Restricted gene flow within and between rapidly diverging Neotropical plant species

Speciation involves the evolution of traits and genetic differences that contribute to reproductive isolation and the cessation of gene flow, and studying closely related species and divergent populations gives insight into how these phenomena proceed. Here, we document patterns of gene flow within and between two members of a rapid Neotropical species radiation, Costus pulverulentus and Costus scaber (Costaceae). These species co‐occur in the tropical rainforest and share pollinators, but are reproductively isolated by a series of prezygotic barriers, some of which show evidence of reinforcement at sympatric sites. Here, we genotype microsatellite markers in plants from eight sites that span the geographical range of both species, including four sympatric sites. We also genotype putative hybrids found at two sympatric sites. We find high levels of genetic isolation among populations within each species and low but detectable levels of introgression between species at sympatric sites. Putative hybrids identified by morphology are consistent with F1 or more advanced hybrids. Our results highlight the effectiveness of prezygotic isolating mechanisms at maintaining species boundaries in young radiations and provide empirical data on levels of gene flow consistent with reinforcement.     

Studies on the Utilization of Hydrocarbons by Microorganisms

In the course of investigation of alicyclic hydrocarbon-utilizing microorganisms, five strains of ethylcyclohexane-utilizing bacteria were isolated from soil samples.

Among those bacteria, the strain S6B1 that was identified as Alcaligenes faecalis, showed the best growth in shaking culture.

The strain S6B1 was found to produce 4-ethylcyclohexanol from ethylcyclohexane.

This substance separated from culture broth was purified and identified to be trans-4-ethylcyclohexanol by the use of NMR.     

Phylogenetic plant community structure along elevation is lineage specific

The trend of closely related taxa to retain similar environmental preferences mediated by inherited traits suggests that several patterns observed at the community scale originate from longer evolutionary processes. While the effects of phylogenetic relatedness have been previously studied within a single genus or family, lineage‐specific effects on the ecological processes governing community assembly have rarely been studied for entire communities or flora. Here, we measured how community phylogenetic structure varies across a wide elevation gradient for plant lineages represented by 35 families, using a co‐occurrence index and net relatedness index (NRI). We propose a framework that analyses each lineage separately and reveals the trend of ecological assembly at tree nodes. We found prevailing phylogenetic clustering for more ancient nodes and overdispersion in more recent tree nodes. Closely related species may thus rapidly evolve new environmental tolerances to radiate into distinct communities, while older lineages likely retain inherent environmental tolerances to occupy communities in similar environments, either through efficient dispersal mechanisms or the exclusion of older lineages with more divergent environmental tolerances. Our study illustrates the importance of disentangling the patterns of community assembly among lineages to better interpret the ecological role of traits. It also sheds light on studies reporting absence of phylogenetic signal, and opens new perspectives on the analysis of niche and trait conservatism across lineages.     

Modelling shifts in agroclimate and crop cultivar response under climate change

This paper aims: (i) to identify at national scale areas where crop yield formation is currently most prone to climate‐induced stresses, (ii) to evaluate how the severity of these stresses is likely to develop in time and space, and (iii) to appraise and quantify the performance of two strategies for adapting crop cultivation to a wide range of (uncertain) climate change projections. To this end we made use of extensive climate, crop, and soil data, and of two modelling tools: N‐AgriCLIM and the WOFOST crop simulation model. N‐AgriCLIM was developed for the automatic generation of indicators describing basic agroclimatic conditions and was applied over the whole of Finland. WOFOST was used to simulate detailed crop responses at four representative locations. N‐AgriCLIM calculations have been performed nationally for 3829 grid boxes at a 10 × 10 km resolution and for 32 climate scenarios. Ranges of projected shifts in indicator values for heat, drought and other crop‐relevant stresses across the scenarios vary widely – so do the spatial patterns of change. Overall, under reference climate the most risk‐prone areas for spring cereals are found in south‐west Finland, shifting to south‐east Finland towards the end of this century. Conditions for grass are likely to improve. WOFOST simulation results suggest that CO₂ fertilization and adjusted sowing combined can lead to small yield increases of current barley cultivars under most climate scenarios on favourable soils, but not under extreme climate scenarios and poor soils. This information can be valuable for appraising alternative adaptation strategies. It facilitates the identification of regions in which climatic changes might be rapid or otherwise notable for crop production, requiring a more detailed evaluation of adaptation measures. The results also suggest that utilizing the diversity of cultivar responses seems beneficial given the high uncertainty in climate change projections.     

Fungal response from oat (Avena sativa) plants and surface residue in relation to soil aggregation and organic carbon

Abstract

The influence of soil fungi on soil organic carbon (OC) from surface residue was tested in outdoor plots in southern Ontario, Canada, 2004. Fungal hyphal length, soil aggregation, OC and light and heavy fractions of organic matter were compared with factors of plant growth (with or without oat [Avena sativa]) and surface residue (no residue, oat straw (low C:N) or corn (Zea mays) stalks (high C:N)) in a factorial arrangement. Significant increases were observed in soil OC from the oat plants, and from corn stalks compared to straw residue, in the growing season with very moist, high OC, sandy soil. In treatments with corn stalk residue, fungal hyphal length was increased with interaction from the oat plants and residue and was positively correlated with the heavy fraction organic matter along with soil OC. Fungal hyphae, plant roots and high C:N residue were all factors in soil OC increases.     

