Patchy Population Research Articles

Phylogeny and genetic structure of the Yellow ground squirrel, Spermophilus fulvus (Lichtenstein, 1823), in Iran

Old world ground squirrels (genus Spermophilus) are distributed throughout the Holarctic and Palearctic regions, of which two Iranian species, the Yellow ground squirrel S. fulvus and the Asia Minor ground squirrel S. xanthoprymnus, comprise the southernmost distribution of the genus in the Palearctic. The two species are found in fragmented populations from northeastern to northwestern Iran, with S. fulvus being more common and widespread in the country. The enormous geographical distance (more than 1000 km) between Yellow ground squirrel’s patchy populations in eastern and western Iran has led to ambiguous evolutionary relationships and consequently uncertain conservation planning for the species. We studied the phylogenetic relationships and spatial genetic structure of the isolated populations using the mitochondrial Cytochrome b (cyt b) among 79 individuals. Our phylogenetic analysis found that S. fulvus was divided into three main mtDNA clades in Iran. Molecular dating suggested an ancestral expansion from high latitudes towards Iran during the cold periods (before the Holsteinian temperate period), followed by contraction of populations into interglacial refugia around the Holsteinian temperate period (430-350 Kya), leading to their isolation from their ancestral pool about 427 Kya. Furthermore, we found a non-deep phylogenetic divergence between patchy isolated populations of the species in Iran. A major genetic break was detected between populations of eastern Iran (steppes in Hezar Masjed and Binalud mountains, near Iran-Turkmenistan-Afghanistan borderline) and the others, probably associated with their confinement to interglacial refugia during the Domnitz temperate period (340-300 Kya). However, the recent divergence between northeastern and western populations of Iran probably resulted from their contraction into interglacial refugia in the Saale/Drenthe temperate period (250-190 Kya). These results may suggest that populations of the Yellow ground squirrel in Iran fell under the influence of glacial and interglacial cycles along a longitudinal axis. Finally, we propose the three isolated clades of the Yellow ground squirrel identified in Iran as three ESUs.

Patchy spread patterns in three-species bistable systems with facultative mutualism

A three-species population system under a facultative mutualistic relationship of one of the species is studied. The considered interactions are as follows: facultative between the first species and the second species, obligatory mutualism between the second species and the first one, and the third species is a predator of the first species. For this purpose, we extend the model proposed by Morozov et al., originally used to describe obligatory mutualism, to consider obligatory and facultative mutualism and prove that under adequately selected parameters this system produces a spatial patchy spread of populations or continuous wave fronts. Since the analytical treatment of a three-species model is often prohibitive, we first analyze the interaction between two mutualist species without diffusion and without the presence of the predator. Some parameters are fixed in the bistable regime of the mutualistic species to further consider the influence of the third species. The remaining parameters are then selected to produce patchy patterns under different mortality rates. Finally, the equations of the final three-species system are numerically solved to test the influence of different initial conditions in the formation of patchy populations. It is confirmed that the velocity and the profile of a traveling front are independent on the initial conditions. Our approach opens the way to study more general biological situations.

The Evolving Protection of Borders of the Reborn Second Republic of Poland

The Second Republic of Poland, after regaining independence as a new state and creating state structures, faced many serious challenges. Barely formed boundaries required effective protection as soon as possible. An important problem was the process of gradually gaining power over the borders. While its protection system was developing on the western border, regular military operations continued in the east. This task was not facilitated by the incompletely resolved border conflicts and the ethnically patchy population living in the border areas. One of the most serious problems was the lack of experience in protecting the state borders caused by the loss of independence. For the above reasons, the process of developing the border protection system of the Second Polish Republic lasted several years. How difficult that task was is shown by the number of border formations that were brought into existence at that time, subjecting them to various modifications. As a consequence, due to difficult relations between the Republic and neighboring states, the developed system of border protection was not uniform. It also had to face still not fully stabilised situation in Europe.

