Interpopulation Connectivity Research Articles

The structural and functional connectivity of the grassland plant Lychnis flos-cuculi

Understanding the relationship between structural and functional connectivity is essential for successful restoration and conservation management, particularly in intensely managed agricultural landscapes. We evaluated the relationship between structural and functional connectivity of the wetland plant Lychnis flos-cuculi in a fragmented agricultural landscape using landscape genetic and network approaches. First, we studied the effect of structural connectivity, such as geographic distance and various landscape elements (forest, agricultural land, settlements and ditch verges), on gene flow among populations as a measurement of functional connectivity. Second, we examined the effect of structural graph-theoretic connectivity measures on gene flow among populations and on genetic diversity within populations of L. flos-cuculi. Among landscape elements, forests hindered gene flow in L. flos-cuculi, whereas gene flow was independent of geographic distance. Among the structural graph-theoretic connectivity variables, only intrapopulation connectivity, which was based on population size, had a significant positive effect on gene flow, that is, more gene flow took place among larger populations. Unexpectedly, interpopulation connectivity of populations, which takes into account the spatial location and distance among populations, did not influence gene flow in L. flos-cuculi. However, higher observed heterozygosity and lower inbreeding was observed in populations characterised by higher structural interpopulation connectivity. This finding shows that a spatially coherent network of populations is significant for maintaining the genetic diversity of populations. Nevertheless, lack of significant relationships between gene flow and most of the structural connectivity measures suggests that structural connectivity does not necessarily correspond to functional connectivity.

Intercolony movement of pre‐breeding seabirds over oceanic scales: implications of cryptic age‐classes for conservation and metapopulation dynamics

AbstractAimDemographic linkage between subpopulations plays a critical role in population processes. Metapopulation dynamics, however, remains one of the most poorly understood aspects of population biology. This is especially true for small, pelagic seabirds because their discrete subpopulations are located on offshore islands, separated by vast areas of open ocean, making monitoring logistically challenging. Seabird populations often contain large numbers of immature pre‐breeders that may be important for subpopulation connectivity and demography, but are poorly studied. Here we provide evidence for intercolony movement of pre‐breedingLeach's storm‐petrelsOceanodroma leucorhoaamong three colonies spanning theNorthAtlanticOcean. We discuss their influence on metapopulation dynamics and the extinction risk of a subpopulation under threat from extreme predation.LocationNorthAtlanticOceanIslands (Scotland,Canada &Iceland).MethodsWe use a novel application ofBayesian stable isotope mixing models to infer recent movement of pre‐breeding birds between three major breeding populations in theNorthAtlantic. Carbon and nitrogen stable isotope values from breeding birds (central place foragers) sampled at each colony were used as model sources and pre‐breeding birds as model mixtures.ResultsOf 134 pre‐breeding Leach's storm‐petrels sampled at three colonies across theNorthAtlantic, five had isotope mixing model estimates dissimilar (< 25%) to their colony of capture and were instead isotopically similar to another breeding region. Nineteen further pre‐breeders had highly mixed signatures (< 50% for the colony of capture), indicating possible recent movement between colonies.Main conclusionsOur findings provide evidence for interpopulation connectivity of pre‐breedingLeach's storm‐petrels among colonies spanning theNorthAtlantic. These results highlight the significance of cryptic young age‐classes in metapopulation dynamics and the demographic processes. Moreover, they provide us with a better understanding of how one subpopulation remains extant, despite experiencing extreme predation rates.

Isolation by distance and low connectivity in the peppery furrow shell Scrobicularia plana (Bivalvia)

