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  • 1
    Publication Date: 2019-02-27
    Description: Predictive species distribution models are mostly based on statistical dependence between environmental and distributional data and therefore may fail to account for physiological limits and biological interactions that are fundamental when modelling species distributions under future climate conditions. Here, we developed a state-of-the-art method integrating biological theory with survey and experimental data in a way that allows us to explicitly model both physical tolerance limits of species and inherent natural variability in regional conditions and thereby improve the reliability of species distribution predictions under future climate conditions. By using a macroalga-herbivore association (Fucus vesiculosus - Idotea balthica) as a case study, we illustrated how salinity reduction and temperature increase under future climate conditions may significantly reduce the occurrence and biomass of these important coastal species. Moreover, we showed that the reduction of herbivore occurrence is linked to reduction of their host macroalgae. Spatial predictive modelling and experimental biology have been traditionally seen as separate fields but stronger interlinkages between these disciplines can improve species distribution projections under climate change. Experiments enable qualitative prior knowledge to be defined and identify cause-effect relationships, and thereby better foresee alterations in ecosystem structure and functioning under future climate conditions that are not necessarily seen in projections based on non-causal statistical relationships alone.
    Type: Article , PeerReviewed
    Format: text
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  • 2
    ISSN: 1748-7692
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Detailed knowledge about the history of colonization, population dynamics and behavior greatly enhance evaluation of genetic models of population units and migration rates in spatially structured populations. Here, the genetic uniqueness of harbor seals (Phoca vitulinia) in the eastern Baltic is evaluated in the light of new information on the distribution and abundance of Baltic and eastern North Sea populations during the last 11,000 yr, recent hunting statistics, and population counts. Archaeological records reveal that the Baltic population of harbor seals was founded about 8,000 yr ago. Adjacent populations in the North Sea areas were either small, or went extinct, and became significant only during the last 300 yr. This information generates the hypothesis that the Baltic population has been isolated during the last 8,000 yr, despite the lack of geographical barriers. We show that stochastic effects, isolation, and a documented recent population bottleneck can account for the low observed genetic variation in Baltic harbor seals.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-8477
    Keywords: Atlantic rocky shores ; dispersal ; gene flow ; habitat choice ; migration ; sympatric morphs ; transplant experiment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Local migration patterns may be crucial to gene flow in species of marine gastropods which do not broadcast pelagic larvae. In some species, dispersal over distances of a few metres may influence micro-scale population structures. We investigated the migration pattern in Galician populations of the snail Littorina saxatilis in which populations of contrasting morphologies occupy different tidal levels of the same rocky shore. Two distinct morphs, one at the upper and one at the lower shore, overlap in distribution in a small mid-shore region where hybrids are produced. We documented the distances and directions of migration of both parental morphs and hybrids 1 month after they had been marked and released at different shore levels. When placed at their native shore level, snails migrated less than about 2m and usually in independent directions. This supports the suggestion of a low local gene flow. At an alien shore level, however, the morphs often moved further and more directionally compared with native morphs. These differences may help to keep the two morphs separated at different shore levels. As fitness of an individual is highest in its native habitat, this seems to be an adaptive strategy.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-5117
    Keywords: phylogeny ; electrophoresis ; genetic distance ; Littorina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The evolutionary history of 19 populations of Littorina saxatilis (Olivi) was estimated by four different approaches. Three of these operate upon a population by population matrix of genetic distances: average linkage clustering, and two versions of the Fitch-Margoliash method. The fourth method was a maximum likelihood estimate based on differences in allele frequencies between populations. The study aims to assess how well each method estimates the phylogeny by including seven populations of the closely related species L. arcana Hannaford Ellis. The rationale behind this is that a good estimation technique should be able to separate these two monophyletic taxa. The results show that, by our criteria, the maximum likelihood method yields the best estimate and the unconstrained Fitch-Margoliash technique gives reasonable estimates. Both average-linkage clustering and the Fitch-Margoliash method with evolutionary clock perform less well. We argue that this is expected since both these techniques are based on probably unrealistic assumptions such as the overall rate of evolutionary divergence being homogeneous over phyletic lines.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-5117
