall densities and shell growth, and we installed between 23 and 45 larvae collectors to assess reproductive success. We observed stabilization of population densities and positive shell growth of individuals. However, no incorporation of recruits into this ageing population was observed. Our results highlighted the lack of species recovery and the first signs of probable local population extinction. Therefore, urgent management and conservation actions focused on restoring the ecosystem and protecting P. nobilis individuals are needed to avoid this population extinction and loss of one of the last reservoirs of this emblematic species.

An Updated Review of The Quaternary Hippopotamus Fossil Records from the Iberian Peninsula

This work presents a comprehensive review of the Quaternary fossil records of hippopotamuses from the Iberian Peninsula, unveiling biogeographical insights of global significance. The results presented herein include the inference of a delayed arrival of Hippopotamus (Hippopotamus antiquus) populations onto the Iberian Peninsula compared to other European Mediterranean regions, with an estimated age of ca. 1.7 Ma, in contrast to 2.1–2.2 Ma elsewhere. Moreover, we hypothesize the possibility of a short-lived coexistence between H. antiquus and Hippopotamus amphibius, close to the extinction of the former taxon (ca. 0.45 Ma). The local extinction of all hippopotamus populations on the Iberian Peninsula between MIS 5 and 3 is suggested here, mirroring proposals made for the Italian peninsula. Notable aspects of this fossil record include the abundance of specimens, previously undocumented anatomical elements, and partially complete individuals with articulated body segments. The remains analyzed herein also present different ontogenetic stages and sexual dimorphism. Moreover, the presence of specimens displaying paleopathologies provides valuable insights into ethological and paleoecological studies. The exceptional record of at least three events of human exploitation of hippopotamus stands out, with this being a rarity in the broader context of the archaeological and paleontological record of the European continent.

Genome size variation within Crithmum maritimum: Clues on the colonization of insular environments

Angiosperms present an astonishing diversity of genome sizes that can vary intra- or interspecifically. The remarkable new cytogenomic data shed some light on our understanding of evolution, but few studies were performed with insular and mainland populations to test possible correlations with dispersal, speciation, and adaptations to insular environments. Here, patterns of cytogenomic diversity were assessed among geographic samples (ca. 114) of Crithmum maritimum (Apiaceae), collected across the Azores and Madeira archipelagos, as well as in adjacent continental areas of Portugal. Using flow cytometry, the results indicated a significant intraspecific genome size variation, spanning from reduced sizes in the insular populations to larger ones in the mainland populations. Moreover, there was a tendency for an increase in genome size along the mainland populations, associated with lower temperatures, higher precipitation, and lower precipitation seasonality. However, this gradient might be the result of historic phylogeographical events associated with previous dispersal and extinction of local populations. Overall, our findings provided evidence that smaller genome sizes might play a critical role in the colonization of islands, corroborating other studies that argue that organisms with smaller genomes use fewer resources, having a selective advantage under insular environments. Although further studies are needed to improve our understanding of the mechanisms underlying genome size evolution on islands, conservation strategies must be promoted to protect the rich cytogenomic diversity found among C. maritimum populations, which occur in coastal areas that are particularly threatened by human activity, pollution, invasive species, and climate changes.

Contrasting long‐term trends in juvenile abundance of a widespread cold‐water salmonid along a latitudinal gradient: effects of climate, stream size and migration strategy