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 462:111-124 (2012) - DOI: https://doi.org/10.3354/meps09834 Isolation by distance and low connectivity in the peppery furrow shell Scrobicularia plana (Bivalvia) Sílvia Santos1,*, Catarina Cruzeiro1,2, Jeanine L. Olsen3, Henk W. van der Veer1, Pieternella C. Luttikhuizen1 1Royal Netherlands Institute for Sea Research (NIOZ), 1790 AB Den Burg Texel, The Netherlands 2CIMAR/CIIMAR—Centro Interdisciplinar de Investigação Marinha e Ambiental, Universidade do Porto, 4050-123 Porto, Portugal 3Department of Marine Benthic Ecology and Evolution, Centre for Ecological and Evolutionary Studies, University of Groningen, 9747 AG Groningen, The Netherlands *Email: silvia.santos@nioz.nl ABSTRACT: Scrobicularia plana da Costa, 1778, a commercially important bivalve species in southern Europe, is commonly found along the NE Atlantic and Mediterranean coasts. Like other intertidal mollusk species, it has a wide distributional range and high potential for larval dispersal. However, S. plana has a patchier distribution than most co-distributed soft sediment bivalves of the intertidal, which could lead to lower interpopulation connectivity and stronger population structure. We surveyed 18 locations from throughout the species’ range to determine overall population structure, phylogeographic distribution and historical demography. We sequenced a portion of the mitochondrial cytochrome-c-oxidase I gene (COI) for 423 individuals. Three population clusters (Trondheim, Atlantic and Pisa) were identified on the basis of pairwise FSTs. Demographic parameters were analysed in a coalescence framework. Strong differentiation was found between most Atlantic locations and the single Mediterranean location (Pisa). Among Atlantic locations, differentiation was weak and non-significant, though significant isolation-by-distance was detected. A star-shaped phylogeny with mostly 1-step mutations was found. Although 65 haplotypes were detected, 50 were private. The higher diversity observed in southern Europe, Brittany and Norway was consistent with glacial refugia. Population expansion occurred recently with the oldest split, which was between all Atlantic groups and the Mediterranean group, taking place 0.3 to 1.1 million years ago (Myr). Negative values for neutrality tests and the star-shaped haplotype network were also indicative of recent population expansion, although such a pattern can also be the result of a selective sweep. An isolation-by-distance effect and absence of migration reveal low interpopulation connectivity, which is likely reinforced by the species’ patchy spatial distribution. KEY WORDS: Scrobicularia plana · Mitochondrial DNA · Genetic structure · Phylogeography · Glacial refugia Full text in pdf format Supplementary material PreviousNextCite this article as: Santos S, Cruzeiro C, Olsen JL, van der Veer HW, Luttikhuizen PC (2012) Isolation by distance and low connectivity in the peppery furrow shell Scrobicularia plana (Bivalvia). Mar Ecol Prog Ser 462:111-124. https://doi.org/10.3354/meps09834 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 462. Online publication date: August 21, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Gene flow networks among American Aedes aegypti populations

The mosquito Aedes aegypti, the dengue virus vector, has spread throughout the tropics in historical times. While this suggests man-mediated dispersal, estimating contemporary connectivity among populations has remained elusive. Here, we use a large mtDNA dataset and a Bayesian coalescent framework to test a set of hypotheses about gene flow among American Ae. aegypti populations. We assessed gene flow patterns at the continental and subregional (Amazon basin) scales. For the Americas, our data favor a stepping-stone model in which gene flow is higher among adjacent populations but in which, at the same time, North American and southeastern Brazilian populations are directly connected, likely via sea trade. Within Amazonia, the model with highest support suggests extensive gene flow among major cities; Manaus, located at the center of the subregional transport network, emerges as a potentially important connecting hub. Our results suggest substantial connectivity across Ae. aegypti populations in the Americas. As long-distance active dispersal has not been observed in this species, our data support man-mediated dispersal as a major determinant of the genetic structure of American Ae. aegypti populations. The inferred topology of interpopulation connectivity can inform network models of Ae. aegypti and dengue spread.

Influence of connection type on phase synchrony: analysis of a neural mass model

Empirical studies have demonstrated synchronized frontal and parietal electrophysiological signals at 22-34Hz during a conjunctive visual search task and at 36-56Hz during a pop-out visual search task. Bidirectional (conjunctive) versus unidirectional (pop-out) information transfer between neuronal populations is hypothesized to underly this difference in synchronization frequency. This study modeled the influence of connection type (i.e., unidirectional vs. bidirectional) on phase synchrony between two neural populations using a neural mass model. Phase-locking values (PLVs) were used as the measure of synchrony between populations. Consistent with the connectivity hypothesis, the model revealed greater PLVs at 22-34Hz when the two populations were connected bidirectionally than unidirectionally, but greater PLVs at 34-52Hz when connected unidirectionally than bidirectionally. The model suggests that inter-population connectivity also changes with bottom-up versus top-down control of attention.