A functional group approach reveals important fish recruitments driven by flood pulses in floodplain ecosystem

The periodical flood pulses, assisting by the connectivity between rivers and lakes in floodplain ecosystems, are of paramount importance in underpins fish meta-communities. Regardless of the unprecedented anthropogenic disturbances on natural flood regimes, there is limited understanding for the response of fish assemblages to flood pulses. Most studies documented the issue sorely on floodplain rivers or floodplain lakes, but the dynamics of fish communities in the transitional floodplains accounting for both lentic and lotic environments are rarely reported. Here we measure temporal (high and low water seasons) and spatial (lotic and lentic environments) patterns of fish assemblages in the transitional floodplain between the Yangtze River and Lake Caizi using taxonomic and functional group metrics. Our results demonstrated significantly variations in fish community composition among different environments between high and low water seasons. During flooding season in high water phase, we observed significantly patchy population recruitments of riverine fish species. Then in low water season, widespread lake residents dominated the lentic environments due to their higher environment tolerance. Benefitting from the functional group measurement, we identified three flooding related functional groups i.e., G2, G9 and G10 (consisting of riverine catfishes, gudgeons, and loaches), that may bear the brunt of natural flood pulses alterations. Despite the significant variations of richness in taxonomic diversity, we detected higher sensitivity of functional diversity, since three functional diversity indices were significantly higher in high water season. This findings demonstrated important functional recruitments triggered by flood pulses, highlighting a pressing need to sustain natural flood regime with hydrological connectivity for better conservation of fish assemblages in floodplain ecosystem.

Asexual reproduction and heterozygote selection in an Antarctic demosponge (Stylocordyla chupachus, Suberitida)

Antarctic bottoms harbor stable, benthic communities, subjected to low temperatures. Environmental stability may promote the asexual (clonal) reproduction of sponges to maintain adapted genotypes to those particular conditions. Stylocordyla chupachups forms patchy populations across the Antarctic continental shelf. Individuals are mostly similar in size without distinct cohorts, which indicates fast growth of the new recruits. Settlement of incubated (clonal?) functional sponges may accelerate sponge growth and success at early colonization phases. To analyze the weight of clonal reproduction in the species, a genetic study was performed on three close populations using eight polymorphic microsatellite loci that were designed from massive sequencing. The three study populations showed a relatively low genetic diversity and low loci polymorphism (from 2 to 6 alleles). The estimators of genetic structure, the Analysis of the Molecular Variance (AMOVA), and the presence of private alleles indicated low but significant structure between the populations. A relatively high rate of asexual reproduction (ca. 25% of the individuals) was detected. The program MLGsim found five identical multilocus genotypes (MLGs) with an asexual origin. An excess of heterozygotes (in five out of the eight loci genotyped) was found, which suggests a positive selection mechanism for heterozygotes. The relatively high rates of asexual reproduction may be the result of adaptation to the environmental stability, while heterozygote selection would help maintain some genetic diversity in the populations. S. chupachups has been reported to be one of the first sponge species recolonizing bare areas resulting from iceberg scouring, which indicates a high species fitness and adaptation to Antarctic bottoms. Two out of the three study populations showed bottleneck, which may indicate a recent founder effect and supports the pioneer nature of this species.

<b>Distribution and population status of <I>Kingiodendron pinnatum</I> (Angiosperms: Fabaceae) an endemic and endangered legume tree in southern Western Ghats, Kerala, India</b>