A changing climate reshapes the range distribution of many organisms, and species with relatively low thermal optima, like many salmonids, are increasingly expected to face local population extinctions at lower latitudes. Understanding where and how fast these changes are happening is of pivotal importance for successful mitigation and conservation efforts.We used an extensive electrofishing database to explore temporal trends of juveniles of brown troutSalmo truttain 218 locations from 174 Swedish streams, over the last 30 years (1991–2020). We hypothesized that 1) declines in abundance have occurred predominately in the warmer, southern regions, while increases have occurred in the colder, northern regions, 2) larger stream sizes may partly offset negative effects of climate, and 3) migrating and resident populations are affected differently by a warming climate.We found that abundance of brown trout juveniles generally declined in warmer regions especially in smaller streams (≤ 6 m wide), while the abundance increased in colder regions. In larger streams, negative effects of higher temperatures were seemingly buffered, as we found lower rates of decline or even positive trends. The rate of change (i.e. the slopes of the trends in abundance) was more pronounced towards the climate extremes, and was on average zero in regions with a normal annual air temperature (average temperature over 30 year period) around 5–6 °C. Warmer climate had stronger effects on migrating compared to resident populations, suggesting that climate‐induced loss of stream connectivity could be an additional factor that hinders recruitment in anadromous populations in a changing climate.Considering predictions of increasing temperatures and frequency of summer droughts, management of cold‐water salmonid populations should focus on conserving and restoring riparian vegetation, wetlands, climate and thermal refugia, and habitat integrity overall. Such measures may, however, not suffice for small streams at lower latitudes, unless hydrological connectivity is maintained.

Genetic Diversity and Population Structure Derived from Body Remains of the Endangered Flightless Longhorn Beetle Iberodorcadion fuliginator in Grassland Fragments in Central Europe

Knowledge of patterns of genetic diversity in populations of threatened species is vital for their effective conservation. However, destructive sampling should be avoided in threatened species so as not to additionally increase the risk of local population extinction. We exclusively used beetle remains and beetles collected after death to analyze local and regional patterns of genetic variation in the endangered flightless longhorn beetle Iberodorcadion fuliginator in the border region of Switzerland, France and Germany, in grassland remnants. We extracted DNA from the beetles’ remains and genotyped 243 individuals at 6 microsatellite loci. We found moderate genetic differentiation between populations, each belonging to one of two metapopulations situated on either side of the river Rhine, but distinct genetic differentiation between populations across metapopulation. The genetic distance between populations was correlated with the geographic distance between the sites sampled. Genetic structure analysis inferred the presence of two genetic clusters. The populations in the Alsace (France) represent one cluster, together with the Swiss populations near Basel, which is separated by the river Rhine from the cluster composed of the populations in southwestern Germany. Thus, the historical separation by the river Rhine surpasses more recent effects of human-induced habitat fragmentation on the genetic differentiation in I. fuliginator.

Anthropogenic threats to the Vulnerable Andean Condor in northern South America.

Vultures comprise one of the most threatened groups of birds worldwide. With a total population not exceeding 6700 mature individuals, and in rapid decline across its range, the Andean Condor (Vultur gryphus) is listed as a Vulnerable species in the IUCN red list. Local population extinctions and decline are of particular concern in northern South America, where no more than 340 condors may exist at present. Despite this, no quantitative assessments exist in Ecuador, Colombia, and Venezuela regarding the threats affecting Andean Condor populations. To address this, we compiled records of Andean Condors injured, or killed, between 1979 and 2021. We obtained data of 164 condors affected by different causes of injury, of which 83.5% were reported in Ecuador, 15.2% in Colombia, and 1.2% in Venezuela. Of the total number, 84.7% of the injured individuals died. Between 1979 and 2021, in Ecuador, Colombia and Venezuela, at least 103 Andean Condors were presumably poisoned, 22 were shot, and 39 individuals were affected by other causes. The total number of individuals affected by different causes represents between 48% and 72% of the total population estimated in northern South America. Of great concern is the fact that, between 2007 and 2021, poisoning and shooting together caused the loss of 19-31% of the estimated population of condors in Ecuador, and 7-21% of the estimated population in Colombia. Given the important mortality induced by humans, environmental education programs, socio-ecological research, application of environmental laws, and management strategies based on scientific evidence to prevent and mitigate human-wildlife conflicts are urgently required for effective Andean Condor conservation in northern South America.

