Plant growth over one growing season of Medicago truncatula in competition with conspecifics of different genetic relatedness

Kin recognition and kin selection have long been known to occur in animals
where it shapes altruistic behavior towards relatives. More recently,
studies have found that kin recognition and altered behavior towards kin
can also occur in plants. However, inferring the underlying mechanism
responsible for variation in plant performance in experimental studies is
challenging as often, results can be explained by alternative and
non-exclusive mechanisms such as niche differences, kin competition
avoidance, and genetic variation in growth rate and competitive ability.
Plant-plant interactions may change with the life stage of plants, and
competition is often most intense towards the end of plants growing
season. However, changes in plant-plant interaction intensity across
plants life cycle are rarely considered in kin interaction studies. Here,
we adapt a model of plant growth over time modified to specifically
include effects of kin and non-kin competition. The model decompose
competitive interactions at different stages during plant growth from
initial growth to the end of the growing season. It estimates genotype
specific variation in growth rate, and how sensitive individual genotypes
are to competition  neighbors. Furthermore, it estimates size
asymmetry among plants accounting for both variation in growth rate,
neighbor relatedness, and resource variation (here water availability). We
use this model to analyze the results from a competition experiment where
plants grew in mini-communities with neighbor plants that were either kin
or non-kin. We find that when applied to our experiments, this approach
can disentangle kin effects from other effects caused by genotypic
variation in growth rate and competitive response to neighbors, and thus
significantly help to detect whether plants exhibit kin-cooperative
behavior