Experimental climate change impacts on Baltic coastal wetland plant communities.

Coastal wetlands provide a range of important ecosystem services, yet they are under threat from a range of stressors including climate change. This is predominantly as a result of alterations to the hydroregime and associated edaphic factors. We used a three-year mesocosm experiment to assess changes in coastal plant community composition for three plant communities in response to altered water level and salinity scenarios. Species richness and abundance were calculated by year and abundance was plotted using rank abundance curves. The permutational multivariate analysis of variance with Bray-Curtis dissimilarity was used to examine differences among treatments in plant community composition. A Non-metric Multi-dimensional Scaling analysis (NMDS) was used to visualize the responses of communities to treatments by year. Results showed that all three plant communities responded differently to altered water levels and salinity. Species richness and abundance increased significantly in an Open Pioneer plant community while Lower and Upper Shore plant communities showed less change. Species abundances changed in all plant communities with shifts in species composition significantly influenced by temporal effects and treatment. The observed responses to experimentally altered conditions highlight the need for conservation of these important ecosystems in the face of predicted climate change, since these habitats are important for wading birds and livestock grazing.

Extrapolation of in situ data from 1-km squares to adjacent squares using remote sensed imagery and airborne lidar data for the assessment of habitat diversity and extent.

Habitat surveillance and subsequent monitoring at a national level is usually carried out by recording data from in situ sample sites located according to predefined strata. This paper describes the application of remote sensing to the extension of such field data recorded in 1-km squares to adjacent squares, in order to increase sample number without further field visits. Habitats were mapped in eight central squares in northeast Estonia in 2010 using a standardized recording procedure. Around one of the squares, a special study site was established which consisted of the central square and eight surrounding squares. A Landsat-7 Enhanced Thematic Mapper Plus (ETM+) image was used for correlation with in situ data. An airborne light detection and ranging (lidar) vegetation height map was also included in the classification. A series of tests were carried out by including the lidar data and contrasting analytical techniques, which are described in detail in the paper. Training accuracy in the central square varied from 75 to 100 %. In the extrapolation procedure to the surrounding squares, accuracy varied from 53.1 to 63.1 %, which improved by 10 % with the inclusion of lidar data. The reasons for this relatively low classification accuracy were mainly inherent variability in the spectral signatures of habitats but also differences between the dates of imagery acquisition and field sampling. Improvements could therefore be made by better synchronization of the field survey and image acquisition as well as by dividing general habitat categories (GHCs) into units which are more likely to have similar spectral signatures. However, the increase in the number of sample kilometre squares compensates for the loss of accuracy in the measurements of individual squares. The methodology can be applied in other studies as the procedures used are readily available.

Peripheral glia direct axon guidance across the CNS/PNS transition zone.

CNS glia have integral roles in directing axon migration of both vertebrates and insects. In contrast, very little is known about the roles of PNS glia in axonal pathfinding. In vertebrates and Drosophila, anatomical evidence shows that peripheral glia prefigure the transition zones through which axons migrate into and out of the CNS. Therefore, peripheral glia could guide axons at the transition zone. We used the Drosophila model system to test this hypothesis by ablating peripheral glia early in embryonic neurodevelopment via targeted overexpression of cell death genes grim and ced-3. The effects of peripheral glial loss on sensory and motor neuron development were analyzed. Motor axons initially exit the CNS in abnormal patterns in the absence of peripheral glia. However, they must use other cues within the periphery to find their correct target muscles since early pathfinding errors are largely overcome. When peripheral glia are lost, sensory axons show disrupted migration as they travel centrally. This is not a result of motor neuron defects, as determined by motor/sensory double-labeling experiments. We conclude that peripheral glia prefigure the CNS/PNS transition zone and guide axons as they traverse this region.

Developmental dynamics of peripheral glia in Drosophila melanogaster.

To study the roles of peripheral glia in nervous system development, a thorough characterization of wild type glial development must first be performed. We present a developmental profile of peripheral glia in Drosophila melanogaster that includes glial genesis, developmental morphology, the establishment of transient cellular contacts, migration patterns, and the extent of nerve wrapping in the embryonic and larval stages. In early embryonic development, immature peripheral glia that are born in the CNS seem to be intermediate targets for neurites that are migrating into the periphery. During migration to the PNS, peripheral glia follow the routes of pioneer neurons. The glia preferentially adhere to sensory axonal projections, extending cytoplasmic processes along them such that by the end of embryogenesis peripheral glial coverage of the sensory system is complete. In contrast, significant lengths of motor branch termini are unsheathed in the mature embryo. During larval stages however, peripheral glia further extend and elaborate their cytoplasmic processes until they often reach to the neuromuscular junction. Throughout the embryonic and larval developmental stages, we have also observed a number of similarities of peripheral glia to vertebrate Schwann cells and astrocytes. Peripheral glia seem to have dynamic and diverse roles and their similarities to vertebrate glia suggest that Drosophila may serve as a powerful tool for analysis of glial roles in PNS development in the future.

Conversion of lacZ enhancer trap lines to GAL4 lines using targeted transposition in Drosophila melanogaster.

Since the development of the enhancer trap technique, many large libraries of nuclear localized lacZ P-element stocks have been generated. These lines can lend themselves to the molecular and biological characterization of new genes. However they are not as useful for the study of development of cellular morphologies. With the advent of the GAL4 expression system, enhancer traps have a far greater potential for utility in biological studies. Yet generation of GAL4 lines by standard random mobilization has been reported to have a low efficiency. To avoid this problem we have employed targeted transposition to generate glial-specific GAL4 lines for the study of glial cellular development. Targeted transposition is the precise exchange of one P element for another. We report the successful and complete replacement of two glial enhancer trap P[lacZ, ry+] elements with the P[GAL4, w+] element. The frequencies of transposition to the target loci were 1.3% and 0.4%. We have thus found it more efficient to generate GAL4 lines from preexisting P-element lines than to obtain tissue-specific expression of GAL4 by random P-element mobilization. It is likely that similar screens can be performed to convert many other P-element lines to the GAL4 system.