Oceanographic Currents and Local Ecological Knowledge Indicate,and Genetics Does Not Refute,a Contemporary Pattern of Larval Dispersal for The Ornate Spiny Lobster,Panulirus ornatus in the South-East Asian Archipelago

Here we utilize a combination of genetic data, oceanographic data, and local ecological knowledge to assess connectivity patterns of the ornate spiny lobster Panulirus ornatus (Fabricius, 1798) in the South-East Asian archipelago from Vietnam to Australia. Partial mitochondrial DNA control region and 10 polymorphic microsatellites did not detect genetic structure of 216 wild P. ornatus samples from Australia, Indonesia and Vietnam. Analyses show no evidence for genetic differentiation among populations (mtDNA control region sequences Φ_ST = -0.008; microsatellite loci F_ST = 0.003). A lack of evidence for regional or localized mtDNA haplotype clusters, or geographic clusters of microsatellite genotypes, reveals a pattern of high gene flow in P. ornatus throughout the South-East Asian Archipelago. This lack of genetic structure may be due to the oceanography-driven connectivity of the pelagic lobster larvae between spawning grounds in Papua New Guinea, the Philippines and, possibly, Indonesia. The connectivity cycle necessitates three generations. The lack of genetic structure of P. ornatus population in the South-East Asian archipelago has important implications for the sustainable management of this lobster in that the species within the region needs to be managed as one genetic stock.     

Should I Stay or Should I Go? Dispersal and Population Structure in Small,Isolated Desert Populations of West African Crocodiles

The maintenance of both spatial and genetic connectivity is paramount to the long-term persistence of small, isolated populations living in environments with extreme climates. We aim to identify the distribution of genetic diversity and assess population sub-structuring and dispersal across dwarfed desert populations of Crocodylus suchus, which occur in isolated groups, usually less than five individuals, along the mountains of Mauritania (West Africa). We used both invasive and non-invasive sampling methods and a combination of mitochondrial DNA (12 S and ND4) and microsatellite markers (32 loci and a subset of 12 loci). Our results showed high genetic differentiation and geographic structure in Mauritanian populations of C. suchus. We identified a metapopulation system acting within four river sub-basins (high gene flow and absence of genetic structure) and considerable genetic differentiation between sub-basins (F _ST range: 0.12–0.24) with rare dispersal events. Effective population sizes tend to be low within sub-basins while genetic diversity is maintained. Our study suggests that hydrographic networks (temporal connections along seasonal rivers during rainy periods) allow C. suchus to disperse and maintain metapopulation dynamics within sub-basins, which attenuate the loss of genetic diversity and the risk of extinction. We highlight the need of hydrographic conservation to protect vulnerable crocodiles isolated in small water bodies. We propose C. suchus as an umbrella species in Mauritania based on ecological affinities shared with other water-dependent species in desert environments.     

Population genetic structure of the endangered Eastern Bristlebird, Dasyornis brachypterus; implications for conservation

For species that are habitat specialists or sedentary, population fragmentation may lead to genetic divergence between populations and reduced genetic diversity within populations, with frequent inbreeding. Hundreds of kilometres separate three geographical regions in which small populations of the endangered Eastern Bristlebird, Dasyornis brachypterus, a small, ground-dwelling passerine that occurs in fire-prone bushland in eastern Australia, are currently found. Here, we use mitochondrial and microsatellite DNA markers to: (i) assess the sub-specific taxonomy designated to northern range-edge, and central and southern range-edge D. brachypterus, respectively, and (ii) assess levels of standing genetic variation and the degree of genetic subdivision of remnant populations. The phylogenetic relationship among mtDNA haplotypes and their spatial distribution did not support the recognised subspecies boundaries. Populations in different regions were highly genetically differentiated, but in addition, the two largest, neighboring populations (located within the central region and separated by ~50 km) were moderately differentiated, and thus are likely closed to migration (microsatellites, F _ST = 0.06; mtDNA, F _ST = 0.12, ?? _ST = 0.08). Birds within these two populations were genotypically diverse and apparently randomly mating. A long-term plan for the conservation of D. brachypterus??s genetic diversity should consider individual populations as separate management units. Moreover, managers should avoid actively mixing birds from different populations or regions, to conserve the genetic integrity of local populations and avoid outbreeding depression, should further translocations be used as a recovery tool for this species.     

