Sexual competition and kin recognition co-shape the traits of neighboring dioecious Diospyros morrisiana seedlings

Belowground ecological interactions in dioecious plants: why do opposites attract but similar ones repel?

Dioecious plant species exhibit sexual dimorphism in various aspects, including morphology, physiology, life history, and behavior, potentially influencing sex-specific interactions. While it is generally accepted that intersexual interactions in dioecious species are less intense compared with intrasexual interactions, the mechanisms underlying belowground facilitation in intersexual combinations remain less understood. Here, we explore these mechanisms, which encompass resource complementarity, mycorrhizal fungal networks, root exudate-mediated belowground chemical communication, as well as plant-soil feedback. We address the reason for the lack of consistency in the strength of inter- and intrasexual interactions. We also propose that a comprehensive understanding of the potential positive consequences of sex-specific interactions can contribute to maintaining ecological equilibrium, conserving biodiversity, and enhancing the productivity of agroforestry.

Allelochemicals and soil microorganisms jointly mediate sex-specific belowground interactions in dioecious Populus cathayana

Little is known about how sex differences in root zone characteristics, such as contents of allelochemicals and soil microbial composition, mediate intra- and intersexual interactions in dioecious plants. We examined the processes and mechanisms of sex-specific belowground interactions mediated by allelochemicals and soil microorganisms in Populus cathayana females and males in replicated 30-yr-old experimental stands in situ and in a series of controlled experiments. Female roots released a greater amount and more diverse phenolic allelochemicals into the soil environment, resulting in growth inhibition of the same sex neighbors and deterioration of the community of soil microorganisms. When grown with males, the growth of females was consistently enhanced, especially the root growth. Compared with female monocultures, the presence of males reduced the total phenolic accumulation in the soil, resulting in a shift from allelopathic inhibition to chemical facilitation. This association was enhanced by a favorable soil bacterial community and increased bacterial diversity, and it induced changes in the orientation of female roots. Our study highlighted a novel mechanism that enhances female performance by males through alterations in the allelochemical content and soil microbial composition. The possibility to improve productivity by chemical mediation provides novel opportunities for managing plantations of dioecious plants.

Effects of tree sex, maturity, local abiotic, and biotic neighborhoods on the growth of a subtropical dioecious tree species Diospyros morrisiana

PREMISE

Understanding the drivers of the growth in long-lived woody trees is the key to predicting their responses to and maintaining their populations under global change. However, the role of tree sex and differential investment to reproduction are often not considered in models of individual tree growth, despite many gymnosperm and angiosperm species having separate male and female sexes. Thus, better models of tree growth should include tree sex and life stage along with the abiotic and biotic neighborhoods.

METHODS

We used a sex-specific molecular marker to determine the sex of 2188 individual trees >1 cm DBH of the dioecious tree species Diospyros morrisiana in a 50-ha subtropical forest plot in China. We used long-term census data from about 300,000 trees, together with 625 soil samples and 2352 hemispherical photographs to characterize the spatially explicit biotic and abiotic neighborhoods.

RESULTS

We found a male-biased effective sex ratio and a female-biased overall population sex ratio of D. morrisiana. No sex spatial segregation was detected for the overall population, mature, or immature trees. Immature trees grew faster than mature trees and females grew slower than males. Further, conspecific neighbors significantly decreased tree growth, while the abiotic neighborhood showed no significant effect.

CONCLUSIONS

Our findings suggest that variation in resource allocation patterns within and across individual trees of different sexes and life-history stages should be more widely accounted for in models of tree growth. In addition, our study highlights the importance of sex-specific molecular markers for studying populations of long-lived dioecious tree species.

Kin and Non-Kin Connected Plants Benefit More Than Disconnected Kin and Non-Kin Plants under Nutrient-Competitive Environments

In the natural environment, plants grow and interact with both conspecific and heterospecific neighbours under different environmental conditions. In this study, we tested whether Chenopodium quinoa Willd genotypes differ in growth performance when grown with kin and non-kin under nutrient limitation in pot partitioning treatments. Biomass accumulation, allocation, organ efficiency, and specific leaf area were measured at the end of the experiment. Response variables were differentially impacted by kinship, fertility, and barrier. Total dry mass, shoot dry mass, and root and stem allocation were greater for plants grown with kin in connected pots than with non-kin in connected pots across the nutrient treatments. Kin connected and disconnected plants had a greater specific root length, specific stem length, and average leaf mass than non-kin connected and disconnected plants. Non-kin connected and disconnected plants had greater LAR and SLA than kin connected and disconnected plants under low- and high-nutrient treatments. Plants always grew better in the presence of their kin than non-kin. These results conclude that quinoa plant production benefits from planting closely related individuals under both high- and low-nutrient conditions.