Search results for "MAR"

Riella heliospora (Riellaceae) a new monoicous species of Riella subgenus Trabutiella from California

2012

14 páginas, 8 figuras, 1 tabla.

Taxonomic revision of Riella subgenus Trabutiella (Riellaceae, Sphaerocarpales)

2014

The genus Riella (Riellaceae, Sphaerocarpales) includes some 24 species of thalloid aquatic liverworts with unique morphological and ecological features among hepatics. These include the development of sporophytes enclosed within involucres and growing submerged in seasonal fresh or brackish water ponds. Riella subgenus Trabutiella includes species with winged involucres. Seven taxa have been described, however, four to five taxa have been recognized at a time depending on authors. In this study we have conducted a morphological revision of the species of this subgenus, based on 59 traits measured under light and Scanning Electron Microscopy analyses and that were the subject of statistical…

Variability in δ13C values between individual Daphnia ephippia: Implications for palaeo-studies

2018

The stable carbon isotope ratio (δ13 C value) of Daphnia spp. resting egg shells (ephippia) provides information on past changes in Daphnia diet. Measurements are typically performed on samples of _20 ephippia, which obscures the range of values associated with individual ephippia. Using a recently developed laser ablation-based technique, we perform multiple δ13 C analyses on individual ephippia, which show a high degree of reproducibility (standard deviations 0.1e0.5‰). We further measured δ13 C values of 13 ephippia from surface sediments of three Swiss lakes. In the well-oxygenated lake with low methane concentrations, δ13 C values are close to values typical for algae (_31.4‰) and the …

Ultraviolet radiation exposure of a high arctic lake in Svalbard during the Holocene

2014

Long-term fluctuations in lake-water optical properties were examined using a Holocene sediment sequence and multi-proxy palaeolimnological approach in Lake Einstaken, Nordaustlandet, Svalbard. UV-absorbance of sedimentary cladoceran remains provided information on underwater UV exposure and changes in lake-catchment coupling processes were inferred from sediment geochemistry. In addition, aquatic community succession was used as an indicator for lake-water bio-optical properties and a Holocene record of sun activity (sunspots) was utilized to evaluate long-term solar forcing. The results indicated that the UV-absorbance of cladoceran remains was highest (i.e. maximum UV-induced pigmentatio…

DNA barcoding the phyllosoma of Scyllarides squammosus (H. Milne Edwards, 1837) (Decapoda: Achelata: Scyllaridae)

2016

Scyllarides has the largest number of species with commercial importance within the Scyllaridae family. As for other achelate lobsters, however, little is known of the unique long-lived planktonic phyllosoma stages of any of these tropical and temperate species. Recently, a large and diverse collection of Scyllaridae phyllosoma, compiled from cruises along the Coral Sea and spanning several years, has been analysed. Molecular evidence from DNA-barcoding and phylogenetic analyses is provided here on the identity of S. squammosus phyllosoma larvae, including stages that were previously undescribed or poorly known. As a consequence, the growth and morphological changes that occur during the mi…

Another alien bug in Europe: the first case of transcontinental introduction <br />of the Asiatic burrower bug Macroscytus subaeneus (Dallas, 1…

2019

The Oriental burrower bug Macroscytus subaeneus (Dallas, 1851) (Hemiptera: Heteroptera: Cydnidae: Cydninae), presently known only from single localities in Flores (Indonesia), the Philippines and Thailand, is recorded from the United Kingdom (hereafter U.K.). A single female specimen was collected on the semi-rural edge of Bath city by a Starling (Sturnus vulgaris L.) and taken to its nest from which it was retrieved during 2015. The specimen is illustrated and its diagnostic characters are provided. We hypothesize that this specimen could have been imported with a shipping container from Thailand. 

The invasive Asparagopsis taxiformis hosts a low diverse and less trophic structured molluscan assemblage compared with the native Ericaria brachycar…

2021

Abstract Invasive seaweeds threaten biodiversity and socio-economics values of worldwide marine ecosystems. Understanding to what extent invasive seaweeds can modify local biodiversity is one of the main priorities in conservation ecology. We compared the molluscan assemblage of the invasive Asparagopsis taxiformis with that of the native Ericaria brachycarpa and explore if variation in the molluscan assemblage diversity was related to the substrate attributes (biomass, and thallus, canopy, and interstitial volumes) of the algae. Results showed that A. taxiformis harboured lower diversity and trophic structure of the molluscan assemblage compared to E. brachycarpa. Biomass was the variable …

2016

Ecological communities are structured by competitive, predatory, mutualistic and parasitic interactions combined with chance events. Separating deterministic from stochastic processes is possible, but finding statistical evidence for specific biological interactions is challenging. We attempt to solve this problem for ant communities nesting in epiphytic bird’s nest ferns (Asplenium nidus) in Borneo’s lowland rainforest. By recording the frequencies with which each and every single ant species occurred together, we were able to test statistically for patterns associated with interspecific competition. We found evidence for competition, but the resulting co-occurrence pattern was the opposit…

Classification of the European marsh vegetation (Phragmito‐Magnocaricetea) to the association level

2020

Aims: To create a comprehensive, consistent and unequivocal phytosociological classification of European marsh vegetation of the class Phragmito-Magnocaricetea. Location: Europe. Methods: We applied the Cocktail method to a European data set of 249, 800 vegetation plots. We identified the main purposes and attributes on which to base the classification, defined assignment rules for vegetation plots, and prepared formal definitions for all the associations, alliances and orders of the class Phragmito-Magnocaricetea using formal logic. Each formula consists of the combination of “functional species groups”, cover values of individual species, and in the case of high-rank syntaxa also of “disc…

Reconstruction of Atlantic herring ( Clupea harengus ) recruitment in the North Sea for the past 455 years based on the δ 13 C from annual shell incr…

2019

Understanding the recruitment variability of the Atlantic herring North Sea stock remains a key objective of stock assessment and management. Although many efforts have been undertaken linking climatic and stock dynamic factors to herring recruitment, no major attempt has been made to estimate recruitment levels before the 20th century. Here, we present a novel annually resolved, absolutely dated herring recruitment reconstruction, derived from stable carbon isotope geochemistry (δ¹³C), from ocean quahog shells from the Fladen Ground (northern North Sea). Our age model is based on a growth increment chronology obtained from fourteen shells. Ten of these were micromilled at annual resolution…