Directed endozoochorous dispersal by scavengers facilitate sexual reproduction in otherwise clonal plants at cadaver sites

The regeneration niche of many plant species involves spatially and temporally unpredictable disturbances, called recruitment windows of opportunity. However, even species with clear dispersal adaptations such as fleshy berries may not successfully reach such elusive regeneration microsites. Ericaceous, berry-producing species in the northern hemisphere demonstrate this dispersal limitation. They are said to display a reproductive paradox owing to their lack of regeneration in apparently suitable microsites despite considerable investment in producing large quantities of berries. Cadavers generate vegetation-denuded and nutrient-rich disturbances termed cadaver decomposition islands. Cadavers attract facultative scavengers with considerable capacity for endozoochorous seed dispersal. We hypothesize that cadaver decomposition islands facilitate recruitment in berry-producing ericaceous species due to endozoochorous dispersal directed towards favorable microsites with low competition. We examined seedling establishment within a permanent, semi-regular 10 × 10 m grid across an ungulate mass die-off on the Hardangervidda plateau in southeastern Norway. Competing models regarding the relative importance of factors governing recruitment were evaluated, specifically cadaver location (elevated seed rain) and microsite conditions (competition). We found that cadaver decomposition islands did facilitate seedling establishment, as cadaver density was the best predictor of seedling distribution. Other important factors governing seedling establishment such as percentage cover of soil and vascular plants alone were inadequate to explain seedling establishment. Synthesis: This study provides a novel understanding of sexual reproduction in species with cryptic generative reproduction. The directed nature of endozoochorous dispersal combined with long-distance dispersal abilities of medium to large vertebrate scavengers towards cadavers allows plants to exploit the advantageous but ephemeral resource provided by cadaver decomposition islands.