Identifying Hot Moments in Road-Mortality Risk for Freshwater Turtles

ABSTRACT Risk assessments can be used to identify threats, which vary both in space and time, to declining species. Just as hot spots describe locations where threat processes operate at a higher rate than in surrounding areas, hot moments refer to periods when threat rates are highest. However, the identification of hot moments can be challenging because the temporal complexity of some threat processes makes their effects on population viability difficult to predict. Declining throughout much of their range, Blanding's turtle (Emydoidea blandingii) populations are potentially most vulnerable to road mortality where road densities and traffic volumes are high. The temporal variations in road-mortality risk faced by these and other semiaquatic turtles at the population level are a consequence of several factors, including sex-specific movement characteristics and seasonal changes in traffic volume. We examined these risk factors for Blanding's turtle populations in Maine, USA, by integrating temporally explicit roadkill probabilities with demographic parameters informed by local and range-wide studies. Specifically, we used population simulations to estimate the relative risk for 14 2-week periods during the turtles’ active season. Our analysis clearly identified early summer as a period of elevated risk, with June through mid-July signaling a road-mortality hot moment for Blanding's turtles (for both M and F). These findings provide guidance for the implementation of temporally explicit conservation measures such as cautionary road signage, traffic management, and public outreach that, if timed strategically, could help to mitigate population impacts from road mortality.     

Variation in demographic and fine-scale genetic structure with population-history stage of <Emphasis Type="Italic">Hemerocallis taeanensis</Emphasis> (Liliaceae) across the landscape

Fine-scale genetic structure (FSGS) in plant populations is expected to be influenced by variation in demographic processes across space and over time. I chose Hemerocallis taeanensis (Liliaceae), a perennial herb with a rapid population turnover, to quantify how demographic structure and FSGS change with a population’s history (i.e., density). Nonaccumulative O-ring statistic and spatial autocorrelation analysis (kinship coefficient, F _ij ) were used to quantify spatial patterns of individuals and FSGS in four populations belonging to two population stages (expansion and maturation) in west-central Korea. The O-ring function revealed that significant aggregation of individuals occurs at short spatial scales during the earlier stage of population expansion, which reflects restricted seed dispersal around maternal individuals. However, this pattern disappears as the population density increases during population maturation, probably due to a high population density. Significant evidence of FSGS was found in two populations at the stage of population expansion (Sp, a statistic which describes the rate of decrease of pairwise kinship with distance, was 0.018 and 0.029). The results show that most seeds fall around maternal plants when initially established colonists proliferate at suitable microhabitats. In contrast to this, much lower Sp values (−0.003 and 0.004) were estimated for two populations at the stage of population maturation, which may result from the overlapping of seed shadows due to high adult density. All of these results demonstrate considerable variation in within-population demographic and genetic structures of H. taeanensis with respect to population temporal stage across the landscape.     

Source-sink dynamics within a plant population: the impact of substrate and herbivory on palm demography

Site factors have frequently been shown to affect survival, growth, and reproduction in plant populations. The source-sink concept proposed by Pulliam is one way of integrating this spatial demographic variation into population models. Source-sink models describe a population where propagules from “source” habitats sustain less productive “sink” areas. We adapted this concept to model the population dynamics of the understory palm Chamaedorea radicalis on two substrates, rock outcrops and forest floor. In our model, sources and sinks correspond to fine-scale demographic structure within the population, rather than spatially discrete subpopulations as described in the Pulliam model. We constructed a stage-structured population matrix model that integrates the site-specific demography of individuals across two habitats types that are linked by migration. We then parameterized this model with field data from C. radicalis. To address whether observed differences in palm demography between rock outcrops and the forest floor were due to natural variation between microsites or due to differences in browsing intensity from free range livestock, we parameterized separate models based on the substrate-specific demography of protected, non-browsed palms and of palms exposed to burro browse. Results showed that herbivory reduced survival and fecundity on the forest floor, which in the absence of seed migration resulted in a projected decline of forest floor palms (sinks). However with seed dispersal, palms persisted and total population growth (both substrates) was projected to be positive, indicating that seed dispersal from non-browsed palms on rock outcrops (sources) was sufficient to sustain C. radicalis on the forest floor.     

