High Dispersal Ability Research Articles

Spatial patterns of functional diversity and composition in marine benthic ciliates along the coast of China

Large-scale patterns of community composition and diversity along environmental gradients have been well studied for macroorganisms. However, the biogeography of microorganisms, especially ciliated protozoa, remains understudied. Here, we analyzed a comprehensive database of marine benthic ciliates found along the coast of China from 1991 to 2018 to examine the geographical patterns in species and trait composition and functional diversity. According to redundancy analysis conducted at large spatial scales, environmental variables, i.e. habitat type and salinity, explained more variance in species composition than latitude. In contrast, trait composition was better explained by spatial and climatic variables. At small spatial scales, both species and trait composition were probably influenced by mass effects due to the high dispersal ability of ciliates at such small scales, resulting in spatially homogenized communities. Several traits, including body size, feeding type and mobility, exhibited significant positive or negative latitudinal gradients. Functional diversity showed a significant positive correlation with latitude between 20 and 40° N, which may be caused by certain groups of ciliates possessing particular traits related to temperature. Our study is the first comprehensive evaluation of how trait composition and functional diversity of marine ciliated protozoa vary at large scales and can thus make a major contribution to the study of microbial biogeography.

Genetic isolation by distance in the yellowfin goby populations revealed by RAD sequencing

Population genetic studies of marine species sometimes find no clear patterns of genetic differentiation, but signals of geographic gene flow typified by isolation by distance (IBD) due to high dispersal ability. A previous study of mitochondrial DNA of the yellowfin goby Acanthogobius flavimanus indicated that this species also does not have clearly differentiated population groups around the Japanese archipelago, in contrast with other coastal goby species that have highly differentiated groups between the Sea of Japan and Pacific Ocean populations. Here, to clearly reveal phylogeographic structures of the yellowfin goby around the Japanese archipelago, we conducted large-scale RAD-sequencing analysis of their nuclear genomic SNP loci. As a result, IBD patterns were confirmed across the yellowfin goby populations, and the larval dispersal distance of this species was revealed to be approximately 19 km on average. In addition, different larval dispersal distances were estimated for its Sea of Japan and Pacific Ocean populations, suggesting that different coastal environments and/or ecological features may affect its dispersal rates. These results would provide foundations for ecological and conservation studies of the yellowfin goby and coastal fishes having similar dispersal strategy to this species.

Ecological specialization resulting in restricted gene flow promotes differentiation in door snails

We tested the hypothesis that ecological specialization that affects dispersal promotes diversification by a comparison of the genetic structure of two sister species of door snails across their broadly overlapping ranges in the Crimean Mountains. The hypothesized effect of ecological specialization on diversification is supported by STRUCTURE analyses that showed that Mentissa gracilicosta that is restricted to limestone rocks, is subdivided into several distinct clusters, whereas all populations of the species adapted to more continuous habitat, the forests-dwelling Mentissa canalifera, were assigned to a single cluster. Furthermore, it is supported by AMOVAs that showed that a larger part of the genetic variation of M. gracilicosta is apportioned among populations than in M. canalifera. The stronger genetic differentiation of the M. gracilicosta populations corresponds to their more distinct morphological differentiation that resulted in the classification of M. gracilicosta into several geographical subspecies, whereas the more continuously distributed M. canalifera was not subdivided into subspecies. The stronger differentiation of populations of M. gracilicosta compared to M. canalifera can be ascribed to reduced gene flow between the isolated populations of M. gracilicosta and to founder events associated with the long distance dispersal events that are necessary for the colonization of isolated rocks by M. gracilicosta. In Central Europe, the Pleistocene climatic oscillations selected for species with high dispersal abilities, whereas the more stable climate in southern Europe facilitated the non-adaptive radiation of rock-dwelling door snails. Thus, the intrinsic ecological properties of these species groups contributed to the latitudinal diversity gradient.

