Colonization Of New Habitats Research Articles

Tracking temperate fish reveals their relevance for plant seed dispersal

Abstract Seed dispersal is a fundamental process for plant communities, especially now that our changing world demands rapid colonization of new habitats. Long‐distance dispersal is especially important for plant population persistence and range expansions. The contribution of fishes to plant seed dispersal in aquatic ecosystems (ichthyochory) has long been overlooked. Although we know fish disperse seeds, it is largely unknown where, when and how far—especially in temperate regions. Here we studied the potential of fish to disperse seeds locally and over long distances, specifically hypothesizing that (a) dispersal by fish depends on the season, (b) individual fish contribute differently to seed dispersal and (c) water‐regulating structures (barriers) inhibit seed dispersal. We tested our hypotheses by acoustically tracking 71 common carp Cyprinus carpio with 21 hydrophones in a 38‐km long study system for >2 years in the Netherlands. We calculated potential seed dispersal throughout this system by combining nearly 1.5 million location registrations with experimentally assessed retention times of seeds after ingestion (i.e. time between ingestion and egestion). Seed dispersal on local scales was quantitatively most important during summer and autumn, with high dispersal potential in a range of 4 km from the location of seed ingestion. Long‐distance dispersal up to 16 km was possible at low probabilities in spring. In winter, most seeds were egested within two km. Maximum and median dispersal distances varied widely among individuals, emphasizing variation in effectiveness among individual fish for seed dispersal. Less than two per cent of all fish movements reached beyond sluices and weirs, indicating that anthropogenic barriers in freshwater systems strongly reduced the potential of common carp to disperse seeds to these areas. This study shows that common carp can locally disperse plant seeds with high probabilities, and over distances up to 16 km with low probabilities throughout temperate ecosystems. This can contribute to restoration and maintenance of plant community diversity. However, this ecosystem function of fish to plants requires intact fish populations—because not all individual fish contribute equally to dispersal—and unrestricted connectivity throughout aquatic ecosystems. A free Plain Language Summary can be found within the Supporting Information of this article.

Species of the genus Epilobium (Onagraceae) in plant communities in Ukraine

To assess the coenotic peculiarities of species of the genus Epilobium (Onagraceae), in particular their coenotic amplitudes in the syntaxa of vegetation of Ukraine, 986 relevés from literature sources were analyzed. The names of syntaxa are provided in accordance with the Prodromus of the vegetation of Ukraine. Species of the genus Epilobium are widely represented in many plant communities and participate in the formation of natural, semi-natural and ruderal coenoses, where they are often diagnostic or characteristic species of associations, alliances, orders and classes of vegetation, or only present in their floristic composition. Epilobium species are present in 28 classes, which is evidence of their broad coenotic amplitudes and representation in different vegetation types: wetland, grassland, halophytic, forest, shrubs, chasmophytic, alpine, and anthropogenic (synanthropic). The widest coenotic amplitudes were revealed in such species as: E. hirsutum, E. palustre, E. angustifolium, E. parviflorum, E. tetragonum, E. montanum, E. alsinifolium, and E. collinum. According to the range of coenotic amplitude, all species can be subdivided into three groups: hemistenotopic, which occur within one class (E. adenocaulon, E. dodonaei, E. lamyi, E. nutans), hemi-eurytopic (within two or three classes) – E. alpestre, E. roseum, and eurytopic (within more than three classes) – E. alsinifolium, E. angustifolium, E. collinum, E. hirsutum, E. montanum, E. palustre, E. parviflorum, E. tetragonum. As for participation of species in the coenosis, the vast majority of them are assectators, and only a small portion can be temporary edificators (in some groups, at certain successive stages of vegetation development: E. angustifolium). Plants of Epilobium species can reproduce rapidly, both vegetatively and by seeds, which promotes their active colonization of new habitats. However, they usually do not tolerate increased shading and coenotic competition with other plant species, so their strategy is mainly ruderal.

