Low Dispersal Potential Research Articles

Impact of persistent barrier to gene flow and catastrophic events on red algae evolutionary history along the Chilean coast.

Historical vicariance events, linked to the existence of stable physical barriers to gene flow, generate concordant genetic breaks in co-distributed species while stochastic processes (e.g., costal uplift) could cause species-specific genetic breaks as a result of local strong demographic bottlenecks or extinction. In Chile, previous studies show that the area of the 30°S-33°S could correspond to a stable barrier to gene flow that have affected the genetic structure of various algae and marine invertebrates. Here we sequenced two organellar genes (COI and rbcL) in four taxonomically accepted co-distributed red seaweeds species characterized by a low dispersal potential: Mazzaella laminarioides, M. membranacea, Asterfilopsis disciplinalis, and Ahnfeltiopsis vermicularis. Our results revealed the existence of ten strongly differentiated linages in the taxa studied. Strong genetic breaks, concordant in both space and time (divergence estimated to have occurred some 2.9-12.4 million years ago), were observed between taxa distributed across the 33°S. Conversely, in the Central/South part of the Chilean coast, the localization of the genetic breaks/sub-structure observed varied widely (36°S, 38°S, 39°S, and 40°S). These results suggest that a major historical vicariance event has modeled the genetic structure of several Chilean marine organisms in the north of the Chilean coast during the mid-Miocene, while more recent stochastic events and genetic drift could be the driving forces of genetic divergence/structuration in the central-southern part of the coast.

Both high and low dispersal? Apparently contradictory genetic patterns in the Antarctic littorinid gastropod Laevilacunaria antarctica

How the near-shore marine benthic communities survived Quaternary glaciations in Antarctica is a major question for Southern Ocean biogeographers. Several hypotheses that consider life-history traits, such as bathymetric ranges and developmental modes, have been proposed. Near-shore species with high dispersive potential are expected to show star-like genealogies, with broadly distributed haplotypes surrounded by closely related variants at low frequencies, a consequence of rapid population post-glacial expansion mediated by larvae. By contrast, shallow-water taxa with low dispersal potential are expected to evidence marked genetic structure or even consist of separate cryptic species, due to their survival in small refugial populations subject to repeated bottlenecks. In this study we performed phylogeographic analyses on the high-latitude littorinid Laevilacunaria antarctica across its distribution from maritime Antarctica to South Georgia. This species is a highly abundant near-shore gastropod, commonly found on macroalgae, with low autonomous vagility and exhibits benthic protected development with no free-living dispersive stages. Such characteristics make this species a suitable model to test the above hypotheses. Contrary to low dispersal potential predictions, L. antarctica comprises a single unstructured unit across its distribution in maritime Antarctica, exhibiting a typical high-dispersal star-like, short-branched genealogy centered on a dominant broadly distributed haplotype. The South Georgia population, however, consists of a separate genetic unit, strongly differentiated from those of the maritime Antarctic. We estimate that these two genetic groups separated ~1.2 My, long before the Last Glacial Maximum and evolved independently in these areas. Our results thus provide partial support for the expected pattern for a near-shore marine benthic species with low innate dispersive potential. On a wider geographic scale (maritime Antarctica vs South Georgia), our results in L. antarctica provide support for the expected pattern for a near-shore marine benthic species with low innate dispersive potential. However, on a narrower scale (maritime Antarctica) life-history characters including the close association of the species with macroalgae, would allow dispersal and a species with low dispersal potential exhibits paradoxically an absence of genetic structure across hundreds of kilometers probably mediated by rafting.

