Ontogenetic Niche Shifts Within Floodplain Meadow Species

Cameron, Fiona (2014). Ontogenetic Niche Shifts Within Floodplain Meadow Species. MPhil thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000efef

Abstract

Ontogenetic niche shifts, (ONSs), or changes in niche breadth or position during development, can be a critical component of effective target-species conservation, as long-term survival demands that the intergenerational requirements of species be fully met. However, although ONSs could occur in 80% of animal taxa, previous studies have rarely involved plants, and those that do exist have often been hampered by the lack of long-term, field-based data or appropriate measures. Analysis of the twenty years of botanical and hydrological data collated by the Floodplain Meadow Partnership, in combination with a multi-site, fully factorial planting experiment with two levels of competition, allows the following questions to be addressed; a) are ONSs occurring within floodplain meadow species, including the scarce Fritillaria meleagris, and how can the hydrological regime driving such shifts be quantified? b) Does flooding enhance recruitment within a range of meadow species? and, c) what are the mechanisms underlying flood-related gap creation? Results revealed that occurrence of ONSs varies according to species. Abundance of juvenile fritillaries was correlated with interquartile range in water-table depth prior to parental seed dispersal, suggesting micro-site limitation, with subsequent generations associated with predominantly dry conditions. Further differences in associate species and community membership of juveniles versus flowering adults were detected, which, results suggested, may be due to differential soil profile characteristics or other legacy effects. Seasonal as opposed to annually-derived hydrological variables were of particular relevance to the study of ONSs, and spring of the year before survey identified as the critical period for germination of all the selected species. Whereas flooding enhances recruitment and appears to drive ONSs within both Fritillaria meleagris and Leontodon autumnalis, germination of the obligate hemi-parasite Rhinonathus minor decreased in gaps lacking host species. A correlation between die-back of flood-sensitive grasses following flood-events and increased fritillary juvenile abundance was established.

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