Local Extinction Rates Research Articles

Rapid assessment of metapopulation viability under climate and land-use change

In order to predict species response to climate and land-use change, numerically fast and easily applicable assessment tools for species survival are required. We present a set of formulae to calculate the mean lifetime of a metapopulation in a spatially heterogeneous and dynamic landscape subject to habitat patch diminution, loss and/or spatial shift of the habitat network. The formulae require as inputs (i) information about the number, location and size of the habitat patches for several time steps to quantify landscape dynamics in terms of patch destruction, diminution or shifting rates and (ii) data on species traits such as their vulnerability to environmental variation and their dispersal ability to quantify local colonisation and extinction rates. We validate the formulae with a spatially explicit simulation. The analysis is complemented by a protocol for the easy use of the approach and practical application examples. A software implementation is available on request from the authors.

White-tailed deer florivory influences the population demography of Polemonium vanbruntiae

White-tailed deer (Odocoileus virginianus Zimm.) may influence reproduction and dispersal of plant species through herbivory of flowering stems. We examined the effects of white-tailed deer herbivory on the seed production of Bog Jacob’s-ladder (Polemonium vanbruntiae Britt.), a facultative wetland plant considered rare throughout its range. We monitored life-stage transitions in 10 local populations in Canaan Valley, West Virginia, from 2005–2007, modeled the population growth rates, and estimated extinction rates for each population accounting for the loss of seeds due to white-tailed deer florivory. Seed loss due to consumption of flowering stems ranged between 0 and 96% within individual populations ( = 52 ± 4.5%). A significant difference in seed production occurred between browsed ( = 0.6 ± 0.18) and unbrowsed ( = 24 ± 1.43) plants. Predicted seed loss was significantly higher ( = 57 ± 19%), where no hunting was allowed, than where deer hunting occurred ( = 40 ± 18%). The observed levels of white-tailed deer florivory have the potential to significantly reduce population growth rates (p < 0.0001). Although white-tailed deer florivory may not increase local population extinction rates, loss of seed production may result in a loss of the potential for colonization of new patches.

Small‐scale and regional spatial dynamics of an annual plant with contrasting sexual systems

Summary Plant demography is known to depend on both spatial dynamics and life history, but how these two factors interact is poorly understood. We conducted a longitudinal study of the wind‐pollinated annual plant Mercurialis annua that varies geographically in its sexual system to investigate this interaction. Metapopulation demographic models predict that regular population turnover should be a more common feature of monomorphic than dimorphic populations because males and females cannot found new populations by selfing but hermaphrodites can. We tested the prediction that rates of population turnover would be higher in monomorphic compared to dimorphic regions. We surveyed 356 populations of M. annua along five regional transects in Morocco and the Iberian Peninsula over a 3‐year period to examine their demography and persistence. Each transect crossed a transition in the sexual system, from a monomorphic region where almost all populations were hermaphroditic to a dimorphic one in which most populations had separate sexes (males with females or hermaphrodites). As predicted, rates of local apparent extinctions (i.e., the disappearance of adult plants) were nearly 50% higher in monomorphic compared to dimorphic regions. Local extinctions appeared to be driven by changes in vegetation cover, with extinctions tending to occur in sites in which perennial cover also declined. This suggests that disturbance is a primary agent of local extinctions. We further examined the influence of regional dynamics on local demographic properties by investigating patterns of spatial autocorrelation in population density across years. We found positive spatial autocorrelations in plant densities within regions for both sexual systems. However, these positive autocorrelations extended over shorter distances in monomorphic regions, perhaps as a result of greater population flux in these regions. Synthesis. Our study shows that population dynamics may be influenced by processes acting at a range of spatial scales: within patches, across patches within sites, and across sites within regions, as well as by life‐history variation. In Mercurialis annua, regional variation in apparent extinction rates is affected by life history and implicated in regulating the geographical distribution of populations with different sexual systems.