Soil biocrusts reduce seed germination and contribute to the decline in Artemisia ordosica Krasch. shrub populations in the Mu Us Sandy Land of North China

The sand-stabilising, xeric shrub Artemisia ordosica Krasch. has experienced widespread decline decades after being widely distributed through seeding in the Mu Us Sandy Land in China. The role of biocrusts in the decline of A. ordosica populations has received attention but has not been directly confirmed. To clarify the effects of biocrusts on shrub decline, a field study was conducted with different biocrust treatments (bare sand, lichen biocrust, moss biocrust, biocrust removed) in August 2019 in the Mu Us Sandy Land in North China. In each biocrust treatment, the age structure, dynamic indices, and reproductive allocation patterns of the A. ordosica population were determined, in addition to soil characteristics. A separate laboratory study was conducted to determine the effects of soil moisture and nutrients on seed germination. With the development of biocrust, the age structure of A. ordosica populations began to decline, but when the biocrust was removed, A. ordosica seedlings re-established. Soil moisture and nutrient contents were higher under lichen biocrust (earlier stage of biocrust development) and biocrust removal than under moss biocrust (later stage of biocrust development). In response to the adverse conditions under biocrust, A. ordosica increased reproductive output while reducing vegetative growth, thereby increasing the possibility for offspring dispersal and colonisation of new habitats. By contrast, with biocrust removal, A. ordosica reduced reproductive allocation. In addition, with the development of biocrust, soil moisture was reduced, and seed germination was limited. Thus, biocrusts are important in the decline of A. ordosica in sandy lands because of reductions in seed germination, which further suggests that moderate removal of biocrusts to improve seed germination can be key in the sustainable development of sandy land vegetation.

Phenotypic plasticity and the colonization of new habitats: a study of a colonial spider in the Chaco region and the Cerrado

In social animals, group prey capture could facilitate colonization of new areas with low resource availability. Parawixia bistriata is a colonial spider inhabiting seasonal dry forests and mesic habitats in South America. Individuals capture prey as a group, which allows individuals to broaden their foraging niche by incorporating large prey that cannot be subdued in solitary captures. P. bistriata exhibits two behavioural ecotypes a “dry” (plastic) ecotype which modifies individual’s tendency to capture prey in a group depending on food resources and a “wet” (fixed) ecotype, whose tendency to group prey capture is only modulated by the size of the prey but not by prey availability. By reconstructing the range expansion of the species using phylogeographic and species distribution modelling techniques, we indirectly examined whether group prey capture could have helped P. bistriata in colonization of low resource habitats. Based on cytochrome c oxidase subunit I gene genealogy, we found older populations in northern Cerrado in Brazil with more recent populations located further south in Dry and Humid Chaco in Argentina, with the latter being the most derived. Species distribution modelling for each ecotype suggests that suitable habitat for each ecotype started to overlap at some point during the Last Glacial Maximum (21 ky BP). These results suggest that P. bistriata expanded from northern Cerrado south to the Gran Chaco, being able to colonize mesic habitats at a later stage when individuals reached southern territories in the Chaco. This evidence is opposite to the idea that GPC facilitated P. bistriata colonization from mesic to harsher environments. However, plasticity in group prey capture could have been important to allow individuals to establish in mesic habitats by reducing the cost of group capture when under high resource levels.

Saltmarsh seeds in motion: the relative importance of dispersal units and abiotic conditions