Freshwater Reservoir, Ecological Traps and Source-Sink Dynamics

Odonata are biodiversity indicators that adequately represent many aquatic and semi-aquatic animal species. We recorded over two field seasons a rich lentic community of Odonata (18 species) in a large artificial freshwater reservoir (ca. 55 ha) built 40 years ago. The release of water from the dam in summer for crop irrigation leads to the desiccation of large parts of the reservoir, which prevents the reproduction of half of the species of this Odonata community. We identify two adaptations that allow eight species to cope with desiccation, i.e., a precocious breeding period allowing the emergence of adults before the retreat of water, or a delayed adult emergence due to egg diapause from oviposition to the end of winter. The reservoir acts thus as an ecological trap for individuals of 10 species that developed elsewhere and were attracted to the site without successfully breeding there. As consequence of the local population extinction at each generation, the presence of individuals of these 10 species at the reservoir depends on source-sink population dynamics in the landscape. In the context of global warming that encourages the creation of artificial freshwater reservoirs, the multiplication of such sinks could threaten the persistence in the landscape of species maladapted to desiccation.

The Critically Endangered El Rincon stream frog: Population viability and management actions in Patagonia, Argentina

Abstract The El Rincon stream frog (Pleurodema somuncurense) is a microendemic species currently restricted to the thermal headwaters of the Valcheta Stream in the Somuncura Plateau, Northern Patagonia, Argentina. This species is listed as Critically Endangered on the IUCN Red List. The critical status of the El Rincon stream frog requires urgent management actions. Population viability analysis is one of the most effective tools to predict extinction risk and assess the potential effect of management actions. It is also helpful in knowing the minimum viable population (MVP) and minimum area requirements (MAR). However, this tool is rarely used to model viability in endangered amphibians. This work aimed to: (i) estimate the extinction risk of each local population of El Rincon stream frogs; (ii) estimate the MVP and MAR; and (iii) model reintroduction and supplementation of the population as management strategies for this species. Practical management actions are also suggested for each relict population. Population viability analyses were developed in Vortex 10.3.5.0 to estimate each local population's extinction risk, MVP and MAR. Supplementation and reinforcement of individuals were also modelled for local populations that are below the MVP. The estimated MVP was 430 individuals, while MAR reached 683 m2. Modelling of reintroducing individuals showed that a single reintroduction of at least 50 adults, 140 juveniles, or 1,000 tadpoles would be needed to achieve a viable population. Local populations below the MVP would benefit from supplementation of a pair of adult frogs every 17 to 20 years. This study provides a fundamental basis for assessing and improving current management and planning future conservation strategies within the framework of the El Rincon stream frog action plan.

Short and long-term exposure to the pesticides fipronil and 2,4-D: Effects on behavior and life history of Daphnia magna

The high levels of contamination in aquatic ecosystems caused by pesticides and the organisms’ consequent continuous exposure to it has made them vulnerable to damage. However, mobile organisms can avoid this continued exposure to contaminants by moving to less disturbed habitats. Therefore, through the use of the Heterogenous Multi-Habitat Assay System (HeMHAS), our objective was to evaluate the ability of Daphnia magna to detect and avoid habitats contaminated by fipronil and 2,4-D, in a spatially connected landscape. Further, the role of contamination by these pesticides, isolated and in mixtures, concerning the colonization of habitats by daphnids was also evaluated. Given that not all organisms successfully escape contamination, the chronic toxicity of the same pesticides using different parameters for D. magna (maternal survival, fecundity and maternal body length) was also evaluated. When evaluating the avoidance response by D. magna exposed to pesticides, there was no preference for the less contaminated areas for both compounds. However, organisms did not move to contaminated zones in the colonization experiments, with no immigration of daphnids to the zones with intermediate and the highest levels of fipronil, nor to the highest concentration of 2,4-D. Finally, the colonization by daphnids was significantly prevented when exposed to a mixture of the pesticides, in which the areas with the highest combinations of pesticide concentrations were not colonized by D. magna. Regarding the long-term chronic effects, negative consequences were observed, particularly for maternal body length, fecundity and maternal survival, due to the exposure to fipronil. Considering that pesticides can limit the areas colonized by organisms by making them unattractive, the risk of local population extinction may be underestimated if only standard endpoints involving forced exposure are studied.