An extensive survey and population analysis of the endemic and endangered tree Kingiodendron pinnatum, was carried out in the Kerala area of the Western Ghats. The aim was to assess the pattern of distribution, population size and natural regeneration of the species. The fragmented and patchy populations of the species are distributed in evergreen/semi evergreen habitats within an altitudinal range of 176-680m elevation. The tree attained a first layer/canopy species with a height range from 24–30m. Altogether 17 populations were identified and mapped in 13 forest locations in the region. A total of 140 adult individuals of the species were enumerated within the 13 forest locations. Natural regeneration of the species recorded from three zones among the 13 forest locations covering 21,000m2 area representing the Kerala state. The flowering trees displayed a height and dbh range of 10-30m and 85-320cm, respectively. The individuals are spatially arranged in aggregation among patchy populations. The populations are well represented by reproductive individuals with 77% and pre reproductive with 23%. Seedlings of 35.9% attained a height below 1m and 64.01% of a height above 1m. Considering the extent of distribution in the state, increase in the number of mature individuals (in addition to the enumerated area), and fair count of seedlings suggests a healthier conservation status of the species in the region. The economic and medicinal values, occurrence of isolated and fragmented populations, irregularities in the flowering and fruiting period among populations, however, extends urgent concerns over the pollination biology, detection of diverse genotypes subsequent multiplication and restoration of dwindling populations for the effective conservation and management of the species in situ.

Invasion waves in the biochemical warfare between living organisms.

Microorganisms and plants very commonly release toxic secondary chemical compounds (allelochemicals) that inhibit or kill sensitive strains or individuals from their own or other species. In this work we study a model that describes two species interacting through allelopathic suppression and competing for resources. Employing linear stability analysis, the conditions for coexistence or extinction of species in spatially homogeneous systems were determined. We found that the borders between the regimes of bistability, coexistence, and the extinction of the weaker by the stronger competitor, are altered by allelopathic interactions. In addition, traveling wave solutions for one species invasion were obtained considering the spatially explicit nature of the model. Our findings indicate that the minimum speed of the invasion wavefronts depends primarily on the competition coefficients and the parameters characterizing the species' functional responses to their allelochemicals. As a general rule, the species provided with the most effective chemical weapons dominates the population dynamics. Finally, we found a tristability at the coexistence region due to the combination of allelopathy and patchy population distributions in space. So, our model provides a distinct mechanism, independent of social behaviors, that produces such unexpected tristability impossible in classical competition models involving one-to-one individual interactions.

Noteworthy bird records from northeastern Peru reveal connectivity and isolation in the western Amazonian avifauna

ABSTRACT Amazonian bird species often have patchy spatial distributions, and previous work has attributed this pattern to habitat specialization and dispersal limitation; however, we know comparatively little about the origins and maintenance of the isolated populations that constitute a patchy distribution. In this study, we ask whether patchy populations are interconnected by dispersal. We formulated 2 alternative hypotheses: (1) patchy populations are relicts of ancient connectivity or dispersal; and (2) patchy populations are centers of local abundance embedded in a matrix of contemporary dispersal or diffuse intervening populations. We confronted these hypotheses with circumstantial evidence derived from a unique suite of noteworthy bird records and geological observations from northeastern Peru. We found support for both hypotheses in different species, and sometimes within single species at different spatial scales. Phenotypically differentiated populations in relictual habitat patches provide stro...

Population structure in two geographically sympatric and congeneric ectoparasites (Cimex adjunctusandCimex lectularius) in the North American Great Lakes region

Subdivided populations can be described by different models of population structure that reflect population organization, dynamics, and connectivity. We used genetic data to investigate population structure in two geographically sympatric, congeneric species of generalist ectoparasites of warm-blooded animals. We characterized the spatial genetic structure of the eastern bat bug (Cimex adjunctus Barber, 1939), an understudied and fairly abundant species, using microsatellite markers at a spatial scale representing contemporary dispersal of the species. We found seven genetic clusters, global [Formula: see text] of 0.2, 33% of genetic variation among sites, and nonsignificant isolation-by-distance. We compared these results with the common bed bug (Cimex lectularius L., 1758), a closely related but conversely well-known species, in the same geographic area. We found stronger genetic structuring in C. lectularius than in C. adjunctus, with 11 genetic clusters, [Formula: see text] of 0.7, 57% of genetic variation among sites, and significant but weak isolation-by-distance (R2= 0.09). These results suggest that while both species can be described as having classic metapopulation structure, C. adjunctus leans more towards a patchy population and C. lectularius leans more towards a nonequilibrium metapopulation. The difference in population structure between these species may be attributable to differences in movement potential and extinction–colonization dynamics.