Predicting local colonization and extinction rates of freshwater mussels based on biological traits in a case of Lake Poyang

Predicting local colonization and extinction rates of freshwater mussels based on biological traits in a case of Lake Poyang

Habitat use by grey-crowned babbler, Pomatostomus temporalis, in urban and peri-urban environments

Habitat loss in the urban environment leads to a high rate of local extinction of native fauna. In contrast, where key habitat structures, such as woody debris, shrubs and trees, are maintained, urban landscapes can retain many native species. To manage urban habitats successfully for urban bird communities, it is, therefore, necessary to understand the habitat requirements of the species using them. We have previously shown that the grey-crowned babbler, Pomatostomus temporalis, exhibits similar mean weight, sex ratio and group size in natural and altered habitat in and around Dubbo, New South Wales. In the present study, we detail the movements and habitat use of the groups that inhabit urban areas. We found that groups behaved similarly in urban and peri-urban areas, but showed small differences in the frequency of behaviours, based on the habitat feature that was available. The results suggested that, despite the decline of the grey-crowned babbler in the southern parts of its range, this species is able to survive in altered habitats, if nesting habitat and ground cover remain available and neighbouring groups persist nearby. Because other woodland bird species have shown similar responses to urban environments, managers of urban parkland should provide foraging substrates for a variety of woodland bird species, including vulnerable species, to ameliorate threatening processes and protect key habitat requirements.

Smart Protected Area Placement Decelerates Biodiversity Loss: A Representation‐extinction Feedback Leads Rare Species to Extinction

AbstractProtected areas (PAs) spearhead global conservation efforts, but it has been repeatedly demonstrated that narrowly distributed species are more likely to be unrepresented in PAs. This means that where local extinctions are more likely outside PAs, a positive feedback loop could render PAs largely ineffective in decelerating extinctions, even where PAs effectively abate threats. Here we empirically test the elements of this feedback loop using distribution data for 1,572 threatened plants in Japan. Narrowly distributed species were indeed less likely to overlap PAs than widespread species, and local extinction rates for unprotected populations over 15 years were 1.5 times higher than those inside PAs. A simulation model showed that new PAs will substantially reduce extinction risk for widespread species, but not for narrowly distributed species, unless they are placed very precisely in the landscape. Our results suggest that a representation‐extinction feedback will limit the effectiveness of PAs in preventing extinctions unless PA placement is carefully targeted.

Landscape-scale response to local habitat restoration in the regal fritillary butterfly (Speyeria idalia) (Lepidoptera: Nymphalidae)

The butterfly Speyeria idalia was once a widespread species in the midwestern United States, but declined precipitously during the 1980s. By the early 1990s in NW Indiana and adjacent NE Illinois, it was reduced to a single site where it persisted as a precarious three deme metapopulation managed using prescribed fire. In 1996, a large-scale high diversity restoration was initiated at the site to restore ecological connectivity for grassland and oak barrens communities across the site. Among many restoration goals, we included restoring connectivity for habitat restricted insect communities across the highly fragmented site. In support of that goal, we included over 620 local genotype plant species in the restoration. S. idalia responded positively to the restoration and was the most abundant butterfly across the site in 2014. Ironically, we incorrectly considered the primary hostplant at the site, Viola bicolor, to be non-native when we initiated the restoration and did not include it in our seed mixes. This weedy annual aggressively expanded into the restoration without our assistance. We believe that we transformed the precarious metapopulation into a well-connected patchy population across the restoration. In addition, the butterfly occupied previously unoccupied habitats far beyond the restoration. This suggests that we have created a regional mainland—island metapopulation structure, with the restoration serving as a source of immigrants that sustains colonization rates at or above the rate of local deme extinction across a landscape that currently spans almost 60 km.

Interaction of turbulent premixed flames with combustion products: Role of stoichiometry