Phylogeography of widespread species in Eurasia: Current progress and future prospects

The geographical distribution patterns of the widespread species in Eurasia are classified into four major categories: global distribution, holarctic distribution, mid-high latitude Eurasian distribution, and mid-low latitude Eurasian distribution patterns. By comparing the results of recent phylogeographic studies on the widespread species in Eurasia, we have outlined three phylogeographic patterns: (i) “single-component,” (ii) “east-west component,” and (iii) “peripatric component” patterns. The present study summarizes the factors that potentially influence the phylogeographic patterns of the widespread species in Eurasia. These factors include the following: (i) the relatively high environmental tolerance and dispersal ability of the species as well as the influence of human trade, transportation, and domestication activities; (ii) the east-west diverging Pleistocene glacial climate and the inland arid belt: during glaciation, most regions of Europe were covered with ice sheets; therefore, the species retreated to refuge areas and during the interglacial periods, they recolonized to suitable areas, which facilitated survival after the Last Glacial Maximum. The glacial climates in most parts of Asia were relatively mild, particularly in east Asia, which was less extensively glaciated, as a result of which the glacial period had a relatively low impact on the distribution patterns of species in such areas. In addition, the rapid uplift of the Qinghai-Tibetan Plateau during the Pleistocene and the intensification of the Asian summer monsoon have promoted the formation of the inland arid belt of Eurasia, resulting in long-term ecological isolation. Lastly, (iii) the influence of peripatric speciation: populations disperse to the new marginal environment. Due to geographic or environmental isolation, genetic drift is fixed in small isolated populations, resulting in genetic differentiation among populations. Analyzing the unique and consistent response mechanisms of the widespread species in Eurasia under similar geographical and geological histories would facilitate our understanding of the mechanisms underlying the establishment of geographical populations of the widely distributed species in Eurasia. In addition, this will summarize and identify appropriate diversities and universal principles influencing the phylogeographical patterns of the Eurasian species. Finally, the present study reveals prospective research directions in phylogeography on the widespread species in Eurasia based on large-scale nuclear genome markers and the integration of life history traits into predictive phylogeography.

A novel integrative approach elucidates fine-scale dispersal patchiness in marine populations

Dispersal is one of the main determining factors of population structure. In the marine habitat, well-connected populations with large numbers of reproducing individuals are common but even so population structure can exist on a small-scale. Variation in dispersal patterns between populations or over time is often associated to geographic distance or changing oceanographic barriers. Consequently, detecting structure and variation in dispersal on a fine-scale within marine populations still remains a challenge. Here we propose and use a novel approach of combining a clustering model, early-life history trait information from fish otoliths, spatial coordinates and genetic markers to detect very fine-scale dispersal patterns. We collected 1573 individuals (946 adults and 627 juveniles) of the black-faced blenny across a small-scale (2 km) coastline as well as at a larger-scale area (<50 kms). A total of 178 single nucleotide polymorphism markers were used to evaluate relatedness patterns within this well-connected population. In our clustering models we categorized SHORT-range dispersers to be potential local recruits based on their high relatedness within and low relatedness towards other spatial clusters. Local retention and/or dispersal of this potential local recruitment varied across the 2 km coastline with higher frequency of SHORT-range dispersers towards the southwest of the area for adults. An inverse pattern was found for juveniles, showing an increase of SHORT-range dispersers towards the northeast. As we rule out selective movement and mortality from one year to the next, this pattern reveals a complex but not full genetic mixing, and variability in coastal circulation is most likely the main driver of this fine-scale chaotic genetic patchiness within this otherwise homogeneous population. When focusing on the patterns within one recruitment season, we found large differences in temperatures (from approx. 17 °C to 25 °C) as well as pelagic larval duration (PLD) for juveniles from the beginning of the season and the end of the season. We were able to detect fine-scale differences in LONG-range juvenile dispersers, representing distant migrants, depending on whether they were born at the beginning of the season with a longer PLD, or at the end of the reproductive season. The ability to detect such fine-scale dispersal patchiness will aid in our understanding of the underlying mechanisms of population structuring and chaotic patchiness in a wide range of species even with high potential dispersal abilities.