Lower settlement following a forced displacement experiment: nonbreeding as a dispersal cost in a wild bird?

Dispersal is a key life history trait impacting ecological and evolutionary processes. Yet, the fitness consequences of dispersal remain poorly investigated. Using a displacement experiment of 616 individuals in a patchy population of collared flycatchers, Ficedula albicollis, we investigated behavioural responses to forced movement in terms of settlement, subsequent breeding performance and return rate. Newly arrived birds were caught and displaced between patches or released back in the patch of capture. We analysed (1) the probability of successful settlement within the study area, (2) for displaced birds, the probability of accepting the forced movement rather than returning to the patch of capture, (3) components of reproductive performance and (4) return rate in subsequent years according to experimental treatment. The probability of settling within the study area tended to be lower for displaced than control birds and was lower for immigrants than local birds. This suggests that displacement induced long-distance dispersal movements or nonbreeding, which could reflect costs of unfamiliarity with the environment. Nondispersers (individuals caught early in the breeding season in the same patch as their previous one) were more likely to return to their patch of capture, probably because of higher benefits of familiarity. Once individuals had settled, their breeding performance did not vary markedly between treatments, although displaced individuals that did not return to their patch of capture raised lighter young than other individuals. This could indicate a lower phenotypic quality of these individuals or, again, a cost of breeding in an unfamiliar environment. Finally, individuals that settled (and nondispersers) were more likely to return to the study area in subsequent years than individuals that disappeared (and immigrants/dispersers, respectively). Together, these results suggest that, in addition to the costs of transience, dispersal (here forced) may entail costs linked to settlement in an unfamiliar habitat.

Natal dispersers pay a lifetime cost to increased reproductive effort in a wild bird population.

Natal dispersal is assumed to be costly. Such costs can be difficult to detect, and fitness consequences of dispersal are therefore poorly known. Because of lower phenotypic quality and/or familiarity with the environment, natal dispersers may be less buffered against a sudden increase in reproductive effort. Consequently, reproductive costs associated with natal dispersal may mostly be detected in harsh breeding conditions. We tested this prediction by comparing lifetime reproductive success between natal dispersers and non-dispersers in a patchy population of collared flycatchers (Ficedula albicollis) when they reared either a non-manipulated brood or an experimentally increased or decreased brood. Natal dispersers achieved lower lifetime reproductive success than non-dispersers only under more stressful breeding conditions (i.e. when brood size was experimentally increased). This was mostly due to a lower number of recruits produced in the year of the increase. Our results suggest a cost associated with natal dispersal paid immediately after an increase in reproductive effort and not subsequently compensated for through increased survival or future offspring recruitment. Natal dispersers adjusted their breeding investment when reproductive effort is as predicted but seemed unable to efficiently face a sudden increase in effort, which could affect the influence of environmental predictability on dispersal evolution.

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.

Does population distribution matter? Influence of a patchy versus continuous distribution on genetic patterns in a wind‐pollinated shrub

