Patterns Of Genetic Connectivity Research Articles

Contrasting patterns of genetic connectivity in brooding and spawning corals across a remote atoll system in northwest Australia

An understanding of larval dispersal and connectivity in corals provides valuable insight into the processes of population maintenance and replenishment and is vital for effective management. Here, we used a genotyping by sequencing approach to explore patterns of genetic connectivity in two species of coral with different reproductive modes (brooding and broadcast spawning) at the Rowley Shoals in northwest Australia. Our data revealed strikingly different patterns of genetic structure in the two species. High levels of genetic subdivision in the brooding coral I. brueggemanni was consistent with extensive self-recruitment and restricted connectivity. In contrast, the broadcast spawning coral A. digitifera formed a single panmictic population with extensive gene flow. Our results highlight the wide variation in metapopulation connectivity that exists among corals and support the well-established link between reproductive mode and population genetic structure in the marine environment.

Genome-wide SNPs resolve spatiotemporal patterns of connectivity within striped marlin (Kajikia audax), a broadly distributed and highly migratory pelagic species.

Genomic methodologies offer unprecedented opportunities for statistically robust studies of species broadly distributed in environments conducive to high gene flow, providing valuable information for wildlife conservation and management. Here, we sequence restriction site‐associated DNA to characterize genome‐wide single nucleotide polymorphisms (SNPs) in a broadly distributed and highly migratory large pelagic fish, striped marlin (Kajikia audax). Assessment of over 4,000 SNPs resolved spatiotemporal patterns of genetic connectivity throughout the species range in the Pacific and, for the first time, Indian oceans. Individual‐based cluster analyses identified six genetically distinct populations corresponding with the western Indian, eastern Indian, western South Pacific, and eastern central Pacific oceans, as well as two populations in the North Pacific Ocean (F ST = 0.0137–0.0819). F ST outlier analyses identified a subset of SNPs (n = 59) putatively under the influence of natural selection and capable of resolving populations separated by comparatively high degrees of genetic differentiation. Temporal collections available for some regions demonstrated the stability of allele frequencies over three to five generations of striped marlin. Relative migration rates reflected lower levels of genetic connectivity between Indian Ocean populations (m R ≤ 0.37) compared with most populations in the Pacific Ocean (m R ≥ 0.57) and highlight the importance of the western South Pacific in facilitating gene flow between ocean basins. Collectively, our results provide novel insights into rangewide population structure for striped marlin and highlight substantial inconsistencies between genetically distinct populations and stocks currently recognized for fisheries management. More broadly, we demonstrate that species capable of long‐distance dispersal in environments lacking obvious physical barriers to movement can display substantial population subdivision that persists over multiple generations and that may be facilitated by both neutral and adaptive processes. Importantly, surveys of genome‐wide markers enable inference of population‐level relationships using sample sizes practical for large pelagic fishes of conservation concern.

Comparative landscape genetics reveals the evolution of viviparity reduces genetic connectivity in fire salamanders.

Evolutionary changes in reproductive mode may affect co-evolving traits, such as dispersal, although this subject remains largely underexplored. The shift from aquatic oviparous or larviparous reproduction to terrestrial viviparous reproduction in some amphibians entails skipping the aquatic larval stage and, thus, greater independence from water. Accordingly, amphibians exhibiting terrestrial viviparous reproduction may potentially disperse across a wider variety of suboptimal habitats and increase population connectivity in fragmented landscapes compared to aquatic-breeding species. We investigated this hypothesis in the fire salamander (Salamandra salamandra), which exhibits both aquatic- (larviparity) and terrestrial-breeding (viviparity) strategies. We genotyped 426 larviparous and 360 viviparous adult salamanders for 13 microsatellite loci and sequenced a mitochondrial marker for 133 larviparous and 119 viviparous individuals to compare population connectivity and landscape resistance to gene flow within a landscape genetics framework. Contrary to our predictions, viviparous populations exhibited greater differentiation and reduced genetic connectivity compared to larviparous populations. Landscape genetic analyses indicate viviparity may be partially responsible for this pattern, as water courses comprised a significant barrier only in viviparous salamanders, probably due to their fully terrestrial life cycle. Agricultural areas and, to a lesser extent, topography also decreased genetic connectivity in both larviparous and viviparous populations. This study is one of very few to explicitly demonstrate the evolution of a derived reproductive mode affects patterns of genetic connectivity. Our findings open avenues for future research to better understand the eco-evolutionary implications underlying the emergence of terrestrial reproduction in amphibians.