Genetic differentiation and connectivity of morphological types of the broadcast‐spawning coral Galaxea fascicularis in the Nansei Islands,Japan

Population connectivity resulting from larval dispersal is essential for the maintenance or recovery of populations in marine ecosystems, including coral reefs. Studies of species diversity and genetic connectivity within species are essential for the conservation of corals and coral reef ecosystems. We analyzed mitochondrial DNA sequence types and microsatellite genotypes of the broadcast‐spawning coral, Galaxea fascicularis, from four regions in the subtropical Nansei Islands in the northwestern Pacific Ocean. Two types (soft and hard types) of nematocyst morphology are known in G. fascicularis and are significantly correlated with the length of a mitochondrial DNA noncoding sequence (soft type: mt‐L; hard type: mt‐S type). Using microsatellites, significant genetic differentiation was detected between the mitochondrial DNA sequence types in all regions. We also found a third genetic cluster (mt‐L+), and this unexpected type may be a cryptic species of Galaxea. High clonal diversity was detected in both mt‐L and mt‐S types. Significant genetic differentiation, which was found among regions within a given type (F _ST = 0.009–0.024, all Ps ≤ 0.005 in mt‐L; 0.009–0.032, all Ps ≤ 0.01 in mt‐S), may result from the shorter larval development than in other broadcast‐spawning corals, such as the genus Acropora. Nevertheless, intraspecific genetic diversity and connectivity have been maintained, and with both sexual and asexual reproduction, this species appears to have a potential for the recovery of populations after disturbance.     

Microsatellite markers and mtDNA data indicate two distinct groups in dwarf galaxias, Galaxiella pusilla (Mack) (Pisces: Galaxiidae), a threatened freshwater fish from south-eastern Australia

Galaxiella pusilla is a small, non-migratory freshwater fish, endemic to south-eastern Australia and considered nationally threatened. To assist in the conservation of the species, microsatellite markers were developed and used to characterize genetic variation in 20 geographically distinct populations across its range. Substantial genetic differentiation was found between an eastern (Victoria east of the Otway Ranges and Tasmania) and western (South Australia and Victoria west of, and including, the Otway Ranges) region. This major separation was also observed in data from a mitochondrial gene and supports a previously proposed split. Populations from the eastern region had overall lower genetic diversity for both the microsatellite and mtDNA markers. There was substantial genetic differentiation between populations within the two regions, suggesting that gene flow is limited by the isolation of freshwater streams. Genetic structure, consistent with an isolation-by-distance model, was also evident in both regions. Patterns of genetic variation in this threatened species are compared to those obtained for other taxa across the same region. The need to consider separate conservation strategies for the two sets of populations is emphasized.     

East–west genetic differentiation in Musk Ducks (<Emphasis Type="Italic">Biziura lobata</Emphasis>) of Australia suggests late Pleistocene divergence at the Nullarbor Plain

Musk Ducks (Biziura lobata) are endemic to Australia and occur as two geographically isolated populations separated by the Nullarbor Plain, a vast arid region in southern Australia. We studied genetic variation in Musk Duck populations at coarse (eastern versus western Australia) and fine scales (four sites within eastern Australia). We found significant genetic structure between eastern and western Australia in the mtDNA control region (Φ_ST = 0.747), one nuclear intron (Φ_ST = 0.193) and eight microsatellite loci (F_ST = 0.035). In contrast, there was little genetic structure between Kangaroo Island and adjacent mainland regions within eastern Australia. One small population of Musk Ducks in Victoria (Lake Wendouree) differed from both Kangaroo Island and the remainder of mainland eastern Australia, possibly due to genetic drift exacerbated by inbreeding and small population size. The observed low pairwise distance between the eastern and western mtDNA lineages (0.36%) suggests that they diverged near the end of the Pleistocene, a period characterised by frequent shifts between wet and arid conditions in central Australia. Our genetic results corroborate the display call divergence and Mathews’ (Austral Avian Record 2:83–107, 1914) subspecies classification, and confirm that eastern and western populations of Musk Duck are currently isolated from each other.     