AbstractAimUniform spatial population distributions are predicted to result in lower among‐population genetic differentiation and higher within‐population genetic diversity than naturally patchy distributions, but there have been surprisingly few attempts to isolate this effect from confounding factors. We studied the widespread wind‐pollinated shrub Allocasuarina humilis that is common in a geologically stable landscape characterized by long‐term population persistence to test the influence of semi‐continuous versus patchy population distributions on genetic patterns. We also investigated whether A. humilis shows the high population connectedness and genetic diversity typically associated with wind pollination, a relatively uncommon and little‐studied syndrome in this landscape.LocationHeath‐shrublands (‘heath’) and forests of south‐western Australia.MethodsPopulations were sampled from heath and forest regions, which respectively exhibited semi‐continuous and patchy population distributions. Genetic structure and diversity were assessed for 27 populations using eight nuclear microsatellite markers and three chloroplast regions. Phylogeographical history was examined using Bayesian phylogeny reconstruction, parsimony analysis and tests of expansion.ResultsHigh haplotype diversity is consistent with long‐term population persistence across most of the species’ range. Nuclear markers showed low overall population differentiation and no geographical structure over c. 900 km, reflecting extensive pollen dispersal. For both marker types, patchily distributed forest populations were substantially more differentiated with significantly lower within‐population diversity than semi‐continuous heath populations. Phylogeographical analysis revealed evidence for earlier colonization of heath than forest and recent expansion into wetter forests, consistent with progressive long‐term climatic drying.Main conclusionsHigh population connectedness and genetic diversity probably resulted from wind pollination in combination with dioecy and long life span. Patchy population distributions appear to have influenced genetic structure and diversity through lower pollen and seed dispersal, lower effective population sizes and greater genetic drift. Our approach illustrates the value of minimizing confounding variables by testing the effect of a variable ecological trait within a single species.

Differences in the oxidative balance of dispersing and non-dispersing individuals: an experimental approach in a passerine bird.

BackgroundDispersal is often associated with a suite of phenotypic traits that might reduce dispersal costs, but can be energetically costly themselves outside dispersal. Hence, dispersing and philopatric individuals might differ throughout their life cycle in their management of energy production. Because higher energy expenditure can lead to the production of highly reactive oxidative molecules that are deleterious to the organism if left uncontrolled, dispersing and philopatric individuals might differ in their management of oxidative balance. Here, we experimentally increased flight costs during reproduction via a wing load manipulation in female collared flycatchers (Ficedula albicollis) breeding in a patchy population. We measured the effects of the manipulation on plasmatic markers of oxidative balance and reproductive success in dispersing and philopatric females.ResultsThe impact of the wing load manipulation on the oxidative balance differed according to dispersal status. The concentration of reactive oxygen metabolites (ROMs), a marker of pro-oxidant status, was higher in philopatric than dispersing females in the manipulated group only. Differences between dispersing and philopatric individuals also depended on habitat quality, as measured by local breeding density. In low quality habitats, ROMs as well as nestling body mass were higher in philopatric females compared to dispersing ones. Independently of the manipulation or of habitat quality, plasma antioxidant capacity differed according to dispersal status: philopatric females showed higher antioxidant capacity than dispersing ones. Nestlings raised by philopatric females also had a higher fledging success.ConclusionsOur results suggest that dispersing individuals maintain a stable oxidative balance when facing challenging environmental conditions, at the cost of lower reproductive success. Conversely, philopatric individuals increase their effort, and thus oxidative costs, in challenging conditions thereby maintaining their reproductive success. Our study sheds light on energetics and oxidative balance as possible processes underlying phenotypic differences between dispersing and philopatric individuals.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0697-x) contains supplementary material, which is available to authorized users.

Lichen colonization patterns show minor effects of dispersal distance at landscape scale

The role of dispersal in controlling the distribution of species at landscape scale (102–104 m) is still a matter of dispute. Here, we use the early colonization pattern of 23 epiphytic lichen species in a former tree‐less heathland landscape (170 km2) to test three hypotheses on how a landscape is colonized: A) mainly by long‐distance dispersal (LDD), B) by rare LDD events followed by limited local dispersal, and C) mainly by limited dispersal, resulting in a colonization front. The study system consisted of a chronosequence of 94 habitat patches constituting 0.4% of the landscape area, with a minimum inter‐site distance of 0.2 km. We used generalized linear mixed models with Bayesian inference to test predictions from the hypotheses. When age of sites and habitat area were accounted for, additional effects of geographical position of sites (distance from old sites, distance‐dependent relative propagule pressure, and distance from border of study area) on the probability of colonization by lichen species were small. Furthermore, species richness of sites did not depend on geographical position, either. Our results support a colonization process mainly governed by LDD at landscape scale, and that local stepwise colonization was not important. We argue that passively dispersed species with numerous small propagules tend to exhibit patchy populations with extensive dispersal at the landscape scale, rather than behaving like classical metapopulations.