Genetic structure of the commercially important Asian monsoon scallop, Amusium pleuronectes (Linnaeus 1758), across the Indonesian Archipelago

AbstractThe Asian monsoon scallop, Amusium pleuronectes, is a key member of the most commercially harvested shellfish community in Asia. Patterns of genetic diversity and natural population structure in the target species were investigated to gain a better understanding of its evolutionary history. Samples were collected from five sites across the Indonesian Archipelago. We characterized sequence variation in an mtDNA control region fragment in 249 individuals. The genetic diversity (h = ranging from 0.83 to 0.92) and nucleotide diversity (π = ranging from 0.24 to 0.32) were low compared to the estimates reported for many other similar shellfish taxa. Nonetheless, analysis of molecular variance revealed significant genetic differentiation, FST = 0.0203 (p < .005 after Bonferroni corrections). Furthermore, both Pairwise fixation index values showed significance among majority population sites, indicating that dispersal potential and gene flow were low in the past. This pattern likely reflects a low dispersal potential, potentially allowing local adaptation to sites that augment any oceanographic and geographic contribution to genetic structure. The results described herein provide a foundation for developing better conservation strategies for the target species in the future.

Natural mega disturbances drive spatial and temporal changes in diversity and genetic structure on the toadfish Aphos porosus

Natural disturbances can modify extinction-colonization dynamics, driving changes in the genetic diversity and structure of marine populations. Along Chilean coast (36°S, 73°W), a strong hypoxic-upwelling event in 2008, and a mega earthquake-tsunami in 2010 caused mass mortality within the Aphos porosus population, which is a vulnerable species with low dispersal potential. We evaluated the effects of these two major disturbances on the diversity and spatial-temporal genetic structure of Aphos porosus in two neighboring areas that were impacted on different levels (High level: Coliumo Bay; Low level: Itata Shelf). Thirteen microsatellites (from 2008 to 2015) amplified in individuals collected from both locations were used to evaluate the effects of the two disturbances. Results showed that after the strong hypoxic-upwelling event and the mega earthquake-tsunami, Aphos porosus populations exhibited lower genetic diversity and less effective population sizes (Ne < 20), as well as asymmetries in migration and spatial-temporal genetic structure. These findings suggest a rise in extinction-recolonization dynamics in local Aphos porosus populations after the disturbances, which led to a loss of local genetic diversity (mainly in Coliumo Bay area impacted the most), and to greater spatial-temporal genetic structure caused by drift and gene flow. Our results suggest that continuous genetic monitoring is needed in order to assess potential risks for Aphos porosus in light of new natural and anthropogenic disturbances.

Living in a changing world: effects of roads and Pinus monocultures on an anuran metacommunity in southern Brazil

The loss of species with unique traits and evolutionary histories resulting from anthropogenic land-use changes poses a risk to the maintenance of ecosystems. We investigated the influence of Pinus monocultures and roads on functional, phylogenetic, and taxonomic composition, as well as on functional dispersion of an anuran metacommunity in Brazil. We expected the influence of anthropogenic stressors to (1) vary according to the diversity component, with greater influence on the functional and phylogenetic components than on the taxonomic component; and (2) traits related to habitat exploration to be more influenced by monocultures, while the traits related to dispersal and physiological control to be influenced by roads and monocultures, especially for species with smaller body size and low dispersal potential. We found that, while the distance from ponds to monocultures influences the phylogenetic composition, distance to roads influences functional composition and dispersion. The anthropogenic stressors affect the structure of these communities, even those formed by generalist species in terms of habitat use. The phylogenetic composition shows that the distribution of evolutionary clades in human-modified areas is linked to the preferred habitat of species, while functional composition is related to body size. Furthermore, functional dispersion was higher in areas closer to roads, contrary to our expectations. Our results represent new evidence for the conservation of anurans in modified landscapes reinforcing the importance of including functional and phylogenetic information in conservation-driven studies.

Species' attributes predict the relative magnitude of ecological and genetic recovery following mass mortality.

