Does Seed Retention Potential Affect the Distribution of Plant Species in Highly Fragmented Calcareous Grasslands?

• Published in: Ecography (Copenhagen) Vol. 30; no. 4; pp. 505 - 514
• Main Authors: Adriaens, Dries, Honnay, Olivier, Hermy, Martin
• Format: Journal Article
• Language: English
• Published: Blackwell Publishing 01.08.2007
• Subjects: Animals; Connectivity; Forest ecology; Habitat fragmentation; Landscapes; Plant morphology; Plants; Seed dispersal; Sheep; Species
• ISSN: 0906-7590; 1600-0587
• DOI: 10.1111/2007.0906-7590.05049.x

Long-distance dispersal is a crucial factor in the life-cycle of plants, especially in our modern, highly fragmented landscapes. Because natural herds of large animals have disappeared and grazing practices have been abandoned, important potential vectors for seed dispersal over large distances may have been lost. In the context of the re-establishment of grazing management for nature conservation purposes, it is therefore important to gain insight in the ability of grazing animals to act as seed dispersal vectors. Whereas local dispersal mainly occurs through standard vectors typically described based on morphological adaptations of the diaspore, large herbivores act as non-standard seed dispersers. Therefore, traditional dispersal classes are loosing scientific relevance and continuous predictors of dispersal potential have been proposed. Here, we explored whether dispersal related plant traits, including the "seed retention potential", could explain the distribution patterns of 180 plant species over 64 fragmented semi-natural calcareous grasslands in Belgium. The distribution of habitat specialist plant species was strongly determined by the degree of isolation of the grasslands. Interestingly, species distribution patterns were clearly linked with a species' potential to migrate through large grazers, as quantified by its retention potential: species producing seeds with high retention capacity were less affected by habitat isolation. Categorical dispersal classes based on seed morphology did not explain a species' response to fragment isolation. Although seed retention potential outperformed simple seed dimensional traits, plant height, which is an indicator of epizoochorous attachment potential, was even more important. Therefore we suggest further extension of the epizoochorous retention potential model by incorporating basic ecological mechanisms that effectively contribute to successful dispersal events.