根际微生物群落功能与调控的研究进展

根际微生物群落是随植物长期进化及地球生境变迁而形成的动态微生物系统。随着多组学技术的不断发展，人们对根际微生物群落结构与功能的研究日益深入。根际微生物群落中的功能微生物类群，如植物促生细菌、植物促生真菌等，通过与植物建立紧密的物质、能量与信息联系，参与植物激素合成、难溶营养物解离、生物固氮、微生物拮抗、生长因子供应等系列生物学过程，从而提高植物营养物质吸收与抗逆能力，为植物的健康和高效生长提供重要保障。这些微生物中的某些成员已被开发成微生物刺激剂，广泛应用于作物增产抗逆与农田地力提升。近年来，多学科的交叉融合为根际微生物群落结构-功能-调控策略的交互式研究提供新的机遇，推动了基于合成生物学与材料科学技术的合成微生物组的发展。尤其是在核心微生物互作方面，人工蛋白创制、磁性组装、生物炭强化等策略能够增强核心微生物与目标植物之间的物理连接作用，大幅提高合成微生物组的工作效率和稳定性，从而有效驱动作物增产增收，提高污染修复效率。因此，根际微生物群落结构、功能与调控的深入研究，必将为绿色农业发展提供不竭动力。     

A typology of sloping and mountainous olive plantation systems to address natural resources management

Olive plantation systems occur in a wide variety throughout the Mediterranean, especially in sloping and mountainous areas. Recent drivers of change, including the widespread introduction of mechanisation, increased use of (chemical) inputs and (drip)irrigation have considerably added to this diversity. The various systems have very different resource use patterns and environmental and social performances. This article attempts to grasp these differences and to link systems characteristics to options for natural resources management in the spirit of contemporary agricultural policies that seek to promote a more sustainable agriculture. Cluster analysis was employed to classify 28 olive plantation systems distinguished by regional typologies developed for six study areas: Trás‐os‐Montes (Portugal), Córdoba and Granada/Jaén (both in Spain), Haffouz (Tunisia), Basilicata/Salerno (Italy) and West‐Crete (Greece). Six types of olive plantation systems resulted: (a) very extensive, (b) traditional extensive, (c) semi‐intensive low input, (d) semi‐intensive high input, (b) intensive and (e) organic. Natural resources management options to address soil erosion, low biodiversity, wildfire risk and excessive water use are explored for each of these systems. In the discussion, it becomes evident that an important quality for a typology lies in its capacity to differentiate likely future development pathways. If options are known, policy‐makers can make choices as to what the desired pathway is and what instruments to design to facilitate it.     

Seamounts: identity crisis or split personality?

At present, researchers propose that over 14,000 seamounts exist and, like their terrestrial analogues, function like islands. In addition, seamounts are described as oases, biodiversity hotspots, and lush coral/sponge gardens. Here I discuss the extent to which these tenets regarding seamounts may be inappropriate, suffer from a lack of support, and be over-generalizations of a broad range of environmental types encountered on seamounts. Ultimately, for seamount science to progress, we need to challenge our conventional wisdom on these habitats and the extent to which all seamounts function in a similar manner.
     

The influence of light and temperature on the germination of two Ugandan medicinal trees

For reasons of the problems of establishment of some Ugandan trees in certain environments, we investigated the influence of temperature and light on germination and seedling growth of two locally threatened medicinal trees, Hallea rubrostipulata and Sarcocephalus latifolius, to facilitate their establishment. Field and controlled laboratory experiments were carried out to investigate the species germination requirements and seedling growth. Both species needed light to germinate. Hallea rubrostipulata had a temperature optimum of 25°C with 79% germination, while for S. latifolius, the total germination after 28 days was close to 60% at temperatures from 20 to 35°C. Seedlings of S. latifolius survived well at 35°C, while those of H. rubrostipulata died at this high temperature. Conversely, seedling of S. latifolius died at the low temperature of 15°C. However, in field experiment S. latifolius failed to germinate in the available degraded environments, probably because of predation and because the soil is not able to retain water long enough to support seedling growth. We, therefore, conclude that in this part of Uganda, nursery assistance is needed to establish healthy populations of Sarcocephalus and many other endangered trees.     

