When to help juveniles, adults, or both: analyzing the evolutionary models of stage-structured mutualism

Mutualism is common in nature and is crucial for population dynamics, community structure, and ecosystem functioning. Studies have recently pointed out that life-history stage structure (e.g., juveniles and adults) is a key factor to better understand the ecological consequences of mutualism (termed stage-structured mutualism). Despite the potential importance, little is known about what kinds of stage-structured mutualism can evolve and when it is likely to occur. Here, we theoretically investigated how a mutualistic partner species should allocate efforts of mutualistic associations for different life-history stages of its host species to maximize its fitness. We assessed the partner’s optimal strategy by using a one host–one partner model with the host’s juvenile-adult stage structure. The results showed that different forms of stage-structured mutualism can evolve, such as juvenile-specialized association, adult-specialized association, and inter-stage partner sharing (i.e., the partner associates with both the juvenile and adult stages of the host) depending on the shape of association trade-off, i.e., how much association with one stage is weakened when the partner strengthens its association with the other stage. In general, stage-specialized association (either juvenile-specialized or adult-specialized association) tends to evolve when being associated with that stage is relatively beneficial. Meanwhile, when the association trade-off is weak, inter-stage partner sharing can occur if the mutualistic benefits of juvenile-specific and adult-specific associations are sufficiently large. We also found that when the association trade-off is strong, alternative stable states occur in which either juvenile-specialized or adult-specialized associations evolve depending on the initial trait value. These results suggest that pairwise interspecific mutualism is more complicated than previously thought, implying that we may under-or overestimate the strength of mutualistic interactions when looking at only certain life-history stages. This study provides a conceptual basis for better understanding the mechanisms underlying ontogenetic shifts of mutualistic partners and more complex mutualistic networks mediated by the life-history stages of organisms and their stage-structured interactions

Effects of indirect plant–plant interaction via root exudate on growth and leaf chemical contents in Rumex obtusifolius

Belowground plant–plant interactions can affect the concentrations of leaf chemicals, but the mechanism is not clear. Here, we investigated the effects of intra- and interspecific root exudates on the growth and leaf chemical content of Rumex obtusifolius. Seedlings of R. obtusifolius were grown with exposure to root exudates collected from other R. obtusifolius plants or from Trifolium repens, Festuca ovina, or Plantago asiatica plants, and the total phenolic, condensed tannin, dry biomass, and chlorophyll contents of the leaves were examined. The root exudates from conspecific plants had no effect on the total phenolic, condensed tannin, and chlorophyll contents of the leaves but did significantly reduce the dry leaf biomass. Root exudates from heterospecific plants had different effects depending on the species. These results were different from the results of a previous study that examined the effects of direct plant–plant interaction in R. obtusifolius. Thus, indirect interaction via root exudates induces different effects in leaves from direct interaction

El Diario de Pontevedra : periódico liberal: Ano XVIII Número 5007 - 1901 xaneiro 28

Numerous organisms integrate information from multiple sources and express adaptive behaviours, but how they do so at different developmental stages remains to be identified. Seeds, which are the embryonic stage of plants, need to make decisions about the timing of emergence in response to environmental cues related to survival. We investigated the timing of emergence of <i>Plantago asiatica</i> (Plantaginaceae) seed while manipulating the presence of <i>Trifolium repens</i> seed and the relatedness of neighbouring <i>P. asiatica</i> seed. The relatedness of neighbouring <i>P. asiatica</i> seed and the presence of seeds of <i>T. repens</i> did not on their own influence the timing of <i>P. asiatica</i> emergence. However, when encountering a <i>T. repens</i> seed, a <i>P. asiatica</i> seed emerged faster in the presence of a sibling seed than in the presence of a non-sibling seed. Water extracts of seeds gave the same result. We show that <i>P. asiatica</i> seeds integrate information about the relatedness of neighbouring <i>P. asiatica</i> seeds and the presence of seeds of a different species via water-soluble chemicals and adjust their emergence behaviour in response. These findings suggest the presence of kin-dependent interspecific interactions

Aboveground plant-to-plant communication reduces root nodule symbiosis and soil nutrient concentrations

Abstract Aboveground communication between plants is well known to change defense traits in leaves, but its effects on belowground plant traits and soil characteristics have not been elucidated. We hypothesized that aboveground plant-to-plant communication reduces root nodule symbiosis via induction of bactericidal chemical defense substances and changes the soil nutrient environment. Soybean plants were exposed to the volatile organic compounds (VOCs) from damaged shoots of Solidago canadensis var. scabra, and leaf defense traits (total phenolics, saponins), root saponins, and root nodule symbiosis traits (number and biomass of root nodules) were measured. Soil C/N ratios and mineral concentrations were also measured to estimate the effects of resource uptake by the plants. We found that total phenolics were not affected. However, plants that received VOCs had higher saponin concentrations in both leaves and roots, and fewer root nodules than untreated plants. Although the concentrations of soil minerals did not differ between treatments, soil C/N ratio was significantly higher in the soil of communicated plants. Thus, the aboveground plant-to-plant communication led to reductions in root nodule symbiosis and soil nutrient concentrations. Our results suggest that there are broader effects of induced chemical defenses in aboveground plant organs upon belowground microbial interactions and soil nutrients, and emphasize that plant response based on plant-to-plant communications are a bridge between above- and below-ground ecosystems

