Kin recognition and competition in plants

1. Plants recognize their kin and respond to growing with relatives with changes in functional traits. Here, we integrate competition and evolutionary theory to evaluate these changes. 2. We draw parallels between the definitions and empirical measurement of competitive effect and competitive response from competition theory, and the costs and benefits of altruistic and selfish behaviours from kin selection theory. 3. Do plants compete less with relatives, as these parallels suggest? While functional traits respond to the presence of relatives or strangers, no study has directly demonstrated that plants are less competitive with siblings. 4. However, there are empirical challenges in identifying the competitive value of traits that are measured destructively, such as root allocation. 5. If these challenges can be addressed, kin recognition responses can offer new insights into plant competition.