Adaptive landscape genetics: pitfalls and benefits

Landscape genetics offers a promising framework for assessing the interactions between the environment and adaptive genetic variation in natural populations. A recent workshop held at the University of Neuchatel brought together leading experts in this field to address current insights and future research directions in adaptive landscape genetics. Considerable amounts of genetic and/or environmental data can now be collected, but the forthcoming challenge is to do more with such manna. This requires a markedly better understanding of the genetic variation that is adaptive and prompts for advances in information management together with the development of a balance between theory and data. Moreover, showing the links between landscapes and adaptive genetic variation will ultimately move the field beyond association studies.     

Electric Fencing as a Measure to Reduce Moose-Vehicle Collisions

Abstract: We tested the effectiveness of electric fences to reduce moose (Alces alces)-vehicle collisions in 2 fenced sectors (5 km and 10 km) using weekly track surveys and Global Positioning System telemetry. Number of moose tracks along highways decreased by approximately 80% following fence installation. Only 30% (16/53) of moose tracks observed on the road side of the fence were left by moose that crossed an operational fence; moose mostly entered the fenced corridor through openings (e.g., secondary roads) or at fence extremities. Electric fences also prevented 78% (7/9) of collared moose from crossing the highway in fenced sectors. Fences were less effective during occasional power failures. We suggest that circuit breakers should be used to prevent power failures and that there should be no opening along the fence line unless anti-ungulate structures are used.     

Live or let live: life-history decisions of the breeding female Monteiro's Hornbill Tockus monteiri

Life-history theory maintains that long-lived species such as hornbills (Bucerotiformes) maximize lifetime fecundity by ensuring adult survival, rather than investing in current reproductive output. Unusually, female Tockus hornbills are sealed into the nest cavity during breeding, placing a large burden on the male who feeds her and the nestlings for up to 9 weeks. Early departure to help feed young may improve nestling survival, but could reduce female survival if moult is incomplete. We investigated whether departure time of the female Monteiro's Hornbill Tockus monteiri is more strongly related to measures of female fitness or juvenile condition. Departure was independent of nestling development and growth, instead depending on female state. At departure, variability in condition between females was smaller than at any other stage, implying a strong stabilizing selection on optimal female departure condition. Similarly, moult showed signs of being completed, and variability in the state of moult between females was lowest at departure. Both predictions were met in favour of the hypothesis that Monteiro's Hornbills would base the timing of their departure from the nest on maximizing their own survival. Thus, as predicted, future reproductive potential takes precedence over current reproductive output in a trade-off decision in this species.     

Killickia (Lamiaceae): a new genus from KwaZulu-Natal, South Africa

The genus Killickia is described to accommodate the South African endemic species formerly placed in Micromeria sect. Hesperothymus . Morphological data, as well as results from unpublished phylogenetic studies support its separation from the genera Micromeria and Clinopodium . A new species Killickia lutea Bräuchler is described and three new combinations are made. Killickia is characterised as comprising solitary- or few-flowered cymes, a campanulate to subcampanulate (obconical) calyx with similar teeth, a corolla tube with two pubescent ridges and nutlets with scattered minute hairs. A thickened marginal vein in the leaves as typical for Micromeria is absent. As currently understood all species are restricted to the Drakensberg mountains and KwaZulu-Natal Midlands in eastern South Africa. A key to the species, brief notes on anatomy and ecology are provided.  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 157 , 575–586.     

Clonality and recombination in the arctic plant Saxifraga cernua

The circumarctic clonal plant Saxifraga cernua reproduces efficiently via bulbils, largely depends on insects for pollination and appears to set seed very rarely. However, high levels of genotypic variation observed at small spatial scales in the arctic archipelago of Svalbard have been taken as evidence of occasional sexual reproduction. Here we assess the relative contributions of mutation and recombination to random amplified polymorphic DNA variation in four populations in East Greenland and re-analyse the Svalbard data. Greater variation due to recombination was predicted in Greenland than in Svalbard, because the higher summer temperatures and longer growing season likely increase the chances for sexual reproduction. Although we observed higher levels of genotypic diversity in Greenland than in Svalbard, matrix incompatibility and linkage disequilibrium measures provided no evidence of more sexuality, suggesting differences in glacial/postglacial history. The genetic structure and spatial distribution of clones suggest that clonal migration may increase variability in local populations, which is consistent with frequent large-scale migration in this species inferred from a circumarctic analysis of chloroplast DNA haplotypes. We conclude that a combination of somatic mutations and sexual reproduction has contributed to the observed patterns of genotypic diversity in the Greenland and Svalbard populations of S. cernua , and that sexual reproduction is important in maintaining genotypic diversity, despite the rarity of observations of seed setting.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 152 , 209–217.     

Coleoid beaks from the Nusplingen Lithographic Limestone (Upper Kimmeridgian, SW Germany)

Over twenty specimens of coleoid beaks were recovered from the Nusplingen Lithographic Limestone (Upper Jurassic, Late Kimmeridgian, Beckeri Zone, Ulmense Subzone; SW Germany). Based on their morphology, four forms of lower beaks and three forms of upper beaks can be distinguished among the finds. Two gladii of Trachyteuthis hastiformis are associated with a complete beak and hence enable taxonomic assignment of two beak forms. In one of the two specimens, the beaks are still articulated. A third specimen shows another form of upper and lower beak on one slab, which is tentatively interpreted as the beak elements of Plesioteuthis prisca. The largest type of upper beak probably belongs to Leptotheuthis based on its scarcity and size. The remaining two forms are of uncertain taxonomic affiliation. The lower beak of Trachyteuthis resembles that of Recent Octopus and thus suggests a close phylogenetic relation to the Octopoda, as the lower beak of Vampyroteuthis has a different morphology. These originally partially chitinous structures were discovered in the Fossillagerstätte of Nusplingen because the bituminous sediments still contain a significant portion of the original organic matter. This might be the case because of a low permeability of the respective strata. Otherwise, without the color contrast, these delicate structures would hardly be discernible against the carbonate matrix.     

