The mating system was examined in two annual populations of eelgrass (Zostera marina), a marine angiosperm displaying subaqueous pollination. Multilocus genotyping using microsatellite DNA markers ...allowed the assessment of the pollen source based on single progeny as units of observation. Outcrossing was detectable by the presence of non‐maternal alleles at one or more of the loci. In outcrossing cases, three microsatellite alleles were present in unripe seeds, consisting of both maternal alleles and the paternal allele composing the triploid primary endosperm. In ripe seeds, only the diploid embryonal genotype was amplifiable by PCR. Two intertidal populations situated in the German Wadden Sea were almost entirely outcrossing (t ± SE 0.96 ± 0.03, N=60 and 0.97 ± 0.029, N=37). Because of the high polymorphism displayed by the eight chosen microsatellites, representing a total of 69 and 76 alleles, the likelihood of erroneously inferring selfing was small (α=0.0026 and 0.0007). In order to study the correlation of paternity, the coefficient of relatedness was determined within sibships. Relatedness (r ± SE) was calculated as 0.357 ± 0.059 and 0.343 ± 0.037, indicating multiple paternities within inflorescences. Small amounts of tissue (≤0.1 mg) such as the developing seeds of recently fertilized ovules, were sufficient for PCR‐amplification. Hence, PCR‐based methods, such as multilocus microsatellite genotyping, allow the detection of pollen origin early in the development of progeny. They will be useful to distinguish postfertilization processes such as selective abortion and germination from other prefertilization determinants of plant mating systems.
We examined the spatial distribution of genotypes in a perennial population of eelgrass, Zostera marina L., at two spatial scales. We mapped and sampled 80 ramets in a subtidal area of 20 × 80 m, and ...an additional 15 ramets in two 1-m2 sub-quadrats. Ramets were genotyped for seven polymorphic microsatellite loci. Among a total number of 54 genotypes detected, 12 occurred more than once. The ramets of ten of these genotypes occurred in clusters and represented genets based on their expected multi-locus genotype frequencies. The size distribution of genets was uneven with estimated ramet numbers ranging from 2 to 5000. Whereas some areas displayed a high genet diversity, which may indicate past disturbances, large genets (≥10 m2) predominated in other locations of the sampled plot. Spatial heterogeneity in clone distribution was also obvious at the smaller sampling scale (15 ramets sampled within 1 m2) where the clonal diversity (genets identified/ramets sampled) was 0.24 in one quadrat, and 0.077 in the other. Ramets belonging to the largest clone were maximally 17 m apart, which corresponds to a genet age of 67 yr based on annual rhizome growth rates. We conclude that the spatial arrangement of clones in seagrasses allows inferences about the past demography and the disturbance regime at a given site which may prove useful for coastal zone management of ecologically valuable seagrass meadows.
In marine invertebrates multiple modes of development, or poecilogony, may occur in a single species. However, after close examination, many of such putative cases turned out to be sibling species. A ...case in point may be the cosmopolitan orbiniid polychaete Scoloplos armiger, which inhabits marine shallow sediments. In addition to the well-known direct, holobenthic development from egg cocoons, pelagic larvae have also been described. Our culture experiments revealed a spatially segregated source of the two developmental modes. All females of an intertidal population produced egg cocoons and no pelagic larvae. All but 2 out of 15 females of an adjacent subtidal population produced pelagic larvae and no egg cocoons. Based on these results we performed a molecular genetic analysis (RAPD-PCR) on three intertidal and four subtidal populations in the North Sea. Selected samples from all sites were analysed also by the AFLP method. We found significantly higher genetic diversity within subtidal than within intertidal populations. This is consistent with a wider dispersal by pelagic larvae and a smaller effective population size when development is holobenthic. Total genetic divergence is not related to distance but to the intertidal/subtidal division. We suggest that S. armiger actually represents two sibling species.
Nutrient enrichment of marine sediments or the water column has been used to study plant nutrient limitation and its cascading effects on community structure. Here we develop methodological ...recommendations for in situ enrichment. We review 18 published enrichment methods. Nutrient concentrations varied through time and among sites, with sediment depth, distance from the source, fertilizer type and load. Combining available data, we could predict an increase in sediment porewater phosphate (r super(2) = 0.48) but not ammonium (r super(2) = 0.07) concentrations in a multiple regression model. In three comparative field experiments we applied a coated slow-release fertilizer in the sediment and the water column and followed nutrient concentrations over time. We recommend coated fertilizer pellets, because they provide gradual nutrient release, allow for realistic nutrient gradients, and even application but we emphasize that nutrient concentrations need to be monitored through time.
