Pollen limitation may be a common Allee effect in marine hydrophilous plants: implications for decline and recovery in seagrasses.
Pollen limitation may be an important factor in accelerated decline of sparse or fragmented populations. Little is known whether hydrophilous plants (pollen transport by water) suffer from an Allee effect due to pollen limitation or not. Hydrophilous pollination is a typical trait of marine angiosperms or seagrasses. Although seagrass flowers usually have high pollen production, floral densities are highly variable. We evaluated pollen limitation for intertidal populations of the seagrass Zostera noltei in The Netherlands and found a significant positive relation between flowering spathe density and fruit-set, which was suboptimal at <1200 flowering spathes m(-2) (corresponding to <600 reproductive shoots m(-2)). A fragmented population had ≈35 % lower fruit-set at similar reproductive density than a continuous population. 75 % of all European populations studied over a large latitudinal gradient had flowering spathe densities below that required for optimal fruit-set, particularly in Southern countries. Literature review of the reproductive output of hydrophilous pollinated plants revealed that seed- or fruit-set of marine hydrophilous plants is generally low, as compared to hydrophilous freshwater and wind-pollinated plants. We conclude that pollen limitation as found in Z. noltei may be a common Allee effect for seagrasses, potentially accelerating decline and impairing recovery even after environmental conditions have improved substantially.
Department of Environmental Science, Institute for Wetland and Water Research, Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands.|Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Apdo Postal 1152, Cancún, Q. Roo, Mexico.
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Van Tussenbroek
Department of Estuarine and Delta Systems (EDS), NIOZ Royal Netherlands Institute for Sea Research, Utrecht University, 4400 AC, Yerseke, The Netherlands. laura.soissons@nioz.nl.
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LM
Soissons
Department of Estuarine and Delta Systems (EDS), NIOZ Royal Netherlands Institute for Sea Research, Utrecht University, 4400 AC, Yerseke, The Netherlands.
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TJ
Bouma
Alfred-Wegener-Institut Helmholtz-Zentrum für Polar-und Meeresforschung, Wadden Sea Station Sylt, Hafenstrasse 43, 25992, List, Germany.
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Asmus
IFREMER-LER/AR, Quai du Commandant Silhouette, 33120, Arcachon, France.
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Auby
Departamento de Biología, Área de Ecología, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, Puerto Real, 11510, Cádiz, Spain.
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Brun
Department of Life Sciences, IMAR-Institute of Marine Research, University of Coimbra, 3004-517, Coimbra, Portugal.
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Cardoso
IFREMER-LER Dinard, 38 rue du Port Blanc, 35800, Dinard, France.
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Desroy
UMR 7208 BOREA, Station de Biologie Marine MNHN, CNRS, Place de la Croix, BP 225, 29182, Concarneau Cedex, France.
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Fournier
IFREMER-LER/AR, Quai du Commandant Silhouette, 33120, Arcachon, France.
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Ganthy
Marine Research Division, AZTI-Tecnalia, Herrera Kaia Portualdea z/g, 20110, Pasaia, Spain.
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Garmendia
CNRS, UMR 6554 LETG-Nantes Géolittomer, Université de Nantes, B.P. 81227, 44312, Nantes Cedex 3, France.
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Godet
Department of Life Sciences, CFE-Centre for Functional Ecology, University of Coimbra, 3001-455, Coimbra, Portugal.
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Grilo
Alfred-Wegener-Institut Helmholtz-Zentrum für Polar-und Meeresforschung, Wadden Sea Station Sylt, Hafenstrasse 43, 25992, List, Germany.
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Kadel
Environmental Hydraulics Institute "IH Cantabria", Parque Científico y Tecnológico de Cantabria, Universidad de Cantabria, C/Isabel Torres No 15, 39011, Santander, Spain.
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Ondiviela
Departamento de Biología, Área de Ecología, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, Puerto Real, 11510, Cádiz, Spain.
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Peralta
Environmental Hydraulics Institute "IH Cantabria", Parque Científico y Tecnológico de Cantabria, Universidad de Cantabria, C/Isabel Torres No 15, 39011, Santander, Spain.
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Recio
Marine Research Division, AZTI-Tecnalia, Herrera Kaia Portualdea z/g, 20110, Pasaia, Spain.|Central Research Department, Universidad Laica Eloy Alfaro de Manabí, Ciudadela Universitaria, vía San Mateo s/n, 13-05-2732, Manta, Manabí, Ecuador.
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Valle
Department of Aquatic Ecology and Environmental Biology, Institute for Wetland and Water Research, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands.
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Van der Heide
Department of Environmental Science, Institute for Wetland and Water Research, Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands.
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Van Katwijk
D035264:Flowers; D019684:Magnoliopsida; D011058:Pollen; D054817:Pollination; D012098:Reproduction; D012639:Seeds
Abiotic pollination; Density dependence; Habitat fragmentation; Seed production; Zostera noltei