Phylogenetic analysis of the Pinnotheridae (Crustacea, Brachyura) based on larval morphology, with emphasis on the Dissodactylus species complex

Comparative larval morphology was used to elucidate phylogenetic relationships within the Pinnotheridae and the Dissodactylus species complex. Within the family, seven zoeal and six megalopal characters suggested two equally parsimonious phylogenetic hypotheses for pinnotherid larvae, both with Ostracotheres tridacnae representing the sister group for the Dissodactylus complex. Results indicated that the genus Pinnotheres is a polyphyletic taxon, and that the traditional subfamilial arrangement comprises paraphyletic taxa within the subfamilies Pinnotherinae and Pinnothereliinae. Certain evidence has suggested that Fabia and Juxtafubia should be excluded from the Pinnotherinae and placed into the Pinnothereliinae. Larval and adult morphology suggested that Pinnotheres politus should be included within Tumidotheres. The phylogenetic analysis within the Dissodactylus complex involved one zoeal and 16 megalopal characters. Results suggested a single phylogenetic hypothesis based on larval morphology. Combining adult morphology with larval evidence resulted in two equally parsimonious phylogenetic hypotheses, one of which agreed with a previously suggested hypothesis based only on adult characters.     

Impact of habitat fragmentation on the genetics of populations in dendritic landscapes

1. The effect of habitat fragmentation on freshwater species has been addressed using brown trout Salmo trutta L. as a model species with a dendritic population structure. 2. Microsatellite loci were employed as molecular markers. Levels of gene flow and population subdivision were determined in more than 1200 brown trout individuals inhabiting four south European rivers with contrasting patterns of fragmentation, defined by the presence of barriers. 3. The genetic units in the four rivers were restricted by artificial barriers, and gene flow among samples within each river was associated with the level of fragmentation of the river. 4. Loss of genetic diversity and dislocation of the dendritic model have been detected in fragmented rivers. These results emphasise the importance of mitigating the impact of dams by constructing passages to restore gene flow along the river, for fish and other migratory species, as well as the need for caution in relation to stocking in isolated areas to avoid problems of inbreeding.     

Two new species of freshwater ostracods from Southern India

Two new species of freshwater ostracods are described from Southern India and their taxonomic validity is discussed.     

Effects of scale on detecting interactions between Coleophora and Eriocrania leaf-miners

Abstract.

• 1 The possibility of interactions between leaf-miners in the genus Eriocrania and Coleophora serratella L. on birch (Betula pendula Ehrh. and B.pubescens Roth.) was studied via: (i) co-occurrence patterns on random samples of leaves; (ii) palatability of Eriocraniidae-mined leaves to C.serratella, in laboratory and field preference tests.
• 2 In the field, C.serratella and Eriocrania spp. fed on common leaves less frequently than expected by chance. This result is consistent with, and could be explained by, the avoidance of mined leaves shown by C.serratella in most of the feeding trials.
• 3 Avoidance was not observed at the between-tree level, i.e. the number of leaves mined by each type of insect was unrelated. However, when tree species was taken into account, an inverse distribution was observed: mine abundance was higher for Eriocrania spp. on B.pubescens, whereas for C.serratella it was higher on B.pendula.
• 4 B.pubescens leaves mined by Eriocrania spp. had consistently higher phenolic contents and were better at precipitating proteins than unmined leaves. These induced chemical changes could explain the reduced preference shown by C.serrate1la for Eriocrania mined leaves.
• 5 We speculate about the evolution of adult host-plant selection shown by these insects in response to potential larval interactions.

     

Characterization and astronomically calibrated age of the first occurrence of Turborotalia frontosa in the Gorrondatxe section, a prospective Lutetian GSSP: implications for the Eocene time scale

The Gorrondatxe section, a prospective Lutetian Global Stratotype Section and Point (GSSP), has recently been used as the master reference section to reassess the correlation between Eocene magnetostratigraphic and calcareous planktonic biostratigraphic scales. However, the exact calibration of some events remained ill defined, as they were thought to be missing in Gorrondatxe due to a fault. The most important missing events were the first occurrence of the planktonic foraminifera Turborotalia frontosa and the C22n/C21r chron boundary. Either might be a reliable correlation criterion for the Ypresian/Lutetian boundary, as both approach the age of the original Lutetian Stratotype. New studies allowed the identification of the former event 9 m above the Gorrondatxe fault, within magnetic polarity Chron C21r and calcareous nannofossil Zone CP12a. Distinctive test features that characterize the most primitive morphotype of T. frontosa are described. Despite the high turbidite content, recurrent pelagic limestone–marl couplets and bundles occur, whose formation was driven by precession and eccentricity astronomical cycles. The first occurrence of T. frontosa was found 27 couplets and 5.5 bundles (60 m) below the first occurrence of the calcareous nannofossil Blackites inflatus , which is dated at 48 Ma. Hence, the age of the first occurrence of T. frontosa is estimated at 48.55 Ma, confirming that it is the most suitable planktonic foraminiferal correlation criterion for the Ypresian/Lutetian boundary. These results show that the stratigraphic interval missing due to the Gorrondatxe fault cannot be greater than a few metres and reinforce the value of this section as a prospective Lutetian GSSP.     

Spatial heterogeneity in soil nutrient supply modulates nutrient and biomass responses to multiple global change drivers in model grassland communities

Changes in the atmospheric concentration of carbon dioxide ([CO₂]), nutrient availability and biotic diversity are three major drivers of the ongoing global change impacting terrestrial ecosystems worldwide. While it is well established that soil nutrient heterogeneity exerts a strong influence on the development of plant individuals and communities, it is virtually unknown how nutrient heterogeneity and global change drivers interact to affect plant performance and ecosystem functioning. We conducted a microcosm experiment to evaluate the effect of simultaneous changes in [CO₂], nutrient heterogeneity (NH), nutrient availability (NA) and species evenness on the biomass and nutrient uptake patterns of assemblages formed by Lolium perenne, Plantago lanceolata and Holcus lanatus. When the nutrients were heterogeneously supplied, assemblages exhibited precise root foraging patterns, and had higher above‐ and belowground biomass (average increases of 32% and 29% for above‐ and belowground biomass, respectively). Nutrient heterogeneity also modulated the effects of NA on biomass production, complementarity in nitrogen uptake and below: aboveground ratio, as well as those of [CO₂] on the nutrient use efficiency at the assemblage level. Our results show that nutrient heterogeneity has the potential to influence the response of plant assemblages to simultaneous changes in [CO₂], nutrient availability and biotic diversity, and suggest that it is an important environmental factor to interpret and assess plant assemblage responses to global change.