Theoretically, species' characteristics should allow estimation of dispersal potential and, in turn, explain levels of population genetic differentiation. However, a mismatch between traits and genetic patterns is often reported for marine species, and interpreted as evidence that life-history traits do not influence dispersal. Here, we couple ecological and genomic methods to test the hypothesis that species with attributes favouring greater dispersal potential-e.g., longer pelagic duration, higher fecundity and larger population size-have greater realized dispersal overall. We used a natural experiment created by a large-scale and multispecies mortality event which created a "clean slate" on which to study recruitment dynamics, thus simplifying a usually complex problem. We surveyed four species of differing dispersal potential to quantify the abundance and distribution of recruits and to genetically assign these recruits to probable parental sources. Species with higher dispersal potential recolonized a broader extent of the impacted range, did so more quickly and recovered more genetic diversity than species with lower dispersal potential. Moreover, populations of taxa with higher dispersal potential exhibited more immigration (71%-92% of recruits) than taxa with lower dispersal potential (17%-44% of recruits). By linking ecological with genomic perspectives, we demonstrate that a suite of interacting life-history and demographic attributes do influence species' realized dispersal and genetic neighbourhoods. To better understand species' resilience and recovery in this time of global change, integrative eco-evolutionary approaches are needed to more rigorously evaluate the effect of dispersal-linked attributes on realized dispersal and population genetic differentiation.

Limitations of DNA barcoding in determining the origin of smuggled seahorses and pipefishes

• Syngnathids are highly susceptible to overfishing and exploitation. • Shipments often contain specimens from various species and locations. • The COI mitochondrial gene is suitable to identify specimens to species level. • The COI gene is unable to identify the precise origin of a specimen. Seahorses and pipefishes are heavily exploited for use in Traditional Chinese Medicine (TCM), and less frequently for curio markets or as aquarium fish. A number of recent studies have used DNA barcoding to identify species sold at TCM markets in East Asia, but the usefulness of this approach in determining the region of origin remains poorly explored. Here, we generated DNA barcodes of dried seahorses and pipefishes destined for TCM that were confiscated at South Africa’s largest airport because they lacked the export permits required for the CITES-listed seahorses. These were compared with published sequences and new sequences generated for Mozambican seahorses, with the aim of determining whether it is possible to identify their country of origin. All pipefishes were identified as Syngnathoides biaculeatus , a widespread Indo-Pacific species, but the published sequence data did not provide sufficient resolution to identify the country of origin. The same was true of the majority of seahorses, which could not even be identified to species level because they clustered among an unresolved species complex whose sequences were published under the names Hippocampus kuda and H. fuscus . The presence of a few specimens of a second seahorse, H. camelopardalis , suggests that the shipment originated from East Africa because the range of this seahorse is centred around this region, but it was not possible to determine from which East African country they originated. Even though seahorses and pipefishes have high levels of genetic population structure because of their low dispersal potential, DNA barcoding was only suitable to tentatively identify species, but not their country of origin. DNA barcoding is increasingly used to identify illegally traded wildlife, but our results show that more sophisticated methods are needed to monitor and police the trade in seahorses and pipefishes.

High Clonality and Geographically Separated Cryptic Lineages in the Threatened Temperate Coral, Acropora pruinosa

Acropora pruinosa is a threatened zooxanthellate scleractinian coral that is distributed in the temperate areas along the coastline of Japan and the northern area of the South China Sea. Since A. pruinosa propagates both asexually and sexually, assessing clonal diversity and genetic connectivity among populations is important for conservation. In addition, high morphological variations in the field create confusion during species identification. To examine the existence of hidden genetic lineages, clonality, and genetic connectivity of A. pruinosa for conservation, we applied microsatellite analysis. Clustering analysis indicated two distinct geographically separated genetic lineages: one is distributed in the west, and the other is distributed in the east. The two lineages co-existed in Nishidomari, Kochi. There was no obvious difference in morphological characteristics between the two lineages. Although the factors influencing the observed distribution patterns remain unknown, there is a possibility that the two lineages might have diverged somewhere in the north-western Kyushu and north-eastern Pacific coast habitats in the past, and then periodically colonized the current habitats. A low clonal diversity was observed in most of the populations, indicating a high rate of asexual reproduction associated with their branching morphologies. In addition, there are strong genetic structuring in this species, indicating weak connectivity among populations. These results indicated a low larval dispersal potential among populations and that populations are basically sustained by a high rate of clone propagation and self-seeding. The existence of cryptic lineages and genetically isolated populations with high clonality emphasized the importance of conservation of A. pruinosa.

Whole genome genotyping reveals discrete genetic diversity in north-east Atlantic maerl beds.

