To compete or not to compete: an experimental study of interactions between plant species with contrasting root behaviour

Abstract

Game-theoretic models predict that plants with root systems that avoid belowground competition will be displaced by plants that overproduce roots in substrate shared with competitors. Despite this, both types of root response to neighbours have been documented. We used two co-occurring clonal species (Glechoma hederacea and Fragaria vesca) with contrasting root responses to neighbours (avoidance of competition and contesting of resources, respectively) to examine whether functional variation in other traits affected the success of each rooting strategy, leading to a different outcome from that predicted on the basis of root behaviour alone. Vegetative propagation rates, morphology and biomass allocation patterns were examined when each species was challenged with competition from physically separate ramets with either the same rooting strategy (intraclonal competition) or the contrasting rooting strategy (interspecific competition). Contrary to the predictions of game-theoretic models, the species that exhibits avoidance of root competition (Glechoma) was not competitively inferior to the species that does not (Fragaria). Glechoma achieved greater total mass in the interspecific treatment than in the intraclonal treatment. However, Fragaria did not experience more intense competition from Glechoma than it did in the intraclonal treatment. Strong interference between the two species appeared to be avoided because Glechoma invested preferentially in rapid exploitation of unoccupied space, whereas Fragaria invested in increasing the competitive ability and local persistence of established ramets. Our results suggest that interspecific trade-offs between traits related to competitive ability and resource exploitation can allow coexistence of species with contrasting rooting behaviours. Full assessment of the adaptive value of different root responses to neighbours therefore requires concurrent consideration of the combined effects of a wide array of functional traits.

Different sets of belowground traits predict the ability of plant species to suppress and tolerate their competitors

“…The direction and magnitude of these plastic responses was not significantly correlated with competitive ability. These results support findings showing that plant species exhibit a wide range of behavioural strategies to deal with belowground competition (Semchenko et al 2007(Semchenko et al , 2010Valverde-Barrantes et al 2013;Belter and Cahill 2015). Therefore, although plasticity in functional traits in response to competition may play an important role in community assembly, the apparent diversity of possible responses makes it difficult to predict the way in which it operates.…”

Which stem parts of Slender speedwell (Veronica filiformis) are the most successful in plant regeneration?

“…These species exhibit avoidance of root competition and are not competitively inferior to the species that does not (e.g. Potentilla reptans, Ranunculus repens, genus Fragaria) (Steinbach & Gottsberger 1994;Leeflang 1999;Vermeulen et al 2008;Semchenko et al 2010). It was found that G. hederacea invests preferentially in rapid exploitation of unoccupied places, whereas F. vesca invests in increasing the competitive ability and local persistence of established ramets (Semchenko et al 2010).…”

“…Potentilla reptans, Ranunculus repens, genus Fragaria) (Steinbach & Gottsberger 1994;Leeflang 1999;Vermeulen et al 2008;Semchenko et al 2010). It was found that G. hederacea invests preferentially in rapid exploitation of unoccupied places, whereas F. vesca invests in increasing the competitive ability and local persistence of established ramets (Semchenko et al 2010). Slender speedwell grew very fast from two-node segments in bare loam soil (Harris & Lovell 1980), but its body is delicate and not so competitive with other species in the lawn.…”

The spatial signature of biotic interactions of a clonal and a non‐clonal palmetto in a subtropical plant community

“…Several laboratory or greenhouse experimental studies tested these interactions by examining root-placement patterns (Huber-Sannwald et al 1998, Falik et al 2003, Holzapfel and Alpert 2003, Gruntman and Novoplansky 2004, Semchenko et al 2007, Semchenko et al 2010. In general, clonal plants appear to be capable of discriminating between the roots of clonemates and those of other genets and can respond by changing root-placement patterns (de Kroon 2007).…”

“…Relatively few studies have tested biotic interactions between clonal plant species. Semchenko and her colleagues (Semchenko et al 2007, Semchenko et al 2010 examined biotic interactions between woodland strawberry (Fragaria vesca) and ground ivy. Root behavior in response to interspecific competition varied between the species.…”