Genetic structure of the endangered Irrawaddy dolphin (Orcaella brevirostris) in the Gulf of Thailand

The Irrawaddy dolphin (Orcaella brevirostris) is an endangered, small cetacean species which is widely distributed in rivers, estuaries, and coastal waters throughout the tropical and subtropical Indo-Pacific. Despite the extensive distribution of this species, little is known of individual movements or genetic exchange among regions in Thailand. Here, we evaluate the genetic diversity and genetic structure of O. brevirostris in the eastern, northern and western Gulf of Thailand, and Andaman Sea. Although phylogenetic relationships and network analysis based on 15 haplotypes obtained from 32 individuals reveal no obvious divergence, significant genetic differentiation in mitochondrial DNA (overall F_ST = 0.226, P < 0.001; Φ_ST = 0.252, P < 0.001) is apparent among regions. Of 18 tested microsatellite loci, 10 are polymorphic and successfully characterized in 28 individuals, revealing significant genetic differentiation (overall F_ST = 0.077, P < 0.05) among the four sampling sites. Structure analysis reveals two inferred genetic clusters. Additionally, Mantel analysis demonstrates individual-by-individual genetic distances and geographic distances follow an isolation-by-distance model. We speculate that the significant genetic structure of O. brevirostris in Thailand is associated with a combination of geographical distribution patterns, environmental and anthropogenic factors, and local adaptations.     

Population Differentiation and Hybridisation of Australian Snubfin (Orcaella heinsohni) and Indo-Pacific Humpback (Sousa chinensis) Dolphins in North-Western Australia

Little is known about the Australian snubfin (Orcaella heinsohni) and Indo-Pacific humpback (Sousa chinensis) dolphins (‘snubfin’ and ‘humpback dolphins’, hereafter) of north-western Australia. While both species are listed as ‘near threatened’ by the IUCN, data deficiencies are impeding rigorous assessment of their conservation status across Australia. Understanding the genetic structure of populations, including levels of gene flow among populations, is important for the assessment of conservation status and the effective management of a species. Using nuclear and mitochondrial DNA markers, we assessed population genetic diversity and differentiation between snubfin dolphins from Cygnet (n = 32) and Roebuck Bays (n = 25), and humpback dolphins from the Dampier Archipelago (n = 19) and the North West Cape (n = 18). All sampling locations were separated by geographic distances >200 km. For each species, we found significant genetic differentiation between sampling locations based on 12 (for snubfin dolphins) and 13 (for humpback dolphins) microsatellite loci (F _ST = 0.05–0.09; P<0.001) and a 422 bp sequence of the mitochondrial control region (F _ST = 0.50–0.70; P<0.001). The estimated proportion of migrants in a population ranged from 0.01 (95% CI 0.00–0.06) to 0.13 (0.03–0.24). These are the first estimates of genetic diversity and differentiation for snubfin and humpback dolphins in Western Australia, providing valuable information towards the assessment of their conservation status in this rapidly developing region. Our results suggest that north-western Australian snubfin and humpback dolphins may exist as metapopulations of small, largely isolated population fragments, and should be managed accordingly. Management plans should seek to maintain effective population size and gene flow. Additionally, while interactions of a socio-sexual nature between these two species have been observed previously, here we provide strong evidence for the first documented case of hybridisation between a female snubfin dolphin and a male humpback dolphin.     

Strong population genetic structure and its implications for the conservation and management of the endangered Itasenpara bitterling

To infer the population genetic structure and genetic diversity of Itasenpara bitterling (Acheilognathus longipinnis), a cyprinid species endemic to Japan and distributed in only three specific regions, we investigated mitochondrial DNA variation. The distribution of the haplotypes among the three regions showed distinct geographic structure, and no common haplotypes were observed among regions. Analysis of molecular variance revealed a significant proportion of the genetic variance was partitioned among regions (93.1 %, P < 0.001), and pairwise estimates of D_A and Φ_ST between regions also revealed strong population structure. Given the strong genetic structure and low genetic diversity within regions, we strongly suggest that each region should be treated as a separate unit in any conservation program and any inter-regional translocations should be avoided.     

