Abstract
(1) Environmental conditions experienced in the past may lead to intraspecific differences in ecological and chemical traits of plants, which likely affect future responses to altered or new environments. Whether competition by neighbors is such a trait-shaping factor is not yet well known. We aimed to understand how the level of ancestral plant competition affects traits related to plant fitness and resource allocation, reproduction, and (phyto-)toxin accumulation in offspring, and whether a potential differentiation in these traits can be found in different geographic origins of which one belongs to the native and one to the invaded range. (2) We compared differentiation of the following traits in offspring plants of multiple populations in Erodium cicutarium (Geraniaceae): biomass, seed production, seed traits related to dispersal and germination, and concentrations of foliar mono- and sesquiterpenes. We tested the allelopatic potential of aqueous extracts of the same E. cicutarium plants on seeds of five different plant families. (3) In plants originating from populations that experienced high levels of competition, we found twice as high monoterpene concentrations. These plants also produced more biomass and a higher proportion of ripe to unripe seeds until harvesting. Seeds originating from high competition sites were shorter. Aqueous E. cicutarium leaf extracts with high terpenoid content reduced radicle length of Zea mays and radicle and hypocotyl length of E. cicutarium seedlings. (4) The results of this study provide first evidence that the surrounding vegetation may shape chemo-ecological plant traits that may be fundamental for competitive ability. Our study calls for more research testing whether competition experienced in the native range may lead to an enhanced capability of plants to establish populations and spread in a new range.
Highlights
Plants are strongly influenced by their neighbors within the local environment
Seed length and mericarp weight were positively correlated for seeds originating from plants with low competition (Spearman’s rank correlation, S = 1,06,150, rho = 0.51, P-value < 0.001, see Figure S1), but there was no such correlation for seeds from high competition sites (Spearman’s rank correlation, S = 260,600, rho = 0.14, P-value = 0.13)
We found foliar monoterpene concentrations in E. cicutarium to respond to the level of ancestral competition, but foliar sesquiterpenes were responsive to the geographic region of seed origin
Summary
It has been shown that persistent competition of plants for above- and belowground resources, such as light (Rajcan and Swanton, 2001), space, nutrients, and water results in a plethora of competition avoidance traits, such as early germination, elongation and pre-emption of space (Weinig, 2000), morphological and physiological adaptation, and the release of phytotoxins (i.e., allelopathy) (Weidenhamer et al, 1989; Fernandez et al, 2016) Such plant traits matching the ancestral competitive environment and potentially increasing fitness for the following generations can be passed on to the offspring (Heger et al, 2014). E.g., by earlier germination or other trait changes enhancing competition avoidance or competitive strength, could be more efficient if paired with a change in seed morphology, enhancing short distance dispersal (Baythavong et al, 2009)
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