Environmental conditions lead to shifts in individual communication, which can cause cascading effects on soundscape composition.

Climate change is increasing aridity in grassland and desert habitats across the southwestern United States, reducing available resources and drastically changing the breeding habitat of many bird species. Increases in aridity reduce sound propagation distances, potentially impacting habitat soundscapes, and could lead to a breakdown of the avian soundscapes in the form of loss of vocal culture, reduced mating opportunities, and local population extinctions. We developed an agent‐based model to examine how changes in aridity will affect both sound propagation and the ability of territorial birds to audibly contact their neighbors. We simulated vocal signal attenuation under a variety of environmental scenarios for the south, central semi‐arid prairies of the United States, ranging from contemporary weather conditions to predicted droughts under climate change. We also simulated how changes in physiological conditions, mainly evaporative water loss (EWL), would affect singing behavior. Under contemporary and climate change‐induced drought conditions, we found that significantly fewer individuals successfully contacted all adjacent neighbors than did individuals in either the contemporary or predicted climate change conditions. We also found that at higher sound frequencies and higher EWL, fewer individuals were able to successfully contact all their neighbors, particularly in drought and climate change drought conditions. These results indicate that climate change‐mediated aridification may alter the avian soundscape, such that vocal communication no longer effectively functions for mate attraction or territorial defense. As climate change progresses, increased aridity in current grasslands may favor shifts toward low‐frequency songs, colonial resource use, and altered songbird community compositions.

Genetic diversity loss in the Anthropocene.

Anthropogenic habitat loss and climate change are reducing species' geographic ranges, increasing extinction risk and losses of species' genetic diversity. Although preserving genetic diversity is key to maintaining species' adaptability, we lack predictive tools and global estimates of genetic diversity loss across ecosystems. We introduce a mathematical framework that bridges biodiversity theory and population genetics to understand the loss of naturally occurring DNA mutations with decreasing habitat. By analyzing genomic variation of 10,095 georeferenced individuals from 20 plant and animal species, we show that genome-wide diversity follows a mutations-area relationship power law with geographic area, which can predict genetic diversity loss from local population extinctions. We estimate that more than 10% of genetic diversity may already be lost for many threatened and nonthreatened species, surpassing the United Nations' post-2020 targets for genetic preservation.

Climate matching and anthropogenic factors contribute to the colonization and extinction of local populations during avian invasions

AbstractAimConcern about the impacts of biological invasions has generated a great deal of interest in understanding factors that determine invasion success. Most of our current knowledge comes from static approaches that use spatial patterns as a proxy of temporal processes. These approaches assume that species are present in areas where environmental conditions are the most favourable. However, this assumption is problematic when applied to dynamic processes such as species expansions when equilibrium has not been reached.LocationIberian Peninsula.TaxonBirds.MethodsIn our work, we analyse the roles played by human activities, climatic matching and spatial connectivity on the two main underlying processes shaping the spread of invasive species (i.e. colonization and extinction) using a dynamic modelling approach. We use a large data set that has recorded the occurrence of two invasive bird species—the ring‐necked (Psittacula krameri) and the monk (Myiopsitta monachus) parakeets—in the Iberian Peninsula from 1991 to 2016.ResultsHuman activities and climate matching play a role on species range dynamics. Human influence and urbanization were the most relevant factors explaining colonization. Additionally, an effect of climate matching was found. Persistence (the inverse of extinction) was mainly affected by human influence for the monk parakeet and by the extent of urban environments for the ring‐necked parakeet.Main conclusionsHuman activities play a major role not only on colonization of new locations, but also on persistence during range expansion. Additionally, natural processes—notably climate matching—also affect new colonizations. These findings add to our understanding of the mechanisms that might allow alien species to expand their geographic range at new locations and might help to improve our capacity to assess invasion risks and impacts accurately.

Tracking population genetic signatures of local extinction with herbarium specimens.