Stabilization methods of turbulent flames often involve mixing of reactants with hot products of combustion. The stabilizing effect of combustion product enthalpy has been long recognized, but the role played by the chemical composition of the product gases is typically overlooked. We employ a counterflow system to pinpoint the effects of the combustion product stoichiometry on the structure of turbulent premixed flames under conditions of both stable burning and local extinction. To that end, a turbulent jet of lean-to-rich, CH4/O2/N2-premixed reactants at a turbulent Reynolds number of 1050 was opposed to a stream of hot products of combustion that were generated in a preburner. While the combustion product stream temperature was kept constant, its stoichiometry was varied independently from that of the reactant stream, leading to reactant-to-product stratification of relevance to practical combustion systems. The detailed structure of the turbulent flame front was analyzed in two series of experiments using laser-induced fluorescence (LIF): joint CH2O LIF and OH LIF measurements and joint CO LIF and OH LIF measurements. Results revealed that a decrease in local CH2O+OH and CO+OH reaction rates coincide with the depletion of OH radicals in the vicinity of the combustion product stream. These critical combustion reaction rates were more readily quenched in the presence of products of combustion from a stoichiometric flame, whereas they were favored by lean combustion products. As a result, stoichiometric combustion products contributed to a greater occurrence of local extinction. Furthermore, they limited the capacity of premixed reactants to ignite and of the turbulent premixed flames to stabilize. In contrast, lean and rich combustion products facilitated flame ignition and stability and reduced the rate of local extinction. The influence of the combustion product stream on the turbulent flame front was limited to a zone of approximately two millimeters from the gas mixing layer interface (GMLI) of the product stream. Flame fronts that were separated from the GMLI by larger distances were unaffected by the product stream stoichiometry.

Vertebrate Hosts as Islands: Dynamics of Selection, Immigration, Loss, Persistence, and Potential Function of Bacteria on Salamander Skin.

Skin bacterial communities can protect amphibians from a fungal pathogen; however, little is known about how these communities are maintained. We used a neutral model of community ecology to identify bacteria that are maintained on salamanders by selection or by dispersal from a bacterial reservoir (soil) and ecological drift. We found that 75% (9/12) of bacteria that were consistent with positive selection, <1% of bacteria that were consistent with random dispersal and none of the bacteria that were consistent under negative selection had a 97% or greater match to antifungal isolates. Additionally we performed an experiment where salamanders were either provided or denied a bacterial reservoir and estimated immigration and loss (emigration and local extinction) rates of bacteria on salamanders in both treatments. Loss was strongly related to bacterial richness, suggesting competition is important for structuring the community. Bacteria closely related to antifungal isolates were more likely to persist on salamanders with or without a bacterial reservoir, suggesting they had a competitive advantage. Furthermore, over-represented and under-represented operational taxonomic units (OTUs) had similar persistence on salamanders when a bacterial reservoir was present. However, under-represented OTUs were less likely to persist in the absence of a bacterial reservoir, suggesting that the over-represented and under-represented bacteria were selected against or for on salamanders through time. Our findings from the neutral model, migration and persistence analyses show that bacteria that exhibit a high similarity to antifungal isolates persist on salamanders, which likely protect hosts against pathogens and improve fitness. This research is one of the first to apply ecological theory to investigate assembly of host associated-bacterial communities, which can provide insights for probiotic bioaugmentation as a conservation strategy against disease.

Dynamic landscapes shape post‐wildfire recolonisation and genetic structure of the endangered Hermes copper (Lycaena hermes) butterfly

1. The coastal sage scrub vegetation community experiences frequent fires, so the long‐term survival of species depends on the rate of recolonisations exceeding the rate of local extinctions. Recolonisation of these post‐wildfire habitats probably requires long‐distance dispersal events. These movements can also counter detrimental impacts associated with inbreeding.2. The Hermes copper (Lycaena hermes) is an extremely rare butterfly inhabiting coastal sage scrub adjacent to San Diego, California, USA. Habitat loss due to urbanisation and impacts of recent wildfires has greatly restricted its range, prompting the United States Fish and Wildlife Service to list the Hermes copper as a Candidate Species in 2011.3. Surveys for Hermes copper butterflies in 2010–2013 documented only two recolonisation events following wildfires in 2003 and 2007. Larger populations were readily detected each year, but detection of smaller populations was inconsistent.4. Amplified fragment length polymorphism was used to identify potential genetic discontinuities within this species across the landscape. Results indicated that movements across much of the landscape were possible historically. However, individuals from three peripheral populations exhibited a higher degree of differentiation, suggesting more restricted dispersal in these regions.5. From the results, it can be concluded that historically Hermes copper butterflies were able to move among habitat patches prior to recent changes in the landscape. However, low post‐fire recolonisation rates suggest limited contemporary dispersal, probably due to recent habitat fragmentation. This fragmentation is a relatively new event, as the human population in San Diego County experienced substantial growth in the late 20th Century.