A Genome-Wide Approach to the Phylogeography of the Mussel Mytilus galloprovincialis in the Adriatic and the Black Seas

Connectivity between populations shapes the genetic structure of species being crucial for an effective management of environmental resources. Genetic approaches can provide indirect measures of connectivity, allowing the identification of genetically differentiated - unconnected - populations. In this study, we applied a 2b-RAD approach based on hundreds of polymorphic loci to provide the first detailed insight into the population genomics of the Mediterranean mussel Mytilus galloprovincialis in part of its native geographical range. We sampled 19 localities within the Mediterranean and Black Seas, and analyzed a total of 478 samples. We detected strong differences between the two seas, whereas no differences were found between samples from the Western and Central Mediterranean and within Western Mediterranean samples. In the Central Mediterranean a significant differentiation emerged comparing Central Adriatic samples with those from South Adriatic and Ionian Seas. Furthermore, an East-to-West genetic structuring was found in the Central Adriatic Sea, which was not present in the Southern Adriatic and Ionian Seas. These results possibly reflect the local oceanography, with a Middle Adriatic gyre unable to prevent genetic differentiation in this species, and a Southern Adriatic gyre that effectively mixes propagules in Southern areas. In the Black Sea, no signal of genetic structure was found, although samples were spaced at similar distances as in the Adriatic-Ionian area. Genetic connectivity patterns of M. galloprovincialis reveal peculiar species-specific features respect to other species with similar larval duration, suggesting caution in using genetic connectivity data of single species in defining conservation units. We recommend of using genetic connectivity data of many species representing a variety of life history traits, and we call for new investigations using high resolution population genomics, particularly in the Black Sea, to understand if areas separated by hundreds of kilometers can be considered genetically connected as mussels’ data suggest. This information will be critical to ensure “a well-connected system of protected areas” according to Aichi Target 11 of the Convention on Biological Diversity.

Unexpected patterns of genetic connectivity in Lobophyllia corymbosa (Forskål, 1775) around Sulawesi, Indonesia

Abstract. Umar W, Tassakka ACMAR, Barber PH, Jompa J. 2019. Unexpected patterns of genetic connectivity in Lobophyllia corymbosa (Forskål, 1775) around Sulawesi, Indonesia. Biodiversitas 20: 2744-2749. Sulawesi is a strategic area for the biological networks of marine organisms, especially for Scleractinian corals. Sulawesi is located centrally in Indonesia and influenced by Pacific and Indian Ocean currents and shown in unique biodiversity patterns. However, research in this region is very limited. The wide distribution and lack of information on dispersal and connectivity make Lobophyllia corymbosa an exciting candidate in this study for genetic connectivity at the heart of the Indonesian Coral Triangle Area (ICTA), using Mitochondrial DNA (mtDNA) genome. Sampling sites (Palu, Mamuju, Sinjai, and Luwuk Banggai) with different coral fragments were collected from each site, DNA extracted, and mitochondrial COI gene was amplified. The results of the analysis were unexpected, and we hypothesise that the observed pattern was due to the evolution of different lineages within this region. The distance index and genetic diversity showed a close relationship between Mamuju and Luwuk Banggai, while Sinjai and Palu had a different genetic pattern. The global current patterns, complicated geography, and habitat condition could lead to such an outcome. Hard coral larvae arriving in an area might bypass a number of possible "stepping stones", resulting in unique patterns and leading to unexpected genetic connections within and between areas.

Sporadic Genetic Connectivity among Small Insular Populations of the Rare Geoendemic Plant Caulanthus amplexicaulis var. barbarae (Santa Barbara Jewelflower).