Conservation genetics of evolutionary lineages of the endangered mountain yellow-legged frog, Rana muscosa (Amphibia: Ranidae), in southern California

Severe population declines led to the listing of southern California Rana muscosa (Ranidae) as endangered in 2002. Nine small populations inhabit watersheds in three isolated mountain ranges, the San Gabriel, San Bernardino and San Jacinto. One population from the Dark Canyon tributary in the San Jacinto Mountains has been used to establish a captive breeding population at the San Diego Zoo Institute for Conservation Research. Because these populations may still be declining, it is critical to gather information on how genetic variation is structured in these populations and what historical inter-population connectivity existed between populations. Additionally, it is not clear whether these populations are rapidly losing genetic diversity due to population bottlenecks. Using mitochondrial and microsatellite data, we examine patterns of genetic variation in southern California and one of the last remaining populations of R. muscosa in the southern Sierra Nevada. We find low levels of genetic variation within each population and evidence of genetic bottlenecks. Additionally, substantial population structure is evident, suggesting a high degree of historical isolation within and between mountain ranges. Based on estimates from a multi-population isolation with migration analysis, these populations diversified during glacial episodes of the Pleistocene, with little gene flow during population divergence. Our data demonstrate that unique evolutionary lineages of R. muscosa occupy each mountain range in southern California and should be managed separately. The captive breeding program at Dark Canyon is promising, although mitigating the loss of neutral genetic diversity relative to the natural population might require additional breeding frogs.

High connectivity among argali sheep from Afghanistan and adjacent countries: Inferences from neutral and candidate gene microsatellites

We quantified population connectivity and genetic variation in the Marco Polo subspecies of argali mountain sheep (Ovis ammon polii) by genotyping 9 neutral and 8 candidate gene microsatellite loci in 172 individuals noninvasively sampled across five study areas in Afghanistan, China, and Tajikistan. Heterozygosity and allelic richness were generally high (mean H = 0.67, mean A = 6.1), but were significantly lower in the China study area (H = 0.61, P < 0.001; A = 4.9, P < 0.01). One marker in an immune system gene (TCRG4) showed an excess of rare alleles compared to neutral expectations. Another immune system gene (GLYCAM-1) showed excessive differentiation (high F ST) between study areas. Estimates of genetic differentiation were similar (F ST = 0.035 vs. 0.033) with and without the two loci deviating from neutrality, suggesting that selection is not a primary driver of overall molecular variation, and that candidate gene loci can be used for connectivity monitoring, as long as selection tests are conducted to avoid biased gene flow estimates. Adequate protection of argali and maintenance of inter-population connectivity will require monitoring and international cooperation because argali exhibit high gene flow across international borders.

Genetic structure among populations in the endemic Hawaiian Plantago lineage: insights from microsatellite variation

AbstractEndemic Hawaiian species in the genus Plantago show considerable morphological and ecological diversity. Despite their variation, a recent phylogenetic analysis based on DNA sequence data showed that the group is monophyletic and that sequence variation among species and morphotypes is low. This lack of sequence polymorphisms resulted in an inability to resolve species and population affinities within the most recently derived clade of this lineage. To assess species boundaries, population genetic structure and interpopulation connectivity among the morphologically and ecologically distinct populations within this clade, genetic variation was examined using eight microsatellite loci. Within‐population genetic diversity was found to be lowest in the Maunaiu, Hawai'i population of the endangered P. hawaiensis, and highest in the large P. pachyphylla population from 'Eke, West Maui. Isolation by distance across the range of populations was detected and indicated restricted dispersal. This result is likely to be attributable to few interisland dispersal events in the evolutionary history of this lineage. Genetic differentiation within islands tended to be higher among populations occurring in contrasting bog and woodland habitats, suggesting ecological barriers to gene flow and the potential role of ecological divergence in population diversification. Overall, these results are consistent with findings from phylogenetic analysis of the entire lineage. Our data bring new insights regarding patterns of dispersal and population genetic structure to this endemic and endangered group of island taxa. As island environments become increasingly fragmented, information of this type has important implications for the successful management of these fragile populations and habitats.