Molecular and morphological differentiation among Torrent Duck (Merganetta armata) populations in the Andes

AbstractBirds living in riverine environments may show weak population structure because high dispersal abilities required to track habitat dynamics can result in gene flow over broad spatial scales. Alternatively, the configuration of river networks may result in restricted dispersal within river courses or basins, leading to high genetic structure. Although several bird species are riverine specialists in the Andes, no study has extensively evaluated the population genetic structure of any of them. We examined evidence from genetic and morphological data to address questions about the biogeography and taxonomy of the Torrent Duck (Merganetta armata), a riverine specialist bird with a broad distribution in Andean riverine habitats which certainly comprises different subspecies and may comprise more than one species. We found deep subdivisions of Torrent Duck populations from the northern, central and southern portions of the Andes. These lineages, which partly coincide with subspecies described based on plumage variation and body size, do not share mtDNA haplotypes, have private nuclear alleles and exhibit marked differences in morphometric traits. Some geographic barriers presumably restricting gene flow between groups partially coincide with those associated with major genetic breaks in forest species with similar distributions along the Andes, suggesting that bird assemblages including species occupying different habitats were likely affected by common biogeographical events. The three groups of Torrent Ducks may be considered different species under some species definitions and are distinct evolutionary lineages to be conserved and managed separately.

Uncovering population structure in the Humboldt penguin (Spheniscus humboldti) along the Pacific coast at South America.

The upwelling hypothesis has been proposed to explain reduced or lack of population structure in seabird species specialized in food resources available at cold-water upwellings. However, population genetic structure may be challenging to detect in species with large population sizes, since variation in allele frequencies are more robust under genetic drift. High gene flow among populations, that can be constant or pulses of migration in a short period, may also decrease power of algorithms to detect genetic structure. Penguin species usually have large population sizes, high migratory ability but philopatric behavior, and recent investigations debate the existence of subtle population structure for some species not detected before. Previous study on Humboldt penguins found lack of population genetic structure for colonies of Punta San Juan and from South Chile. Here, we used mtDNA and nuclear markers (10 microsatellites and RAG1 intron) to evaluate population structure for 11 main breeding colonies of Humboldt penguins, covering the whole spatial distribution of this species. Although mtDNA failed to detect population structure, microsatellite loci and nuclear intron detected population structure along its latitudinal distribution. Microsatellite showed significant Rst values between most of pairwise locations (44 of 56 locations, Rst = 0.003 to 0.081) and 86% of individuals were assigned to their sampled colony, suggesting philopatry. STRUCTURE detected three main genetic clusters according to geographical locations: i) Peru; ii) North of Chile; and iii) Central-South of Chile. The Humboldt penguin shows signal population expansion after the Last Glacial Maximum (LGM), suggesting that the genetic structure of the species is a result of population dynamics and foraging colder water upwelling that favor gene flow and phylopatric rate. Our findings thus highlight that variable markers and wide sampling along the species distribution are crucial to better understand genetic population structure in animals with high dispersal ability.

Metacommunity patterns of Amazonian Odonata: the role of environmental gradients and major rivers.

BackgroundWe identified and classified damselfly (Zygoptera) and dragonfly (Anisoptera) metacommunities in Brazilian Amazonia, relating species distribution patterns to known biological gradients and biogeographical history. We expected a random distribution of both Zygoptera and Anisoptera within interfluves. At the Amazonian scale, we expected Anisoptera metacommunities to be randomly distributed due to their higher dispersal ability and large environmental tolerance. In contrast, we expected Zygoptera communities to exhibit a Clementsian pattern, limited by the large Amazonia rivers due to their low dispersal ability.MethodsWe used a dataset of 58 first-to-third order well-sampled streamlets in four Amazonian interfluves and applied an extension of the Elements of Metacommunity Structure (EMS) framework, in which we order Zygoptera and Anisoptera metacommunities by known spatial and biogeographic predictors.ResultsAt the Amazonian scale, both Zygoptera and Anisoptera presented a Clementsian pattern, driven by the same environmental and biogeographical predictors, namely biogeographic region (interfluve), annual mean temperature, habitat integrity and annual precipitation. At the interfluve scale, results were less consistent and only partially support our hypothesis. Zygoptera metacommunities at Guiana and Anisoptera metacommunities at Tapajós were classified as random, suggesting that neutral processes gain importance at smaller spatial scales.DiscussionOur findings were consistent with previous studies showing that environmental gradients and major rivers limit the distribution of Odonata communities, supporting that larger Amazonian rivers act as barriers for the dispersal of this group. In addition, the importance of habitat integrity indicates that intactness of riparian vegetation is an important filter shaping metacommunity structure of Amazonian stream Odonata.