Globally, a small number of plants have adapted to terrestrial outcroppings of serpentine geology, which are characterized by soils with low levels of essential mineral nutrients (N, P, K, Ca, Mo) and toxic levels of heavy metals (Ni, Cr, Co). Paradoxically, many of these plants are restricted to this harsh environment. Caulanthus ampexlicaulis var. barbarae (Brassicaceae) is a rare annual plant that is strictly endemic to a small set of isolated serpentine outcrops in the coastal mountains of central California. The goals of the work presented here were to 1) determine the patterns of genetic connectivity among all known populations of C. ampexlicaulis var. barbarae, and 2) estimate contemporary effective population sizes (Ne), to inform ongoing genomic analyses of the evolutionary history of this taxon, and to provide a foundation upon which to model its future evolutionary potential and long-term viability in a changing environment. Eleven populations of this taxon were sampled, and population-genetic parameters were estimated using 11 nuclear microsatellite markers. Contemporary effective population sizes were estimated using multiple methods and found to be strikingly small (typically Ne < 10). Further, our data showed that a substantial component of genetic connectivity of this taxon is not at equilibrium, and instead showed sporadic gene flow. Several lines of evidence indicate that gene flow between isolated populations is maintained through long-distance seed dispersal (e.g., >1 km), possibly via zoochory.

The Antarctic Circumpolar Current isolates and connects: Structured circumpolarity in the sea star Glabraster antarctica.

AimThe Antarctic Circumpolar Current (ACC) connects benthic populations by transporting larvae around the continent, but also isolates faunas north and south of the Antarctic Convergence. We test circumpolar panmixia and dispersal across the Antarctic Convergence barrier in the benthic sea star Glabraster antarctica.LocationThe Southern Ocean and south Atlantic Ocean, with comprehensive sampling including the Magellanic region, Scotia Arc, Antarctic Peninsula, Ross Sea, and East Antarctica.MethodsThe cytochrome c oxidase subunit I (COI) gene (n = 285) and the internal transcribed spacer region 2 (ITS2; n = 33) were sequenced. We calculated haplotype networks for each genetic marker and estimated population connectivity and the geographic distribution of genetic structure using ΦST for COI data.Results Glabraster antarctica is a single circum‐Antarctic species with instances of gene flow between distant locations. Despite the homogenizing potential of the ACC, population structure is high (ΦST = 0.5236), and some subpopulations are genetically isolated. Genetic breaks in the Magellanic region do not align with the Antarctic Convergence, in contrast with prior studies. Connectivity patterns in East Antarctic sites are not uniform, with some regional isolation and some surprising affinities to the distant Magellanic and Scotia Arc regions.Main conclusionsDespite gene flow over extraordinary distances, there is strong phylogeographic structuring and genetic barriers evident between geographically proximate regions (e.g., Shag Rocks and South Georgia). Circumpolar panmixia is rejected, although some subpopulations show a circumpolar distribution. Stepping‐stone dispersal occurs within the Scotia Arc but does not appear to facilitate connectivity across the Antarctic Convergence. The patterns of genetic connectivity in Antarctica are complex and should be considered in protected area planning for Antarctica.

Dispersal capacity and genetic relatedness in Acropora cervicornis on the Florida Reef Tract

Sexual reproduction in scleractinian corals is a critical component of species recovery, fostering population connectivity and enhancing genetic diveristy. The relative contribution of sexual reproduction to both connectivity and diversity in Acropora cervicornis may be variable due to this species’ capacity to reproduce effectively by fragmentation. Using a biophysical model and genomic data in this threatened species, we construct potential connectivity pathways on the Florida Reef Tract (FRT) and compare them to inferred migration rates derived from next-generation sequencing, using a link and node-based approach. Larval connectivity on the FRT can be divided into two zones: the northern region, where most transport is unidirectional to the north with the Florida Current, and the southern region that is more dynamic and exhibits complex spatial patterns. These biophysical linkages are poorly correlated with genetic connectivity patterns, which resolve many reciprocal connections and suggest a less sparse network. These results are difficult to reconcile with genetic data which indicate that individual reefs are diverse, suggesting important contributions of sexual reproduction and recruitment. Larval connectivity models highlight potential resources for recovery, such as areas with high larval export like the Lower Keys, or areas that are well connected to most other regions on the FRT, such as the Dry Tortugas.

Structure and phylogeography of two tropical predators, spinner (Stenella longirostris) and pantropical spotted (S. attenuata) dolphins, from SNP data.