Population Structure of the Giant Garter Snake, Thamnophis gigas

The giant garter snake, Thamnophis gigas, is a threatened species endemic to California’s Central Valley. We tested the hypothesis that current watershed boundaries have caused genetic differentiation among populations of T. gigas. We sampled 14 populations throughout the current geographic range of T. gigas and amplified 859 bp from the mitochondrial gene ND4 and one nuclear microsatellite locus. DNA sequence variation from the mitochondrial gene indicates there is some genetic structuring of the populations, with high F_ST values and unique haplotypes occurring at high frequency in several populations. We found that clustering populations by watershed boundary results in significant between-region genetic variance for mtDNA. However, analysis of allele frequencies at the microsatellite locus NSU3 reveals very low F_ST values and little between-region variation in allele frequencies. The discordance found between mitochondrial and microsatellite data may be explained by aspects of molecular evolution and/or T. gigas life history characteristics. Differences in effective population size between mitochondrial and nuclear DNA, or male-biased gene flow, result in a lower migration rate of mitochondrial haplotypes relative to nuclear alleles. However, we cannot exclude homoplasy as one explanation for homogeneity found for the single microsatellite locus. The mitochondrial nucleotide sequence data supports conservation practices that identify separate management units for T. gigas.     

Life history,larval dispersal,and connectivity in coral reef fish among the Scattered Islands of the Mozambique Channel

The Western Indian Ocean harbors one of the world’s most diverse marine biota yet is threatened by exploitation with few conservation measures in place. Primary candidates for conservation in the region are the Scattered Islands (Îles Éparses), a group of relatively pristine and uninhabited islands in the Mozambique Channel. However, while optimal conservation strategies depend on the degree of population connectivity among spatially isolated habitats, very few studies have been conducted in the area. Here, we use highly variable microsatellite markers from two damselfishes (Amphiprion akallopisos and Dascyllus trimaculatus) with differing life history traits [pelagic larval duration (PLD), adult habitat] to compare genetic structure and connectivity among these islands using classic population structure indices as well as Bayesian clustering methods. All classical fixation indexes F _ST, R _ST, G′_ST, and Jost’s D show stronger genetic differentiation among islands for A. akallopisos compared to D. trimaculatus, consistent with the former species’ shorter PLD and stronger adult site attachment, which may restrict larval dispersal potential. In agreement with these results, the Bayesian analysis revealed clear genetic differentiation among the islands in A. akallopisos, separating the southern group (Bassas da India and Europa) from the center (Juan de Nova) and northern (Îles Glorieuses) islands, but not for D. trimaculatus. Local oceanographic patterns such as eddies that occur along the Mozambique Channel appear to parallel the results reported for A. akallopisos, but such features seem to have little effect on the genetic differentiation of D. trimaculatus. The contrasting patterns of genetic differentiation between species within the same family highlight the importance of accounting for diverse life history traits when assessing community-wide connectivity, an increasingly common consideration in conservation planning.

     

Low levels of genetic differentiation characterize Australian humpback whale (Megaptera novaeangliae) populations

Humpback whales undertake long‐distance seasonal migrations between low latitude winter breeding grounds and high latitude summer feeding grounds. We report the first in‐depth population genetic study of the humpback whales that migrate to separate winter breeding grounds along the northwestern and northeastern coasts of Australia, but overlap on summer feeding grounds around Antarctica. Weak but significant differentiation between eastern and western Australia was detected across ten microsatellite loci (F_ST = 0.005, P = 0.001; D_EST = 0.031, P = 0.001, n = 364) and mitochondrial control region sequences (F_ST = 0.017 and Φ_ST = 0.069, P = 0.001, n = 364). Bayesian clustering analyses using microsatellite data could not resolve any population structure unless sampling location was provided as a prior. This study supports the emerging evidence that weak genetic differentiation is characteristic among neighboring Southern Hemisphere humpback whale breeding populations. This may be a consequence of relatively high gene flow facilitated by overlapping summer feeding areas in Antarctic waters.     