Potential Effects of the United States‐Mexico Border Fence on Wildlife

Security infrastructure along international boundaries threatens to degrade connectivity for wildlife. To explore potential effects of a fence under construction along the U.S.-Mexico border on wildlife, we assessed movement behavior of two species with different life histories whose regional persistence may depend on transboundary movements. We used radiotelemetry to assess how vegetation and landscape structure affect flight and natal dispersal behaviors of Ferruginous Pygmy-Owls (Glaucidium brasilianum), and satellite telemetry, gene-flow estimates, and least-cost path models to assess movement behavior and interpopulation connectivity of desert bighorn sheep (Ovis canadensis mexicana). Flight height of Pygmy-Owls averaged only 1.4 m (SE 0.1) above ground, and only 23% of flights exceeded 4 m. Juvenile Pygmy-Owls dispersed at slower speeds, changed direction more, and had lower colonization success in landscapes with larger vegetation openings or higher levels of disturbance (p < or = 0.047), which suggests large vegetation gaps coupled with tall fences may limit transboundary movements. Female bighorn sheep crossed valleys up to 4.9 km wide, and microsatellite analyses indicated relatively high levels of gene flow and migration (95% CI for F(ST)=0.010-0.115, Nm = 1.9-24.8, M =10.4-15.4) between populations divided by an 11-km valley. Models of gene flow based on regional topography and movement barriers suggested that nine populations of bighorn sheep in northwestern Sonora are linked by dispersal with those in neighboring Arizona. Disruption of transboundary movement corridors by impermeable fencing would isolate some populations on the Arizona side. Connectivity for other species with similar movement abilities and spatial distributions may be affected by border development, yet mitigation strategies could address needs of wildlife and humans.

Fine‐scale spatial genetic structure and dispersal among spotted salamander (Ambystoma maculatum) breeding populations

We examined fine-scale genetic variation among breeding aggregations of the spotted salamander (Ambystoma maculatum) to quantify dispersal, interpopulation connectivity and population genetic structure. Spotted salamanders rely on temporary ponds or wetlands for aggregate breeding. Adequate breeding sites are relatively isolated from one another and field studies suggest considerable adult site fidelity; therefore, we expected to find population structure and differentiation at small spatial scales. We used microsatellites to estimate population structure and dispersal among 29 breeding aggregations in Tompkins County, New York, USA, an area encompassing 1272 km(2). Bayesian and frequency-based analyses revealed fine-scale genetic structure with two genetically defined demes: the North deme included seven breeding ponds, and the South deme included 13 ponds. Nine ponds showed evidence of admixture between these two genetic pools. Bayesian assignment tests for detection of interpopulation dispersal indicate that immigration among ponds is common within demes, and that certain populations serve as sources of immigrants to neighbouring ponds. Likewise, spatial genetic correlation analyses showed that populations < or = 4.8 km distant from each other show significant genetic correlation that is not evident at higher scales. Within-population levels of relatedness are consistently larger than expected if mating were completely random across ponds, and in the case of a few ponds, within-population processes such as inbreeding or reproductive skew contribute significantly to differentiation from neighbouring ponds. Our data underscore the importance of these within-population processes as a source of genetic diversity across the landscape, despite considerable population connectivity. Our data further suggest that spotted salamander breeding groups behave as metapopulations, with population clusters as functional units, but sufficient migration among demes to allow for potential rescue and recolonization. Amphibian habitats are becoming increasingly fragmented and a clear understanding of dispersal and patterns of population connectivity for taxa with different ecologies and life histories is crucial for their conservation.

MOVEMENTS, CONNECTIVITY, AND RESOURCE SELECTION OF ROCKY MOUNTAIN BIGHORN SHEEP

Abstract Species that exist in naturally fragmented subpopulations can maintain long-term viability through interpopulation connectivity and recolonization of suitable habitat. We used radiotelemetry to study movements of 3 herds of bighorn sheep (Ovis canadensis) that recently colonized previously unoccupied parts of western Montana. These herds also provided a unique opportunity to compare resource-selection patterns in newly colonized habitats, and we used logistic regression in a global information system framework to generate predictive models for females in each herd. We detected relatively long (19- to 33-km) extra–home range movements by males in all 3 herds, and connectivity with nearby bighorn and domestic sheep herds. An information-theoretic approach to model selection revealed greater differences in resource selection among herds than anticipated. Initial evaluation of resource-selection models by resubstituting data showed excellent predictive accuracy (P ≤ 0.002), but testing models across ...

Determining the extent and spatial scale of population connectivity: decapods and coral reef fishes compared

Patchily distributed demersal marine organisms that possess a pelagic larval stage have the potential to form complex linkages among sedentary adult populations through larval dispersal. Unfortunately, determining the extent of this inter-population connectivity in specific cases is quite difficult: larval dispersal is a complex result of several biotic and non-biotic processes, and marine larvae are minute creatures that are difficult to track or manipulate. Nevertheless, effective management of such open populations requires that we know how they are organized and interact. Coral reef fishes and many decapod crustaceans share patchy demersal distributions and pelagic larvae. We review progress made in determining connectivity among crab, lobster and reef fish populations, considering the questions that need to be answered and the techniques that have been applied. We highlight common research strengths and gaps among researchers working on reef fishes and benthic decapods, as well as those areas given greater attention by one group, the lead of which the other group will need to follow. Finally, we suggest that greater progress towards understanding dispersal and connectivity in the future will best be achieved by integrating the approaches we review into large-scale, multidisciplinary, collaborative research programs developed and carried out in association with natural resource managers.