Maerl beds are vital habitats for a diverse array of marine species across trophic levels, but they are increasingly threatened by human activities and climate change. Furthermore, little is known about the genetic diversity of maerl‐forming species and the population structure of maerl beds, both of which are important for understanding the ability of these species to adapt to changing environments and for informing marine reserve planning. In this study, we used a whole genome genotyping approach to explore the population genomics of Phymatolithon calcareum, a maerl‐forming red algal species, whose geographical distribution spans the north‐east Atlantic, from Norway to Portugal. Our results, using 14,150 genome‐wide SNPs (single nucleotide polymorphisms), showed that P. calcareum maerl beds across the north‐east Atlantic are generally structured geographically, a pattern likely explained by low dispersal potential and limited connectivity between regions. Additionally, we found that P. calcareum from the Fal Estuary, south‐west England, is genetically distinct from all other P. calcareum sampled, even from The Manacles, a site located only 13 km away. Further analysis revealed that this finding is not the result of introgression from two closely related species, Phymatolithon purpureum or Lithothamnion corallioides. Instead, this unique diversity may have been shaped over time by geographical isolation of the Fal Estuary maerl bed and a lack of gene flow with other P. calcareum populations. The genomic data presented in this study suggest that P. calcareum genetic diversity has accumulated over large temporal and spatial scales, the preservation of which will be important for maximizing the resilience of this species to changes in climate and the environment. Moreover, our findings underline the importance of managing the conservation of maerl beds across western Europe as distinct units, at a site‐by‐site level.

Inbreeding vs outbreeding depression in a marine species with low dispersal potential

AbstractInbreeding depression strongly affects the biological fitness of organisms throughout their life cycle. These negative effects are more pronounced in species with low dispersal potentials, where mating among relatives is more likely. However, in some species, an outbreeding depression could be expressed when local adaptive and genetic beneficial interactions are disrupted when mating occurs between individuals from different localities. The amphipod Orchestoidea tuberculata inhabits the upper level of sandy beaches. This species has direct development and adults are poor swimmers, resulting in low dispersal potential. We herein evaluated potential inbreeding and outbreeding depression responses in O. tuberculata estimated in fecundity, egg size, and mate choice. Artificial families were used with individuals from different sites within a single beach and from distinct beaches. Results showed that the highest fecundity (66.7%) and the largest egg size (50.1 mm3) were recorded in females that mated with males from the same site, rather than males from other sites and beaches. We also observed potential recognition mechanisms that clearly favored inbreeding (81.8% of males chose females from the same site). These results suggest a potential outbreeding depression in O. tuberculata. Additional studies are needed to elucidate underlying adaptive mechanisms favoring inbreeding in this species.

Concordant geographic and genetic structure revealed by genotyping-by-sequencing in a New Zealand marine isopod.

Population genetic structure in the marine environment can be influenced by life‐history traits such as developmental mode (biphasic, with distinct adult and larval morphology, and direct development, in which larvae resemble adults) or habitat specificity, as well as geography and selection. Developmental mode is thought to significantly influence dispersal, with direct developers expected to have much lower dispersal potential. However, this prediction can be complicated by the presence of geophysical barriers to dispersal. In this study, we use a panel of 8,020 SNPs to investigate population structure and biogeography over multiple spatial scales for a direct‐developing species, the New Zealand endemic marine isopod Isocladus armatus. Because our sampling range is intersected by two well‐known biogeographic barriers (the East Cape and the Cook Strait), our study provides an opportunity to understand how such barriers influence dispersal in direct developers. On a small spatial scale (20 km), gene flow between locations is extremely high, suggestive of an island model of migration. However, over larger spatial scales (600 km), populations exhibit a clear pattern of isolation‐by‐distance. Our results indicate that I. armatus exhibits significant migration across the hypothesized barriers and suggest that large‐scale ocean currents associated with these locations do not present a barrier to dispersal. Interestingly, we find evidence of a north‐south population genetic break occurring between Māhia and Wellington. While no known geophysical barrier is apparent in this area, it coincides with the location of a proposed border between bioregions. Analysis of loci under selection revealed that both isolation‐by‐distance and adaption may be contributing to the degree of population structure we have observed here. We conclude that developmental life history largely predicts dispersal in the intertidal isopod I. armatus. However, localized biogeographic processes can disrupt this expectation, and this may explain the potential meta‐population detected in the Auckland region.

