BRANTA — Jordi Figuerola
The role of waterfowl in the passive transport of aquatic organisms: from local processes to long-distance dispersal
Institution: Estación Biológica de Do├▒ana, CSIC, Spain
Supervisors: AJ Green
Details: PhD 2002 (Completed)
Address: Department of Applied Biology, Estación Biológica de Do├▒ana, CSIC, Avda. Maria Luisa s/n, 41013 Sevilla, Spain (Oct 2005) Email
Subject Keywords: Long distance dispersal, dispersal capacity, seed dispersal, egg dispersal, habitat colonisation, community composition, local adaptation, gene flow
Species Keywords: Anas spp., Aythya spp., Marbled Teal Marmaronetta angustirostris, Red-crested PochardNetta rufina, Common Coot Fulica atra, waders, waterfowl
Abstract
Transport of propagules of aquatic organisms by waterbirds is a frequent process at a local scale. This transport occurs both through the ingestion and defaecation of propagules and by the transport of propagules adhered to the feathers and body of the birds.
Bill morphology explained a significant portion of the interspecific differences in the abundance of propagules in duck faeces. Duck species with a coarse filtering structure in the bill had a higer abundance of undigested propagules in their faeces.
There is a high interspecific and seasonal variablity in the quantity and quality components of dispersal of Ruppia maritima seeds provided by waterfowl. Gizzard and grit mass were related to interspecific differences in the proportion of seeds destroyed during digestion and with the viability of seeds after ingestion.
Potamogeton pectinatus seeds germinate at a higher rate after ingestion by ducks. This effect on germination appears more related to the scarification process in the gut than to the acidic treatment during gut passage.
No effects of ingestion by ducks were detected on the developent of Potamogeton pectinatus seedlings in experiments done in tanks exposed to climatic conditions similar to those in the field. A higher germinability of ingested seeds planted at the start of winter was detected in comparison with non ingested seeds. After a period of winter stratification in the freezer, the germinability of seeds was similar for ingested and uningested seeds.
Herbivory by waterfowl can have an effect on the cost-benefits trade-off resulting from Ruppia maritima seed ingestion by birds. Ingested and uningested seeds produced a similar number of plants when protected from natural levels of herbivory in the field. However, a reduced number of plants originated from ingested seeds when exposed to herbivore presence.
The statoblasts of Cristatella mucedo can survive ingestion by ducks, supporting the possible role of waterfowl migration in explaining the high gene flow between populations of this bryozoan. Most propagules remained inside birds gut for a short time period (less than 4 hours), but a small number of statoblasts were retained for much longer times (up to 44 hours). Although most of the propagules will be transported over short distances, the potential exists for long-distance dispersal between localities in the migratory flyway of birds.
If birds start a period of fasting immediately before starting the migratory flight, this may have an effect on the potential for long distance dispersal. Experiments in captivity simulating a fasting period before migration indicate that fasting increased the number of propagules retained for long time periods (16 hours), and that were defecated after the end of fasting. Consequently, migratory fasting can increase the potential for long distance dispersal.
Waterfowl movements estimated from ring recoveries explained a significant amount of variance in the patterns of gene flow for three invertebrate species over North America. For another species, bird migration appeared unrelated to bird movements, probably due to a reduced resistance of propagules of this species to ingestion and dessication.
The capacity of tubers of Potamogeton pectinatus to grow over a gradient of latitudes in Europe was asymmetric. Genotypes from North Europe grow without problems in southern Europe, however genotypes from southern Europe have a lower survival and poorer development when growing under the climatic conditions of North Europe. These suggest that, whilst north-south dispersal will not be limited by the components of local adaptation studied, the dispersal from south to north will be limited by a reduced fitness compared to local genotypes.
Published Papers
Figuerola, J. & Green, A.J. 2005. Effects of premigratory fasting on the potential for long distance dispersal of seed by waterfowl: an experiment with Marbled Teal. Revue d’Ecologie – la Terre et la Vie in press.
Figuerola, J., Green, A.J. & Michot, T.C. 2005. Invertebrate can fly: evidence of waterfowl mediated gene-flow in aquatic invertebrates. American Naturalist 165:274-280.
Figuerola, J., Santamaria, L., Green, A.J., Luque, I., Alvarez, R. & Charalambidou, I. 2005. Endozoochorous dispersal of aquatic plants: does seed gut passage result in increased fitness? American Journal of Botany92:695-699.
Figuerola, J. & Green, A.J. 2004. Effects of seed ingestion and herbivory by waterfowl on seedling establishment: a field experiment with wigeongrass Ruppia maritima in Do├▒ana, south-west Spain. Plant Ecology173:33-38.
Figuerola, J., Green, A.J. & Santamaria, L. 2003. Passive internal transport of aquatic organisms by waterfowl in Do├▒ana, south-west Spain. Global Ecology & Biogeography 12:427-436.
Santamaria, L., Charalambidou, I., Figuerola, J. & Green, A.J. 2003. Effect of passage through duck gut on germination of fennel pondweed seeds. Archiv für Hydrobiologie 156:11-22.
Santamaria, L., Figuerola, J., Pilon, J.J., Mjelde, M., Green, A.J., De Boer, T., King, R.A. & Gornall, R.J.2003. Plant performance across latitude: the role of plasticity and local adaptation in an aquatic plant. Ecology84:2454-2461.
Figuerola, J. & Green, A.J. 2002. Dispersal of aquatic organisms by waterbirds: a review of past research and priorities for future studies. Freshwater Biology 47:483-494.
Figuerola, J. & Green, A.J. 2002. How frequent is external transport of seeds and invertebrate eggs by waterbirds? A study in Do├▒ana, SW Spain. Archiv für Hydrobiologie 155:557-565.
Figuerola, J., Green, A.J. & Santamaria, L. 2002. Comparative dispersal effectiveness of wigeongrass seeds by waterfowl wintering in south-west Spain: quantitative and qualitative aspects. Journal of Ecology 90:989-1001.
Green, A.J., Figuerola, J. & Sanchez, M.I. 2002. Implications of waterbirds ecology for the dispersal of aquatic organisms. Acta Oecologica 23:177-189.