Habitat degradation and landscape fragmentation dramatically lower population sizes of rare plant species. Decreasing population sizes may, in turn, negatively affect genetic diversity and reproductive fitness, which can ultimately lead to local extinction of populations. Although such extinction vortex dynamics have been postulated in theory and modelling for decades, empirical evidence from local extinctions of plant populations is scarce. In particular, comparisons between current vs. historical genetic diversity and differentiation are lacking despite their potential to guide conservation management. We studied the population genetic signatures of the local extinction of Biscutella laevigata subsp. gracilis populations in Central Germany. We used microsatellites to genotype individuals from 15 current populations, one ex situ population, and 81 herbarium samples from five extant and 22 extinct populations. In the current populations, we recorded population size and fitness proxies, collected seeds for a germination trial and conducted a vegetation survey. The latter served as a surrogate for habitat conditions to study how habitat dissimilarity affects functional connectivity among the current populations. Bayesian clustering revealed similar gene pool distribution in current and historical samples but also indicated that a distinct genetic cluster was significantly associated with extinction probability. Gene flow was affected by both the spatial distance and floristic composition of population sites, highlighting the potential of floristic composition as a powerful predictor of functional connectivity which may promote decision-making for reintroduction measures. For an extinct population, we found a negative relationship between sampling year and heterozygosity. Inbreeding negatively affected germination. Our study illustrates the usefulness of historical DNA to study extinction vortices in threatened species. Our novel combination of classical population genetics together with data from herbarium specimens, an ex situ population and a germination trial underlines the need for genetic rescue measures to prevent extinction of B. laevigata in Central Germany.

Declining pollination success reinforces negative climate and fire change impacts in a serotinous, fire-killed plant

Climate change projections predict that Mediterranean-type ecosystems (MTEs) are becoming hotter and drier and that fires will become more frequent and severe. While most plant species in these important biodiversity hotspots are adapted to hot, dry summers and recurrent fire, the Interval Squeeze framework suggests that reduced seed production (demographic shift), reduced seedling establishment after fire (post fire recruitment shift), and reduction in the time between successive fires (fire interval shift) will threaten fire killed species under climate change. One additional potential driver of accelerated species decline, however, has not been considered so far: the decrease in pollination success observed in many ecosystems worldwide has the potential to further reduce seed accumulation and thus population persistence also in these already threatened systems. Using the well-studied fire-killed and serotinous shrub species Banksia hookeriana as an example, we apply a new spatially implicit population simulation model to explore population dynamics under past (1988–2002) and current (2003–2017) climate conditions, deterministic and stochastic fire regimes, and alternative scenarios of pollination decline. Overall, model results suggest that while B. hookeriana populations were stable under past climate conditions, they will not continue to persist under current (and prospective future) climate. Negative effects of climatic changes and more frequent fires are reinforced by the measured decline in seed set leading to further reduction in the mean persistence time by 12–17%. These findings clearly indicate that declining pollination rates can be a critical factor that increases further the pressure on the persistence of fire-killed plants. Future research needs to investigate whether other fire-killed species are similarly threatened, and if local population extinction may be compensated by recolonization events, facilitating persistence in spatially structured meta-communities.

Fire as a driver and mediator of predator-prey interactions.