Propagule dispersal is fundamental to the colonization of new habitats, metapopulation connectivity, and gene flow and thus enables saltmarsh species to cope with global change. In this study, mesocosm and flume experiments were used to quantify the effects of different dispersal units (i.e. seed, spikelet, inflorescence, and plant fragment-containing seeds) and abiotic conditions on the dispersal processes of 4 globally distributed saltmarsh species: Salicornia europaea, Scirpus maritimus, Spartina anglica, and Elymus athericus. The results showed that (1) moving seawater has a species-specific effect on buoyancy, leading to prolonged floatability of high tidal-flat species E. athericus and reduced floatability of pioneer species; (2) tidal currents increase dispersal speed, whereas wind can have additive or antagonistic effects on current-dominated dispersal speed depending on its direction; (3) wave action reduces dispersal speed, but this effect becomes smaller with increasing wave magnitudes and/or applied co-directional wind; (4) dispersal speed may vary depending on the physical forcing and type and morphology of the dispersal units, but the largest species effect is related to the period in which units remain buoyant; and (5) the dispersal potential of saltmarsh species in wind wave-dominated coastal environments can be ordered as follows: E. athericus > S. maritimus > S. anglica > S. europaea. This study provides valuable guidance for future numerical hydrodynamic models of saltmarsh dispersal and establishment, allowing more accurate prediction of the distributional responses of saltmarsh species to climate change, thereby supporting appropriate management and restoration strategies.

Diversity, structure and demography of coral assemblages on underwater lava flows of different ages at Reunion Island and implications for ecological succession hypotheses

Understanding colonization of new habitats and ecological successions is key to ecosystem conservation. However, studies on primary successions are scarce for reef-building corals, due to the rarity of newly formed substratum and the long-term monitoring efforts required for their long life cycle and slow growth rate. We analysed data describing the diversity, structure and demography of coral assemblages on lava flows of different ages and coral reefs at Reunion Island, to evaluate the strength and mechanisms of succession, and its agreement to the theoretical models. No significant differences were observed between the two habitats for most structure and demographic descriptors. In contrast, species richness and composition differentiated coral reefs from lava flows, but were not related to the age of the lava flow. We observed a strong dominance of Pocillopora colonies, which underline the opportunistic nature of this taxa, with life-history traits advantageous to dominance on primary and secondary successional stages. Although some results argue in favor of the tolerance model of succession, the sequences of primary successions as theorized in other ecosystems were difficult to observe, which is likely due to the high frequency and intensity of disturbances at Reunion, that likely distort or set back the expected successional sequences.

Wing morphological responses to latitude and colonisation in a range expanding butterfly.

Populations undergoing rapid climate-driven range expansion experience distinct selection regimes dominated both by increased dispersal at the leading edges and steep environmental gradients. Characterisation of traits associated with such expansions provides insight into the selection pressures and evolutionary constraints that shape demographic and evolutionary responses. Here we investigate patterns in three components of wing morphology (size, shape, colour) often linked to dispersal ability and thermoregulation, along latitudinal gradients of range expansion in the Speckled Wood butterfly (Pararge aegeria) in Britain (two regions of expansion in England and Scotland). We measured 774 males from 54 sites spanning 799 km with a 10-year mean average temperature gradient of 4 °C. A geometric morphometric method was used to investigate variation in size and shape of forewings and hindwings; colour, pattern, and contrast of the wings were examined using a measure of lightness (inverse degree of melanism). Overall, wing size increased with latitude by ∼2% per 100 km, consistent with Bergmann’s rule. Forewings became more rounded and hindwings more elongated with history of colonisation, possibly reflecting selection for increased dispersal ability. Contrary to thermal melanism expectations, wing colour was lighter where larvae developed at cooler temperatures and unrelated to long-term temperature. Changes in wing spot pattern were also detected. High heterogeneity in variance among sites for all of the traits studied may reflect evolutionary time-lags and genetic drift due to colonisation of new habitats. Our study suggests that temperature-sensitive plastic responses for size and colour interact with selection for dispersal traits (wing size and shape). Whilst the plastic and evolutionary responses may in some cases act antagonistically, the rapid expansion of P. aegeria implies an overall reinforcing effect between these two mechanisms.