Temporal variability of a single population can determine the vulnerability of communities to perturbations

Summary Many aspects of global change affect the variability of species population densities, in terms of both the magnitude and pattern of density fluctuations. However, we have limited empirical understanding of the consequences of altered temporal variability of populations, independent of changes in their mean densities, for the structure and stability of natural communities and the responses of ecosystems to additional stressors. We used a field experiment to test the effects of altered temporal variability of a single consumer species on community structure and stability. Specifically, we manipulated the temporal variability of populations of a key grazer species on temperate rocky shores (Littorina littorea), independent of their mean densities, over 12 months and measured the responses of algal communities in terms of multiple measures of structure and stability. Further, we tested whether consumer variability determined the effects of an additional perturbation, elevated sedimentation, on algal communities. The effects of sedimentation on the structure and stability of algal communities were regulated by the temporal variability of consumer populations. In particular, elevated sedimentation led to a decrease in algal evenness, but only when consumer densities were held constant, and resulted in a decrease in the rate of local algal extinctions, but only when consumer temporal variability was increased. Independent of sedimentation, increased temporal variability of consumer populations led to a shift in algal assemblage structure and affected the stability of algal communities in terms of both compositional turnover and resistance to environmental perturbations. Further, these effects varied according to the temporal pattern of consumer density fluctuations. Synthesis. Our results demonstrate that changes in the temporal variability of a single species can modify multiple aspects of both the structure and stability of natural communities and alter their responses to perturbations. However, the effects of consumer variability cannot be predicted without knowledge of the temporal pattern of density fluctuations. These findings have profound implications for our understanding of the effects of multiple disturbances on ecosystems.

Occupancy dynamics in human‐modified landscapes in a tropical island: implications for conservation design

AbstractAimAvian communities in human‐modified landscapes exhibit varying patterns of local colonization and extinction rates, determinants of species occurrence. Our objective was to model these processes to identify habitat features that might enable movements and account for occupancy patterns in habitat matrices between the Guanica and Susua forest reserves. This knowledge is central to conservation design, particularly in ever changing insular landscapes.LocationSouth‐western Puerto Rico.MethodsWe used a multiseason occupancy modelling approach to quantify seasonal estimates of occupancy, and colonization and extinction rates of seven resident avian species surveyed over five seasons from January 2010 to June 2011. We modelled parameters by matrix type, expressions of survey station isolation, quality, amount of forest cover and context (embedded in forest patch).ResultsSeasonal occupancy remained stable throughout the study for all species, consistent with seasonally constant colonization and extinction probabilities. Occupancy was mediated by matrix type, higher in reserves and forested matrix than in the urban and agricultural matrices. This pattern is in accord with the forest affinities of all but an open‐habitat specialist. Puerto Rican Spindalis (Spindalis portoricensis) exhibited high occupancy in the urban matrix, highlighting the adaptability of some insular species to novel environments. Highest colonization rates occurred when perching structures were at ≤ 500 m. Survey stations with at least three fruiting tree species and 61% forest cover exhibited lowest seasonal extinction rates.Main conclusionsOur work identified habitat features that influenced seasonal probabilities of colonization and extinction in a human‐modified landscape. Conservation design decisions are better informed with increased knowledge about interpatch distances to improve matrix permeability, and habitat features that increase persistence or continued use of habitat stepping stones. A focus on dynamic processes is valuable because conservation actions directly influence colonization and extinction rates, and thus, a quantitative means to gauge their benefit.

The effects of habitat, climate, and Barred Owls on long-term demography of Northern Spotted Owls

ABSTRACT Estimates of species' vital rates and an understanding of the factors affecting those parameters over time and space can provide crucial information for management and conservation. We used mark–recapture, reproductive output, and territory occupancy data collected during 1985–2013 to evaluate population processes of Northern Spotted Owls (Strix occidentalis caurina) in 11 study areas in Washington, Oregon, and northern California, USA. We estimated apparent survival, fecundity, recruitment, rate of population change, and local extinction and colonization rates, and investigated relationships between these parameters and the amount of suitable habitat, local and regional variation in meteorological conditions, and competition with Barred Owls (Strix varia). Data were analyzed for each area separately and in a meta-analysis of all areas combined, following a strict protocol for data collection, preparation, and analysis. We used mixed effects linear models for analyses of fecundity, Cormack-Jolly-...