Spatiotemporal variation in reproductive parameters of yellow-bellied marmots

Spatiotemporal variation in reproductive rates is a common phenomenon in many wildlife populations, but the population dynamic consequences of spatial and temporal variability in different components of reproduction remain poorly understood. We used 43 years (1962–2004) of data from 17 locations and a capture–mark–recapture (CMR) modeling framework to investigate the spatiotemporal variation in reproductive parameters of yellow-bellied marmots (Marmota flaviventris), and its influence on the realized population growth rate. Specifically, we estimated and modeled breeding probabilities of two-year-old females (earliest age of first reproduction), >2-year-old females that have not reproduced before (subadults), and >2-year-old females that have reproduced before (adults), as well as the litter sizes of two-year old and >2-year-old females. Most reproductive parameters exhibited spatial and/or temporal variation. However, reproductive parameters differed with respect to their relative influence on the realized population growth rate (λ). Litter size had a stronger influence than did breeding probabilities on both spatial and temporal variations in λ. Our analysis indicated that λ was proportionately more sensitive to survival than recruitment. However, the annual fluctuation in litter size, abetted by the breeding probabilities, accounted for most of the temporal variation in λ. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Synergistic effects of food shortage and an insecticide on a <Emphasis Type="Italic">Daphnia</Emphasis> population: rapid decline of food density at the peak of population density reduces tolerance to the chemical and induces a large population crash

Laboratory populations of cloned Daphnia magna were exposed at different population phases (growing phase, density peak, stable phase) to the insecticide carbaryl at 15 μg 1⁻¹, which was harmful to juveniles but not to adults, and their population dynamics were analyzed. The population declined most at the density peak, when not only juveniles but also many adult individuals died. To analyze the factors affecting population vulnerability to carbaryl, acute toxicity tests were conducted using Daphnia individuals of different body sizes under different food conditions. The test revealed that daphnid sensitivity to carbaryl increased greatly when food density was changed from a high food level to a low level. This food condition, of low availability, might be the condition to which the Daphnia populations were exposed at their density peak. The synergism of the negative impacts of anthropogenic and natural stresses such as insecticides and food shortage may control aquatic populations.     

Population size and survival of the Brazilian Torrent Frog Hylodes heyeri (Anura,Hylodidae)

Population dynamics are influenced by environmental variability and understanding the abundance and persistence of individuals and populations is a fundamental goal of population ecology. Thus, estimating demographic parameters to identify the factors important for population variability is required to understand temporal and spatial dynamics. The stream-living diurnal frog Hylodes heyeri is endemic to the Atlantic Forest of Brazil in the states of Paraná, São Paulo and Santa Catarina. Here we use capture-mark-recapture methods to estimate survival rates and population size of this Brazilian Torrent Frog in Pico do Marumbi State Park, Paraná. We used CJS models for an open population to estimate apparent survival, capturability and population size in two streams. The number of captures during each session was positively correlated with the minimum weekly temperature. Despite that correlation, the most parsimonious model of survival and capturability was the constant model for both parameters, resulting in a monthly survival rate of 0.38 (95% CI = 0.30–0.46). Thus, only the abundance of the frog differed in the two streams (79 vs. 36), with the population size estimate of 187 individuals. Reproduction is seasonal in the Brazilian Torrent Frog and so the low monthly survival rate suggests that animals move over time rather than die, because 38% month⁻¹ survival should result in <1% of the population remaining after 5 months. Thus, researchers must recognize that populations are labile and individuals often move or are washed downstream during heavy rainfall, generating apparently rapid local turnover that is unlikely to reflect true mortality.     