Outbreak of Orthotomicus erosus (Coleoptera, Curculionidae) on Aleppo Pine in the Mediterranean Region in Croatia

Background and Purpose: Orthotomicus erosus, Mediterranean pine engraver, is widely distributed across the Mediterranean and southern Europe, Asia and North Africa. It is considered as secondary pest found on recently dead or felled trees, but can also attack weakened living trees. In high population levels this species can attack healthy trees and cause their dieback. Severe outbreaks occur after dry periods, or after fire in adjoining stands in warmer parts of the Mediterranean region, while this scenario has never happened in Croatia up to now. Bark beetles are important forest pests which have already been researched and discussed in relation to climate change, indicating that the predicted increase in temperature would lead to higher survival rates and faster development, thus directly influencing their population dynamics. Increase in temperature may stimulate changes in insects’ rate of development, voltinism, population density, size, genetic composition, extent of host plant exploitation, longitudinal and latitudinal distribution. Since climate conditions might have changed in the last few years as predicted in the Mediterranean region, the aim of our research is to document the first outbreak with high population levels of O. erosus in Croatia. Materials and Methods: The extent of dieback was evaluated by counting trees with dieback symptoms on diagonal transects plotted through each of 33 forest management sections of Marjan Forest Park (Split). Trunk sections from several trees with early stage symptoms were collected for further laboratory analysis, which consisted of incubation phase and subsequent morphological identification. During regular yearly surveys in forests of Croatia, the pest was observed on several sites and damages were recorded for both years 2017 and 2018. The records were entered into a map using QGIS version 3.2.1-Bonn. Spatial data was downloaded from DIVA-GIS server. Monitoring efforts were initiated in affected areas where 13 flight barrier pheromone traps (Theyson®) equipped with pheromone lure Erosowit® (Witasek, Austria) were set-up in late March in state-owned and privately owned forests across Dalmatia. Catches in the traps were collected and O. erosus adults were counted on a weekly basis in order to identify the abundance of the pest in monitored sites, as well as to obtain the first information about population dynamics and to assess voltinism. Results: On-site survey and the evaluation of dieback extent included sampling of 5% of all trees in Marjan Forest Park ,and the results showed that 23% of all trees in the forest park were affected by dieback symptoms. Visual examination of trunks, branches and bark showed symptoms of bark beetle infestation, while preliminary on-site examination of the observed adults pointed out to O. erosus. After two weeks in controlled conditions, bark beetle adults started to emerge from trunk sections which were placed in several mesh cages for incubation. Morphological identification by using stereomicroscope and the key for European bark beetles resulted in identification of O. erosus species. Over the course of the year 2017 one more site was reported to be infested with O. erosus, and eight additional sites were reported over the course of year 2018. In total, 446 ha were reported as infested, varying in intensity, in several different management units of state-owned and privately owned forests. The total number of trapped beetles in pheromone traps varied largely among sites. Our data indicate that several generations (at least 5 generations per year) were present in the year 2018. Conclusions: Sudden surge in observed damages, as well as the number of beetles trapped during monitoring, in years 2017 and 2018 throughout Aleppo pine forests in Dalmatia are the first record of O. erosus outbreak in Croatia. O. erosus is native to Croatia and so far it has been considered only as a minor pest whose outbreaks have never been recorded. Drought intensity and frequency and aridification trends in the research area (Dalmatia, Croatia) cause cumulative stress to trees and have increased O. erosus occurrence. O. erosus is expected to exhibit increased voltinism, better overwintering performance and earlier spring flights. Our first results confirm this epidemic stage of O. erosus with high abundances in Dalmatia in 2018 and at least 5 generations per year, which alter the population level of this pest. Finally, with high dispersal abilities of O. erosus through active flight and easy transportation with infested material (logs and branches with bark), O. erosus has the potential to become an important forest pest in Croatia. Thus, extensive studies on its biology, ecology, natural enemies and interaction with ophiostomatoid fungal species are needed in order to predict further spread and suggest viable and effective management measures.