Polyandry provides reproductive and genetic benefits in colonising populations

Polyandry, when females mate with more than one male, is theorised to play an important role in successful colonisation of new habitats. In addition to possible benefits from sexual selection, even mild polyandry could facilitate colonisation by protecting against inbreeding and reducing the costs of mating with incompatible or infertile males. Here, we measure the importance of mild polyandry for population viability and reproductive fitness following experimental founder events into a higher‐temperature regime. Using colonisation experiments with the model beetle Tribolium castaneum, in which females can produce offspring for up to 140 days following a single mating, we founded more than 100 replicate populations using single females that had been given the opportunity to mate with either one or two males and then tracked their subsequent population dynamics. Following population viability and fitness across 10 generations, we found that extinction rates were significantly lower in populations founded by females given polyandrous opportunities to mate with two males (9%) compared to populations founded by monogamous females (34%). In addition, populations founded by females that had been provided with opportunities to store sperm from two different males showed double the median productivity following colonisation compared to monogamous‐founded populations. Notably, we identified short‐term and longer‐term benefits to post‐colonisation populations from double‐mating, with results suggesting that polyandry acts to both protect against mating with incompatible males through the founder event, and reduce inbreeding depression as the colonisation proceeds for 10 generations. Our results therefore show that even mild polyandry provides both reproductive and genetic benefits for colonising populations.

Post-glacial establishment of locally adapted fish populations over a steep salinity gradient.

Studies of colonization of new habitats that appear from rapidly changing environments are interesting and highly relevant to our understanding of divergence and speciation. Here, we analyse phenotypic and genetic variation involved in the successful establishment of a marine fish (sand goby, Pomatoschistus minutus) over a steep salinity drop from 35 PSU in the North Sea (NE Atlantic) to two PSU in the inner parts of the post-glacial Baltic Sea. We first show that populations are adapted to local salinity in a key reproductive trait, the proportion of motile sperm. Thereafter, we show that genome variation at 22,190 single nucleotide polymorphisms (SNPs) shows strong differentiation among populations along the gradient. Sequences containing outlier SNPs and transcriptome sequences, mapped to a draft genome, reveal associations with genes with relevant functions for adaptation in this environment but without overall evidence of functional enrichment. The many contigs involved suggest polygenic differentiation. We trace the origin of this differentiation using demographic modelling and find the most likely scenario is that at least part of the genetic differentiation is older than the Baltic Sea and is a result of isolation of two lineages prior to the current contact over the North Sea-Baltic Sea transition zone.

Otolith microchemistry shows natal philopatry of walleye in western Lake Erie

Natal philopatry is important to the structure of fish populations because it can lead to local adaptations among component stocks of a mixed population, reducing the risk of recruitment failure. By contrast, straying between component stocks may bolster declining populations or allow for colonization of new habitat. To examine rates of natal philopatry and straying among western Lake Erie walleye (Sander vitreus) stocks, we used the concentration of strontium [Sr] in otolith cores to determine the natal origin of adults captured at three major spawning sites: the Sandusky (n = 62) and Maumee (n = 55) rivers and the Ohio reef complex (n = 50) during the 2012–2013 spawning seasons. Mean otolith core [Sr] was consistently and significantly higher for individuals captured in the Sandusky River than for those captured in the Maumee River or Ohio reef complex. Although logistic regression indicates that no individuals with a Maumee River or Ohio reef complex origin were captured in the Sandusky River, quadratic discriminant analysis suggests low rates of straying of fish between the Maumee and Sandusky rivers. Our results suggest little straying and high rates of natal philopatry in the Sandusky River walleye stock. Similar rates of natal philopatry may also exist across western Lake Erie walleye stocks, demonstrating a need for stock-specific management.

The role of preadaptation, propagule pressure and competition in the colonization of new habitats

To successfully colonize new habitats, organisms not only need to gain access to it, they also need to cope with the selective pressures imposed by the local biotic and abiotic conditions. The number of immigrants, the preadaptation to the local habitat and the presence of competitors are important factors determining the success of colonization. Here, using two experimental set‐ups, we studied the effect of interspecific competition in combination with propagule pressure and preadaptation on the colonization success of new habitats. Our model system consisted of tomato plants (the novel habitat), the two‐spotted spider mite Tetranychus urticae as our focal species and the red spider mite Tetranychus evansi as a competitor. Our results show that propagule pressure and preadaptation positively affect colonization success. More successful populations reach larger final population sizes either by having higher per capita growth rates (due to preadaptation effects) or by starting a population with a larger number of individuals. Although populations are more successful colonizing non‐competitive environments than competitive ones, propagule pressure and preadaptation counteract the negative effects of competition, promoting colonization success. Our study shows the importance of propagule pressure and preadaptation for successful colonization of new habitats by providing the ability to cope with both the exigencies of new environments and the community context.

