Allochrony as a potential driver for reproductive isolation in adaptive radiations of European whitefish ecomorphs

In northern Fennoscandian lakes, monophylogenetic lineages of postglacial fishes are radiating into several adaptive forms, but the speciation process is still at an incipient stage. The speciation process has received increased attention over the years, but the underlying mechanisms and drivers are still debated and poorly understood. European whitefish (Coregonus lavaretus [L.]) is the most abundant fish species in these lakes and has evolved into several ecomorphs adapted to different trophic niches and habitats. Genetic divergence has been observed among these ecomorphs, but the mechanism(s) responsible for the ongoing build-up of reproductive isolation has still to be revealed. As these systems are young in evolutionary time (<10 kyr), prezygotic and postzygotic extrinsic isolation mechanisms are thought to be more likely to contribute to the reproductive isolation than intrinsic isolation mechanisms. We determined the gonadosomatic index (GSI) of three ecomorphs in two replicated lake systems and used GSI as a proxy to investigate the prezygotic isolation mechanism, allochrony, as a driving factor of divergence in this adaptive radiation of whitefish. We found that the three ecomorphs differed in GSI values within and between lakes, suggesting different spawning times of the ecomorphs. We also show that males of one ecomorph had equal onset of maturity as another ecomorph, giving novel insights into the ongoing gene flow observed between ecomorphs. The result supports allochrony as a driver for the divergence process of whitefish ecomorphs, but more evidence is still needed to rule out that the three ecomorphs make use of different spawning grounds.     

Threshold and weighted-distance methods: a combined multiscale approach improves explanatory power of forest carabid beetle abundance in agricultural landscape

Landscape Ecology - To analyze the scales at which landscape structure influences ecological processes, two approaches with different underlying ecological assumptions exist; the usual threshold...     

Synthetic Aperture Radar (SAR) images improve habitat suitability models

Context

The ability to detect ecological networks in landscapes is of utmost importance for managing biodiversity and planning corridors.

Objectives

The objective of this study was to evaluate the information provided by a synthetic aperture radar (SAR) image for landscape connectivity modeling compared to aerial photographs (APs).

Methods

We present a novel method that integrates habitat suitability derived from remote sensing imagery into a connectivity model to explain species abundance. More precisely, we compared how two resistance maps constructed using landscape and/or local metrics derived from AP or SAR imagery yield different connectivity values (based on graph theory), considering hedgerow networks and forest carabid beetle species as a model.

Results

We found that resistance maps using landscape and local metrics derived from SAR imagery improve landscape connectivity measures. The SAR model is the most informative, explaining 58% of the variance in forest carabid beetle abundance. This model calculates resistance values associated with homogeneous patches within hedgerows according to their suitability (canopy cover density and landscape grain) for the model species.

Conclusions

Our approach combines two important methods in landscape ecology: the construction of resistance maps and the use of buffers around sampling points to determine the importance of landscape factors. This study was carried out through an interdisciplinary approach involving remote sensing scientists and landscape ecologists. This study is a step forward in developing landscape metrics from satellites to monitor biodiversity.

     

A report of 7 cases of feline vulval adenocarcinoma

Seven cases of feline vulval adenocarcinoma are reported. Follow-up information was available for 5 cats, and all but 1 of these was euthanized within 2-18 mo of diagnosis (median 9.2 mo) for reoccurrence of local disease (3 cases) and/or clinical signs consistent with metastases (3 cases). There was no relationship between histological features of the tumor and outcome.     

Larval performances and life cycle completion of the Siberian moth, <Emphasis Type="Italic">Dendrolimus sibiricus</Emphasis> (Lepidoptera: Lasiocampidae), on potential host plants in Europe: a laboratory study on potted trees

The Siberian moth, Dendrolimus sibiricus, Tschtv. is the most harmful defoliator of coniferous forests in North Asia. The pest has already spread over the Urals and continues moving westwards. Recently, it has been recommended for quarantine in member countries by European and Mediterranean Plant Protection Organization (EPPO). The performances of the pest on coniferous species planted in Europe were assessed on a range of potted trees corresponding to the spectrum of economically important conifers in the EU: European larch Larix decidua, Norway spruce Picea abies, Scots pine Pinus sylvestris, European black pine Pinus nigra, and the North American species: Douglas fir Pseudotsuga menziesii and grand fir Abies grandis. Larvae showed a potential to survive and complete the development on all these host tree species. Favorable hosts were grand fir, European larch, and Douglas fir that allowed higher survival, better larval development, and as a result, yielded heavier pupae and adult moths with higher longevity. Black pine was a poor host but, however, could still support larval and pupal development. Norway spruce and Scots pine had an intermediate behavior. If accidentally introduced to Europe, the Siberian moth may become especially damaging in forest stands predominated by European larch and by the North American firs. Norway spruce and especially the two-needle pines will be less prone to intensive defoliation by this species. The fact that the pest may damage the range of economically important coniferous species should be taken into account in the pest risk assessment for Europe and also for North America where the Siberian moth occurrence is considered likely.     