Phylogeography and population genetic structure of double-crested cormorants (Phalacrocorax auritus)

We examined the genetic structure of double-crested cormorants (Phalacrocorax auritus) across their range in the United States and Canada. Sequences of the mitochondrial control region were analyzed for 248 cormorants from 23 breeding sites. Variation was also examined at eight microsatellite loci for 409 cormorants from the same sites. The mitochondrial and microsatellite data provided strong evidence that the Alaskan subspecies (P. a. cincinnatus) is genetically divergent from other populations in North America (net sequence divergence = 5.85 %; Φ_ST for mitochondrial control region = 0.708; F_ST for microsatellite loci = 0.052). Historical records, contemporary population estimates, and field observations are consistent with recognition of the Alaskan subspecies as distinct and potentially of conservation interest. Our data also indicated the presence of another divergent lineage, associated with the southwestern portion of the species range, as evidenced by highly unique haplotypes sampled in southern California. In contrast, there was little support for recognition of subspecies within the conterminous U.S. and Canada. Rather than genetically distinct regions corresponding to the putative subspecies [P. a. albociliatus (Pacific), P. a. auritus (Interior and North Atlantic), and P. a. floridanus (Southeast)], we observed a distribution of genetic variation consistent with a pattern of isolation by distance. This pattern implies that genetic differences across the range are due to geographic distance, rather than discrete subspecific breaks. Although three of the four traditional subspecies were not genetically distinct, possible demographic separation, habitat differences, and documented declines at some colonies within the regions, suggests that the Pacific and possibly North Atlantic portions of the breeding range may warrant differential consideration from the Interior and Southeast breeding regions.     

Functional characterization of the Saccharomyces cerevisiae protein Chl1 reveals the role of sister chromatid cohesion in the maintenance of spindle length during S-phase arrest

Background

Reconstructing the evolutionary history of a species is challenging. It often depends not only on the past biogeographic and climatic events but also the contemporary and ecological factors, such as current connectivity and habitat heterogeneity. In fact, these factors might interact with each other and shape the current species distribution. However, to what extent the current population genetic structure reflects the past and the contemporary factors is largely unknown. Here we investigated spatio-temporal genetic structures of Nile tilapia (Oreochromis niloticus) populations, across their natural distribution in Africa. While its large biogeographic distribution can cause genetic differentiation at the paleo-biogeographic scales, its restricted dispersal capacity might induce a strong genetic structure at micro-geographic scales.

Results

Using nine microsatellite loci and 350 samples from ten natural populations, we found the highest genetic differentiation among the three ichthyofaunal provinces and regions (Ethiopian, Nilotic and Sudano-Sahelian) (R _ST = 0.38 - 0.69). This result suggests the predominant effect of paleo-geographic events at macro-geographic scale. In addition, intermediate divergences were found between rivers and lakes within the regions, presumably reflecting relatively recent interruptions of gene flow between hydrographic basins (R _ST = 0.24 - 0.32). The lowest differentiations were observed among connected populations within a basin (R _ST = 0.015 in the Volta basin). Comparison of temporal sample series revealed subtle changes in the gene pools in a few generations (F = 0 - 0.053). The estimated effective population sizes were 23 - 143 and the estimated migration rate was moderate (m ~ 0.094 - 0.097) in the Volta populations.

Conclusions

This study revealed clear hierarchical patterns of the population genetic structuring of O. niloticus in Africa. The effects of paleo-geographic and climatic events were predominant at macro-geographic scale, and the significant effect of geographic connectivity was detected at micro-geographic scale. The estimated effective population size, the moderate level of dispersal and the rapid temporal change in genetic composition might reflect a potential effect of life history strategy on population dynamics. This hypothesis deserves further investigation. The dynamic pattern revealed at micro-geographic and temporal scales appears important from a genetic resource management as well as from a biodiversity conservation point of view.     