Table S2.doc from Seeds integrate biological information about conspecific and allospecific neighbours

Numerous organisms integrate information from multiple sources and express adaptive behaviours, but how they do so at different developmental stages remains to be identified. Seeds, which are the embryonic stage of plants, need to make decisions about the timing of emergence in response to environmental cues related to survival. We investigated the timing of emergence of <i>Plantago asiatica</i> (Plantaginaceae) seed while manipulating the presence of <i>Trifolium repens</i> seed and the relatedness of neighbouring <i>P. asiatica</i> seed. The relatedness of neighbouring <i>P. asiatica</i> seed and the presence of seeds of <i>T. repens</i> did not on their own influence the timing of <i>P. asiatica</i> emergence. However, when encountering a <i>T. repens</i> seed, a <i>P. asiatica</i> seed emerged faster in the presence of a sibling seed than in the presence of a non-sibling seed. Water extracts of seeds gave the same result. We show that <i>P. asiatica</i> seeds integrate information about the relatedness of neighbouring <i>P. asiatica</i> seeds and the presence of seeds of a different species via water-soluble chemicals and adjust their emergence behaviour in response. These findings suggest the presence of kin-dependent interspecific interactions

Fig. S2.docx from Seeds integrate biological information about conspecific and allospecific neighbours

Numerous organisms integrate information from multiple sources and express adaptive behaviours, but how they do so at different developmental stages remains to be identified. Seeds, which are the embryonic stage of plants, need to make decisions about the timing of emergence in response to environmental cues related to survival. We investigated the timing of emergence of <i>Plantago asiatica</i> (Plantaginaceae) seed while manipulating the presence of <i>Trifolium repens</i> seed and the relatedness of neighbouring <i>P. asiatica</i> seed. The relatedness of neighbouring <i>P. asiatica</i> seed and the presence of seeds of <i>T. repens</i> did not on their own influence the timing of <i>P. asiatica</i> emergence. However, when encountering a <i>T. repens</i> seed, a <i>P. asiatica</i> seed emerged faster in the presence of a sibling seed than in the presence of a non-sibling seed. Water extracts of seeds gave the same result. We show that <i>P. asiatica</i> seeds integrate information about the relatedness of neighbouring <i>P. asiatica</i> seeds and the presence of seeds of a different species via water-soluble chemicals and adjust their emergence behaviour in response. These findings suggest the presence of kin-dependent interspecific interactions

Fig. S5.docx from Seeds integrate biological information about conspecific and allospecific neighbours

Numerous organisms integrate information from multiple sources and express adaptive behaviours, but how they do so at different developmental stages remains to be identified. Seeds, which are the embryonic stage of plants, need to make decisions about the timing of emergence in response to environmental cues related to survival. We investigated the timing of emergence of <i>Plantago asiatica</i> (Plantaginaceae) seed while manipulating the presence of <i>Trifolium repens</i> seed and the relatedness of neighbouring <i>P. asiatica</i> seed. The relatedness of neighbouring <i>P. asiatica</i> seed and the presence of seeds of <i>T. repens</i> did not on their own influence the timing of <i>P. asiatica</i> emergence. However, when encountering a <i>T. repens</i> seed, a <i>P. asiatica</i> seed emerged faster in the presence of a sibling seed than in the presence of a non-sibling seed. Water extracts of seeds gave the same result. We show that <i>P. asiatica</i> seeds integrate information about the relatedness of neighbouring <i>P. asiatica</i> seeds and the presence of seeds of a different species via water-soluble chemicals and adjust their emergence behaviour in response. These findings suggest the presence of kin-dependent interspecific interactions

Adaptive Advantage of Myrmecochory in the Ant-Dispersed Herb Lamium amplexicaule (Lamiaceae): Predation Avoidance through the Deterrence of Post-Dispersal Seed Predators.

Seed dispersal by ants (myrmecochory) is found worldwide, but the benefits that plants obtain from this mutualism remain uncertain. In the present study, we conducted laboratory experiments to demonstrate seed predator avoidance as a benefit of myrmecochory using the annual ant-dispersed herb Lamium amplexicaule, the disperser ant Tetramorium tsushimae, and the seed predatory burrower bug Adomerus rotundus. We compared the predation intensity of Lamium amplexicaule seeds by Adomerus rotundus under the presence or absence of Tetramorium tsushimae. Both the number of seeds sucked by Adomerus rotundus adults and the feeding duration of sucked seeds by nymphs were significantly reduced in the presence of ants. This effect was most likely due to the behavioral alteration of Adomerus rotundus in response to the ant presence, because ants seldom predated Adomerus rotundus during the experiment. Our results demonstrated that the presence of ants decreases post-dispersal seed predation, even when the ants do not bury the seeds. The present study thus suggests that the non-consumptive effects of ants on seed predators benefit myrmecochorous plants