High density polyethylene (HDPE) microplastics impair development and swimming activity of Pacific oyster D-larvae, Crassostrea gigas, depending on particle size

Understanding the effects of plastic debris on marine ecosystems is essential in encouraging decision-makers to take action. The present study investigates the effect of a 24 h experimental exposure to high density polyethylene (HDPE) microplastics (MPs) of different sizes (4–6, 11–13 and 20–25 μm) and at three concentrations (0.1, 1 and 10 mg MP.L−1) on the development and locomotor activity of early stages of Pacific oyster, Crassostrea gigas. The bivalve embryo-larval assay (NF ISO 17244, 2015) was used in this study but with additional toxicity criteria: developmental arrests, abnormal D-larvae, maximum speed and swimming trajectory. Copper (Cu), was used as a positive control. Our results show that smaller MPs (4–6 and 11–13 μm) induced higher rates of malformations and developmental arrests than the larger ones (20–25 μm). In addition, a dose-dependent decrease of maximum swimming speed was observed for larvae exposed to MPs of 4–6 and 11–13 μm. On the other hand, there was no significant difference in swimming speed with the largest MPs size tested (20–25 μm). For all three sizes of MPs, there was a decrease in straight-line swimming trajectories, and an increase in circular trajectories. This abnormal swimming behaviour could affect larvae survival as well as colonization of new habitats.

Extreme genetic signatures of local adaptation during Lotus japonicus colonization of Japan

Colonization of new habitats is expected to require genetic adaptations to overcome environmental challenges. Here, we use full genome re-sequencing and extensive common garden experiments to investigate demographic and selective processes associated with colonization of Japan by Lotus japonicus over the past ~20,000 years. Based on patterns of genomic variation, we infer the details of the colonization process where L. japonicus gradually spread from subtropical conditions to much colder climates in northern Japan. We identify genomic regions with extreme genetic differentiation between northern and southern subpopulations and perform population structure-corrected association mapping of phenotypic traits measured in a common garden. Comparing the results of these analyses, we find that signatures of extreme subpopulation differentiation overlap strongly with phenotype association signals for overwintering and flowering time traits. Our results provide evidence that these traits were direct targets of selection during colonization and point to associated candidate genes.

Environmental differences are correlated with the distribution pattern of cytotypes in Veronica subsection Pentasepalae at a broad scale.

The distribution of cytotypes and its potential correlation with environmental variables represent a cornerstone to understanding the origin and maintenance of polyploid lineages. Although many studies have addressed this question in single species at a regional scale, only a few have attempted to decipher this enigma in groups of closely related species at a broad intercontinental geographical scale. Here, we consider approx. 20 species of a diploid-polyploid complex (Veronica subsect. Pentasepalae) of recent and rapid diversification represented in Europe and North Africa to study the frequency and distribution of cytotypes and their relationship to environmental variables. A total of 680 individuals (207 populations) were sampled. Ploidy levels were determined using flow cytometry. Ecological differentiation among cytotypes was tested using climatic and environmental variables related to temperature, precipitation, vegetation and biogeographical region, among others, and by performing univariate and multivariate (constrained principal coordinates analysis) analyses. Four ploidy levels (2x, 4x, 6x and 8x) were found and genome downsizing was observed to occur within the group. Plants of different ploidy level are ecologically differentiated, with hexaploids and octoploids occurring in wetter and colder habitats with a higher seasonality than diploids. A south to north distribution pattern was found, with diploids occupying southern refugial areas and octoploids being more frequent in northern regions of Europe above the permafrost boundary. The distribution of cytotypes can be explained by ecological differentiation, the geographical position of refuge areas during the Quaternary climatic oscillations as well as by ice and permafrost retreat patterns. The Balkan Peninsula constitutes the most important contact zone between cytotypes. This work provides the first comprehensive ploidy screening within V. subsect. Pentasepalae at a broad scale and indicates that polyploidy and genome downsizing might have contributed to the colonization of new habitats in a recently diverged polyploid complex.