Egg fertilisation in a freshwater mussel: effects of distance, flow and male density

Summary Small or sparse populations can experience Allee effects if egg fertilisation is reduced because of a shortage of sperm. Freshwater mussels are spermcasters that often occur as sparse, patchy populations. Previous studies suggested that sperm shortage limits these populations unless facultative hermaphroditism and self‐fertilisation occur at low density. We conducted experiments in ponds to examine fertilisation in the mussel, Lampsilis straminea, in response to flow, presence of and distance from males, male density, and the presence of upstream females that could compete for sperm with downstream females. Self‐fertilisation in the absence of males did not occur in either experiment. Female fertilisation success was uniformly high in most treatments and was not related to flow or distance from males (1–25 m). Fertilisation success was significantly lower at low male density (0.02 m−2, compared with 0.16 m−2) but remained relatively high even in most low male density treatments. The proportion of females that became gravid was higher in the presence of upstream females, but fecundity was significantly lower when upstream females were present; these conflicting results made it difficult to assess the role of competition among females for sperm. Overall, high fertilisation success occurred at densities three orders of magnitude lower than previously proposed thresholds for mussels. Sperm dispersal and acquisition and egg fertilisation appear to be complex processes associated with adaptations for spermcasting. These adaptations are likely to facilitate persistence at low population density and buffer mussels from reproductive Allee effects.

Movement ecology of amphibians: from individual migratory behaviour to spatially structured populations in heterogeneous landscapes,

Both genetic cohesion among local populations of animals and range expansion depend on the frequency of dispersers moving at an interpatch scale. Animal movement has an individual component that reflects behaviour and an ecological component that reflects the spatial organization of populations. The total movement capacity of an individual describes maximum movement distance theoretically achievable during a lifetime, whereas its variation among the members of a local population determines the magnitude of interpatch movements and thus of gene flow between neighbouring patches within metapopulation or patchy population systems. Here, I review information on dispersal and migration as components of the movement capacity of juvenile and adult pond-breeding amphibians and discuss how these components inform the spatial structure of populations. Amphibians disperse as juveniles and adults, but movement distances detected in tracking or capture–mark–recapture studies are usually far below the corresponding estimates based on molecular gene-flow data. This discrepancy reflects the constraints of available tracking methods for free-ranging individuals leading to inappropriate surrogates of annual movement capacity, but can be resolved using probabilistic approaches based on dispersal functions. There is remarkable capacity for and plasticity in movements in amphibians. Annual within-patch movements (migrations) of individuals can be large and likely represent an underestimated capacity for movement at the interpatch scale. Landscape resistance may influence the paths of dispersing amphibians, but rarely impedes interpatch movements. Juveniles emigrating unpredictably far from the natal pond and adults switching from within-patch migrations to dispersal to another patch demonstrate the plasticity of individual movement behaviour. Three basic conclusions can be drawn with respect to the linkage of individual movement behaviour and spatial or genetic structure of local amphibian populations embedded in a heterogeneous landscape: (1) individual movements or consecutive short-term series of movements are misleading surrogate measures of total movement capacity; (2) probabilistic modelling of movement capacity is the best available behavioural predictor of interpatch gene flow; (3) connectivity of local populations in heterogeneous landscapes is less affected by landscape resistance than previously expected.