Little is known about global patterns of genetic connectivity in pelagic dolphins, including how circumtropical pelagic dolphins spread globally following the rapid and recent radiation of the subfamily delphininae. In this study, we tested phylogeographic hypotheses for two circumtropical species, the spinner dolphin (Stenella longirostris) and the pantropical spotted dolphin (Stenella attenuata), using more than 3000 nuclear DNA single nucleotide polymorphisms (SNPs) in each species. Analyses for population structure indicated significant genetic differentiation between almost all subspecies and populations in both species. Bayesian phylogeographic analyses of spinner dolphins showed deep divergence between Indo-Pacific, Atlantic and eastern tropical Pacific Ocean (ETP) lineages. Despite high morphological variation, our results show very close relationships between endemic ETP spinner subspecies in relation to global diversity. The dwarf spinner dolphin is a monophyletic subspecies nested within a major clade of pantropical spinner dolphins from the Indian and western Pacific Ocean populations. Population-level division among the dwarf spinner dolphins was detected—with the northern Australia population being very different from that in Indonesia. In contrast to spinner dolphins, the major boundary for spotted dolphins is between offshore and coastal habitats in the ETP, supporting the current subspecies-level taxonomy. Comparing these species underscores the different scale at which population structure can arise, even in species that are similar in habitat (i.e. pelagic) and distribution.

Seascape genetics and biophysical connectivity modelling support conservation of the seagrass Zostera marina in the Skagerrak-Kattegat region of the eastern North Sea.

Maintaining and enabling evolutionary processes within meta‐populations are critical to resistance, resilience and adaptive potential. Knowledge about which populations act as sources or sinks, and the direction of gene flow, can help to focus conservation efforts more effectively and forecast how populations might respond to future anthropogenic and environmental pressures. As a foundation species and habitat provider, Zostera marina (eelgrass) is of critical importance to ecosystem functions including fisheries. Here, we estimate connectivity of Z. marina in the Skagerrak–Kattegat region of the North Sea based on genetic and biophysical modelling. Genetic diversity, population structure and migration were analysed at 23 locations using 20 microsatellite loci and a suite of analytical approaches. Oceanographic connectivity was analysed using Lagrangian dispersal simulations based on contemporary and historical distribution data dating back to the late 19th century. Population clusters, barriers and networks of connectivity were found to be very similar based on either genetic or oceanographic analyses. A single‐generation model of dispersal was not realistic, whereas multigeneration models that integrate stepping‐stone dispersal and extant and historic distribution data were able to capture and model genetic connectivity patterns well. Passive rafting of flowering shoots along oceanographic currents is the main driver of gene flow at this spatial–temporal scale, and extant genetic connectivity strongly reflects the “ghost of dispersal past“ sensu Benzie, 1999. The identification of distinct clusters, connectivity hotspots and areas where connectivity has become limited over the last century is critical information for spatial management, conservation and restoration of eelgrass.

Evidence of subtle genetic structure in the sympatric species Mullus barbatus and Mullus surmuletus (Linnaeus, 1758) in the Mediterranean Sea

Using thirteen microsatellite loci for Mullus barbatus and Mullus surmuletus collected in the Mediterranean Sea, the biogeographic boundaries, genetic distribution among and within basins and the impact of prolonged exploitation in both species were investigated as a basis for understanding their population dynamics and for improving Mullus spp. stock management. Different level of diversity indices among these co-occurring species were obtained, with M. barbatus showing higher allele richness and higher mean observed and expected heterozygosity than M. surmuletus. Reduced contemporary effective population size (Ne) and M-ratio values found in both species likely reflects recent demographic changes, due to a combination of high fishing pressures, habitat fragmentation and naturally occurring fluctuations in population size. Different patterns of genetic connectivity among populations sampled within the Mediterranean were observed for both species. Higher genetic structure was found for M. barbatus as opposed to a more homogenous pattern observed in M. surmuletus samples. Adriatic populations, previously considered panmictic and isolated from other Mediterranean regions, showed geographical partitioning within the basin but also population connectivity with the northern Ionian and Tyrrhenian Seas. Our results highlight the need for temporal sampling in understanding the complex pattern of population connectivity in the Mediterranean, particularly for management purposes.