Effects of climate, species interactions, and dispersal on decadal colonization and extinction rates of Iberian tree species

We studied the relative importance of climate, abundance of potentially competing species, and dispersal in explaining local colonization and extinction rates of tree species throughout mainland Spain. We used a Bayesian framework to parameterize a patch occupancy model to 23 species censused in 46,596 permanent plots in a 1×1km grid across most Spanish forests. For most species, dispersal was the single best predictor of colonization, whereas climate and dispersal were equally important as predictors of extinction. Precipitation was positively correlated with the colonization rate of 12 out of 13 deciduous broad-leaved species, and negatively correlated with the extinction rate of nine of them. In contrast, precipitation equally decreased colonization and extinction of five out of eight of needle-leaved species (Juniperus and Pinus spp.). There was, however, marked variation among species in the magnitude of these effects, with some species exhibiting contrasting patterns for the colonization and the extinction process. Abundance of competing tree species (= summed plot basal area) was consistently correlated with decreased colonization of all needle-leaved species, and it increased the extinction rate of 6 out of 8 of these species. It had, nonetheless, weak facilitative effect on some broad-leaved species by promoting colonization (3 of 13 species) and decreasing extinction (7 of 13 species). With local colonization and extinction data, non-equilibrial and dynamic species distribution modelling can be improved by incorporating measures of biotic interactions and dispersal effects, along with traditional climate variables.

Predicting local extinctions of Amazonian vertebrates in forest islands created by a mega dam

Hydropower projects are rapidly expanding across lowland Amazonia, driving the conversion of large tracts of once-continuous forests into archipelagos embedded within a vast open-water matrix. Forest vertebrate populations thus become stranded in habitat islands, with their persistence governed by a combination of species life-history traits, habitat patch, and landscape context. We investigate the patterns of species extinction of 34 arboreal and terrestrial vertebrate species within three continuous forest sites and 37 land-bridge islands within one of the largest South American hydroelectric reservoirs, based on a combination of camera trapping, line-transect censuses, sign surveys, and armadillo burrow counts. Forest area was the best predictor of species persistence, so we classified all species into three levels of vulnerability to habitat insularization, with most species defined as ‘area-sensitive’. However, island occupancy was decisively determined by individual species traits, with wide-ranging species and poor dispersers showing high local extinction rates. We detected higher island occupancy rates of large vertebrate species compared to other Neotropical fragmented forest landscapes, suggesting that this is critically attributed to the absence of hunting pressure at Balbina. Nevertheless, most terrestrial and arboreal species have been driven to local extinction within the vast majority of islands, which have been largely defaunated. We predicted species composition across all 3546 islands within the reservoir, indicating that only ⩽2% of all islands continue to harbour at least 75% of all species. To minimise loss of vertebrate diversity, future hydroelectric dam projects in lowland tropical forests, if unavoidable, should consider their geographic location and landscape structure to maximise both island size and landscape connectivity, and set aside strictly protected reserves within reservoir areas.

An occupancy-based quantification of the highly imperiled status of desert fishes of the southwestern United States.

Desert fishes are some of the most imperiled vertebrates worldwide due to their low economic worth and because they compete with humans for water. An ecological complex of fishes, 2 suckers (Catostomus latipinnis, Catostomus discobolus) and a chub (Gila robusta) (collectively managed as the so-called three species) are endemic to the U.S. Colorado River Basin, are affected by multiple stressors, and have allegedly declined dramatically. We built a series of occupancy models to determine relationships between trends in occupancy, local extinction, and local colonization rates, identify potential limiting factors, and evaluate the suitability of managing the 3 species collectively. For a historical period (1889-2011), top performing models (AICc) included a positive time trend in local extinction probability and a negative trend in local colonization probability. As flood frequency decreased post-development local extinction probability increased. By the end of the time series, 47% (95% CI 34-61) and 15% (95% CI 6-33) of sites remained occupied by the suckers and the chub, respectively, and models with the 2 species of sucker as one group and the chub as the other performed best. For a contemporary period (2001-2011), top performing (based on AICc ) models included peak annual discharge. As peak discharge increased, local extinction probability decreased and local colonization probability increased. For the contemporary period, results of models that split all 3 species into separate groups were similar to results of models that combined the 2 suckers but not the chub. Collectively, these results confirmed that declines in these fishes were strongly associated with water development and that relative to their historic distribution all 3 species have declined dramatically. Further, the chub was distinct in that it declined the most dramatically and therefore may need to be managed separately. Our modeling approach may be useful in other situations in which targeted data are sparse and conservation status and best management approach for multiple species are uncertain.

