245,865 research outputs found
Efficient sampling methodologies for lake littoral invertebrates in compliance with the European Water Framework Directive
Lake shores are characterised by a high natural variability, which is increasingly threatened by a multitude of anthropogenic disturbances including morphological alterations to the littoral zone. The European Water Framework Directive (EU WFD) calls for the assessment of lake ecological status by monitoring biological quality elements including benthic macroinvertebrates. To identify cost- and time-efficient sampling strategies for routine lake monitoring, we sampled littoral invertebrates in 32 lakes located in different geographical regions in Europe. We compared the efficiency of two sampling methodologies, defined as habitat-specific and pooled composite sampling protocols. Benthic samples were collected from unmodified and morphologically altered shorelines. Variability within macroinvertebrate communities did not differ significantly between sampling protocols across alteration types, lake types and geographical regions. Community composition showed no significant differences between field composite samples and artificially generated composite samples, and correlation coefficients between macroinvertebrate metrics calculated with both methods and a predefined morphological stressor index were similar. We conclude that proportional composite sampling represents a time- and cost-efficient method for routine lake monitoring as requested under the EU WFD, and may be applied across various European geographical regions
A multi-gene phylogeny of Lactifluus (Basidiomycota, Russulales) translated into a new infrageneric classification of the genus
Infrageneric relations of the genetically diverse milkcap genus Lactifluus (Russulales, Basidiomycota) are poorly known. Currently used classification systems still largely reflect the traditional, mainly morphological, characters used for infrageneric delimitations of milkcaps. Increased sampling, combined with small-scale molecular studies, show that this genus is underexplored and in need of revision. For this study, we assembled an extensive dataset of the genus Lactifluus, comprising 80 % of all known species and 30 % of the type collections. To unravel the infrageneric relationships within this genus, we combined a multi-gene molecular phylogeny, based on nuclear ITS, LSU, RPB2 and RPB1, with a morphological study, focussing on five important characteristics (fruit body type, presence of a secondary velum, colour reaction of the latex/context, pileipellis type and presence of true cystidia). Lactifluus comprises four supported subgenera, each containing several supported clades. With extensive sampling, ten new clades and at least 17 new species were discovered, which highlight the high diversity in this genus. The traditional infrageneric classification is only partly maintained and nomenclatural changes are proposed. Our morphological study shows that the five featured characteristics are important at different evolutionary levels, but further characteristics need to be studied to find morphological support for each clade. This study paves the way for a more detailed investigation of biogeographical history and character evolution within Lactifluus
Morphological filter for lossless image subsampling
We present a morphological filter for lossless image subsampling for a given downsampling-upsampling strategy. This filter is applied in a multiresolution decomposition and results in a more efficient scheme for image coding purposes than other lossy sampling schemes. Its main advantage is a greatly reduced computational load compared to multiresolution schemes performed with linear filters.Peer ReviewedPostprint (published version
HyperSpectral Imaging based approach for monitoring of micro-plastics from marine environment
The possibility to develop a sensor based procedure in order to monitor plastic presence in the marine environment was explored in this work. More in detail, this study was addressed to detect and to recognize different types of microplastics coming from sampling in different sea areas adopting a new approach, based on HyperSpectral Imaging (HSI) sensors. Moreover, a morphological and morphometrical particle characterization was carried by digital image processing. Morphological and morphometrical parameters, combined with hyperspectral imaging information, give a full characterization of each investigated particle, concurring to explain all the transportation, alteration and degradation phenomena suffered by each different polymer particle.
Obtained results can represent an important starting point to develop, implement and set up monitor strategies to characterize marine microplastics. Moreover, the procedure developed in this work is fast, not expensive and reliable, making its utilization very profitable
Relative impacts of morphological alteration to shorelines and eutrophication on littoral macroinvertebrates in Mediterranean lakes
Development of effective methods for assessing the ecological status of lakes based on littoral benthic fauna has been hampered by the lack of quantitative data on the relative impacts of key pressures on the
benthic community. We used variance partitioning at 126 sites belonging to 14 natural Mediterranean lakes to analyze the pure and shared effects of eutrophication, morphological alterations, microhabitat type, lake morphometry and geographic position on the littoral macroinvertebrate community. The spatial arrangement of the sampling sites was responsible for 9.1% of the total variance in littoral benthic community composition, lake morphometry accounted for 4.3% of variation, and microhabitat type accounted for 3.9%. Communities appeared to be affected primarily by morphological alterations to lake shorelines, and their impact was 2.5 times as important as that of eutrophication. The structure of littoral benthic communities was governed by processes acting at several spatial scales from region to lake scale. Thus, several pressures and the various spatial scales at which these act should be taken into account when implementing methods of assessing lake ecological condition based on littoral benthic invertebrates. Region-specific methods for subalpine and volcanic lakes might enhance the validity of assessment of results of morphological alterations and improve management of those water resources
Bayesian total evidence dating reveals the recent crown radiation of penguins
The total-evidence approach to divergence-time dating uses molecular and
morphological data from extant and fossil species to infer phylogenetic
relationships, species divergence times, and macroevolutionary parameters in a
single coherent framework. Current model-based implementations of this approach
