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SummaryIntercropping is a farming practice involving two or more crop species, or genotypes, growing together and coexisting for a time. On the fringes of modern intensive agriculture, intercropping is important in many subsistence or low-input/resource-limited agricultural systems. By allowing genuine yield gains without increased inputs, or greater stability of yield with decreased inputs, intercropping could be one route to delivering 'sustainable intensification'. We discuss how recent knowledge from agronomy, plant physiology and ecology can be combined with the aim of improving intercropping systems. Recent advances in agronomy and plant physiology include better understanding of the mechanisms of interactions between crop genotypes and speciesfor example, enhanced resource availability through niche complementarity. Ecological advances include better understanding of the context-dependency of interactions, the mechanisms behind disease and pest avoidance, the links between above-and below-ground systems, and the role of microtopographic variation in coexistence. This improved understanding can guide approaches for improving intercropping systems, including breeding crops for intercropping. Although such advances can help to improve intercropping systems, we suggest that other topics also need addressing. These include better assessment of the wider benefits of intercropping in terms of multiple ecosystem services, collaboration with agricultural engineering, and more effective interdisciplinary research.

Summary• Knowledge of the diversity of arbuscular mycorrhizal fungi (AMF) in natural ecosystems is a major bottleneck in mycorrhizal ecology. Here, we aimed to apply 454 sequencing -providing a new level of descriptive power -to assess the AMF diversity in a boreonemoral forest.• 454 sequencing reads of the small subunit ribosomal RNA (SSU rRNA) gene of Glomeromycota were assigned to sequence groups by BLAST searches against a custom-made annotated sequence database.• We detected 47 AMF taxa in the roots of 10 plant species in a 10 × 10 m plot, which is almost the same as the number of plant species in the whole studied forest. There was a significant difference between AMF communities in the roots of forest specialist plant species and in the roots of habitat generalist plant species. Forest plant species hosted 22 specialist AMF taxa, and the generalist plants shared all but one AMF taxon with forest plants, including globally distributed generalist fungi. These AMF taxa that have been globally recorded only in forest ecosystems were significantly over-represented in the roots of forest plant species.• Our findings suggest that partner specificity in AM symbiosis may occur at the level of ecological groups, rather than at the species level, of both plant and fungal partners.

Arbuscular mycorrhizal (AM) fungi are biotrophic symbionts colonizing about two-thirds of land plant species and found in all ecosystems. They are of major importance in plant nutrient supply and their diversity is suggested to be an important determinant of plant community composition. The diversity of the AM fungal community composition in the roots of two plant species (Agrostis capillaris and Trifolium repens) that co-occurred in the same grassland ecosystem was characterized using molecular techniques. We analysed the small subunit (SSU) ribosomal RNA gene amplified from a total root DNA extract using AM fungal-specific primers. A total of 2001 cloned fragments from 47 root samples obtained on four dates were analysed by restriction fragment length polymorphism, and 121 of them were sequenced. The diversity found was high: a total of 24 different phylotypes (groups of phylogenetically related sequences) colonized the roots of the two host species. Phylogenetic analyses demonstrate that 19 of these phylotypes belonged to the Glomaceae, three to the Acaulosporaceae and two to the Gigasporaceae. Our study reveals clearly that the AM fungal community colonizing T. repens differed from that colonizing A. capillaris, providing evidence for AM fungal host preference. In addition, our results reveal dynamic changes in the AM fungal community through time.

1. Pea aphids, Acyrthosiphon pisum, harbour a range of facultative accessory bacteria (secondary symbionts), including those informally known as PASS (R-type), PAR, PABS (T-type), and PAUS (U-type).2. To explore the relationship between possession of these bacteria and ecologically important traits of A. pisum, correlations between the accessory bacteria found in 47 parthenogenetic clones of A. pisum and the host plant on which each clone was collected and its susceptibility to natural enemies were surveyed.3. The bacterial complement varied with plant of collection. PAUS (U) was present in all of 12 clones affiliated to Trifolium but was otherwise rare, while PABS (T) and PASS (R) occurred at significantly higher frequency in clones from Lotus and Vicia, respectively, than clones from other plants.4. Possession of PABS (T) was associated strongly with resistance to the parasitoid Aphidius eadyi and weakly with resistance to Aphidius ervi. Aphids carrying PAUS (U) were more resistant to the fungal pathogen Pandora (Erynia) neoaphidis, although this correlation was complicated by a strong association with host-plant use.