Immigration rates and species niche characteristics affect the relationship between species richness and habitat heterogeneity in modeled meta-communities.

The positive relationship between habitat heterogeneity and species richness is a cornerstone of ecology. Recently, it was suggested that this relationship should be unimodal rather than linear due to a tradeoff between environmental heterogeneity and population sizes. Increased environmental heterogeneity will decrease effective habitat sizes, which in turn will increase the rate of local species extinctions. The occurrence of the unimodal richness–heterogeneity relationship at the habitat scale was confirmed in both empirical and theoretical studies. However, it is unclear whether it can occur at broader spatial scales, for meta-communities in diverse and patchy landscapes. Here, I used a spatially explicit meta-community model to quantify the roles of two species-level characteristics, niche width and immigration rates, on the type of the richness–heterogeneity relationship at the landscape scale. I found that both positive and unimodal richness–heterogeneity relationships can occur in meta-communities in patchy landscapes. The type of the relationship was affected by the interactions between inter-patch immigration rates and species’ niche widths. Unimodal relationships were prominent in meta-communities comprising species with wide niches but low inter-patch immigration rates. In contrast, meta-communities consisting of species with narrow niches and high immigration rates exhibited positive relationships. Meta-communities comprising generalist species are therefore likely to exhibit unimodal richness-heterogeneity relationships as long as low immigration rates prevent rescue effects and patches are small. The richness-heterogeneity relationship at the landscape scale is dictated by species’ niche widths and inter-patch immigration rates. These immigration rates, in turn, depend on the interaction between species dispersal capabilities and habitat connectivity, highlighting the roles of both species traits and landscape structure in generating the richness–heterogeneity relationship at the landscape scale.

NansClim – climate effects on biodiversity, abundance and distribution of marine organisms

Human interference with the climate system is occurring, and climate change poses risks for human and natural systems (IPCC, 2014). In recent decades, changes in climate have caused impacts on natural and human systems on all continents and across the oceans. Evidence of climate-change impacts is strongest and most comprehensive for natural systems. Due to climate change projected by the mid 21st century and beyond, global marine-species redistribution and marine-biodiversity reduction in sensitive regions will challenge the sustained provision of fisheries productivity and other ecosystem services (IPCC, 2014). Spatial shifts of marine species due to projected warming will cause high-latitude invasions and high local-extinction rates in the tropics and semi-enclosed seas. Species richness and fisheries catch potential are projected to increase, on average, at mid and high latitudes and decrease at tropical latitudes (IPCC, 2014). The Benguela Current Large Marine Ecosystem (BCLME) is one of four Eastern Boundary Upwelling Ecosystems (EBUE), highly productive marine subregions. Although they comprise <2% of the global ocean area, they contribute nearly 7% of marine primary production and more than 20% of the world’s marine capture fisheries (IPCC, 2014). Catches in the EBUE are dominated by planktivorous species such as sardine, anchovy, and horse/jack mackerel, and piscivorous demersal species such as hake. Upwelling of nutrient-rich water stimulates primary production which is transferred to mid and upper trophic levels, resulting in substantial fish, seabird, and marine mammal populations. As a result, EBUEs are considered ‘hotspots’ of productivity and biodiversity. Previous research on the BCLME has had little emphasis on climate change. As with the other EBUEs, strong inter-annual and inter-decadal variability in physical oceanography makes it challenging to detect biophysical trends attributed to climate change. Nevertheless, the physical conditions of the BCLME are highly sensitive to climate variability over a range of scales. Despite its apparent sensitivity to environmental variability, there is limited evidence of ecological changes in the BCLME caused by climate change (IPCC, 2014). For example, pelagic fish, benthic crustaceans, and seabirds have demonstrated general shifts in distribution (IPCC, 2014). Even though much of the evidence on the recent climate change comes from remote sensing and outputs from coupled atmosphere-ocean models, it is necessary to link the global trends with local observations to detect the effects of this change on marine living resources in a regional context. In the BCLME region, the combined oceanographic and biodiversity database collected through the Ecosystem Approach to Fisheries (EAF) Nansen Programme is potentially a major source of local data covering climate change and its effect on marine resources in the last 30 yr. However, its contributions to the understanding of climate change effects on the BCLME are rather limited so far, since the huge amount of data collected under the programme has not been fully utilised. Based on data collected through the EAF Nansen programme, together with other relevant data, the NansClim project (2009–2014) was established to identify and describe possible trends and variability in ocean climate and corresponding changes in marine biodiversity and fisheries in the Benguela Current System. Observations of effects of climate variability on marine biota in the past, based on the Nansen database in combination with other data series available from the region, allowed NansClim to document some general responses concerning production and distribution of marine biota to set a baseline of observed effects of climate variability. Some of the species in the region are more poorly studied than others, and one of the tasks of the project was therefore to characterize the life cycle of such species which may be important indicators of future climate change.

