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Dryad

Pollen limitation and context-dependent alleviating mechanisms in a co-flowering alpine grassland community

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Jan 16, 2023 version files 8.55 KB

Abstract

1. The consequences of community metrics (e.g., co-flowering diversity and floral density) and plant traits (e.g., pollinator dependency and trait similarity) on pollen limitation may depend on pollinator-mediated competitive or facilitative interactions among plants in co-flowering communities, which could vary with community contexts (i.e. different altitude communities) and under human disturbances (e.g., livestock grazing). However, the mechanisms to alleviate pollen limitation under the different contexts, considering pollinator-mediated interactions among neighbor plants are unclear.

2. We investigated pollen limitation under grazing versus ungrazing conditions in low versus high altitude alpine meadows on the Tibetan Plateau to uncover the underlying mechanisms mediating pollen limitation associated with livestock grazing.

3. Pollen limitation is prevalent in alpine grasslands, irrespective of community contexts. Grazing exclusion decreased pollen limitation in the two sites but in different ways. In the high-altitude site, pollen limitation was reduced by the exclusion of grazers through increased trait similarity (suggesting facilitation). While pollen limitation was reduced by decreased trait similarity (suggesting competition avoidance) under grazing exclusion in the low-altitude site.

4. Synthesis and Applications: This study suggests that flower trait distribution patterns (i.e. trait similarity) influence pollen limitation through reducing competition in the low-altitude site or enhancing facilitation in the high-altitude site under grazing exclusion in alpine grasslands. Our results provide a mechanistic understanding of pollen limitation in co-flowering alpine grassland communities under distinct human disturbances at different altitudes, emphasizing the role of pollinator-mediated interactions among plants on plant reproductive success.