Medicinal understory herbaceous species cultivated under different light and soil conditions in maple forests in southern Québec,Canada

Many northern hardwood understory plants have medicinal properties but their cost of production under conventional cultivation practices is fairly high. Therefore wild harvesting continues putting the natural populations at risk. Their cultivation in a forest farming system seems a promising alternative. This study was aimed at assessing the impact of canopy opening and soil fertility on growth and active component production of four medicinal plants: black cohosh (Actaea racemosa), wild ginger (Asarum canadense), blue cohosh (Caulophyllum thalictroides) and bloodroot (Sanguinaria canadensis). Rhizome sections were planted in two sugar maple forests. Mortality and total leaf area were monitored during 3 years, while subplots were harvested at the end of the second year for biomass and active component analyses. Multiple regressions indicated that all species responded more to acidity related elements (pH, Al, Al + H, Fe, Zn) than to soil fertility (Ca, K, Mg, P, C/N, base saturation and cation exchange capacity). This suggests that adjusting the pH by liming could be appropriate. Growth increased with irradiance, except for blue cohosh, indicating that forest openings could also be part of an appropriate forest management plan for their cultivation. While active component concentrations of rhizomes and roots increased in conditions that negatively affected growth, such as low pH, soil fertility or light availability, their total active component content exhibited responses that were similar to those of the growth variables. Thus, it seems that soil and light conditions that favour the growth of these medicinal plants also favour their total yield in active components.     

Evaluation of two surfacing methods on black spruce wood in relation to gluing performance

Surface quality and gluing performance of black spruce samples prepared by peripheral straight-edge knife planing and sanding were studied. Four wavelengths (1.5, 1.9, 3.1, and 6.5 mm) and four rake angles (15°, 20°, 25°, and 30°) were tested for peripheral planing. Three feed speeds (4, 10.5, and 17 m/min) and three grit size sandpapers (80, 100, and 120) were studied for sanding. The resulting surfaces were glued with an isocyanate adhesive and tested to evaluate their gluing performance (shear strength and percent wood failure). Results revealed that planing with a rake angle of 20° and wavelengths of up to 3.1 mm produced wood surfaces with adequate glueline shear strength. Sanding with 80-grit sandpaper produced the best glueline shear strength, regardless of feed speed. After accelerated aging, the loss of gluing performance was lower for the sanded samples compared with that of planed samples. In general, sanding process produced better wood surfaces for bonding with the adhesive studied.     

Dynamics of microcrack propagation in hardwood during heat treatment investigated by synchrotron-based X-ray tomographic microscopy

The process of crack propagation in wood during pyrolysis is strongly linked to heterogeneities in its hierarchical porous structure. Fundamental understanding of this process is necessary for the analysis of the behavior of wood structural elements during fire exposure. Synchrotron-based X-ray tomographic microscopy combined with a recently developed laser-based furnace at the TOMCAT beamline of the Swiss Light Source provides a unique opportunity to study the heat-induced propagation of microcracks in hardwood in situ with high spatial and temporal resolutions. In this study, attention was focused on the 3D microstructure of beech and the interconnectivity between morphology and cracking patterns. It is shown that thermal cracks initiate mainly along the ray cells in hardwood and in the junction of seasonal growth layers. There is a clear indication of increased total porosity of the wood due to charring.     

Testing fertilizer, gypsum, planting season and varieties of wild leek (Allium tricoccum) in forest farming system

Wild leek (Allium tricoccum) is an edible spring ephemeral of the eastern deciduous forests of North America that takes advantage of the short period of high light conditions between snowmelt and canopy closure to accumulate the carbon required to complete its annual growth and seed production. In Québec (Canada), this slow-growing species has been subjected to great harvesting pressure, which forced the provincial government to ban commercial harvest and sales in 1995. An illegal market has since developed and the plant is still under threat. Conservation of existing natural populations might be possible through commercial production of wild leek. To investigate this possibility, we set up plots in four sugar maple forest stands where different organic fertilizer and gypsum (0 or 3,000 kg ha^?1) applications were tested, together with two wild leek varieties, and bulb planting season. The two varieties, tricoccum and burdickii, despite morphological differences, are both suitable for cultivation. Planting bulbs in the spring seems more advantageous than in autumn, but these results will need to be confirmed. Fertilized plants exhibited better growth the year following transplantation than did non-fertilized plants. Belowground:aboveground biomass ratios indicated that plants receiving more fertilizer produced larger bulbs, but leaf size did not differ statistically. According to leaf nutrient analysis, fertilizers would need to be applied each year, whereas gypsum (as a calcium source) can be applied less frequently. Our results indicated a high potential for wild leek as a forest crop, at least when the bulbs are planted.