Life history traits and abundance can predict local colonisation and extinction rates of freshwater mussels

Droughts typically result in a widespread decline in many vertebrate populations and even the local extinction of some species. However, different species vary considerably in their resistance to the effects of drought. This study aimed to estimate the relative species richness and the colonization and extinction rates in a bird community during an acute drought event in the Brazilian Caatinga. We mist-netted birds during 3 years throughout seven field seasons in two sampling plots to estimate community parameters using multi-season dynamic occupancy models. The relative richness to the regional species pool varied considerably during the study period (16–49%) with markedly low values in the severe onset of the drought. The estimates in the savanna were higher than those in the shrubby-woodland plot (~ 42 vs ~ 31 species, respectively). Pollinators and seed dispersers were characterized by median to high colonization (30–69%) and local extinction rates (37–69%), indicating low site fidelity. By contrast, granivores and insectivores made up the resident component of the community, with low local extinction and colonization rates (< 30%). Our results indicate that the diversity of Caatinga bird assemblages may decline markedly during severe droughts, primarily as a result of the displacement of species that exploit resources whose availability decreases drastically in abnormally dry years. Considering the climate scenarios predicted for tropical arid and semiarid regions worldwide, we believe that pollinators and seed dispersers will be especially vulnerable to population decline and local extinctions, which will alter community structure and the persistence of ecosystem services.

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-...

Interacting populations in heterogeneous environments

Understanding the patterns and drivers of species range shifts is essential to disentangle mechanisms driving species' responses to global change. Here, we quantified local extinction and colonization dynamics of giant pandas (Ailuropoda melanoleuca) using occurrence data collected by harnessing the labor of >1000 workers and >60,000 worker days for each of the three periods (TP1: 1985-1988, TP2: 1998-2002, and TP3: 2011-2014), and evaluated how these patterns were associated with (1) protected area, (2) local rarity/abundance, and (3) abiotic factors (i.e., climate, land-use, and topography). We documented a decreased rate (from 0.433 during TP1-TP2 to 0.317 during TP2-TP3) of local extinction and a relatively stable rate (from 0.060 during TP1-TP2 to 0.056 during TP2-TP3) of local colonization through time. Furthermore, the occupancy gains have exceeded losses by a ratio of approximately 1.5 to 1, illustrating an expansion of panda's range at a rate of 1408.3 km2/decade. We also found that pandas were more likely to become locally extinct outside of protected areas, when locally rare in surrounding areas, and when certain biotic conditions were not met (e.g., increased forest cover). Local colonization was less likely in areas with high local rarity, challenging biotic conditions and unprotected area status. As the network of panda reserves expanded and the forest matured, the relative importance of other factors such as climate, biotic factors, and land-use became more influential in determining patterns of local extinction and colonization. Our findings provide insights into the factors governing the expansion of panda's range and illustrate how the relative influence of biotic and abiotic factors can change over time, indicating that effective conservation intervention may be able to mitigate some of the negative impacts of climate change and habitat degradation. This insight extends beyond pandas and highlights the role of conservation interventions can play in building resilience under a changing climate.

Declines in grassland diversity in response to nutrient addition are a general consequence of global change. This decline in species richness may be driven by multiple underlying processes operating at different time‐scales. Nutrient addition can reduce diversity by enhancing the rate of local extinction via competitive exclusion, or by reducing the rate of colonization by constraining the pool of species able to colonize under new conditions. Partitioning net change into extinction and colonization rates will better delineate the long‐term effect of global change in grasslands. We synthesized changes in richness in response to experimental fertilization with nitrogen, phosphorus and potassium with micronutrients across 30 grasslands. We quantified changes in local richness, colonization, and extinction over 8–10 years of nutrient addition, and compared these rates against control conditions to isolate the effect of nutrient addition from background dynamics. Total richness at steady state in the control plots was the sum of equal, relatively high rates of local colonization and extinction. On aggregate, 30%–35% of initial species were lost and the same proportion of new species were gained at least once over a decade. Absolute turnover increased with site‐level richness but was proportionately greater at lower‐richness sites relative to starting richness. Loss of total richness with nutrient addition, especially N in combination with P or K, was driven by enhanced rates of extinction with a smaller contribution from reduced colonization. Enhanced extinction and reduced colonization were disproportionately among native species, perennials, and forbs. Reduced colonization plateaued after the first few (&lt;5) years after nutrient addition, while enhanced extinction continued throughout the first decade. Synthesis . Our results indicate a high rate of colonizations and extinctions underlying the richness of ambient communities and that nutrient enhancement drives overall declines in diversity primarily by exclusion of previously established species. Moreover, enhanced extinction continues over long time‐scales, suggesting continuous, long‐term community responses and a need for long‐term study to fully realize the extinction impact of increased nutrients on grassland composition.