Methane emission from Siberian arctic polygonal tundra: eddy covariance measurements and modeling

Eddy covariance measurements of methane flux were carried out in an arctic tundra landscape in the central Lena River Delta at 72°N. The measurements covered the seasonal course of mid‐summer to early winter in 2003 and early spring to mid‐summer in 2004, including the periods of spring thaw and autumnal freeze back. The study site is characterized by very cold and deep permafrost and a continental climate with a mean annual air temperature of ?14.7 °C. The surface is characterized by wet polygonal tundra, with a micro‐relief consisting of raised moderately dry sites, depressed wet sites, polygonal ponds, and lakes. We found relatively low fluxes of typically 30 mg CH₄ m^?2 day^?1 during mid‐summer and identified soil temperature and near‐surface atmospheric turbulence as the factors controlling methane emission. The influence of atmospheric turbulence was attributed to the high coverage of open water surfaces in the tundra. The soil thaw depth and water table position were found to have no clear effect on methane fluxes. The excess emission during spring thaw was estimated to be about 3% of the total flux measured during June–October. Winter emissions were modeled based on the functional relationships found in the measured data. The annual methane emission was estimated to be 3.15 g m^?2. This is low compared with values reported for similar ecosystems. Reason for this were thought to be the very low permafrost temperature in the study region, the sandy soil texture and low bio‐availability of nutrients in the soils, and the high surface coverage of moist to dry micro‐sites. The methane emission accounted for about 14% of the annual ecosystem carbon balance. Considering the global warming potential of methane, the methane emission turned the tundra into an effective greenhouse gas source.     

In deep shade, elevated CO2 increases the vigor of tropical climbing plants

Climbing plants have profound influences on tropical forest dynamics and may take particular advantage from atmospheric CO₂ enrichment, thus potentially enhancing tree turnover. Here we test the effect of a four‐step CO₂‐enrichment on growth of three typical Yucatan (Mexico) climbers, across two low photon flux densities, representing typical understory situations. In pairs of two, species of Gonolobus (Asclepiadaceae), Ceratophytum (Bignoniaceae) and Thinouia (Sapindaceae) were grown on Yucatan forest soil in growth cabinets, which simulated the diurnal climate variation. Biomass increased non‐linearly in response to CO₂ enrichment from 280 (preindustrial) to 420 ppm and 560 ppm, but then (700 ppm) leveled off. The relative effect of CO₂‐enrichment between the two lower (280–420 ppm) CO₂ concentrations was 63% at low light (LL == 42 µmol m^2?2 s^2?1), compared to 37% at high light (HL = 87 µmol m^2?2 s^2?1). This overall response of species pairs was the combined effect of linear and non‐linear responses of the individual species across CO₂ treatments. Plant biomass was 61% larger in HL compared to LL. The species‐specific response depended on the neighbor, a species grew with h, irrespective of plant size. Stem length increased, but not consistently across species and light conditions. Specific stem length (SSL, length per dry mass) declined non‐linearly in all three species as CO₂ concentration increased (more pronounced at LL than at HL). SLA (leaf area per unit leaf dry mass) became lower as CO₂ concentration increased (more pronounced in HL). Enhanced vigor of climbers under elevated CO₂ as documented here may accelerate tropical forest dynamics and lead to greater abundance of early succesional tree species. This could reduce forest carbon stocking in the long run.     

Effects of experimental warming of air,soil and permafrost on carbon balance in Alaskan tundra

The carbon (C) storage capacity of northern latitude ecosystems may diminish as warming air temperatures increase permafrost thaw and stimulate decomposition of previously frozen soil organic C. However, warming may also enhance plant growth so that photosynthetic carbon dioxide (CO₂) uptake may, in part, offset respiratory losses. To determine the effects of air and soil warming on CO₂ exchange in tundra, we established an ecosystem warming experiment – the Carbon in Permafrost Experimental Heating Research (CiPEHR) project – in the northern foothills of the Alaska Range in Interior Alaska. We used snow fences coupled with spring snow removal to increase deep soil temperatures and thaw depth (winter warming) and open‐top chambers to increase growing season air temperatures (summer warming). Winter warming increased soil temperature (integrated 5–40 cm depth) by 1.5 °C, which resulted in a 10% increase in growing season thaw depth. Surprisingly, the additional 2 kg of thawed soil C m^?2 in the winter warming plots did not result in significant changes in cumulative growing season respiration, which may have been inhibited by soil saturation at the base of the active layer. In contrast to the limited effects on growing‐season C dynamics, winter warming caused drastic changes in winter respiration and altered the annual C balance of this ecosystem by doubling the net loss of CO₂ to the atmosphere. While most changes to the abiotic environment at CiPEHR were driven by winter warming, summer warming effects on plant and soil processes resulted in 20% increases in both gross primary productivity and growing season ecosystem respiration and significantly altered the age and sources of CO₂ respired from this ecosystem. These results demonstrate the vulnerability of organic C stored in near surface permafrost to increasing temperatures and the strong potential for warming tundra to serve as a positive feedback to global climate change.