Climate change affects timing and size of populations of an invasive cyanobacterium in temperate regions

Cylindrospermopsis raciborskii, an invasive freshwater cyanobacterium, originated from the tropics but has spread to temperate zones over the last few decades. Its northernmost populations in Europe occur in North German lakes. How such dramatic changes in its biogeography are possible and how its population dynamics in the newly invaded habitats are regulated are still unexplained. We therefore conducted a long-term (1993–2005) study of two German lakes to elucidate the mechanisms behind C. raciborskii population dynamics and to identify the abiotic constraints on its development. Our data revealed that pelagic populations of C. raciborskii thrived for three months during the summer, contributing up to 23% of the total cyanobacteria biovolume. Population sizes varied greatly between years without exhibiting any distinct long-term trends. In the annual lifecycle, C. raciborskii filaments emerged in the pelagic habitat when the temperature rose above 15–17 °C. At that time, mean photosynthetically active radiation in the mixed water column (I _mix) overstepped its maximum. Rates of population net increase were highest at the beginning of the season (0.15–0.28 day⁻¹), declined continuously over time, and were significantly positively correlated with I _mix. This indicates that the onset of the pelagic population is temperature-mediated and that I _mix controls its growth. Since I _mix peaks before the population onset, the time of germination is of crucial importance for successful development. To test this hypothesis, we designed a model to simulate pelagic population size, starting at different dates in the annual cycle. Moving the population onset forward by 30 days resulted in a doubling of the population size. We therefore conclude that an earlier rise in water temperature associated with climate change has promoted the spread of C. raciborskii to the temperate zone. Earlier warming permits earlier germination, thereby shifting the pelagic populations to a phase with higher I _mix, which advances growth and the population establishment.     

Environmental variation, fluctuating selection and genetic drift in subdivided populations

Although there have many studies of the population genetical consequences of environmental variation, little is known about the combined effects of genetic drift and fluctuating selection in structured populations. Here we use diffusion theory to investigate the effects of temporally and spatially varying selection on a population of haploid individuals subdivided into a large number of demes. Using a perturbation method for processes with multiple time scales, we show that as the number of demes tends to infinity, the overall frequency converges to a diffusion process that is also the diffusion approximation for a finite, panmictic population subject to temporally fluctuating selection. We find that the coefficients of this process have a complicated dependence on deme size and migration rate, and that changes in these demographic parameters can determine both the balance between the dispersive and stabilizing effects of environmental variation and whether selection favors alleles with lower or higher fitness variance.     

Spatial data replacing temporal data in population viability analyses: An empirical investigation for plants

In conservation management, there is an urgent need for estimates of population viability and for knowledge of the contributions of different life-history stages to population growth rates. Collection of long-term demographic data from a study population is time-consuming and may considerably delay the start of proper management actions. We examined the possibility of replacing a long-term temporal data set (demographic data from several years within a population) with a short-term spatial data set (demographic data from different populations for the same subset of two continuous years) for stochastic estimates of population viability. Using matrix population models for ten perennial plant species, we found that the matrix elements of spatial data sets often deviated from those of temporal data sets and that matrix elements generally varied more spatially than temporally. The appropriateness of replacing temporal data with spatial data depended on the subset of years and populations used to estimate stochastic population growth rates (log λ_s). Still, the precision of log λ_s estimates measured as variation in the yearly change of logarithmic population size rarely differed significantly between the spatial and temporal data sets. Since a spatiotemporal comparison of matrix elements and their variation cannot be used to assess whether spatial and temporal data sets are interchangeable, we recommend further research on the topic.     

Inferring the contribution of sexual reproduction,migration and off‐season survival to the temporal maintenance of microbial populations: a case study on the wheat fungal pathogen Puccinia striiformis f.sp. tritici

Understanding the mode of temporal maintenance of plant pathogens is an important domain of microbial ecology research. Due to the inconspicuous nature of microbes, their temporal maintenance cannot be studied directly through tracking individuals and their progeny. Here, we suggest a series of population genetic analyses on molecular marker variation in temporally spaced samples to infer about the relative contribution of sexual reproduction, off‐season survival and migration to the temporal maintenance of pathogen populations. We used the proposed approach to investigate the temporal maintenance of wheat yellow rust pathogen, Puccinia striiformis f.sp. tritici (PST), in the Himalayan region of Pakistan. Multilocus microsatellite genotyping of PST isolates revealed high genotypic diversity and recombinant population structure across all locations, confirming the existence of sexual reproduction in this region. The genotypes were assigned to four genetic groups, revealing a clear differentiation between zones with and without Berberis spp., the alternate host of PST, with an additional subdivision within the Berberis zone. The lack of any differentiation between samples across two sampling years, and the very infrequent resampling of multilocus genotypes over years at a given location was consistent with limited over‐year clonal survival, and a limited genetic drift. The off‐season oversummering population in the Berberis zone, likely to be maintained locally, served as a source of migrants contributing to the temporal maintenance in the non‐Berberis zone. Our study hence demonstrated the contribution of both sexual recombination and off‐season oversummering survival to the temporal maintenance of the pathogen. These new insights into the population biology of PST highlight the general usefulness of the analytical approach proposed.     