    Keywords: prosobranchia ; population differentiation ; shell shape ; Northeastern Atlantic ; principal component analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The morphological variation of Littorina saxatilis and L. neglecta on a microscale (vertical transects down a shore) and on a geographical scale (Northeastern Atlantic) was examined to see if the sampled snails could be consistently separated into two groups on morphological criteria. Size, shell form and shell banding pattern, subopercular pattern and size at maturity were recorded for 21 samples from different shore levels (barnacle zone — usual habitat of L. neglecta, low littoral fringe and high littoral fringe — usual habitat of L. saxatilis) in Iceland, Norway, Sweden, Isle of Man and Wales. A multivariate approach (principal component analysis) was applied to analyse 14 quantitative shell characters. Between-shore variation in shell shape of samples from similar levels was generally larger than within-shore variation of samples from different levels, while size of snails was consistently smaller in barnacle zone compared to littoral fringe samples. The frequency of snails with qualitative characters, used in earlier studies to define L. neglecta, differed between samples from the littoral fringe and the barnacle zone at each site (except at the Swedish site), but the differences between geographical areas were generally larger. The results indicate that snails fitting earlier descriptions of L. neglecta are present in the barnacle zone in Iceland, Norway, Isle of Man and Wales, but that this form is not clearly distinguishable from L. saxatilis. Snails with intermediate shapes were common and, furthermore, the qualitative and the quantitative characters used to define L. neglecta were not closely coupled. No snails of L. neglecta form were found at the Swedish site, yet shape differences over the intertidal gradient were greatest at this site. The extensive morphological variation found in L. saxatilis, between shores and between microhabitats on the same shore, is likely to be due to low gene-flow within the species and a heterogeneous environment. The area over which mating can be random is probably small, thus a subpopulation will behave as a semi-isolate with more or less unique ecological and evolutionary factors influencing its detailed morphology.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-5117
    Keywords: Prosobranchia ; sibling species ; genetic diversity ; electrophoresis ; ecotypes ; population differentiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Genetic variation was compared within- and between-samples of Littorina saxatilis and L. neglecta from five geographic regions of western Europe (Iceland, Norway, Sweden, Isle of Man and Anglesey). The variation at five highly polymorphic enzymes (Aat-1, Pgm-1, Pgi, Mpi and Np) were revealed in samples from eleven vertical transects extending upshore from the barnacle zone to the upper littoral fringe. Both morphological types, L. saxatilis and L. neglecta, were present in all geographic regions except in Sweden. The results of the genetic analyses show that at four of the five loci between 83 and 95% of the between-sample variation was due to differentiation between geographic areas, while only 4% or less was attributable to differentiation between barnacle zone and high littoral fringe samples. An accompanying morphological study revealed that the barnacle zone snails were mostly of L. neglecta type, except in the Swedish locality (where although they were distinct from the upper shore snails they were not in accordance with the description of L. neglecta), and the littoral fringe snails were of L. saxatilis type. The conclusion is therefore that there is more gene flow between L. neglecta and L. saxatilis type snails within the same locality than there is between snails of similar morphological type, but from geographically separated shores. Although we have not examined material from the type locality of L. neglecta, we suggest it to be a junior synonym of L. saxatilis. One locus, Aat-1, was, in contrast to the other polymorphic loci, more differentiated over the vertical transects (68 % of the between sample variation was attributable to differences between barnacle and high littoral fringe samples) than over the different geographic areas (21%). However, two observations indicated selective rather than stochastic differentiation at Aat-1: (1) The same pattern was found independent whether or not L. neglecta was present. (2) The much smaller degree of differentiation at the other polymorphic loci indicated a gene flow which would prevent such a large differentiation at Aat-1 solely by random genetic drift.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-5117
    Keywords: population genetics ; founder effects ; dispersal rate ; Littorina littorea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Belgian coast has no natural rocky sites but a number of man-made constructions are colonized by rocky shore organisms. The rough periwinkle, Littorina saxatilis (Olivi), lacks a planktonic larval stage but is found on most breakwaters along the Belgian coast, a few built as recently as 1986. This indicates a good potential of dispersal along this sandy shallow coast, nearly as good as for the planktonic developer Littorina littorea (L.) which is found on generally the same sites in Belgium. The breakwater populations of L. saxatilis, however, tend to be somewhat less variable (level of heterozygosity about 10% less) than non-Belgian L. saxatilis populations of natural sites. This suggests that the breakwater populations have passed through bottlenecks when founded, but probably restored population sizes fairly rapidly afterwards. No relationship is found between geographic and genetic distances between populations of L. saxatilis.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-5117