Seascape genomics reveals population isolation in the reef-building honeycomb worm, Sabellaria alveolata (L.)

BackgroundUnder the threat of climate change populations can disperse, acclimatise or evolve in order to avoid fitness loss. In light of this, it is important to understand neutral gene flow patterns as a measure of dispersal potential, but also adaptive genetic variation as a measure of evolutionary potential. In order to assess genetic variation and how this relates to environment in the honeycomb worm (Sabellaria alveolata (L.)), a reef-building polychaete that supports high biodiversity, we carried out RAD sequencing using individuals from along its complete latitudinal range. Patterns of neutral population genetic structure were compared to larval dispersal as predicted by ocean circulation modelling, and outlier analyses and genotype-environment association tests were used to attempt to identify loci under selection in relation to local temperature data.ResultsWe genotyped 482 filtered SNPs, from 68 individuals across nine sites, 27 of which were identified as outliers using BAYESCAN and ARLEQUIN. All outlier loci were potentially under balancing selection, despite previous evidence of local adaptation in the system. Limited gene flow was observed among reef-sites (FST = 0.28 ± 0.10), in line with the low dispersal potential identified by the larval dispersal models. The North Atlantic reef emerged as a distinct population and this was linked to high local larval retention and the effect of the North Atlantic Current on dispersal.ConclusionsAs an isolated population, with limited potential for natural genetic or demographic augmentation from other reefs, the North Atlantic site warrants conservation attention in order to preserve not only this species, but above all the crucial functional ecological roles that are associated with their bioconstructions. Our study highlights the utility of using seascape genomics to identify populations of conservation concern.

Two sides of the same coin: Does alien Impatiens balfourii fall into an ecological trap after releasing from enemies?

The evolution of increased competitive ability (EICA) hypothesis assumes that recently introduced populations of alien species are under low pressure from enemies, which allows them to reduce investment into defence and re-allocate the saved resources into the improvement of characteristics related to competitive abilities. We performed EICA tests to check if the low dispersal potential of Impatiens balfourii in Europe results from a limited evolution of its capability to release from enemies or from the low phenotypic plasticity of this trait.We tested habitat preferences of the species and compared the levels of enemy pressure in different habitats. This allowed us to determine if the tendency to occur along roadsides is manifested at the European scale in this species and if this preference is determined by a lower pressure of enemies in that habitat. It cannot be ruled out that occurrence along roads can be maladaptive for the species, and this habitat can potentially constitute an ecological trap due to frequent mowing.The study was carried out in six European populations differing in age and in five types of habitat. Enemy pressure was estimated by assessing leaf damage in adult plants and fungal pathogen load at the seed stage. We tested if the saved reserves are invested in the size and/or fertility of adult plants or in the seed quality. Activity of pollinators in different populations and habitats was also assessed.The majority of the results for adult plants indicate that the younger populations of I. balfourii release from enemy pressure better than the older ones. However, we found only weak support that the reserves previously spent on defence against natural enemies could be re-allocated into larger size or increased fertility. Only in the youngest population from Andorra was it largely confirmed. However, at seed stage, we found no support for the EICA assumptions in any of the populations. Thus, in general, the results of our study provide a fairly weak support for the EICA hypothesis.In comparisons between the habitats, we found that in five of the six populations, the species preferred roadsides, which was probably determined by the lower enemy pressure there. However, it cannot be excluded that this preference can be maladaptive and that this habitat can potentially constitute an ecological trap due to frequent mowing. Notably, the species was also abundant along streams, where the plants are less disturbed by human activities. This finding was particularly pronounced at the invasion forefront in Andorra, where the species was completely absent from roadsides. Therefore, we assume that unless control measures are undertaken, streamsides may be more important for the future invasion of I. balfourii than roadsides in that area.The ornamental value of I. balfourii makes it an obvious candidate to replace its banned invasive counterpart I. glandulifera in trade. The increase in popularity in trade and cultivation would inevitably lead to an increase in propagule pressure, which could be crucial for increasing the rate of invasion of I. balfourii on a large scale in Europe.