Effect of reproductive modes and environmental heterogeneity in the population dynamics of a geographically widespread clonal desert cactus

The dynamics of plant populations in arid environments are largely affected by the unpredictable environmental conditions and are fine-tuned by biotic factors, such as modes of recruitment. A single species must cope with both spatial and temporal heterogeneity that trigger pulses of sexual and clonal establishment throughout its distributional range. We studied two populations of the clonal, purple prickly pear cactus, Opuntia macrocentra, in order to contrast the factors responsible for the population dynamics of a common, widely distributed species. The study sites were located in protected areas that correspond to extreme latitudinal locations for this species within the Chihuahuan Desert. We studied both populations for four consecutive years and determined the demographic consequences of environmental variability and the mode of reproduction using matrix population models, life table response experiments (LTREs), and loop and perturbation analyses. Although both populations seemed fairly stable (population growth rate, λ∼1), different demographic parameters and different life cycle routes were responsible for this stability in each population. In the southernmost population (MBR) LTRE and loop and elasticity analyses showed that stasis is the demographic process with the highest contributions to λ, followed by sexual reproduction, and clonal propagation contributed the least. The northern population (CR) had both higher elasticities and larger contributions of stasis, followed by clonal propagation and sexual recruitment. Loop analysis also showed that individuals in CR have more paths to complete a life cycle than those in MBR. As a consequence, each population differed in life history traits (e.g., size class structure, size at sexual maturity, and reproductive value). Numerical perturbation analyses showed a small effect of the seed bank on the λ of both populations, while the transition from seeds to seedlings had an important effect mainly in the northern population. Clonal propagation (higher survival and higher contributions to vital rates) seems to be more important for maintaining populations over long time periods than sexual reproduction.     

Spatial and temporal genetic differentiation and effective population size of brown trout (<Emphasis Type="Italic">Salmo trutta</Emphasis>, L.) in small Danish rivers

The spatial and temporal genetic structure of brown trout populations from three small tributaries of Lake Hald, Denmark, was studied using analysis of variation at eight microsatellite loci. From two of the populations temporal samples were available, separated by up to 13 years (3.7 generations). Significant genetic differentiation was observed among all samples, however, hierarchical analysis of molecular variance (AMOVA) showed that differentiation among populations accounted for a non-significant amount of the genetic differentiation, whereas differentiation among temporal samples within populations was highly significant (0.0244, P<0.001). Estimates of effective population size (N _e) using a maximum-likelihood based implementation of the temporal method, yielded small values (N _e ranging from 33 to 79). When a model was applied that allows for migration among populations, N _e estimates were even lower (24–54), and migration rates were suggested to be high (0.13–0.36). All samples displayed a clear signal of a recent bottleneck, probably stemming from a period of unfavourable conditions due to organic pollution in the 1970–1980’s. By comparison to other estimates of N _e in brown trout, Lake Hald trout represent a system of small populations linked by extensive gene flow, whereas other populations in larger rivers exhibit much higher N _e values and experience lower levels of immigration. We suggest that management considerations for systems like Lake Hald brown trout should focus both on a regional scale and at the level of individual populations, as the future persistence of populations depends both on maintaining individual populations and ensuring sufficient migration links among these populations.     