Reduced Global Genetic Differentiation of Exploited Marine Fish Species

Knowledge on genetic structure is key to understand species connectivity patterns and to define the spatiotemporal scales over which conservation management plans should be designed and implemented. The distribution of genetic diversity (within and among populations) greatly influences species ability to cope and adapt to environmental changes, ultimately determining their long-term resilience to ecological disturbances. Yet, the drivers shaping connectivity and structure in marine fish populations remain elusive, as are the effects of fishing activities on genetic subdivision. To investigate these questions, we conducted a meta-analysis and compiled genetic differentiation data (F_ST/Φ_ST estimates) for more than 170 fish species from over 200 published studies globally distributed. We modeled the effects of multiple life-history traits, distance metrics, and methodological factors on observed population differentiation indices and specifically tested whether any signal arising from different exposure to fishing exploitation could be detected. Although the myriad of variables shaping genetic structure makes it challenging to isolate the influence of single drivers, results showed a significant correlation between commercial importance and genetic structure, with widespread lower population differentiation in commercially exploited species. Moreover, models indicate that variables commonly used as proxy for connectivity, such as larval pelagic duration, might be insufficient, and suggest that deep-sea species may disperse further. Overall, these results contribute to the growing body of knowledge on marine genetic connectivity and suggest a potential effect of commercial fisheries on the homogenization of genetic diversity, highlighting the need for additional research focused on dispersal ecology to ensure long-term sustainability of exploited marine species.     

Limited phylogeographic and genetic connectivity in Acacia species of low stature in an arid landscape

Widespread plant species are expected to maintain genetic diversity and gene flow via pollen and seed dispersal. Stature is a key life history trait that affects seed and potentially pollen dispersal, with limited stature associated with limited dispersal and greater genetic differentiation. We sampled Hill’s tabletop wattle (Acacia hilliana) and curry wattle (Acacia spondylophylla), two co‐distributed, widespread, Acacia shrubs of low stature, across the arid Pilbara region of north‐western Australia. Using chloroplast sequence and nuclear microsatellite data we evaluated patterns of population genetic and phylogeographic diversity and structure, demographic signals, ratios of pollen to seed dispersal, evidence for historical refugia, and association between elevation and diversity. Results showed strong phylogeographic (chloroplast, G _ST = 0.831 and 0.898 for A. hilliana and A. spondylophylla, respectively) and contemporary (nuclear, F _ST = 0.260 and 0.349 for A. hilliana and A. spondylophylla, respectively) genetic structure in both species. This indicates limited genetic connectivity via seed and pollen dispersal associated with Acacia species of small stature compared to taller tree and shrub acacias across the Pilbara bioregion. This effect of stature on genetic structure is superimposed on moderate levels of genetic diversity that were expected based on widespread ranges (haplotype diversity h = 25 and 12; nuclear diversity He = 0.60 and 0.47 for A. hilliana and A. spondylophylla, respectively). Contemporary genetic structure was congruent at the greater landscape scale, especially in terms of strong genetic differentiation among geographically disjunct populations in less elevated areas. Measures of diversity and connectivity were associated with traits of greater geographic population proximity, population density, population size, and greater individual longevity, and some evidence for range expansion in A. hilliana. Results illustrate that low stature is associated with limited dispersal and greater patterns of genetic differentiation for congenerics in a common landscape and highlight the complex influence of taxon‐specific life history and ecological traits to seed and pollen dispersal.     

Molecular and quantitative trait variation within and among small fragmented populations of the endangered plant species Psilopeganum sinense

Background and Aims

Natural selection and genetic drift are important evolutionary forces in determining genetic and phenotypic differentiation in plant populations. The extent to which these two distinct evolutionary forces affect locally adaptive quantitative traits has been well studied in common plant and animal species. However, we know less about how quantitative traits respond to selection pressures and drift in endangered species that have small population sizes and fragmented distributions. To address this question, this study assessed the relative strengths of selection and genetic drift in shaping population differentiation of phenotypic traits in Psilopeganum sinense, a naturally rare and recently endangered plant species.

Methods

Population differentiation at five quantitative traits (Q_ST) obtained from a common garden experiment was compared with differentiation at putatively neutral microsatellite markers (F_ST) in seven populations of P. sinense. Q_ST estimates were derived using a Bayesian hierarchical variance component method.

Key Results

Trait-specific Q_ST values were equal to or lower than F_ST. Neutral genetic diversity was not correlated with quantitative genetic variation within the populations of P. sinense.

Conclusions

Despite the prevalent empirical evidence for Q_ST > F_ST, the results instead suggest a definitive role of stabilizing selection and drift leading to phenotypic differentiation among small populations. Three traits exhibited a significantly lower Q_ST relative to F_ST, suggesting that populations of P. sinense might have experienced stabilizing selection for the same optimal phenotypes despite large geographical distances between populations and habitat fragmentation. For the other two traits, Q_ST estimates were of the same magnitude as F_ST, indicating that divergence in these traits could have been achieved by genetic drift alone. The lack of correlation between molecular marker and quantitative genetic variation suggests that sophisticated considerations are required for the inference of conservation measures of P. sinense from neutral genetic markers.     