Aquatic long-distance dispersal and vicariance shape the evolution of an ostracod species complex (Crustacea) in four major Brazilian floodplains

Cladogenesis is often driven by the interplay of dispersal and vicariance. The importance of long-distance dispersal in biogeography and speciation is increasingly recognised, but still ill-understood. Here, we study faunal interconnectivity between four large Brazilian floodplains, namely the Amazon, Araguaia, Pantanal (on Paraguay River) and Upper Paraná River floodplains, investigating a species complex of the non-marine ostracod genus Strandesia.We use DNA sequence data from the mitochondrial COI and the nuclear Elongation Factor 1 alpha genes to construct molecular phylogenies and minimum spanning networks, to identify genetic species, analyse biogeographic histories and provide preliminary age estimates of this species complex.The Strandesia species complex includes five morphological and eleven genetic species, which doubles the known diversity in this lineage. The evolutionary history of this species complex appears to comprise sequences of dispersal and vicariance events. Faunal and genetic patterns of connectivity between floodplains in some genetic species are mirrored in modern hydrological connections. This could explain why we find evidence for (aquatic) long-distance dispersal between floodplains, thousands of kilometres apart. Our phylogenetic reconstructions seem to mostly indicate recent dispersal and vicariance events, but the evolution of the present Strandesia species complex could span up to 25 Myr, which by far exceeds the age of the floodplains and the rivers in their current forms.

Two centuries of human‐mediated gene flow in northern bobwhites

ABSTRACTThe northern bobwhite (Colinus virginianus; hereafter, bobwhite) population decline has prompted several studies over the past decade investigating bobwhite population genetics and overall connectivity. The zeitgeist of current quail conservation is that bobwhite populations have become increasingly fragmented, leading to their decline as a result of reduced fitness associated with effects from small population size. A few studies exploring population‐level patterns of genetic connectivity at the local scale have identified some areas possessing limited gene flow likely due to recent anthropogenic landscape changes. Interestingly, however, multiple studies using genetic methods have also suggested that the species has experienced a recent range‐wide expansion with few barriers to dispersal, suggesting a large panmictic population. Although the above are both supported by empirical data, we highlight another possibility that has been proposed yet rarely investigated. Millions of wild bobwhites have been transported among populations, and millions more captive‐reared bobwhites have been and continue to be released across the species’ range. Given the massive scale at which bobwhites have been artificially dispersed, more research is needed to investigate the effects of introgression of nonlocal birds on our ability to understand recent changes in bobwhite population fragmentation, size, and diversity. Such information has important management implications to long‐term bobwhite population sustainability. By quantifying the level of human‐mediated bobwhite dispersal events, our review cautions against assigning evolutionary or conservation significance to patterns of genetic connectivity among bobwhite populations until a more systematic effort is made to verify that such activities have not affected our ability to identify natural gene‐flow patterns at both local and broad‐scale distributions. © 2017 The Wildlife Society.

Population genomics meet Lagrangian simulations: Oceanographic patterns and long larval duration ensure connectivity among Paracentrotus lividus populations in theAdriatic and Ionian seas.

Connectivity between populations influences both their dynamics and the genetic structuring of species. In this study, we explored connectivity patterns of a marine species with long‐distance dispersal, the edible common sea urchin Paracentrotus lividus, focusing mainly on the Adriatic–Ionian basins (Central Mediterranean). We applied a multidisciplinary approach integrating population genomics, based on 1,122 single nucleotide polymorphisms (SNPs) obtained from 2b‐RAD in 275 samples, with Lagrangian simulations performed with a biophysical model of larval dispersal. We detected genetic homogeneity among eight population samples collected in the focal Adriatic–Ionian area, whereas weak but significant differentiation was found with respect to two samples from the Western Mediterranean (France and Tunisia). This result was not affected by the few putative outlier loci identified in our dataset. Lagrangian simulations found a significant potential for larval exchange among the eight Adriatic–Ionian locations, supporting the hypothesis of connectivity of P. lividus populations in this area. A peculiar pattern emerged from the comparison of our results with those obtained from published P. lividus cytochrome b (cytb) sequences, the latter revealing genetic differentiation in the same geographic area despite a smaller sample size and a lower power to detect differences. The comparison with studies conducted using nuclear markers on other species with similar pelagic larval durations in the same Adriatic–Ionian locations indicates species‐specific differences in genetic connectivity patterns and warns against generalizing single‐species results to the entire community of rocky shore habitats.