ABSTRACTBoth fire and predators have strong influences on the population dynamics and behaviour of animals, and the effects of predators may either be strengthened or weakened by fire. However, knowledge of how fire drives or mediates predator–prey interactions is fragmented and has not been synthesised. Here, we review and synthesise knowledge of how fire influences predator and prey behaviour and interactions. We develop a conceptual model based on predator–prey theory and empirical examples to address four key questions: (i) how and why do predators respond to fire; (ii) how and why does prey vulnerability change post‐fire; (iii) what mechanisms do prey use to reduce predation risk post‐fire; and (iv) what are the outcomes of predator–fire interactions for prey populations? We then discuss these findings in the context of wildlife conservation and ecosystem management before outlining priorities for future research. Fire‐induced changes in vegetation structure, resource availability, and animal behaviour influence predator–prey encounter rates, the amount of time prey are vulnerable during an encounter, and the conditional probability of prey death given an encounter. How a predator responds to fire depends on fire characteristics (e.g. season, severity), their hunting behaviour (ambush or pursuit predator), movement behaviour, territoriality, and intra‐guild dynamics. Prey species that rely on habitat structure for avoiding predation often experience increased predation rates and lower survival in recently burnt areas. By contrast, some prey species benefit from the opening up of habitat after fire because it makes it easier to detect predators and to modify their behaviour appropriately. Reduced prey body condition after fire can increase predation risk either through impaired ability to escape predators, or increased need to forage in risky areas due to being energetically stressed. To reduce risk of predation in the post‐fire environment, prey may change their habitat use, increase sheltering behaviour, change their movement behaviour, or use camouflage through cryptic colouring and background matching. Field experiments and population viability modelling show instances where fire either amplifies or does not amplify the impacts of predators on prey populations, and vice versa. In some instances, intense and sustained post‐fire predation may lead to local extinctions of prey populations. Human disruption of fire regimes is impacting faunal communities, with consequences for predator and prey behaviour and population dynamics. Key areas for future research include: capturing data continuously before, during and after fires; teasing out the relative importance of changes in visibility and shelter availability in different contexts; documenting changes in acoustic and olfactory cues for both predators and prey; addressing taxonomic and geographic biases in the literature; and predicting and testing how changes in fire‐regime characteristics reshape predator–prey interactions. Understanding and managing the consequences for predator–prey communities will be critical for effective ecosystem management and species conservation in this era of global change.

A Change in Conservation Status of Pachyphytum caesium (Crassulaceae), a Threatened Species from Central Mexico Based on Genetic Studies.

Simple SummarySpecies decline has accelerated in recent decades, with rare species often being the first to go extinct, mainly due to low population sizes. This study worked with Pachyphytum cesium (Crassulaceae), an endemic species from central Mexico threatened by human activities and climate change. To increase our knowledge of the species, we analyze the diversity and genetic structure of all known populations of P. caesium to change their current genetic status and propose conservation strategies. The results indicate that this species presents low to moderate levels of genetic diversity and incipiently structured populations due to low genetic flow. We found that genetic parameters are essential to the conservation strategies and status vulnerability reclassification. Based on our results, we propose reclassifying the conservation status of the species in danger of extinction; hence a series of conservation strategies are provided to prevent its disappearance.Genetic studies in rare species are important to determine their patterns of genetic diversity among populations and implement conservation plans aimed to reduce extinction risks. Pachyphytum caesium is an endemic species with extremely small populations in central Mexico. This work analyzes the diversity and genetic structure of Pachyphytum cesium (Crassulaceae) to change the conservation status and propose conservation strategies. Twelve dominant ISSR markers were used to describe the genetic diversity of all known populations. Additionally, we carried out two simulations to explore how the loss of individuals or the local populations extinction affect the genetics parameters of the species. The average results indicated moderate levels of genetic diversity (number of alleles = 89.7 ± 3.9, expected heterozygosity = 0.212 ± 0.0, and percentage of polymorphic loci = 56.1 ± 3.9), parameters that decreased significantly when simulations were performed in P. caesium. Additionally, a genetic structure of the populations was found with low gene flow (Nm = 0.92). Genetic parameters are negatively affected by the loss of individuals and the local extinction of populations. Based on our results, we propose to reclassify the conservation status of the species in danger of extinction, hence a series of conservation strategies are provided to prevent its disappearance.

Network topology and patch connectivity affect dynamics in experimental and model metapopulations.