Impact of the invasion of the imported fire ant

The impact of the imported fire ant (IFA) is complex, in large part, because several very different species of “Fire Ants” have invaded and one of these has two forms, all of which are hard to separate by the public, as well as, some investigators not focused on the ant. Each of these different “IFA” species and forms differ in their impact. Further, these ants impact a number of “things” ranging from the environment and wildlife (plants and animals) as well as people, their environment and infrastructure. In addition, they can not only lead to death of living things (including people), but they can destroy many aspects of our environment and infrastructure at the cost of millions of dollars. But there are some beneficial aspects and some people can make many thousands of dollars due to their presence. This is an attempt to look at these issues.     

山西省重点保护野生植物资源及区系特征研究

以《国家重点保护野生植物名录(第一批)》和《山西省重点保护野生植物名录(第一批)》为依据,建立山西省重点保护野生植物名录。共记录57种保护植物,隶属于38科45属（其中国家Ⅰ级保护2种,国家Ⅱ级保护6种,省级保护49种）。分析结果得出,山西省重点保护野生植物在全省的分布不集中,零散分布于全省61个县区境内,且绝大多数物种的分布范围很狭窄。山西省重点保护野生植物区系具有复杂多样、起源古老、孑遗植物和单种属多等特点,科、属植物区系成分以温带分布型占优势,同时也有较明显的热带性质,过渡性特征比较明显,有其独特的地理优势和保护价值。本研究旨在对山西省重点保护野生植物资源现状及区系特征进行初步研究,从而为野生植物资源的保护和合理有效地利用提供科学的理论依据与参考。     

Seed mass,seed number and evolutionary trade-off across geographic distribution: do they explain invasiveness in Eschscholzia californica,central Chile?

Background: Seed mass is a life history trait that is related to invasiveness. Under limiting conditions, a trade-off is observed whereby an increase in seed mass occurs at the expense of seed numbers; if the above trade-off holds across climatic gradients it can provide an opportunity to assess the fitness/invasive potential of exotic plants.

Aims: To examine the variation in the life history traits of Eschscholzia californica populations across climatic gradients and to relate these traits to observed invasiveness.

Methods: We examined 19 populations in Chile. For each population we related seed mass, seed number, the slope of trade-off between seed mass and number and plant density with annual precipitation and mean annual temperature.

Results: Seed number and the coefficient of variation in seed mass were positively correlated with climatic variables. Trade-off was detected in 26% of the populations and no relationship was detected with climatic gradient. Plant density was negatively associated with precipitation.

Conclusions: The results suggest that for E. californica producing seeds with a variety of sizes is an optimal strategy to face geographic heterogeneity and hence to increase its invasiveness. Increased production of seeds at the cool and wet southern limit of the current range of the species does not contribute to an increase in its invasiveness.     

Maintenance and recovery of rare clonal plants: the Case of the twinflower (Linnaea borealis L.)

Summary

Populations of rare clonally spreading species are increasingly being shown to be composed of one or a few genotypes. Clones have potentially unlimited life but two factors, genetic erosion due to random events and increasing accumulation of genetic load in older genotypes, combine to expose them to sexual failure and loss of fertility. Non-breeding clonal populations are at risk of extinction because they lack the ability to adapt or escape from changing environments.

Twinflower (Linnaea borealis L.) has been lost from nearly 50 % of its pre-1970 sites. It is a clonal self-incompatible plant and sexual failure has been reported from Canada, Britain and Scandinavia. Sexual failure is due to high levels of within-clone pollination by flies. Seed set occurs naturally in Scottish populations which have some genetic diversity. A non-breeding population in Scotland has been restored to viability by experimental cross-pollination with pollen from a distant source. Conservation action for this species should therefore be directed to the prevention of loss of habitat and restoration of population viability by translocation of compatible mates.

Translocating plants into extant, but non-breeding, populations are still a matter of debate and are frequently opposed. However, experimental translocations must now be performed to establish whether intervention can secure the long-term survival of rare clonal plants without the constant need for re-introduction.     

Crop presence,but not genetic diversity,impacts on the rare arable plant Valerianella rimosa

Background: Intensive farming affects farmland biodiversity, and some arable plants in particular. Increasing crop genetic diversity can increase crop productivity or resilience and could also benefit rare arable plants.

Aims: We examined whether barley presence, sowing density and genetic diversity impacted the rare plant Valerianella rimosa and explored possible underlying mechanisms.

Methods: In a field study near Dundee, Scotland, we sowed plots of five single barley genotypes, and all five genotypes combined, at three densities; we also had barley-free plots. Valerianella seeds were sown into half of all plots. Measured responses included early-season cover and harvest biomass of barley and common weeds, abiotic parameters (soil moisture, light) and establishment, biomass and seed production by V. rimosa.

Results: Barley presence promoted V. rimosa establishment early in the growing season, but without barley density or genetic diversity effects. By harvest, the impact of barley presence on V. rimosa abundance was lost; there were no effects on Valerianella seed production. Barley negatively impacted common weeds, but V. rimosa did not benefit from any indirect facilitation by barley, being bigger without barley.

Conclusions: Early beneficial effects of barley on V. rimosa abundance appear offset by late-season competition. However, limited impacts of barley on V. rimosa reproductive success, and negative impacts on common weeds, indicate crops might play a role in conservation management of rare arable plants by creating space in the weed community.