Population structure of the sailfin sandfish, Arctoscopus japonicus (Trichodontidae), in the Sea of Japan

We analyzed patterns of genetic diversity in the sailfin sandfish (Arctoscopus japonicus), focusing on population subdivisions within the Sea of Japan. We observed 270 specimens from nine sampling sites in 1999–2000, i.e., seven sites in the Sea of Japan and two sites from the Pacific coast of Hokkaido. An additional site (30 specimens) was sampled from eastern Korea in the spawning season of 2004 for comparison. Forty haplotypes, compiled into three haplogroups (A–C), were detected based on the comparison of a 400-bp sequence of the anterior part of the mitochondrial control region. In accordance with previous hypotheses from morphological and molecular analyses, genetic discontinuity between the Sea of Japan and the Pacific coast of Hokkaido was conspicuous. Within the Sea of Japan, eight sampling sites were not genetically uniform, and most of the variations among sites were detected between eastern Korea [the “eastern Korea” (EK) population: distributed from the Korean Peninsula to Mishima, Yamaguchi Prefecture] and the other sites along the coast of Japan [the “western Japan” (WJ) population: from Oki Islands to western Hokkaido] (Φ _CT  = 0.096, P = 0.0183). The WJ population, having lower genetic variability, showed significant departure from neutrality, indicating influences through a recent population expansion. The period of the expansion can be estimated to have begun on the order of 10⁴ years ago. We consider that the present Japan Sea populations have been formed through the invasion of a small ancestral stock to the Sea of Japan and its population expansion during the last glacial period or later. On the other hand, we failed to detect distinct evidence of a population expansion in the EK population. Haplogroup C, detected in a high frequency in this population, was estimated to have mixed with haplogroup A after rapid differentiations of the latter. Therefore, the EK population, strongly influenced by such a mixture, might possess haplogroup C in a higher frequency and a different haplotype composition from the WJ population.     

Spatial and temporal dynamics of the male effective population size in bumblebees (Hymenoptera: Apidae)

Eusociality and male haploidy of bumblebees (Bombus spp.) enhance the deleterious effects of population decline and aggravate the degeneration of population fitness compared to solitary and diploid species. The highly dispersive male sex may be the prime driver to connect otherwise isolated populations. We therefore studied the temporal and spatial structure of the male population of Bombus terrestris (Linnaeus 1758) and Bombus lapidarius (Linnaeus 1758) using microsatellite DNA markers. We found that the majority of the males in a 1000 m2 sampling area originated from colonies located outside of the workers foraging range, which was consistent with the genetic distances among colonies. The analyses of temporal population sub-structure based on both colony detection rate over time and the clustering software STRUCTURE consistently suggested one large and temporally unstructured male population. Our results indicate an extended male flight distance for both species. Though the range of queen dispersal remains to be studied, the effective size (N _e) of bumblebees is increased by extended male mating flight ranges (A _m ) exceeding worker foraging distance by factor 1.66 (A _m  = 69.75 km²) and 1.74 (A _m  = 13.41 km²), B. terrestris and B. lapidarius, respectively. Thus this behaviour may counteract genetic deprivation and its effects. All populations were genetically highly diverse and showed no signs of inbreeding. We discuss the implications of our findings in context of bumblebee population dynamics and conservation. We also highlight the effects and benefits of sampling both workers and males for population genetic studies.     

Low Phylogeographic Structure in a Wide Spread Endangered Australian Frog <Emphasis Type="Italic">Litoria aurea</Emphasis> (Anura: Hylidae)

The green and golden bell frog (Litoria aurea) has a widespread distribution along the south-east coast of Australia. The species range, however, is highly fragmented and remaining populations are predominately isolated and restricted to the coastline. Previously, the range extended further inland and the species was considered common. Here we report a study designed to identify the phylogeographic and conservation genetic parameters of L. aurea. Mitochondrial DNA sequences were examined from 263 individuals sampled from 26 locations using both phylogenetic and population analyses. Despite a general consensus that amphibians are highly structured we found no phylogeographic divisions within the species, however, there was significant structure amongst extant populations (F _ST=0.385). Patterns of haplotype relatedness, high haplotypic diversity (mean h=0.547) relative to low nucleotide diversity (mean π=0.003) and mismatch distribution analysis supported a Pleistocene expansion hypothesis with continued restricted dispersal and gene flow. We conclude that the genetic structure of the species may permit ‘well managed’ intervention to mediate gene flow amongst isolated populations and provide some guidelines for the implementation of such conservation strategies.     