1 A number of generalizations have been made as to the effects of the area of occupancy, population size, dispersal ability and body size of species on their relative rates of local colonization and extinction. 2 Here, data on the breeding bird assemblage of Britain are used to test these generalizations. The complete geographical ranges of British birds have been censused twice, in the periods 1968–72 and 1988–91, allowing rates of colonization and extinction between these periods to be estimated. 3 The local colonization dynamics of species are influenced independently by their range sizes and the dispersal abilities of adult birds: species with smaller range sizes and larger dispersal distances were more likely to have colonized new areas between the two census periods. 4 The local extinction dynamics of species are influenced independently by their population sizes and body masses: species with smaller population sizes and body sizes were more likely to have gone extinct from areas inhabited in the first census period. 5 These results remain when controlling for the effects of phylogenetic relatedness. 6 These analyses uphold many commonly held generalizations about the correlates of local colonization and extinction, and suggest that the long-term evolutionary history of these bird species has influenced their potential to respond to current ecological conditions.

Ecologists rely on field surveys to monitor long‐term ecological change but finite sampling and the prevalence of rare species mean that surveys inevitably miss some species present at a given location. These ‘phantom species’ produce pseudo‐turnover by inflating observed rates of local colonization and extinction in resurvey studies, especially among rare species. In this paper, we quantify the probability that pseudo‐turnover occurs due to imprecise plot relocation and/or shifts in where individuals are located. Using sampling models derived from the binomial distribution, we estimate probabilities of missing species as a function of local abundance and sampling intensity. Spatially explicit simulations confirm that our binomial model is robust to non‐random sampling schemes and clumped species distributions. False absences decline predictably as species abundance and sampling intensity increase allowing us to statistically adjust naïve estimates of colonization and extinction for expected rates of pseudo‐turnover. To illustrate the model's real‐world utility, we analyze apparent colonizations and extinctions for 331 species distributed over 83 sites in southern Wisconsin forests surveyed in both the 1950s and 2000s. Limited sampling in the 1950s means expected rates of pseudo‐colonization are appreciable. Accounting for pseudo‐turnover thus reduces estimated community‐wide colonization rates by 51% compared to naïve (observed) rates. More complete sampling in the 2000s limited overestimates of local extinction to 14%. We distinguish three zones of inference based on sampling intensity and species abundance where: 1) naïve estimates approximate true values of turnover, 2) adjustments are important, and 3) species are too rare relative to sampling to reliably infer turnover. Accounting for phantom species substantially improves our ability to accurately estimate local colonization and extinction rates, enhancing our ability to infer community dynamics and monitor long‐term ecological change.

A metapopulation model with stochastic local dynamics is developed assuming a small individual migration rate and many local populations. A diffusion approximation for local population dynamics is employed to derive how rates of local extinction and colonization depend on individual migration rate and habitat occupancy in the metapopulation. For a given migration rate, increasing habitat occupancy increases numbers of migrants and the average size of local populations, which together can substantially decrease the rate of local extinction (rescue effect) and increase the rate of colonization (establishment effect). Coupling with local dynamics influences metapopulation dynamics both qualitatively and quantitatively. For some parameters, multiple equilibria may exist for habitat occupancy, with an unstable equilibrium at low habitat occupancy (a type of Allee effect at the metapopulation level) as suggested by Hanski and Gyllenberg. Decreasing local extinction rate and increasing colonization rate with increasing habitat occupancy both increase the mean time to metapopulation extinction. Large underestimates in metapopulation persistence times can result from neglecting rescue and establishment effects.