Quantifying cortisol concentration in hair is a non-invasive biomarker of long-term hypothalamic-pituitary-adrenal (HPA) activation, and thus can provide important information on laboratory animal ...health. Marmosets (Callithrix jacchus) and capuchins (Cebus apella) are New World primates increasingly used in biomedical and neuroscience research, yet published hair cortisol concentrations for these species are limited. Review of the existing published hair cortisol values from marmosets reveals highly discrepant values and the use of variable techniques for hair collection, processing, and cortisol extraction. In this investigation we utilized a well-established, standardized protocol to extract and quantify cortisol from marmoset (n = 12) and capuchin (n = 4) hair. Shaved hair samples were collected from the upper thigh during scheduled exams and analyzed via methanol extraction and enzyme immunoassay. In marmosets, hair cortisol concentration ranged from 2,710 to 6,267 pg/mg and averaged 4,070 ± 304 pg/mg. In capuchins, hair cortisol concentration ranged from 621 to 2,089 pg/mg and averaged 1,092 ± 338 pg/mg. Hair cortisol concentration was significantly different between marmosets and capuchins, with marmosets having higher concentrations than capuchins. The incorporation of hair cortisol analysis into research protocols provides a non-invasive measure of HPA axis activity over time, which offers insight into animal health. Utilization of standard protocols across laboratories is essential to obtaining valid measurements and allowing for valuable future cross-species comparisons.
Many functionally hermaphroditic plants have evolved mechanisms to reduce interference between the sex functions and to optimize reproductive output. In addition to physical mechanisms such as the ...spatial (herkogamy) and temporal (dichogamy) separation of male and female functions, plasticity in sex expression by means of mate‐recognition (flexible mating) could be important in plants with variable access to cross‐pollen. This applies particularly to clonal plants because of their modular growth form. We experimentally tested for the effects of pollen source and vegetative neighbourhood on instantaneous sex ratio and seed production in the self‐compatible clonal marine angiosperm Zostera marina L. To this end, we exposed the (monoecious) flowering shoots to self and cross‐pollen and to neighbourhoods of their own and a mix of foreign vegetative shoots. Flowering shoots that had been exposed to cross‐pollen showed (1) a significantly lower female/male ratio at peak flowering, evidence for mate‐recognition, and (2) a significantly higher seed set by the end of the season. Both effects were independent of the genetic composition of their vegetative neighbourhood. The results suggest that Z. marina maintains a cryptic self‐incompatibility system not previously described for angiosperms with sub‐aqueous pollination. In Z. marina, and possibly other self‐compatible clonal plant species, mate‐recognition could be a means of increasing the out‐crossing probability for flowering shoots with central positions within their clone.
We perform a systematic study of the electron transport properties of
δ
-doped phosphorus layers in silicon as a function of encapsulation thickness. We find that as the encapsulation thickness is ...reduced from 24 to 0
nm, the carrier density decreases, dropping off rapidly below 8
nm encapsulation. This translates to a corresponding reduction in the mobility as the ionized dopants are not screened as effectively at low densities. We observe good transport through the
δ
-doped layers down to 4
nm encapsulation. However layers with 2.5
nm encapsulation or less were prohibitively resistive.
Communities and their functioning are jointly shaped by ecological and evolutionary processes that manifest in diversity shifts of their component species and genotypes. How both processes contribute ...to community functional change over time is rarely studied. We here repeatedly quantified eco‐evolutionary contributions to CO2‐driven total abundance and mean cell size changes after short‐, mid‐, and longer‐term (80, 168, and > 168 d, respectively) in experimental phytoplankton communities. While the CO2‐driven changes in total abundance and mean size in the short‐ and mid‐term could be predominantly attributed to ecological shifts, the relative contribution of evolution increased. Over the longer‐term, the CO2‐effect and underlying eco‐evolutionary changes disappeared, while total abundance increased, and mean size decreased significantly independently of CO2. The latter could be presumably attributed to CO2‐independent genotype selection which fed back to species composition. In conclusion, ecological changes largely dominated the regulation of environmentally driven phytoplankton functional shifts at first. However, evolutionary changes gained importance with time, and can ultimately feedback on species composition, and thus must be considered when predicting phytoplankton change.
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.
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