Geographic Influence on Genetic Structure in the Widespread Neotropical Tree Simarouba amara (Simaroubaceae)

This study aimed to assess the population genetic structure of a widespread Neotropical tree species, Simarouba amara, at local, regional and continental spatial scales. We used five microsatellite loci to examine genetic variation in 14 natural populations (N?=?478 individuals) of this vertebrate-dispersed rain forest tree species in Panama, Ecuador, and French Guiana. Estimates of genetic differentiation (F _st and R _st) were significant among all but one population pair and global differentiation was moderate (F _st?=?0.25, R _st?=?0.33) with 94% of genetic variation ascribed to differences among three main geographic regions (Central America, Western Ecuador, Amazon basin). There was no evidence of isolation by distance within regions. Allele-size mutations contributed significantly (R _ST > F _ST) to the divergences between cis- and trans-Andean populations, highlighting the role of the northern Andean cordilleras as an important geographic barrier for this species.     

Combining multiple analytical approaches for the identification of population structure and genetic delineation of two subspecies of the endemic Arabian burnet moth Reissita simonyi (Zygaenidae; Lepidoptera)

Habitat fragmentation and landscape topology may influence the genetic structure and connectivity between natural populations. Six microsatellite loci were used to infer the population structure of 35 populations (N = 788) of the alpine Arabian burnet moth Reissita simonyi (Lepidoptera, Zygaenidae) in Yemen and Oman. Due to the patchy distribution of larval food plants, R. simonyi is not continuously distributed throughout the studied area and the two recognized subspecies of this endemic species (Reissita s. simonyi/R. s. yemenicola) are apparently discretely distributed. All microsatellites showed prevalence of null alleles and therefore a thorough investigation of the impact of null alleles on different population genetic parameters (F _ST, inbreeding coefficients, and Population Graph topologies) is given. In general, null alleles reduced genetic covariance and independence of allele frequencies resulting in a more connected genetic topology in Population Graphs and an overestimation of pairwise F _ST values and inbreeding coefficients. Despite the presence of null alleles, Population Graphs also showed a much higher genetic connectivity within subspecies (and lower genetic differentiation (via F _ST)) than between; supporting existing taxonomic distinction. Partial Mantel tests showed that both geographical distance and altitude were highly correlated with the observed distribution of genetic structure within R. simonyi. In conclusion, we identified geographical and altitudinal distances in R. simonyi as well as an intervening desert area to be the main factors for spatial genetic structure in this species and show that the taxonomic division into two subspecies is confirmed by genetic analysis.     

The genetic structure of Nautilus pompilius populations surrounding Australia and the Philippines

Understanding the distribution of genetic diversity in exploited species is fundamental to successful conservation. Genetic structure and the degree of gene flow among populations must be assessed to design appropriate strategies to prevent the loss of distinct populations. The cephalopod Nautilus pompilius is fished unsustainably in the Philippines for the ornamental shell trade and has limited legislative protection, despite the species' recent dramatic decline in the region. Here, we use 14 microsatellite markers to evaluate the population structure of N. pompilius around Australia and the Philippines. Despite their relative geographical proximity, Great Barrier Reef individuals are genetically isolated from Osprey Reef and Shark Reef in the Coral Sea (F_ST = 0.312, 0.229, respectively). Conversely, despite the larger geographical distances between the Philippines and west Australian reefs, samples display a small degree of genetic structure (F_ST = 0.015). Demographic scenarios modelled using approximate Bayesian computation analysis indicate that this limited divergence is not due to contemporary gene flow between the Philippines and west Australia. Instead, present‐day genetic similarity can be explained by very limited genetic drift that has occurred due to large average effective population sizes that persisted at both locations following their separation. The lack of connectivity among populations suggests that immigrants from west Australia would not facilitate natural recolonization if Philippine populations were fished to extinction. These data help to rectify the paucity of information on the species' biology currently inhibiting their conservation classification. Understanding population structure can allow us to facilitate sustainable harvesting, thereby preserving the diversity of genetically distinct stocks.