Seed dispersal as an ecosystem service by a keystone avian frugivore in New Zealand

ABSTRACTSeed dispersal service is the proportion of plant species dispersed by a given disperser. It is important since seed dispersal enables colonisation of new habitats, and because movement of seeds even short distances away from trees can reduce vulnerability of seeds and seedlings to disease, predation and density-dependent effects that occur in the immediate vicinity of parent trees. In New Zealand, indigenous large-fruited canopy tree species are susceptible to recruitment failure because Hemiphaga novaeseelandiae (kererū; Columbidae) is the only widespread avian frugivore capable of swallowing large fruit and dispersing their seeds, and its survival relies on ongoing predator control. In view of the critical nature of this mutualism, seed dispersal service was assessed by measuring the difference in composition of seeds of indigenous large-fruited canopy tree species that were dispersed by H. novaeseelandiae to under the canopies of co-fruiting large-fruited canopy tree species across the Auckland region in New Zealand. If seed dispersal were effective, seeds of all species should be found under the canopies of all tree species, i.e. low beta diversity of seed rain. Beta diversity was higher than expected at two locations, suggesting incomplete seed dispersal service; this pattern was attributed to interactions between frugivore behaviour and the local distribution of fruit. The third location had lower than expected beta diversity, reflecting dispersal of a complete array of tree species’ seeds to sampling sites, plus long-distance dispersal of nonlocal indigenous species of large seeds. Hemiphaga novaeseelandiae appears to be dispersing an array of species of large seeds between co-fruiting tree species at some Auckland locations. However, incomplete seed dispersal service at two of the locations, together with evidence of low recruitment of some species of seeds, could eventually reduce tree species diversity.

Demographic and life history variation in two sky‐island populations of an endangered alpine lizard

AbstractA species’ life history is a strong determinant of its risk of extinction; traits such as body size, growth rate, age at maturity and fecundity influence population viability and persistence, as well as capacity for dispersal and colonisation of new habitats. Yet, despite the potential for substantial geographic variation in life history, most conservation programmes rely upon the species average rather than information specific to individual populations. We use the Guthega Skink (Liopholis guthega), a threatened alpine endemic lizard restricted to two geographically isolated locations in south‐eastern Australia, as a case study to demonstrate how geographic variation in life history traits may better inform conservation management. Liopholis guthega has a relatively short life span, with only a few years of reproductive activity, inter‐annual variation in reproductive output, and less‐than‐annual reproduction. We show that the Victorian population has a significantly slower growth rate, attains a smaller maximum size, reaches reproductive maturity later, and produces significantly smaller litters, despite no difference in longevity suggesting that it may be more vulnerable to extinction. We, therefore, suggest evaluating genetic rescue from the New South Wales population to improve recruitment and longevity of Victorian L. guthega, ongoing population monitoring in both locations, and a dedicated pest control programme to reduce pressure on this population. Our study has far reaching impacts; primarily demonstrating how knowledge of geographic variation in life history has the potential to improve conservation management of threatened species.

Subsets of NLR genes show differential signatures of adaptation during colonization of new habitats.

Nucleotide binding site, leucine-rich repeat receptors (NLRs) are canonical resistance (R) genes in plants, fungi and animals, functioning as central (helper) and peripheral (sensor) genes in a signalling network. We investigate NLR evolution during the colonization of novel habitats in a model tomato species, Solanum chilense. We used R-gene enrichment sequencing to obtain polymorphism data at NLRs of 140 plants sampled across 14 populations covering the whole species range. We inferred the past demographic history of habitat colonization by resequencing whole genomes from three S.chilense plants from three key populations and performing approximate Bayesian computation using data from the 14 populations. Using these parameters, we simulated the genetic differentiation statistics distribution expected under neutral NLR evolution and identified small subsets of outlier NLRs exhibiting signatures of selection across populations. NLRs under selection between habitats are more often helper genes, whereas those showing signatures of adaptation in single populations are more often sensor-NLRs. Thus, centrality in the NLR network does not constrain NLR evolvability, and new mutations in central genes in the network are key for R-gene adaptation during colonization of different habitats.