Dispersal limitation drives biogeographical patterns of anammox bacterial communities across the Yangtze River.

Over the past few decades, anaerobic ammonium oxidation (anammox) has been extensively documented at different scales in natural ecosystems. Previous studies have stated that the community composition of anammox bacteria is shaped mainly by environmental factors, whereas spatial factors have been largely overlooked. This study investigated biogeographical patterns of anammox bacterial communities using 42 sediment samples along a 4300-km stretch of the Yangtze River, the longest river in Asia. A significant distance-decay relationship was observed for anammox bacterial community similarity, which was significantly influenced by mean dendritic distance rather than environmental factors. This implied that dispersal limitation plays an important role in shaping biogeographical pattern of anammox community. Furthermore, our results revealed that neutral processes played vital role in shaping community assembly of anammox bacteria, and their communities were seriously dispersal limited. These findings contrast with previous studies on community similarities between broad taxonomic groups, which are mainly determined by niche-based selection owing to greater niche distances within broad taxonomic groups than in anammox bacteria. Importantly, the slope of the distance-decay curve was much steeper than previously reported for whole bacteria, which indicating the species turnover rate of anammox bacterial community was significantly higher than that of the whole bacterial community. Anammox bacteria harbor strong adhesion ability and low dispersal potential, and ultimately exhibited a high species turnover rate. Together, in the context of biogeography, our results highlight the importance of dispersal limitation in shaping the biogeographical pattern of anammox bacterial community.

Deep ocean seascape and Pseudotanaidae (Crustacea: Tanaidacea) diversity at the Clarion-Clipperton Fracture Zone

Understanding the diversity and spatial distribution of benthic species is fundamental to properly assess the impact of deep sea mining. Tanaidacea provide an exceptional opportunity for assessing spatial patterns in the deep-sea, given their low mobility and limited dispersal potential. The diversity and distribution of pseudotanaid species is characterized here for the Clarion and Clipperton Fractures Zone (CCZ), which is the most extensive deposit field of metallic nodules. Samples were taken from the Belgian, German and French license areas, but also from the APEI 3 (Area of Particular Environmental Interest 3) of the Interoceanmetal consortium associates. The combination of morphological and genetic data uncovered one new pseudotanaid genus (Beksitanais n. gen.) and 14 new species of Pseudotanais (2 of them virtual taxa). Moreover, our results suggest that spatial structuring of pseudotanaid diversity is correlated with deep-sea features, particularly the presence of fractures and seamount chains crossing the CCZ. The presence of geographical barriers delimiting species distributions has important implications for the establishment of protected areas, and the APEI3 protected area contains only one third of the total pseudotanaid species in CCZ. The specimen collection studied here is extremely valuable and represents an important first step in characterizing the diversity and distribution of pseudotanaids within the Tropical Eastern Pacific.

Evaluating the boundaries of marine biogeographic regions of the Southwestern Atlantic using halacarid mites (Halacaridae), meiobenthic organisms with a low dispersal potential.