Dynamic Cellular Automata Based Epidemic Spread Model for Population in Patches with Movement

Epidemiology is the study of spread of diseases among the group of population. If not controlled properly, the epidemic would cause an enormous number of problems and lead to pandemic situation. Here in this paper we consider the situation of populated areas where people live in patches. A dynamic cellular automata model for population in patches is being proposed in this paper. This work not only explores the computing power of cellular automata in modeling the epidemic spread but also provides the pathway in reduction of computing time when using the dynamic cellular automata model for the patchy population when compared to the static cellular automata which is used for a nonpatchy homogeneous population. The variation of the model with movement of population among the patches is also explored which provides an efficient way for evacuation planning and vaccination of infected areas.

Influence of spatial distribution and size of clones on the realized outcrossing rate of the marsh cinquefoil (Comarum palustre)

Clonal growth is a common feature in flowering plants. As clone size increases, the selfing rate in self-compatible species is likely to increase due to more frequent geitono-pollination events (i.e. pollination among flowers within the same genet). This study investigated the breeding system of the marsh cinquefoil (Comarum palustre) and assessed spatial distribution of clones, clone size and architecture, and their effects on realized outcrossing rates. In addition, pollen dispersal was investigated in two patchy populations. The species' breeding system was investigated under controlled conditions through hand pollinations (self- vs. cross-pollination). Using microsatellite markers, an assessment was made of the realized outcrossing rates and the genetic diversity in four natural populations, the clonal structure in two populations within five 15 × 15 m sampling plots following 0.5 × 0.5 m grids, and the pollen dispersal through paternity assignment tests in those two populations. Comarum palustre is a self-compatible species but only presents a low rate of spontaneous self-pollination. The occurrence of inbreeding depression was not detected at the seed set stage (δ(SS) = 0.04). Clones were spatially clumped (A(C) = 0.60-0.80), with intermediate to no intermingling of the ramets (D(C) = 0.40-1.00). Genet size ranged from one to 171 ramets. Patchy populations had low outcrossing rates (t(m) = 0.33-0.46). Large clones showed lower outcrossing rates than small clones. Pollen dispersal mainly occurred within patches as only 1-7 % of the pollination events occurred between patches of >25 m separation. Seedling recruitment events were detected. Genet size together with distances between patches, through increasing geitono-pollination events, appeared to be important factors influencing realized outcrossing rates. The study also revealed seed flow allowing seedling recruitment, which may contribute to increasing the number of new patches, and potentially further enhance gene flow within populations.

Optimizing the trade‐off between spatial and genetic sampling efforts in patchy populations: towards a better assessment of functional connectivity using an individual‐based sampling scheme

Genetic data are increasingly used in landscape ecology for the indirect assessment of functional connectivity, that is, the permeability of landscape to movements of organisms. Among available tools, matrix correlation analyses (e.g. Mantel tests or mixed models) are commonly used to test for the relationship between pairwise genetic distances and movement costs incurred by dispersing individuals. When organisms are spatially clustered, a population-based sampling scheme (PSS) is usually performed, so that a large number of genotypes can be used to compute pairwise genetic distances on the basis of allelic frequencies. Because of financial constraints, this kind of sampling scheme implies a drastic reduction in the number of sampled aggregates, thereby reducing sampling coverage at the landscape level. We used matrix correlation analyses on simulated and empirical genetic data sets to investigate the efficiency of an individual-based sampling scheme (ISS) in detecting isolation-by-distance and isolation-by-barrier patterns. Provided that pseudo-replication issues are taken into account (e.g. through restricted permutations in Mantel tests), we showed that the use of interindividual measures of genotypic dissimilarity may efficiently replace interpopulation measures of genetic differentiation: the sampling of only three or four individuals per aggregate may be sufficient to efficiently detect specific genetic patterns in most situations. The ISS proved to be a promising methodological alternative to the more conventional PSS, offering much flexibility in the spatial design of sampling schemes and ensuring an optimal representativeness of landscape heterogeneity in data, with few aggregates left unsampled. Each strategy offering specific advantages, a combined use of both sampling schemes is discussed.