Integrating measures of long-distance dispersal into vertebrate conservation planning: scaling relationships and parentage-based dispersal analysis in the koala

Improved knowledge of dispersal parameters across multiple populations is essential for the effective management of species exposed to ongoing threats from habitat loss, fragmentation and climate change. Currently, management decisions are based on incomplete or insufficient knowledge of key dispersal parameters, especially long-distance dispersal, and its role in maintaining metapopulation connectivity, facilitating range shifts under climate change, or enabling the colonization of new habitats. Using a combination of microsatellite-based population genetic analyses, scaling relationships and parentage-based dispersal analysis we investigated levels and patterns of long-distance dispersal in the koala. Using home range size as a scalar predicted spatial variation in maximum dispersal distance amongst regional populations (range 13.4–43.4 km), while parentage-based dispersal analysis showed that long-distance dispersal (> 11.2 km) accounted for 16.7–18.5% of movements in a focal population. Common movement patterns were discerned, despite varying levels of imprecision and bias, that suggest an important role for long-distance dispersal in maintaining metapopulation connectivity. Our results suggest that implementation of a systematic approach to the estimation of dispersal across multiple populations would benefit koala conservation and management. This will require the use of both empirical and simulation studies to quantify and minimize sources of imprecision and bias that can occur including those related to incomplete sampling, the presence of fine-scale spatial genetic structure and areas of localized inbreeding. As limitations associated with partial sampling are likely to remain an inherent feature of large-scale dispersal studies, a large number of loci should be assayed.

New record of the non-indigenous copepod Pseudodiaptomus marinus Sato, 1913 (Calanoida, Pseudodiaptomidae) from the Guadalquivir Estuary (Gulf of Cádiz, SW Spain)

Abstract This paper reports the first ocurrence of the Indo-Pacific copepod Pseudodiaptomus marinus in the Guadalquivir Estuary (Gulf of Cádiz, SW Spain), and provides some data on its morphology. The record is based on hundreds of specimens (which include males, females, and ovigerous females) captured in October 2016 at the mouth of the river, a marine protected area under the Fishing Reserve regulation. This reports confirms the presence of a stable population of P. marinus in the southwest of the Iberian Peninsula, a locality intermediate between the previously recorded distribution areas of northern Europe and the Mediterranean Sea, and thus allows an expansion of the hitherto known geographical distribution and supports, once again, the role that maritime transport plays as a vector in the colonization of new habitats by exotic species.

Assessment of swimming behavior of the Pacific oyster D-larvae (Crassostrea gigas) following exposure to model pollutants.

This study describes an image analysis method that has been used to analyze the swimming behavior of native oyster D-larvae (Crassostrea gigas) from the Arcachon Bay (SW, France). In a second time, this study evaluated the impact of copper and S-metolachlor pollutants on D-larvae swimming activity and the possible relationship between developmental malformations and abnormal swimming behavior. Analyses in wild and cultivated oyster D-larvae were investigated during two breeding-seasons (2014 and 2015) at different sampling sites and dates. In controlled conditions, the average speed of larvae was 144μms-1 and the maximum speed was 297μms-1 while the trajectory is mainly rectilinear. In the presence of environmental concentration of copper or S-metolachlor, no significant difference in maximum or average larval speed was observed compared to the control condition but the percentage of circular trajectory increased significantly while the rectilinear swimming larvae significantly declined. The current study demonstrates that rectilinear trajectories are positively correlated to normal larvae while larvae with shell anomalies are positively correlated to circular trajectories. This abnormal behavior could affect the survival and spread of larvae, and consequently, the recruitment and colonization of new habitats.