AimWe evaluated traditional biogeographic boundaries of coastal marine regions in Southwestern Atlantic using DNA sequence data from common, rocky‐shore inhabiting, marine mites of the genera Agauopsis and Rhombognathus, family Halacaridae.MethodsWe investigated geographic population genetic structure using CO1 gene sequences, estimated divergence times using a multigene dataset and absolute time‐calibrated molecular clock analyses, and performed environmental niche modeling (ENM) of common marine mite species.Results Agauopsis legionium has a shallow history (2.01 Ma) with four geographically differentiated groups. Two of them corresponded to the traditional Amazonian and Northeastern ecoregions, but the boundary between the two other groups was inferred at the Abrolhos Plateau, not Cabo Frio. Rhombognathus levigatoides s. lat. was represented by two cryptic species that diverged 7.22 (multilocus data) or 10.01 Ma (CO1‐only analyses), with their boundary, again at the Abrolhos Plateau. ENM showed that A. legionium has suitable habitats scattered along the coast, while the two R. levigatoides cryptic species differ considerably in their niches, especially in parameters related to upwelling. This indicates that genetic isolation associated with the Abrolhos Plateau occurred in both lineages, but for the R. levigatoides species complex, ecological niche specialization was also an important factor.Main conclusionsOur study suggests that the major biogeographic boundary in the Southwestern Atlantic lies not at Cabo Frio but at the Abrolhos Plateau. There two biogeographically relevant factors meet (a) changes in current directions (which limit dispersal) and (b) abrupt changes in environmental parameters associated with the South Atlantic Central Waters (SACW) upwelling (offering distinct ecological niches). We suggest that our result represents a general biogeographic pattern because a barrier at the Abrolhos Plateau was found previously for the fish genus Macrodon (phylogeographic data), prosobranch mollusks, ascidians, and reef fishes (community‐level data).

Anthropogenic pressures drive population genetic structuring across a Critically Endangered lemur species range

In recent decades Madagascar has experienced significant habitat loss and modification, with minimal understanding of how human land use practices have impacted the evolution of its flora and fauna. In light of ongoing and intensifying anthropogenic pressures, we seek new insight into mechanisms driving genetic variability on this island, using a Critically Endangered lemur species, the black-and-white ruffed lemur (Varecia variegata), as a test case. Here, we examine the relative influence of natural and anthropogenic landscape features that we predict will impose barriers to dispersal and promote genetic structuring across the species range. Using circuit theory, we model functional connectivity among 18 sampling localities using population-based genetic distance (FST). We optimized resistance surfaces using genetic algorithms and assessed their performance using maximum-likelihood population-effects mixed models. The best supported resistance model was a composite surface that included two anthropogenic features, habitat cover and distance to villages, suggesting that rapid land cover modification by humans has driven change in the genetic structure of wild lemurs. Primary conservation priority should be placed on mitigating further forest loss and connecting regions identified as having low dispersal potential to prevent further loss of genetic diversity and promote the survival of other moist forest specialists.

To remain or leave: Dispersal variation and its genetic consequences in benthic freshwater invertebrates.

Variation in dispersal capacity may influence population genetic variation and relatedness of freshwater animals thus demonstrating how life‐history traits influence patterns and processes that in turn influence biodiversity. The majority of studies have focused on the consequences of dispersal variation in taxa inhabiting riverine systems whose dendritic nature and upstream/downstream gradients facilitate characterizing populations along networks. We undertook extensive, large‐scale investigations of the impacts of hydrological connectivity on population genetic variation in two freshwater bryozoan species whose dispersive propagules (statoblasts) are either attached to surfaces (Fredericella sultana) or are released as buoyant stages (Cristatella mucedo) and that live primarily in either lotic (F. sultana) or lentic environments (C. mucedo). Describing population genetic structure in multiple sites characterized by varying degrees of hydrological connectivity within each of three (or four) UK regions enabled us to test the following hypotheses: (1) genetic diversity and gene flow will be more influenced by hydrological connectivity in populations of C. mucedo (because F. sultana dispersal stages are retained); (2) populations of F. sultana will be characterized by greater genetic divergence than those of C. mucedo (reflecting their relative dispersal capacities); and (3) genetic variation will be greatest in F. sultana (reflecting a propensity for genetic divergence as a result of its low dispersal potential). We found that hydrological connectivity enhanced genetic diversity and gene flow among C. mucedo populations but not in F. sultana while higher overall measures of clonal diversity and greater genetic divergence characterized populations of F. sultana. We suggest that genetic divergence over time within F. sultana populations reflects a general constraint of releasing propagules that might eventually be swept to sea when taxa inhabit running waters. In contrast, taxa that primarily inhabit lakes and ponds may colonize across hydrologically connected regions, establishing genetically related populations. Our study contributes more nuanced views about drivers of population genetic structures in passively dispersing freshwater invertebrates as outlined by the Monopolization Hypothesis (Acta Oecologica, 23, 2002, 121) by highlighting how a range of demographic and evolutionary processes reflect life‐history attributes of benthic colonial invertebrates (bryozoans) and cyclically parthenogenetic zooplankton. In addition, growing evidence that genetic divergence may commonly characterize populations of diverse groups of riverine taxa suggests that organisms inhabiting lotic systems may be particularly challenged by environmental change. Such change may predispose riverine populations to extinction as a result of genetic divergence combined with limited dispersal and gene flow.Open Research Badges This article has earned an Open Data Badge for making publicly available the digitally‐shareable data necessary to reproduce the reported results. The data is available at https://doi.org/10.5061/dryad.1tm8705.