Temporal change in genetic structure and effective population size in steelhead trout (Oncorhynchus mykiss)

There is a wealth of published molecular population genetic studies, however, most do not include historic samples and thus implicitly assume temporal genetic stability. We tested for changes in genetic diversity and structure in three populations of steelhead trout (Oncorhynchus mykiss) from a northern British Columbia watershed using seven microsatellite loci over 40 years. We found little change in genetic diversity (mean allele numbers and observed and expected heterozygosity), despite large variation in the estimated numbers of steelhead returning to the watershed over the same time period. However, the temporal stability in genetic diversity is not reflected in population structure, which appears to be high among populations, yet significantly variable over time. The neighbour-joining tree showed that, overall, two of the populations (Zymoetz and Kispiox) clustered separately from the third (Babine); a finding which was not consistent with their geographical separation. The clustering pattern was also not temporally consistent. We used the temporal method to estimate the effective number of breeders (Nb ) for the three populations; our values (Nb = 17-102) were low for the large and presumed vigorous populations of steelhead trout sampled. The low Nb values were also not consistent with the generally high genetic diversity estimates, suggesting the possibility of intermittent gene flow among the three populations. The use of temporal analyses in population genetic samples should be a priority; first, to verify observed patterns in contemporary data, and second, to build a dataset of temporal analyses to allow generalizations to be made concerning temporal genetic stability and effective population size in natural populations.     

The effects of traditional gathering on populations of the marine gastropod Strombus luhuanus linne 1758, in southern Papua New Guinea

Summary Little is known of the response of mollusc populations to predation by humans, particularly for tropical species. In this paper, we examine the effects of human predation on populations of the gastropod Strombus luhuanus in Bootless Inlet, Papua New Guinea, by documenting both the population biology of the shellfish and the shell-gathering practices of traditional and contemporary human groups. Strombus luhuanus occurs in local colonies and individuals of each sex from different colonies differed significantly in size. Sexual maturity is reached within two years after settlement, at which time the shell length stabilises at about 35–60 mm, and the shell lip thickens. There was also significant between-colony variation in density (8.35–23.39 individuals/m²), and colonies differed in the depth range of their distributions and the frequency of human collection visits. Traditional gatherers rarely collected individuals which were buried or subtidal. Contemporary collectors used different collecting methods, and gathered subtidal populations to a depth of 2.5 m. Both traditional and contemporary collectors gathered only individuals greater than 30 mm shell length, and in the contemporary sample the probability of being gathered increased significantly with shell length. This was due to size-dependent burying, which was greatest among young juveniles and least among adults. The traditional sample contained fewer shells in the largest size category (>45 mm) and more in the smallest (<40 mm), but this difference largely represents the pooling of shells from different collecting locations rather than widespread juvenisation of colonies due to exploitation. Stromb population densities at collected sites in PNG far exceeded those in comparable uncollected sites in northeastern Australia. We conclude that S. luhuanus displays high resilience to all gathering practices used to date, as a consequence of both its size-dependent burying and partly subtidal distribution, which provide refugia from human predation.     

Protecting evolutionary significant units for the remnant populations of <Emphasis Type="Italic">Berchemiella wilsonii</Emphasis> var. <Emphasis Type="Italic">pubipetiolata</Emphasis> (Rhamnaceae)

Berchemiella wilsonii var. pubipetiolata (Rhamnaceae) is an endangered tree in eastern China. Habitat destruction has resulted in fragmentation of remnant populations and extinction of local populations. AFLP and cpDNA markers were used to determine the population structure of remnant populations of B. wilsonii var. pubipetiolata. Moderate nuclear genomic diversity was found within each of the four remnant populations (H _S = 0.141–0.172), while the cpDNA haplotype diversity in each population ranged from 0.356 to 0.681. Six haplotypes were identified by a combined cpRFLP and cpSSR analysis in a total of 89 individuals. AMOVA revealed significantly AFLP genetic differentiation within and between regions (Φ_SC = 0.196, Φ_CT = 0.396, respectively), and a high cpDNA haplotype differentiation between regions (Φ_CT = 0.849). The results suggest low gene flow between populations of B. wilsonii var. pubipetiolata. Strong genetic divergence between two regional populations as revealed by both AFLP and cpDNA markers provided convincing evidence that two distinct evolutionary lineages existed, and should be recognized as ‘evolutionary significant units’ (ESUs) for conservation concerns.     