Upstream refugia and dispersal ability may override benthic-community responses to high-Andean streams deforestation

Deforestation is a major driver of biodiversity loss in the Tropical region, but the role of upstream refugia and dispersal ability on the community response to this disturbance is unknown. We assessed the relevance of undisturbed upstream patches (“refugia”) on the responses of benthic communities to forest cover loss. We selected four Andean rivers with a well-protected forest in their upstream section and different degree of forest cover loss downstream and evaluated the dissimilarity patterns of three benthic communities (diatoms, Chironomidae, and the assemblage of Ephemeroptera, Plecoptera and Trichoptera—‘EPT’) along their water courses. We evaluated the dissimilarity by using Euclidean (environment), Sorensen (incidence data) and Morisita–Horn (abundance data) pairwise distances. We found that diatom beta-diversity, as organisms with passive but higher dispersal ability, significantly tracked the environmental changes caused by forest loss. However, insect communities, whose a priori are active dispersers and can track for suitable conditions, were weakly affected by deforestation. These results provide evidences that the existence of well-preserved upstream reaches along patched corridors may allow non-tolerant species to remain extant throughout dispersal-driven feedbacks. This being the case in the Andean streams, effects of deforestation on benthic communities were small, and not uniform. Our results reinforce the strategy of preserving upstream sections in order to achieve successful restoration or rehabilitation goals.

Colonisation dynamics during range expansion is poorly predicted by dispersal in the core range

The potential ranges of many species are shifting due to changing ecological conditions. Where populations become patchy towards the range edge, the realised distribution emerges from colonisation–persistence dynamics. Therefore, a greater understanding of the drivers of these processes, and the spatial scales over which they operate, presents an opportunity to improve predictions of species range expansion under environmental change.Species reintroductions offer an ideal opportunity to investigate the drivers and spatial scale of colonisation dynamics at the range edge. To this effect, we performed and monitored experimental translocations of water voles to quantify how colonisation and local persistence were influenced by habitat quality and occupancy. We used a novel statistical method to simultaneously consider effects across a range of spatial scales.Densely occupied neighbourhoods were highly persistent and frequently colonised. Persistence was more likely in high quality habitat, whereas the influence of habitat quality on colonisation was less clear. Colonisation of suitable habitat in distant, sparsely occupied areas was much less frequent than expected from the well documented high dispersal ability of the species. Persistence of these distant populations was also low, which we attribute to the absence of a rescue effect in sparsely populated neighbourhoods.Our results illustrate a mismatch between the spatial scales of colonisation dynamics in the core and edge of a species’ range, suggesting that recolonisation dynamics in established populations may be a poor predictor of colonisation dynamics at the range edge.Such a mismatch leads to predictions of long lags between the emergence and colonisation of new habitat, with detrimental consequences for a species’ realised distribution, conservation status and contribution to ecosystem function. Conservation translocations that also reinforce existing populations at the range edge might stimulate the rescue effect and mitigate lags in expansion.

Pollen dispersal and representation of the “Forest Island” within the Chinese desert-loess transitional zone

Vegetation reconstruction from fossil pollen records depends on an adequate understanding of the relationship between modern pollen and vegetation. In this study, we present the modern pollen dispersal and representation of the “Forest Island” and its surrounding areas within the Chinese desert-loess transitional zone. Forty-four pollen carpet traps, which imitate the natural pollen sediment process, were collected from the Ningxia Daluoshan Mountain and its surrounding areas along a southeast–northwest transect included five vegetation types. The pollen spectra, spatial distribution patterns of the main pollen types and discriminant analysis of pollen data show that: Pinus Diploxylon-type has high pollen production and good dispersal ability and that the over-represented, with values exceeding the 20% (>100 grains cm−2 year−1) within vegetation dominated by Pinus tabuliformis, below 7% (<39 grains) when Pinus tabuliformis trees are absent. Picea has higher pollen production and a limited pollen dispersal ability via wind-borne dispersal, with values exceeding the 20% (>100 grains) within the spruce forest, decreased abruptly and even disappeared completely outside the forest. Another interesting finding of this study is that Poaceae have higher values and higher pollen production. The modern pollen assemblage of the desert steppe, mountain steppe and Picea crassifolia forest, but especially the desert steppe and mountain steppe, can be separated from each other as follows: (1) desert steppe: Chenopodiaceae–Poaceae pollen assemblage; (2) mountain steppe: Poaceae–Artemisia–Aster type pollen assemblage; and (3) Picea crassifolia forest: Picea–Artemisia–Poaceae pollen assemblage. However, overlap occurs between deciduous broadleaved shrubs and coniferous and broadleaved mixed forests. The very low concentration of deciduous broadleaved shrubs may due to an increased contribution of pine pollen. Our study may facilitate the confident use of fossil pollen data to reconstruct vegetation in the desert-loess transitional zone in China and may be able to be used to correctly interpret fossil pollen records from similar areas.