Autochthone Gebirgswälder in der Schweiz anhand von baumbewohnenden Flechten erkennen

Recognizing autochthonous mountain forests in Switzerland by means of epiphytic lichens Old undisturbed forest stands with a long forest history are of particular interest for nature and species conservation. Epiphytic lichens are often used as indicators for such autochthonous stands. In this study, we tested to what extent 14 taxa of epiphytic lichens, which are easy to identify by forest practitioners and have a low dispersal potential, have specific requirements for micro habitats and are often dependent on old trees, would be suitable indicator species for autochthonous forest stands in the Swiss mountain forests. As autochthonous, we considered forest stands with a near-natural conifer composition, a minimum age of 90 years, a continuous forest cover over 120 years and no evidence of historical intervention such as clear cutting or afforestation. For the study, the regular field teams of the Swiss National Forest Inventory (NFI) included the potential indicator species in the third survey (2004–2006) on all plots in the 1.4 km network on about three trees each. The data for the 3510 plots in the mountain forest were then evaluated using the NFI data on forest structure, forest history and forest management. Overall, the number of indicator species was significantly higher in autochthonous forest stands than in non-autochthonous ones, although it varied considerably with altitude and biogeographical region. Our investigations showed that fruticose lichens of the genera Bryoria and Usnea, Evernia divaricata and Letharia vulpina, foliose lichens such as Cetrelia olivetorum and Lobaria pulmonaria, and crustose lichens such as Lecanactis abietina and Microcalicium disseminatum, Calicium sp. div. and Chaenotheca sp. div. as well as Chrysothrix candelaris are reliable indicators for autochthonous stands in Swiss mountain forests, especially if several indicator species occur together. The lichens tested are therefore suitable in practice for a simple identification of autochthonous forest stands, e.g. for delimiting forest reserves or old forest patches. These stands are of high importance for the promotion of biodiversity in a forest landscape that has been managed for centuries.

Fine-scale hierarchical genetic structure and kinship analysis of the ascidian Pyura chilensis in the southeastern Pacific.

Studying population structure and genetic diversity at fine spatial scales is key for a better understanding of demographic processes that influence population connectivity. This is particularly important in marine benthic organisms that rely on larval dispersal to maintain connectivity among populations. Here, we report the results of a genetic survey of the ascidian Pyura chilensis from three localities along the southeastern Pacific. This study follows up on a previous report that described a genetic break in this region among localities only 20 km apart. By implementing a hierarchical sampling design at four spatial levels and using ten polymorphic microsatellite markers, we test whether differences in fine‐scale population structure explain the previously reported genetic break. We compared genetic spatial autocorrelations, as well as kinship and relatedness distributions within and among localities adjacent to the genetic break. We found no evidence of significant autocorrelation at the scale up to 50 m despite the low dispersal potential of P. chilensis that has been reported in the literature. We also found that the proportion of related individuals in close proximity (<1 km) was higher than the proportion of related individuals further apart. These results were consistent in the three localities. Our results suggest that the spatial distribution of related individuals can be nonrandom at small spatial scales and suggests that dispersal might be occasionally limited in this species or that larval cohorts can disperse in the plankton as clustered groups. Overall, this study sheds light on new aspects of the life of this ascidian as well as confirms the presence of a genetic break at 39°S latitude. Also, our data indicate there is not enough evidence to confirm that this genetic break can be explained by differences in fine‐scale genetic patterns among localities.