Present-day connectivity of historical stocks of the ecosystem engineer Perumytilus purpuratus along 4500 km of the Chilean Coast

Historical processes leading to the emergence of marine stocks, the mechanisms maintaining stock structure, and present-day connectivity patterns are elementary pieces of information to design wiser and more sustainable management of marine resources, and to understand speciation processes in the sea. Over geographical scales, biological and genetic continuity in the Southern Pacific coast is determined by historical geological-climate events (e.g., LGM), as well as by present oceanographic processes (Humboldt Current, ENSO and others) that can affect both, local adaptation and dispersal. The relative influence of such processes on the current distribution of species can be comprehensibly inferred from a detailed population sampling comprising the whole species range. In this work, we aimed to provide insights into historical and modern patterns of genetic connectivity between stocks of the intertidal mussel Perumytilus purpuratus, a species reported to have moderate pelagic development times of about 14–18 days. To this end, we analyzed the geographical pattern of variation of microsatellite polymorphisms across 17 localities scattered along ca. 4500km off the Chilean Coast and encompassing four biogeographic regions, previously defined based on compositional changes in marine flora and fauna, and which coincide with large changes in topography, the historical influence of glaciation, circulation patterns and upwelling variability around 26°S, 30°S and 40°S. Genetic structural data suggest that historical geological and climatic events have shaped the actual range of this species in the south-eastern Pacific, creating biogeographical limits, i.e., the north-central stock and the southern stock, that moderate to restricted dispersers cannot cross given present day coastal oceanographic processes. Conversely, the pattern of IBD observed within those two major biogeographical regions suggests that present-day coastal processes modulate the effective dispersal of this species.

Diversity and distribution within the sea spider genus Pallenopsis (Chelicerata: Pycnogonida) in the Western Antarctic as revealed by mitochondrial DNA

Pycnogonids are marine arthropods with cosmopolitan and eurybathic distribution. Of the approximately 1300 pycnogonid species described worldwide, over 260 species occur in the Southern Ocean, and over half of those are endemic to the Antarctic. Morphological data suggest circumpolar distributions for multiple Antarctic species; however, recent molecular inquiries into the genetic structure of Antarctic benthic invertebrate populations have revealed varying patterns of genetic connectivity and, in many cases, radiation of morphologically cryptic species incompatible with the previously hypothesized genetic homogeneity for Southern Ocean invertebrates. To date, little is known about genetic connectivity within Antarctic Pallenopsis species populations, and Pallenopsis phylogeny remains poorly resolved. This study describes genetic structure of Pallenopsis populations of western Antarctic coastal regions, the Scotia Arc, Falkland Islands, and Chilean coast. We present the results of analyses derived from the mitochondrial COI gene that demonstrate patterns of connectivity for these populations. Examination of genetic characters has allowed for the identification of divergent mitochondrial lineages within Pallenopsis and will lead to a description of at least one new species. Future sampling and analyses from other areas of the Antarctic coastline will provide a broader context for the phylogeny of Pallenopsis.

Genetic diversity and connectivity patterns of harvested and aquacultured molluscs in estuaries from Asturias (northern Spain). Implications for management strategies

Estuaries are among the most important habitats of coastal areas. However, they are significantly affected by human activities worldwide, threatening their resources and the commercial uses depending on them. Fisheries and aquaculture are some of the main factors affecting the estuarine ecosystems today. In this work, we pursue the aims of genetically identifying the cultured and harvested oyster and razor clam species inhabiting Asturian estuaries (Eo, Ribadesella and Villaviciosa) and describing the genetic diversity and patterns of genetic connectivity between those species in these estuaries. The results revealed the almost complete dominance of the introduced Crassostrea gigas as the species that supports the oyster's production in Asturias with a striking diversity of gene pools in wild environments (Ría de Villaviciosa and Ribadesella) which significantly exceeds the diversity found in the hatcheries seeds commonly used for culturing. Moreover, we detected two different species of Ensis sp. inhabiting the Asturian estuaries: Ensis ensis inside Ría del Eo and Ensis directus, an invasive species, in Ría de Villaviciosa. Significant genetic differentiation between estuaries for the exotic oyster C. gigas and also for the native razor clam Solen marginatus were found. These results suggest Asturian estuaries are not a single management unit for some species and thus prevention must be taken for avoiding intentional or human-mediated translocations among them. Biodiversity monitoring for discovering newcomer invasive species, measures for environmental recovery of these ecosystems and strict controls to avoid increasing of harvesting pressures are also a necessity to improve the management of these relevant ecosystems.