Biological populations are rarely isolated in space and instead interact with others via dispersal in metapopulations. Theory predicts that network connectivity patterns can have critical effects on network robustness, as certain topologies, such as scale-free networks, are more tolerant to disturbances than other patterns. However, at present, experimental evidence of how these topologies affect population dynamics in a metapopulation framework is lacking. We used experimental metapopulations of the aquatic protist Paramecium tetraurelia to determine how network topology influences occupation patterns. We created metapopulations engineered to be comparable in linkage density, but differing in their degree distribution. We compared random networks to scale-free networks by evaluating local population occupancy and abundance throughout 18-30 protist generations. In parallel, we used simulations to explore differences in patch occupation patterns among topologies. Our experimental results highlighted the importance of the balance between dispersal and extinction in the interaction with spatial network topology. Under low dispersal conditions, random metapopulations of P. tetraurelia reached higher abundance and higher occupancy (proportion of occupied patches) compared to scale-free systems in both experimental and simulated systems. Under high dispersal conditions, we did not detect differences between types of metapopulations. Increasing patch degree (i.e. number of connections per patch) reduced the probability of extinction of local populations in both types of networks. We suggest the interaction between colonization/extinction rates and network topology alters the likelihood of rescue effects which results in differential patterns of occupancy and abundance in metapopulations.

Population extinction and metapopulation synchrony: a reassessment

Synchronous dynamics of populations reduces metapopulation persistence. Thus, determining sources of synchrony is important for understanding metapopulations and biodiversity patterns in response to environmental disturbance. Previously, we found that the experimental extinction of two contiguous subpopulations of the butterfly Parnassius smintheus, increased synchrony among nearby subpopulations relative to distant controls. We hypothesized that increased synchrony was caused by either 1) a Moran‐like effect where the loss of immigrants simultaneously reduced the abundance of surrounding subpopulations or 2) an increase in dispersal among subpopulations surrounding the extinction. Reestablishment following extinction allowed for discrimination of these hypotheses. Additional data and new analyses using 24‐years of population growth in 12 nearby and control subpopulations before, during and after the experimental extinction show that our initial result was wrong. The ‘increase' in synchrony seen during the extinction was due to synchrony being low among treatment subpopulations during the pre‐extinction period, rather than an increase due to the experimental extinction. Lower synchrony among treatment subpopulations prior to extinction may have been due to less dispersal among treatment than among control subpopulations during the pre‐extinction period. Population crashes inducing synchrony (a Moran effect) during the extinction and post‐extinction periods also appear to have had greater and more lasting effects on synchrony for treatment than control subpopulations. Theoretical models show that local population extinction can increase synchrony in metapopulations, particularly for tightly regulated populations, but further experiments are needed to test this hypothesis.

Conservation threats from roadkill in the global road network

AbstractAimThe road network is increasing globally but the consequences of roadkill on the viability of wildlife populations are largely unknown. We provide a framework that allows us to estimate how risk of extinction of local populations increases due to roadkill and to generate a global assessment that identifies which mammalian species are most vulnerable to roadkill and the areas where they occur.LocationGlobal.Time period1995–2015.Major taxa studiedTerrestrial mammals.MethodsWe introduce a framework to quantify the effect of roadkill on terrestrial mammals worldwide that includes three steps: (a) compilation of roadkill rates to estimate the fraction of a local population killed on the roads, (b) prediction of population risk of extinction based on observed roadkill rates (for a target group of species of conservation concern and non‐threatened species with high roadkill rates), and (c) global assessment of vulnerability to roadkill for 4,677 terrestrial mammalian species estimated using phylogenetic regression models that link extinction risk to demographic parameters.ResultsWe identified four populations among the 70 species in the target group that could become extinct in 50 years if observed roadkill levels persist in the study areas: maned wolf Chrysocyon brachyurus (Brazil), little spotted cat Leopardus tigrinus (Brazil), brown hyena Hyaena brunnea (Southern Africa) and leopard Panthera pardus (North India). The global assessment revealed roadkill as an added risk for 2.7% (n = 124) terrestrial mammals, including 83 species Threatened or Near Threatened. We identified regions of concern that have species vulnerable to roadkill with high road densities in areas of South Africa, central and Southeast Asia, and the Andes.Main conclusionsOur framework revealed populations of threatened species that require special attention and can be incorporated into management and planning strategies informing road managers and conservation agencies.