Abstract. In this study we used species inventory data collected in 1970 and 1993 from 132 plots in a 14.5ha deciduous forest to examine local extinction and colonization processes among 45 field layer species. Local colonization rate was positively related to both seed size and seed dispersal features. Local extinction rate was negatively related to seed size. Growth form (clonal vs. non‐clonal) and presence of a seed bank were not found to be associated with local dynamics. Despite an overall constancy in species composition during this period, plants exhibited a considerable mobility among the 132 plots. This pattern conformed to a suggested ‘carousel model’ of species mobility in grasslands. A tentative suggestion is that this mobility acts on a comparatively broader spatio‐temporal scale in deciduous forests as compared with grasslands. Additional data are presented indicating that species abundance (frequency) among field layer plants in deciduous forest communities is consistent among forest fragments, and when comparing local and regional scales. The main conclusion is that life history features of the seed dispersal/recruitment phase, particularly seed size, are causally associated with abundance patterns at least at a local scale, but possibly also on a broader regional scale.

AimPlant communities typically exhibit lagged responses to climate change due to poorly understood effects of colonization and local extinction. Here, we quantify rates of change in mean cold tolerances, and contributions of colonization and local extinction to those rates, recorded in plant macrofossil assemblages from North American hot deserts over the last 30,000 years.LocationMojave, Sonoran and Chihuahuan Deserts.Time period30–0 thousand years before present (kybp).Major taxa studiedVascular plants.MethodsColonization and local extinction dates for 269 plant species were approximated from macrofossils in 15 packrat (Neotoma) midden series. Cold tolerances estimated from contemporary climate were used to quantify assemblage‐mean cold tolerances through time. Rates of colonization and local extinction, and their effects on rates of change in assemblage‐mean cold tolerances, were estimated for 30–20 kybp (Late Pleistocene, no directional warming), 20–10 kybp (deglaciation, rapid warming) and 10–0 kybp (Holocene, no directional warming).ResultsRates of change in all metrics were negligible during the Late Pleistocene. Rates of change in assemblage‐mean cold tolerances (mean 1.0°C × 10−4/yr) lagged behind warming during deglaciation, and continued at similar rates (1.2°C × 10−4/yr) throughout the Holocene. Colonization and local extinction contributed equally to delayed responses to warming, but their dynamics differed through time: Colonization by warm‐adapted species predominated during deglaciation, while the most heat‐adapted species exhibited long delays in colonization. Only the most cold‐adapted species went locally extinct during deglaciation, followed by slow repayment of the extinction debt of cool‐adapted species during the Holocene.Main conclusionsResponses to rapid warming can persist for millennia, even after cessation of warming. Consistent patterns from different midden series across the region support a metacommunity model in which dispersal interacts with environmental filters and buffers against local extinction to drive community–climate disequilibrium during and after periods of warming.

Abstract: We used point‐count and transect surveys to estimate the distribution and abundance of eight scrub‐breeding bird species in 34 habitat fragments and the urban matrix in southern California. We then calculated local extinction and colonization rates by comparing our data with surveys conducted in 1987. We classified factors that influence extinction and colonization rates into two types: (1) extrinsic factors, which are characteristics of the habitat fragments such as area, age, and isolation and (2) intrinsic factors, which are characteristics of the species that inhabit fragments, such as body size and population density. Over the past decade, at least one species went locally extinct in over 50% of the fragments, and local extinctions were almost twice as common as colonizations. Fragment size and, to a lesser extent, fragment age were the most important extrinsic factors determining extinction and colonization. Density indices of scrub birds were the most important intrinsic factors determining extinction rates, predicting the number of sites occupied, the probability of local extinction, relative area requirements, and time to local extinction.