Genetic Structure of the Cortes GeoduckPanopea globosaDall, 1898, from the Mexican Northwest

The geoduck Panopea globosa is found on the Pacific coast of Baja California south of Bahia Magdalena Bay and throughout the Gulf of California, and sustains a vibrant and growing fishery. Despite morphometric analyses that suggest populations from the Pacific are distinct from those inside the Gulf of California, it is unclear whether populations are connected via larval dispersal and gene flow throughout its range. Thirteen microsatellite loci were used to estimate levels of genetic diversity and to evaluate genetic connectivity patterns among four exploited populations, including clams from the Pacific (Bahia Magdalena) and the Gulf of California (San Felipe, Puerto Penasco, and Guaymas). Geoducks from Bahia Magdalena showed significant genetic differentiation from populations inside the Gulf of California, particularly when compared with San Felipe and Puerto Penasco. Gene flow and inferred larval dispersal were found to be predominantly unidirectional, and followed the typical anticyclonic (clockwise) circulation of the northern Gulf of California during late fall and winter when geoducks spawn. San Felipe is located upstream relative to the oceanographic flow and has the largest effective population size. This population also showed evidence of local retention of larvae and may serve as the main source of larvae to downstream populations that show a gradient of reduced diversity and population size along the direction of the prevailing flow. The asymmetry found in connectivity patterns has implications for distributing the fishery effort and no-take zones in the Gulf of California to increase sustainability.

Mitochondrial Genetic Structure and Matrilineal Origin of White Sharks, Carcharodon carcharias, in the Northeastern Pacific: Implications for Their Conservation.

White sharks (Carcharodon carcharias, WS henceforth) are globally and regionally threatened. Understanding their patterns of abundance and connectivity, as they relate to habitat use, is central for delineating conservation units and identifying priority areas for conservation. We analyzed mitochondrial data to test the congruence between patterns of genetic connectivity and of individual movements in the Northeastern Pacific (NEP) and to trace the matrilineal origin of immature WS from coastal California and Baja California to adult aggregation areas. We analyzed 186 mitochondrial control region sequences from sharks sampled in Central California (CC; n = 61), Southern California Bight (SCB; n = 25), Baja California Pacific coast (BCPC; n = 9), Bahía Vizcaíno (BV; n = 39), Guadalupe Island (GI; n = 45), and the Gulf of California (GC; n = 7). Significant mitochondrial differentiation between adult aggregation areas (CC, GI) revealed two reproductive populations in the NEP. We found general concordance between movement patterns of young and adult WS with genetic results. Young sharks from coastal California and Baja California were more likely born from females from GI. Mitochondrial differentiation of young-of-the-year from SCB and BV suggests philopatry to nursery areas in females from GI. These results provide a genetic basis of female reproductive behavior at a regional scale and point to a preponderance of sharks from GI in the use of the sampled coastal region as pupping habitat. These findings should be considered in Mexican and US management and conservation strategies of the WS NEP population.

Spatial Patterns of Genetic Diversity in Mediterranean Eagle OwlBubo buboPopulations

Summary. Little information is available on the patterns of genetic connectivity in owls. We studied the genetic structure of the eagle owl Bubo bubo (Linnaeus, 1758) in southeastern Spain at two different spatial scales. Seven microsatellites previously described for this species were used, although only six loci amplified correctly. The observed low genetic variation could be explained by the short dispersal distance, high mortality rate and high degree of monogamy shown by this large nocturnal predator. As expected, the highest genetic isolation was detected in the geographically most isolated population. Significant genetic differentiation was found among study units separated by less than 50 km. The territorial analysis showed interesting connectivity patterns related with the gene flow and turnover rate of the breeding individuals. The lowest genetic diversity was found in the region with the largest population, which could imply incipient inbreeding.