Identity recognition in response to different levels of genetic relatedness in commercial soya bean.

Identity recognition systems allow plants to tailor competitive phenotypes in response to the genetic relatedness of neighbours. There is limited evidence for the existence of recognition systems in crop species and whether they operate at a level that would allow for identification of different degrees of relatedness. Here, we test the responses of commercial soya bean cultivars to neighbours of varying genetic relatedness consisting of other commercial cultivars (intraspecific), its wild progenitor Glycine soja, and another leguminous species Phaseolus vulgaris (interspecific). We found, for the first time to our knowledge, that a commercial soya bean cultivar, OAC Wallace, showed identity recognition responses to neighbours at different levels of genetic relatedness. OAC Wallace showed no response when grown with other commercial soya bean cultivars (intra-specific neighbours), showed increased allocation to leaves compared with stems with wild soya beans (highly related wild progenitor species), and increased allocation to leaves compared with stems and roots with white beans (interspecific neighbours). Wild soya bean also responded to identity recognition but these responses involved changes in biomass allocation towards stems instead of leaves suggesting that identity recognition responses are species-specific and consistent with the ecology of the species. In conclusion, elucidating identity recognition in crops may provide further knowledge into mechanisms of crop competition and the relationship between crop density and yield.

Fitness consequences of plants growing with siblings: reconciling kin selection, niche partitioning and competitive ability.

Plant studies that have investigated the fitness consequences of growing with siblings have found conflicting evidence that can support different theoretical frameworks. Depending on whether siblings or strangers have higher fitness in competition, kin selection, niche partitioning and competitive ability have been invoked. Here, we bring together these processes in a conceptual synthesis and argue that they can be co-occurring. We propose that these processes can be reconciled and argue for a trait-based approach of measuring natural selection instead of the fitness-based approach to the study of sibling competition. This review will improve the understanding of how plants interact socially under competitive situations, and provide a framework for future studies.

Kin recognition: Competition and cooperation in Impatiens (Balsaminaceae).

The ability to recognize kin is an important element in social behavior and can lead to the evolution of altruism. Recently, it has been shown that plants are capable of kin recognition through root interactions. Here we tested for kin recognition in a North American species of Impatiens that has a high opportunity of growing with kin and responds strongly to aboveground competition. We measured how the plants responded to the aboveground light quality cues of competition and to the presence of root neighbors and determined whether the responses depended on whether the neighbors were siblings or strangers. The study families were identified by DNA sequencing as members of the same species, provisionally identified as Impatiens pallida (hereafter I. cf. pallida). We found that I. cf. pallida plants were capable of kin recognition, but only in the presence of another plant's roots. Several traits responded to relatedness in shared pots, including increased leaf to root allocation with strangers and increased stem elongation and branchiness in response to kin, potentially indicating both increased competition toward strangers and reduced interference (cooperation) toward kin. Impatiens cf. pallida responded to both competition cues simultaneously, with the responses to the aboveground competition cue dependent on the presence of the belowground competition cue.