Model-based riverscape genetics: disentangling the roles of local and connectivity factors in shaping spatial genetic patterns of two Amazonian turtles with different dispersal abilities

Genetic patterns are shaped by the interaction of different factors such as distance, barriers, landscape resistance and local environment. The relative importance of these processes may vary for species with different ecological traits. Here we compared two related Amazonian riverine turtle species (Podocnemis erythrocephala and Podocnemis sextuberculata) with distinct dispersal abilities to assess how differently local and connectivity variables influence their genetic patterns. We used a total of 609 genetic samples to estimate mitochondrial (mtDNA) genetic diversity and differentiation for each locality. We applied model selection on models associating genetic diversity to local variables representing hypotheses of climate and primary productivity, water level variation, hunting pressure and downstream increase in genetic diversity. We modeled the relationship of genetic differentiation with connectivity variables representing hypotheses of isolation by distance (IBD), isolation by resistance (IBR) and isolation by barrier (IBB). Model selection for genetic diversity was only important (excluded the null model) for the high-dispersal species (P. sextuberculata), with best models including hypotheses of productivity and hunting pressure. Genetic diversity was higher in more productive sites and in sites with higher concentration of villages (opposed to expected). Although a variable importance testing showed low importance for connectivity models, IBB (Amazon River) and IBR (resistance by current and past climatic suitability and river color) models explained more genetic differentiation turnover than IBD (riverway distance). Models explained a higher percentage of genetic differentiation for the low-dispersal species (P. erythrocephala), with Amazon River as main predictor. We show that, although local variables are often overlooked in riverscape genetics studies, they can influence intrapopulacional genetic diversity of aquatic species, even those with high dispersal ability. By applying a resistance-model framework and by using riverscape genetics factors relevant in basin-wide context, we provide a novel approach to investigate genetic patterns of other aquatic vertebrates in fluvial systems.

Hitchhiking the high seas: Global genomics of rafting crabs.

Population differentiation and diversification depend in large part on the ability and propensity of organisms to successfully disperse. However, our understanding of these processes in organisms with high dispersal ability is biased by the limited genetic resolution offered by traditional genotypic markers. Many neustonic animals disperse not only as pelagic larvae, but also as juveniles and adults while drifting or rafting at the surface of the open ocean. In theory, the heightened dispersal ability of these animals should limit opportunities for species diversification and population differentiation. To test these predictions, we used next‐generation sequencing of genomewide restriction‐site‐associated DNA tags (RADseq) and traditional mitochondrial DNA sequencing, to investigate the species‐level relationships and global population structure of Planes crabs collected from oceanic flotsam and sea turtles. Our results indicate that species diversity in this clade is low—likely three closely related species—with no evidence of cryptic or undescribed species. Moreover, our results indicate weak population differentiation among widely separated aggregations with genetic indices showing only subtle genetic discontinuities across all oceans of the world (RADseq F ST = 0.08–0.16). The results of this study provide unprecedented resolution of the systematics and global biogeography of this group and contribute valuable information to our understanding of how theoretical dispersal potential relates to actual population differentiation and diversification among marine organisms. Moreover, these results demonstrate the limitations of single gene analyses and the value of genomic‐level resolution for estimating contemporary population structure in organisms with large, highly connected populations.

Macroecological and spatial patterns in the distribution of cladocerans in Alpine lakes

An extensive data set of the occurrence of 55 cladoceran species in 432 Alpine lakes was used to document patterns of species richness, assemblage composition and distribution across the Alpine ecoregion in Italy, determining the spatial and macroecological parameters explaining the observed patterns. Moreover, the influence of dispersal, environmental filtering and life cycle strategies in shaping cladoceran alpha and beta-diversity patterns was examined. Only three species where widely distributed in the Alpine lakes, with more than 80 % of the species present in less than 10 % of the lakes. Alpha-diversity ranged from 1 to 13 species, while beta-diversity was almost exclusively due to spatial turnover. Our data suggest that the excess of rarity in these environments was better explained by post-glacial random recolonization patterns, high dispersal ability, peculiar life strategies including the production of diapausing eggs, and compliance of cladocerans to the monopolization hypothesis. Spatial determinants (studied using Moran’s Eigenvector Maps) were important for large scale species distribution patterns, suggesting that dispersal was not a limiting factor, although altitudinal heterogeneity shaped beta-diversity patterns. The altitudinal gradient (together with the associated macroclimatic factors) was the second main determinant of species distribution, followed by the geological setting of the basins. Local factors played only a minor role in explaining cladoceran distribution patterns at the ecoregional scale.