Genetic differentiation, dispersal and mating system in the schistosome-transmitting freshwater snail Biomphalaria glabrata.

Biomphalaria glabrata is the main intermediate host of Schistosoma mansoni in America and one of the most intensely studied species of freshwater snail, yet very little is known about its population biology. Here, we used seven highly polymorphic microsatellite loci to analyse genetic diversity in populations from three regions (Lesser Antilles, Venezuela and southern Brazil). Considerable genetic variation was detected, with an average (s.d.) H(0) = 0.32 (0.24). More diversity per population was found in the Valencia lake basin in Central Venezuela, which suggests an influence of dispersal (via inter-population connectivity) on the restoring of genetic diversity after the demographic bottlenecks recurrently experienced by populations. A marked population structure was detected and there seems to be a relationship between mean differentiation and genetic diversity within regions. There is also a significant isolation-by-distance pattern. The Lesser Antilles populations appear clearly differentiated from the rest, which suggests a single colonisation event followed by local radiation within these islands or multiple colonisation events from the same source area. Our results indicate that B. glabrata essentially cross-fertilises, with little variation in selfing rates among populations. However, significant deficits in heterozygotes and linkage disequilibria were detected in two Venezuelan populations suggesting a mixture of at least two different genetic entities, probably with differences in their respective mating systems.

Recruitment, Dispersal, and Demographic Rescue in Spatially-Structured White-Tailed Ptarmigan Populations

Abstract We studied recruitment and dispersal of White-tailed Ptarmigan (Lagopus leucurus) breeding in naturally fragmented alpine habitats at four study sites in Colorado from 1987–1998. Almost all recruitment for both sexes, particularly females, was of birds produced outside local populations and also external to nearby studied populations. Populations were more dependent on female recruitment than on male recruitment to sustain them, and patterns of recruitment were not correlated with local survival of adults or production of young the previous year, except at one site for females. Over 95% of recruits were yearlings. Breeding dispersal of adults, an infrequent but regular event, was also important to inter-population connectivity. Our data for multiple populations allowed us to describe movement patterns among populations to assess consistency with conditions required for a rescue system. After widespread reproductive failure in one year, we expected all populations the next year would have low recruitment due to a reduced supply of recruits produced in the region. Recruitment was low, but impact varied among populations. We conducted an over-winter study of radio-marked offspring to determine possible influences of winter site location and relatives on recruitment patterns. Contrary to expectation, offspring remained on or near breeding sites in winter, but were not located near their mothers or siblings. Recruitment location was related to winter site location. White-tailed Ptarmigan exhibit a well developed capacity for external recruitment that allows them to persist in small populations with stochastic conditions for breeding and survival. Extensive external recruitment may be a general pattern for birds.

RECRUITMENT, DISPERSAL, AND DEMOGRAPHIC RESCUE IN SPATIALLY-STRUCTURED WHITE-TAILED PTARMIGAN POPULATIONS

We studied recruitment and dispersal of White-tailed Ptarmigan (Lagopus leucurus) breeding in naturally fragmented alpine habitats at four study sites in Colorado from 1987–1998. Almost all recruitment for both sexes, particularly females, was of birds produced outside local populations and also external to nearby studied populations. Populations were more dependent on female recruitment than on male recruitment to sustain them, and patterns of recruitment were not correlated with local survival of adults or production of young the previous year, except at one site for females. Over 95% of recruits were yearlings. Breeding dispersal of adults, an infrequent but regular event, was also important to inter-population connectivity. Our data for multiple populations allowed us to describe movement patterns among populations to assess consistency with conditions required for a rescue system. After widespread reproductive failure in one year, we expected all populations the next year would have low recruitment due to a reduced supply of recruits produced in the region. Recruitment was low, but impact varied among populations. We conducted an over-winter study of radio-marked offspring to determine possible influences of winter site location and relatives on recruitment patterns. Contrary to expectation, offspring remained on or near breeding sites in winter, but were not located near their mothers or siblings. Recruitment location was related to winter site location. White-tailed Ptarmigan exhibit a well developed capacity for external recruitment that allows them to persist in small populations with stochastic conditions for breeding and survival. Extensive external recruitment may be a general pattern for birds.