    Keywords: reproductive isolation ; mating components ; assortative mating ; sexual selection ; fitness estimate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Galician exposed shore populations of the direct developing periwinkle Littorina saxatilis are strikingly polymorphic, with an ornamented and banded upper shore form and a smooth and unbanded lower shore form. Intermediates between the two pure forms occur in a narrow mid shore zone together with the parental forms. We have previously shown that the two pure forms share the same gene pool but that mating between them is non-random. This is due to a non-random microdistribution in the zone of overlap, and also to assortative mating. In this study we present data which show that intermediate (hybrid) females mate less often than pure females in micropatches dominated by either of the pure forms, but not in micropatches in which the two pure forms are equally common. Thus, sexual fitness in intermediate females depends on the frequency of both pure morphs. Furthermore, sexual selection against intermediate females also varies with the densities of snails within each micro patch. The biological mechanisms which may explain this particular reduction of female hybrid fitness are discussed. Assortative mating between the pure morphs is sometimes almost complete, while both morphs do not mate the intermediates assortatively. In the light of this, sexual selection against intermediate females may contribute considerably to restrict gene flow between the pure forms.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-5117
    Keywords: cross water dispersal ; migration ; Chrysochromulina polylepis bloom ; rafting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Most marine benthic invertebrate species have planktonic larvae, and in species in which juveniles and adults have low vagility a larva is obviously an efficient way of active dispersal. A minority of benthic invertebrate species develop without any pelagic phase at all. A largely unsolved question is how and at what rate do these species disperse. We have addressed this question using the marine littoral snail Littorina saxatilis (Olivi) as an example of a species that completely lacks larval dispersal. In the Koster archipelago (north part of the Swedish west coast), L. saxatilis occupies rocky island habitats of different sizes, from large islands to small intertidal skerries (islets). In 1988 an extremely dense bloom of a toxin-producing flagellate killed more than 99% of this snail species in this area. Populations of larger islands were reduced, often to less than 1%, but were restored over 2–4 yr. In contrast, populations of small intertidal skerries were completely wiped out and thus could not increase by local recruitment. Four years later, however, four of 33 skerries (12%) were successfully recolonized with relatively dense populations, and another five had received a few founder individuals. These results indicate recruitment through founder individuals, and are rough estimates of dispersal rate in a snail species that lacks a pelagic developmental stage.
    Type of Medium: Electronic Resource
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  • 10
    Publication Date: 2019-09-23
    Description: Coastal global oceans are expected to undergo drastic changes driven by climate change and increasing anthropogenic pressures in coming decades. Predicting specific future conditions and assessing the best management strategies to maintain ecosystem integrity and sustainable resource use are difficult, because of multiple interacting pressures, uncertain projections, and a lack of test cases for management. We argue that the Baltic Sea can serve as a time machine to study consequences and mitigation of future coastal perturbations, due to its unique combination of an early history of multistressor disturbance and ecosystem deterioration and early implementation of cross-border environmental management to address these problems. The Baltic Sea also stands out in providing a strong scientific foundation and accessibility to long-term data series that provide a unique opportunity to assess the efficacy of management actions to address the breakdown of ecosystem functions. Trend reversals such as the return of top predators, recovering fish stocks, and reduced input of nutrient and harmful substances could be achieved only by implementing an international, cooperative governance structure transcending its complex multistate policy setting, with integrated management of watershed and sea. The Baltic Sea also demonstrates how rapidly progressing global pressures, particularly warming of Baltic waters and the surrounding catchment area, can offset the efficacy of current management approaches. This situation calls for management that is (i) conservative to provide a buffer against regionally unmanageable global perturbations, (ii) adaptive to react to new management challenges, and, ultimately, (iii) multisectorial and integrative to address conflicts associated with economic trade-offs.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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