Timber harvest interacts with broad-scale forest mortality to affect site occupancy dynamics of a vertebrate seed predator

Extensive ecological disturbances can interact with spatial heterogeneity produced by previous disturbances, influencing responses of vertebrates to environmental change. Recent and ongoing outbreaks of bark beetles (including Dendroctonus spp. and Dryocoetes confuses) in the Rocky Mountains produced an opportunity to investigate effects of broad-scale tree mortality on an important seed predator in Nearctic coniferous forests, the red squirrel (Tamiasciurus hudsonicus), and to evaluate whether those effects interact with forest heterogeneity produced by previous timber harvest. Our study characterized site occupancy dynamics for red squirrels in relation to patch-cutting, a type of group-selection cut, and the bark-beetle outbreak, and evaluated whether patch cutting influenced subsequent effects of bark beetles on these squirrels. We used multi-season occupancy models and covariates for harvest- and outbreak-related habitat characteristics to describe extinction and colonization rates of red squirrels over a 27-yr period in Wyoming, USA. We observed effects of year, patch-cutting, and the bark beetle outbreak on the probability of detecting a red squirrel. We observed a negative association between local extinction rate and increasing snag density, but only to a threshold of 5 snags/0.04ha. Local colonization rate was positively associated with the basal area of live trees. Annual site occupancy varied across years (range pre-harvest: 0.76–0.89; post-harvest: 0.84–0.99), and was lowest (0.70–0.72) during the two years sampling occurred approximately 14years after the bark beetle outbreaks began. Tree mortality was lowest near patch cuts; this pattern was especially pronounced for mature trees (>30cm diameter at breast height), which tend to produce the most cones and would likely contribute the most to red squirrel survival. Strong habitat effects on occupancy dynamics suggest that previously-harvested areas may provide refugia for red squirrels in post-outbreak forests. Our results support managing for uneven-aged stands of mixed species composition in subalpine forests of the Rocky Mountains.

Warming-induced changes in predation, extinction and invasion in an ectotherm food web.

Climate change will alter the forces of predation and competition in temperate ectotherm food webs. This may increase local extinction rates, change the fate of invasions and impede species reintroductions into communities. Invasion success could be modulated by traits (e.g., defenses) and adaptations to climate. We studied how different temperatures affect the time until extinction of species, using bitrophic and tritrophic planktonic food webs to evaluate the relative importance of predatory overexploitation and competitive exclusion, at 15 and 25 °C. In addition, we tested how inclusion of a subtropical as opposed to a temperate strain in this model food web affects times until extinction. Further, we studied the invasion success of the temperate rotifer Brachionus calyciflorus into the planktonic food web at 15 and 25 °C on five consecutive introduction dates, during which the relative forces of predation and competition differed. A higher temperature dramatically shortened times until extinction of all herbivore species due to carnivorous overexploitation in tritrophic systems. Surprisingly, warming did not increase rates of competitive exclusion among the tested herbivore species in bitrophic communities. Including a subtropical herbivore strain reduced top-down control by the carnivore at high temperature. Invasion attempts of temperate B. calyciflorus into the food web always succeeded at 15 °C, but consistently failed at 25 °C due to voracious overexploitation by the carnivore. Pre-induction of defenses (spines) in B. calyciflorus before the invasion attempt did not change its invasion success at the high temperature. We conclude that high temperatures may promote local extinctions in temperate ectotherms and reduce their chances of successful recovery.