The risks of learning: confounding detection and demographic trend when using count‐based indices for population monitoring

Theory recognizes that a treatment of the detection process is required to avoid producing biased estimates of population rate of change. Still, one of three monitoring programmes on animal or plant populations is focused on simply counting individuals or other fixed visible structures, such as natal dens, nests, tree cavities. This type of monitoring design poses concerns about the possibility to respect the assumption of constant detection, as the information acquired in a given year about the spatial distribution of reproductive sites can provide a higher chance to detect the species in subsequent years. We developed an individual‐based simulation model, which evaluates how the accumulation of knowledge about the spatial distribution of a population process can affect the accuracy of population growth rate estimates, when using simple count‐based indices. Then, we assessed the relative importance of each parameter in affecting monitoring performance. We also present the case of wolverines (Gulo gulo) in southern Scandinavia as an example of a monitoring system with an intrinsic tendency to accumulate knowledge and increase detectability. When the occupation of a nest or den is temporally autocorrelated, the monitoring system is prone to increase its knowledge with time. This happens also when there is no intensification in monitoring effort and no change in the monitoring conditions. Such accumulated knowledge is likely to increase detection probability with time and can produce severe bias in the estimation of the rate and direction of population change over time. We recommend that a systematic sampling of the population process under study and an explicit treatment of the underlying detection process should be implemented whenever economic and logistical constraints permit, as failure to include detection probability in the estimation of population growth rate can lead to serious bias and severe consequences for management and conservation.     

Population and evolutionary dynamics in spatially structured seasonally varying environments

Increasingly imperative objectives in ecology are to understand and forecast population dynamic and evolutionary responses to seasonal environmental variation and change. Such population and evolutionary dynamics result from immediate and lagged responses of all key life‐history traits, and resulting demographic rates that affect population growth rate, to seasonal environmental conditions and population density. However, existing population dynamic and eco‐evolutionary theory and models have not yet fully encompassed within‐individual and among‐individual variation, covariation, structure and heterogeneity, and ongoing evolution, in a critical life‐history trait that allows individuals to respond to seasonal environmental conditions: seasonal migration. Meanwhile, empirical studies aided by new animal‐tracking technologies are increasingly demonstrating substantial within‐population variation in the occurrence and form of migration versus year‐round residence, generating diverse forms of ‘partial migration’ spanning diverse species, habitats and spatial scales. Such partially migratory systems form a continuum between the extreme scenarios of full migration and full year‐round residence, and are commonplace in nature. Here, we first review basic scenarios of partial migration and associated models designed to identify conditions that facilitate the maintenance of migratory polymorphism. We highlight that such models have been fundamental to the development of partial migration theory, but are spatially and demographically simplistic compared to the rich bodies of population dynamic theory and models that consider spatially structured populations with dispersal but no migration, or consider populations experiencing strong seasonality and full obligate migration. Second, to provide an overarching conceptual framework for spatio‐temporal population dynamics, we define a ‘partially migratory meta‐population’ system as a spatially structured set of locations that can be occupied by different sets of resident and migrant individuals in different seasons, and where locations that can support reproduction can also be linked by dispersal. We outline key forms of within‐individual and among‐individual variation and structure in migration that could arise within such systems and interact with variation in individual survival, reproduction and dispersal to create complex population dynamics and evolutionary responses across locations, seasons, years and generations. Third, we review approaches by which population dynamic and eco‐evolutionary models could be developed to test hypotheses regarding the dynamics and persistence of partially migratory meta‐populations given diverse forms of seasonal environmental variation and change, and to forecast system‐specific dynamics. To demonstrate one such approach, we use an evolutionary individual‐based model to illustrate that multiple forms of partial migration can readily co‐exist in a simple spatially structured landscape. Finally, we summarise recent empirical studies that demonstrate key components of demographic structure in partial migration, and demonstrate diverse associations with reproduction and survival. We thereby identify key theoretical and empirical knowledge gaps that remain, and consider multiple complementary approaches by which these gaps can be filled in order to elucidate population dynamic and eco‐evolutionary responses to spatio‐temporal seasonal environmental variation and change.