lack an appropriate model for the tree describing the diversification and
fossilization process and can produce estimates that lead to erroneous
conclusions. We address this shortcoming by providing a total-evidence method
implemented in a Bayesian framework. This approach uses a mechanistic tree
prior to describe the underlying diversification process that generated the
tree of extant and fossil taxa. Previous attempts to apply the total-evidence
approach have used tree priors that do not account for the possibility that
fossil samples may be direct ancestors of other samples. The fossilized
birth-death (FBD) process explicitly models the diversification, fossilization,
and sampling processes and naturally allows for sampled ancestors. This model
was recently applied to estimate divergence times based on molecular data and
fossil occurrence dates. We incorporate the FBD model and a model of
morphological trait evolution into a Bayesian total-evidence approach to dating
species phylogenies. We apply this method to extant and fossil penguins and
show that the modern penguins radiated much more recently than has been
previously estimated, with the basal divergence in the crown clade occurring at
~12.7 Ma and most splits leading to extant species occurring in the last 2
million years. Our results demonstrate that including stem-fossil diversity can
greatly improve the estimates of the divergence times of crown taxa. The method
is available in BEAST2 (v. 2.4) www.beast2.org with packages SA (v. at least
1.1.4) and morph-models (v. at least 1.0.4).Comment: 50 pages, 6 figure
Bayesian phylogenetic estimation of fossil ages
Recent advances have allowed for both morphological fossil evidence and
molecular sequences to be integrated into a single combined inference of
divergence dates under the rule of Bayesian probability. In particular the
fossilized birth-death tree prior and the Lewis-Mk model of discrete
morphological evolution allow for the estimation of both divergence times and
phylogenetic relationships between fossil and extant taxa. We exploit this
statistical framework to investigate the internal consistency of these models
by producing phylogenetic estimates of the age of each fossil in turn, within
two rich and well-characterized data sets of fossil and extant species
(penguins and canids). We find that the estimation accuracy of fossil ages is
generally high with credible intervals seldom excluding the true age and median
relative error in the two data sets of 5.7% and 13.2% respectively. The median
relative standard error (RSD) was 9.2% and 7.2% respectively, suggesting good
precision, although with some outliers. In fact in the two data sets we analyze
the phylogenetic estimates of fossil age is on average < 2 My from the midpoint
age of the geological strata from which it was excavated. The high level of
internal consistency found in our analyses suggests that the Bayesian
statistical model employed is an adequate fit for both the geological and
morphological data, and provides evidence from real data that the framework
used can accurately model the evolution of discrete morphological traits coded
from fossil and extant taxa. We anticipate that this approach will have diverse
applications beyond divergence time dating, including dating fossils that are
temporally unconstrained, testing of the "morphological clock", and for
uncovering potential model misspecification and/or data errors when
controversial phylogenetic hypotheses are obtained based on combined divergence
dating analyses.Comment: 28 pages, 8 figure
Morphological types and seasonal variation in eggs of zooplankton species from bottom sediments in Bahia Blanca Estuary, Argentina
Resting egg production is a survival mechanism in zooplankton species against adverse environmental conditions. Egg accumulation in the upper layer of the bottom sediments is fundamental to the resurgence of the populations of these species when conditions become more favourable. Rotifers, such as Synchaeta sp. and planktonic copepods such as Acartia tonsa and Eurytemora americana are commonly found in BahĂa Blanca Estuary and they produce resting eggs. We studied eggs isolated from samples of bottom sediments obtained from two sites located within the inner part of BahĂa Blanca Estuary (Cuatreros Port and Ing. White Port). The aims of our work were to describe the morphological types of eggs found in bottom sediments; to try to identify to which species they belong; to corroborate the identity of some of them by means of incubations; and to determine either the spatial or seasonal presence of morphological types according to the sampling site. Sediment samples were collected from Cuatreros Port on a monthly basis from January to December 2003 and samples from Ing. White Port were collected from the area close to the industrial zone only in April 2004. All samples were treated following the sugar flotation method of OnbĂ©. The eggs were observed under stereomicroscope and light microscope. Besides, incubation experiments with eggs were sometimes carried out. Five morphological types of eggs (type A, B, C, D and E) were found in the sediments from Cuatreros Port whereas three types of eggs were found at Ing. White Port (F, G and H). Of the 8 morphological types of eggs found in this study, only those of the rotifer Synchaeta sp. in Cuatreros Port and the copepod A. tonsa in the two sampling sites were confirmed to be respectively diapausal and “delayed -hatching”. As regards the seasonal variation of the eggs found in the sediments from Cuatreros Port and the active forms of the populations of Synchaeta sp. and A. tonsa, our study confirms the presence of eggs in the sediment either in periods of time during which no active forms have been previously reported in the plankton or in periods of time during which only some active forms have been reported at very low densities. Concerning the spatial variation at Ing.White Port, the differences in the presence of eggs across the sampling areas may be due to sediment modifications produced by anthropic impact, where industrial effluents are discharged.Fil: Diodato, Soledad Lorena. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - BahĂa Blanca. Instituto Argentino de OceanografĂa. Universidad Nacional del Sur. Instituto Argentino de OceanografĂa; ArgentinaFil: Berasategui, Anabela Anhi. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - BahĂa Blanca. Instituto Argentino de OceanografĂa. Universidad Nacional del Sur. Instituto Argentino de OceanografĂa; ArgentinaFil: Hoffmeyer, Monica Susana. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - BahĂa Blanca. Instituto Argentino de OceanografĂa. Universidad Nacional del Sur. Instituto Argentino de OceanografĂa; Argentina. Universidad TecnolĂłgica Nacional; Argentin
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