Arthropod communities in fungal fruitbodies are weakly structured by climate and biogeography across European beech forests

AbstractAimThe tinder fungusFomes fomentariusis a pivotal wood decomposer in European beechFagus sylvaticaforests. The fungus, however, has regionally declined due to centuries of logging. To unravel biogeographical drivers of arthropod communities associated with this fungus, we investigated how space, climate and habitat amount structure alpha and beta diversity of arthropod communities in fruitbodies ofF. fomentarius.LocationTemperate zone of Europe.TaxonArthropods.MethodsWe reared arthropods from fruitbodies sampled from 61 sites throughout the range of European beech and identified 13 orders taxonomically or by metabarcoding. We estimated the total number of species occurring in fruitbodies ofF. fomentariusin European beech forests using the Chao2 estimator and determined the relative importance of space, climate and habitat amount by hierarchical partitioning for alpha diversity and generalized dissimilarity models for beta diversity. A subset of fungi samples was sequenced for identification of the fungus’ genetic structure.ResultsThe total number of arthropod species occurring in fruitbodies ofF. fomentariusacross European beech forests was estimated to be 600. Alpha diversity increased with increasing fruitbody biomass; it decreased with increasing longitude, temperature and latitude. Beta diversity was mainly composed by turnover. Patterns of beta diversity were only weakly linked to space and the overall explanatory power was low. We could distinguish two genotypes ofF. fomentarius,which showed no spatial structuring.Main conclusionFomes fomentariushosts a large number of arthropods in European beech forests. The low biogeographical and climatic structure of the communities suggests that fruitbodies represent a habitat that offers similar conditions across large gradients of climate and space, but are characterized by high local variability in community composition and colonized by species with high dispersal ability. For European beech forests, retention of trees withF. fomentariusand promoting its recolonization where it had declined seems a promising conservation strategy.

Multi‐scale oviposition site selection in two mosquito species

1. In organisms characterised by complex life cycles, habitat selection often occurs at multiple spatial scales. For instance, female mosquitoes searching for an appropriate aquatic habitat to oviposit their eggs should also consider the characteristics of the terrestrial landscape in which it is embedded.2. In this study, a field experiment was conducted to test for multi‐scale oviposition site selection in two mosquito species. Artificial pools were placed in two adjacent landscapes, olive plantations and a citrus orchard, mainly differing in their blooming periods and nectar availability. Pools were organised in three pairs: predatory caged fish were present in both pools, in one pool, or in none.3. Early during the season, most of the egg rafts were laid by Culiseta longiareolata females in pools located within the blooming citrus orchard. When blooming shifted to the olive plantation, C. longiareolata become opportunistic. Culex pipiens females appeared later on during the season, when egg rafts of C. longiareolata were scarce, and they exhibited a higher selectivity to the olive plantation, although its blooming ended. In addition, the selectivity of C. pipiens to fish‐free pools was stronger than that of C. longiareolata.4. Culex pipiens was more selective, possibly due to its high dispersal ability, which can lower movement cost and enhance the ability to gather environmental information. A trade‐off among gonotrophic cycles, combined with a shorter breeding season and limited recognition ability of the predatory fish may have reduced C. longiareolata selectivity. These differential oviposition patterns can strongly affect the population and community dynamics of both species.

