The phenomenon that organisms can distinguish genetically related individuals from strangers (i.e., kin recognition) and exhibit more cooperative behaviours towards their relatives (i.e., positive kin discrimination) has been documented in a wide variety of organisms. However, its occurrence in plants has been considered only recently. Despite the concerns about some methodologies used to document kin recognition, there is sufficient evidence to state that it exists in plants. Effects of kin recognition go well beyond reducing resource competition between related plants and involve interactions with symbionts (e.g., mycorrhizal networks). Kin recognition thus likely has important implications for evolution of plant traits, diversity of plant populations, ecological networks and community structures. Moreover, as kin selection may result in less competitive traits and thus greater population performance, it holds potential promise for crop breeding. Exploration of these evo‐ecological and agricultural implications requires adequate control and measurements of relatedness, sufficient replication at genotypic level and comprehensive measurements of performance/fitness effects of kin discrimination. The primary questions that need to be answered are: when, where and by how much positive kin discrimination improves population performance.
Summary of the physiological mechanisms for kin recognition and the associated kin discrimination effects in plants. Signals and pathways that are proven to mediate belowground kin recognition include root exudates and probably also common mycorrhizal networks. In addition, signals like volatiles and probably also profiles of reflected light can mediate aboveground kin recognition, but they are not the focus of this review. Effects of kin discrimination include not only a reduction of resource competition intensity but also cooperation to increase resource availability, such as more investments in common mycorrhizal network, and probably also in aboveground pollinator attraction (which is not the focus here) [Colour figure can be viewed at wileyonlinelibrary.com]