Meadow fragmentation and reproductive output of the SE Asian seagrass Enhalus acoroides |
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Authors: | Jan E. Vermaat Rene N. Rollon Cristina Day A. Lacap Claire Billot Filipe Alberto Hildie M.E. Nacorda Frank Wiegman Jorge Terrados |
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Affiliation: | aDepartment of Environmental Science and Water Resources, International Institute for Infrastructural, Hydraulic and Environmental Engineering, P.O. Box 3015, 2601 DA Delft, The Netherlands;bMarine Science Institute, University of the Philippines, Diliman, Quezon City, The Philippines;cEnvironmental Science Program, College of Science, University of the Philippines, Diliman, Quezon City 1101, The Philippines;dCentro de Ciencias do Mar, Universidade do Algarve, Gambelas, 8000-810 Faro, Portugal;eIMEDEA (CSIC-UIB) Instituto Mediterráneo de Estudios Avanzados, Miquel Marqués 21, 07190 Esporles, Mallorca, Islas Baleares, Spain;fPresent address : CIRAD-Amis, Biotrop, TA 40/03, Avenue d'Agropolis, 34398 Montpellier Cedex 5, France |
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Abstract: | Flower and fruit production of the abundant, tall, long-lived, dioecious, surface-pollinating seagrass species Enhalus acoroides (L.) Royle were estimated at seven sites in the reef flats off Bolinao (NW Luzon, The Philippines) featuring different fragmentation of the seagrass meadows. Fragmentation of the seagrass meadow was quantified as cover of E. acoroides and all seagrass species present in 20×20 m plots. E. acoroides and overall seagrass cover were correlated positively. The proportion of female flowers of E. acoroides that developed a fruit increased sharply as overall seagrass cover was around 50%. Apparent sex ratio bore no relationship with overall seagrass cover. This threshold-type of relationship suggests that fragmentation of seagrass meadows can have a major effect on the reproductive output of this species. A possible mechanism underlying these results would be a non-linear increase of the efficiency of trapping the surface-dispersed pollen with increasing seagrass canopy density. This provides the first evidence based on real data that fragmentation can affect the population dynamics of seagrass species. |
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Keywords: | Pollen dispersal Hydrochorous pollination efficiency Landscape heterogeneity Nonlinear thresholds Tropical seagrass meadows |
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