New data and hypotheses on the invasiveness, habitat selection, and ecological role of the limicolous earthworm Sparganophilus tamesis Benham, 1892

A recent molecular barcode study certified the conspecificity of mutually distant European populations of the limicolous earthworm Sparganophilus tamesis Benham, 1892 with the most widespread species of Sparganophilus in North America, and that all the analysed European worms descend from a recent introduction, probably via one or more point-source events with subsequent dispersion. We present the first records from Belgium and the Atlantic coast of southern France, and further genetic evidence confirming the species’ high dispersal abilities and historical movement within and across European drainage boundaries, as well as its capacity to establish in different types of aquatic ecosystems, including oligotrophic habitats. Experimental evidence suggests that the activity of Sparganophilus combined with that of oxygen-releasing plants, such as Lobelia dortmanna, may enhance the mobilization of refractory N pools within oligotrophic sediments, and, therefore, act as facilitator for both the macrophyte and the microbial communities in the rhizosphere. © 2018 E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, Germany.

The double role of pigmentation and convolute leaves in community assemblage of Amazonian epiphytic Lejeuneaceae

BackgroundEpiphytic bryophyte communities in the Amazon forest show a vertical gradient in species composition along the trunk of the host trees. The investigation of species traits related to this pattern has focused on the physiology of selected taxa with a clear preference for one of the extremes of the gradient. Although some species are indeed only found on the tree base or in the outer canopy, the vertical gradient is composed mainly by the variation in the abundances of species with a broader occurrence along the height zones. Therefore, this study approaches the differences among community assemblages, rather than among species, to test the role of morphological and dispersal traits on the establishment of the vertical gradient in species composition.MethodsA character state matrix was built for 104 species of the family Lejeuneaceae recorded as epiphytes in the Amazonian terra firme forests, and six binary traits supposed to influence species occurrence: dark pigmentation on leaves; ability to convolute leaves when drying; possession of thickened cell walls; reproduction mode (monoicous or dioicous); occurrence of asexual reproduction; and facultative epiphyllous habit. Based on a previous dataset on community composition along the vertical gradient, trait occurrences in random draws of the metacommunity was compared to trait occurrences in field data, in order to detect significant deviations in the different height zones.ResultsFour out of the six traits tested showed significantly higher or lower occurrence in the species composition of canopy and/or understory communities. Traits related to high dispersal ability did not vary much along the vertical gradient; although facultative epiphylls were overrepresented on tree base. Dark pigmentation and convolute leaves were significantly more frequent in the canopy communities, but also significantly less frequent in communities at the base of the tree.DiscussionDark pigmentation and convolute leaves seem to be advantageous for the establishment in the canopy zones. They may, respectively, prevent light damage and allow longer periods of photosynthesis. Interestingly, these traits occur randomly along the trunk, but are wiped out of communities on the tree base. In the relatively deep shade of the first meters of the understory, they possibly hamper net carbon gain, the first by darkening the leaf surface and the second by delaying desiccation—which can be damaging under high temperatures and low light. The fact that production of asexual propagules is not overrepresented in the most dynamic microenvironment along the gradient, the canopy, challenges current views of bryophyte life strategy theory.

Local vs. landscape characteristics differentially shape emerging and circulating assemblages of carabid beetles in agroecosystems

Knowledge of biodiversity in agroecosystems is crucial for understanding ecosystem functioning, but requires accurate sampling methods. Most studies of ground-active arthropods in fields rely on activity-density measurement using pitfall traps. Assemblages locally observed are likely to composed both resident and immigrant species, and that is especially true for arthropods exhibiting high dispersal abilities and/or larval development that is very different from the adults. Using a spatially paired design of emerging traps vs pitfall traps in 10 pairs of organic (OF) and conventional (CF) fields, we quantified how circulating and emerging assemblages of an abundant taxa of mobile and holometabolous insects, carabid beetles, were impacted by different field farming systems and landscape characteristics. Field sampling was carried out during 5 months of 2015 in Brittany (Western France), during which 24,726 individuals belonging to 85 species were captured. Our results revealed that the number of individuals and species of both emerging and circulating assemblages were significantly higher in OF compared to CF, reinforcing the idea that OF provide more suitable conditions for both resident and mobile arthropods. Landscape and local factors had a similar influence on emerging carabid assemblages, whereas local factors were stronger drivers for circulating carabid assemblages. This study highlights the importance of distinguishing resident (emergent) and mobile (circulating) individuals when assessing the differential role of local vs. landscape factors in community assembly. It also reinforces the idea that spatiotemporal movements of predatory arthropods are impacted by spillover from and between croplands, resulting in source-sink dynamics with habitat quality being the major driver of these processes.