Contribution of native bees and Africanized honey bees (Hymenoptera:Apoidea) to Solanaceae crop pollination in tropical México

In the tropics the contribution of bees as pollinators of important economic indigenous crops remains largely undocumented. We studied the diversity of bee species visiting indigenous tomato (Solanum lycopersicon) and habanero pepper (Capsicum chinense) in subtropical Yucatán, México. The contribution of two native bees, Exomalopsis (E) and Augochloropsis (AG) was compared with that of the introduced Africanized Apis mellífera (HB) for pollinating unvisited flowers in both crops. Apis mellífera and stingless bees were dominant in habanero pepper but solitary bee species were important visitors of tomato. In spite of both crops being autogamic, there was a significant contribution of native bees for pollination of both tomato and habanero pepper. The comparison of fruit weight, number of seeds, and a pollination index based on the latter showed that E and AG were more effective pollinators compared to HB in both crops (ca. Spear’s index of ca. 0.7 vs. 0.35 respectively). In tomato, a further evaluation of the contribution to pollination provided by the three bee species was made using the rate of visits to flowers. Although E and AG were the most efficient pollinators at single flower visits in tomato, none of the three species (including HB) were able to provide single visits to all flowers per unit time to the crop. Our results underline the importance of maintaining diverse assemblages and abundant populations of bee species that can synergically contribute to the productivity of tomato and hot pepper in the Neotropics.     

Priority areas of intraspecific diversity: Larzac, a global hotspot for facultative paedomorphosis in amphibians

Although the designation of biodiversity hotspots is a valuable tool to improve conservation efforts, this is a concept primarily based on species diversity. In consequence, another component of biodiversity, adaptive variation, is often ignored in conservation and to my knowledge no attempt has been made to identify hotspots of remarkable intraspecific patterns. My aim was to focus on the process of facultative paedomorphosis (i.e. the retention of larval traits such as gills in adult variants), a rare developmental pathway. One hundred and seventy-four ponds were inventoried in Larzac (France) to determine the distribution and abundance of paedomorphic palmate newts Triturus helveticus (Amphibia, Caudata) and to compare these results with the current distribution of paedomorphs in this and other species. During this study, paedomorphic newts were found in 46 ponds, 32 of which were described here for the first time. Seventy-nine per cent of known paedomorphic populations of this species were found there, whereas this area covers only 0.5% of the distribution area of the species. This represents the highest known density of facultatively paedomorphic populations, all species being considered. Because these populations face a high threat of disappearance, Larzac should be designated as an intraspecific biodiversity hotspot in order to protect adaptive intraspecific variation. Future conservation-oriented work should focus not only on species distributions but also on phenotypically diverse but spatially localized variation.     

An analysis of nucleotide and amino acid variability in the barcode region of cytochrome c oxidase I (cox1) in fishes

The 655 bp cytochrome c oxidase subunit I barcode region of single specimens of 388 species of fishes (four Holocephali, 61 Elasmobranchii and 323 Actinopterygii) was examined. All but two (Urolophus cruciatus and Urolophus sufflavus) showed different cox1 nucleotide sequences (99.5% species discrimination); the two that could not be resolved are suspected to hybridize. Most of the power of cox1 nucleotide sequence analysis for species identification comes from the degenerate nature of the genetic code and the highly variable nature of the third codon position of amino acids. Variation at the third codon position is bimodally distributed, and the more variable mode is dominated by amino acids with four or six codons, while the less variable mode is dominated by amino acids with two codons. The ratio of nonsynonymous to synomymous changes is much less than one, indicating that this gene is subject to strong purifying selection. Consequently, cox1 amino acid sequence diversity is much less than nucleotide sequence diversity and has very poor species resolution power. Fourteen of the 16 amino acid residues recognized as having important functions in the region of cox1 sequenced were completely conserved over all 388 species (and the bovine cox1 sequence), with one fish species varying at one of these sites, and three fish at another site. No significant differences in amino acid conservation were observed between residues in helices, strands and turns. Patterns of nucleotide and amino acid variability were very similar between elasmobranchs and actinopterygians.     

Using Inquiry and Tree-Thinking to “March Through the Animal Phyla”: Teaching Introductory Comparative Biology in an Evolutionary Context

Biodiversity was originally taught in our Introductory Organismal Biology course at Michigan State University (LB144; freshman/sophomore majors) by rote memorization of isolated facts about organisms. When we moved to an inquiry-based laboratory framework to improve pedagogy, an unfortunate and unforeseen result was the loss of much of our study of biodiversity. In this paper, we describe the restructuring of LB144 to restore the study of biodiversity and organismal groups while retaining the benefits of an inquiry-based approach. The curricular intervention was accomplished through the creation and implementation of a four-week Comparative Biology laboratory stream. During this stream, student research teams recorded and organized observations that they made on a range of organisms and analyzed their data in a phylogenetic framework. During the stream, our students worked through a set of exercises designed to help them learn how to read, interpret, and manipulate phylogenetic trees. We placed particular emphasis on the concept that phylogenetic trees are hypotheses of relationship that can be tested with scientific data. This incorporation of phylogenies and phylogenetic analysis, or “tree-thinking,” into our students’ work provided an explicit synthetic evolutionary framework for their comparative biodiversity studies. End-of-stream products included a team phylogenetic analysis exercise and an individual comparative biology oral presentation.