Habitat modification and fragmentation are key factors responsible for fish population decline worldwide. Previous assessments documented a total of 72 species extinctions for the sole class of Actinopterygii. However, global extinctions are difficult to monitor or study based on fossil records. By contrast, local extinctions occurring at the population level are easier to study. Given this context, an important question relates to whether extinction dynamics studied at the local scale can provide useful information to understand extinctions occurring at larger scales. This would be the case if local extinctions were not balanced by recolonisation as in a classic metapopulation. Our aim is thus to explain the observed regional (per basin) persistence of 252 fish populations by testing contribution of local extinction rates and more generally metapopulation dynamics components. To address this aim, we used the annual extinction probability of 252 regional populations of up to 14 species inhabiting 18 coastal rivers, which became isolated c. 8,500 years ago. We specifically compared extinction probabilities obtained by seven theoretical models to investigate whether regional extinction rates (i.e. loss from a river system) were correlated to local extinction rates (i.e. loss from an occupied site) and the role of metapopulation dynamics to explain regional persistence. Using empirical data, we showed the importance of variables related to metapopulation dynamics to explain extinction rates across the 18 river systems. As expected, the regional extinction rate decreased with the colonisation rate, area, metapopulation size, and percentage of occupied localities. By contrast, an inconsistent relationship emerged between regional and local extinction rates, as species with high local extinction rates were not particularly prone to regional extinction. Our results provide strong support for the contribution of colonisation rates to explain persistence. Overall, our results show that the equilibrium number of occupied localities could be a good predictor of the long‐term persistence of metapopulations in rivers. Finally, our results suggest the importance of connectivity to maintain sustainable populations within the river system.

Local and spatial dynamics of a host–parasitoid system in a field experiment

Mountain areas still feature remnants of traditional land use and consequently constitute a large proportion of the remaining species‐rich habitats in Central Europe. However, their biodiversity is increasingly threatened by changes in climate and land use. The Alpine Ring Ouzel Turdus torquatus alpestris is a typical mountain bird that has recently declined in most of its breeding range. In this study we compared the historical (1986–1987) and recent (2017) distribution of breeding Ring Ouzels in 62 randomly selected 750 × 750 ‐m plots and analysed local colonization and extinction patterns in 558 subunits (= ‘grid cells’) in the southern Black Forest (south‐western Germany). Our study revealed that habitat occupancy has decreased by about one‐third, mainly at lower elevations and in depressed landforms, during the past three decades. Local colonization amounted to 25% and extinction to 66% of the previously vacant or occupied grid cells, respectively. Habitat occupancy and local colonization and extinction were driven by climate and habitat parameters. The Ring Ouzel preferred convex landscape formations such as mountain peaks and ridges with long snow‐cover duration for breeding. Sites with high proportions of deciduous forest and abandoned pasture were avoided. Local colonization was higher at convex landscape formations and by high coniferous forest coverage and forest‐edge length. Local extinction, on the other hand, was lower at convex landscape formations and high‐elevation sites. Our results suggest that shorter persistence of snow fields caused by climate change and degradation of feeding grounds through land‐use abandonment might severely deteriorate food availability for the species, which is likely to have contributed to the observed decline. For conservation of the Alpine Ring Ouzel, we recommend adopting measures to mitigate the negative effects of climate warming and improve habitat quality. The creation of small‐scale mosaics of sparse conifer forests and regularly grazed pastures, especially on north‐ and east‐facing slopes on the lee sides of hills, mountain peaks or ridges, should be supported.

Land-cover and climate change are two main drivers of changes in species ranges. Yet, the majority of studies investigating the impacts of global change on biodiversity focus on one global change driver and usually use simulations to project biodiversity responses to future conditions. We conduct an empirical test of the relative and combined effects of land-cover and climate change on species occurrence changes. Specifically, we examine whether observed local colonization and extinctions of North American birds between 1981-1985 and 2001-2005 are correlated with land-cover and climate change and whether bird life history and ecological traits explain interspecific variation in observed occurrence changes. We fit logistic regression models to test the impact of physical land-cover change, changes in net primary productivity, winter precipitation, mean summer temperature, and mean winter temperature on the probability of Ontario breeding bird local colonization and extinction. Models with climate change, land-cover change, and the combination of these two drivers were the top ranked models of local colonization for 30%, 27%, and 29% of species, respectively. Conversely, models with climate change, land-cover change, and the combination of these two drivers were the top ranked models of local extinction for 61%, 7%, and 9% of species, respectively. The quantitative impacts of land-cover and climate change variables also vary among bird species. We then fit linear regression models to test whether the variation in regional colonization and extinction rate could be explained by mean body mass, migratory strategy, and habitat preference of birds. Overall, species traits were weakly correlated with heterogeneity in species occurrence changes. We provide empirical evidence showing that land-cover change, climate change, and the combination of multiple global change drivers can differentially explain observed species local colonization and extinction.