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Dryad

Intra-specific variability and sex influence the allelopathic capacity of Empetrum nigrum

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Aug 01, 2025 version files 17.85 KB

Abstract

Allelopathic plant species play significant roles in shaping natural ecosystems. While a high degree of inter-species variation in allelopathic capacities is commonly reported, variation across intra-specific groups and between dioecious sexes is limited. Here we use the ecologically important, allelopathic dwarf shrub Empetrum nigrum L. to assess how allelopathic capacity varies between intra-specific groups (i.e., the diploid and dioecious “nigrum” group and the tetraploid and synoecious “hermaphroditum” group of Empetrum) and sex (i.e., male and female plants of the nigrum group). Specifically, we tested Icelandic Empetrum, as its allelopathic nature may influence long-term land degradation across Icelandic highlands. The allelopathic capacity of Empetrum leaves was measured in a series of bioassays as the inhibition of seed germination and seedling root elongation of the grass Festuca richardsonii. A very strong allelopathic response of Empetrum leaves was observed. Intra-specific and sex-related differences in allelopathic capacity were also detected, with the hermaphroditum group possessing a greater germination inhibitory effect compared to the nigrum group, and males of the nigrum group inhibited germination more than females. Targeted liquid chromatography-mass spectrometry (LC-MS) quantification of two known Empetrum allelopathic constituents – Batatasin-III (BIII) and 3,4-dimethoxy-2´,5-dihydroxybibenzyl (DDB) – showed that BIII concentrations were significantly higher in leaves from the hermaphroditum group compared to the nigrum group, but no differences were observed between males and females within the nigrum group. DDB was not detected in the sampled Icelandic Empetrum populations. Our results indicate that Empetrum may differentially impact plant interactions and ecosystem processes depending on the relative abundance of Empetrum intra-specific groups and sexes within populations, and that BIII is not solely responsible for the allelopathic capacity of Icelandic Empetrum.