Effect of ingestion by five avian dispersers on the retention time, retrieval and germination of Ruppia maritima seeds

Abstract

Summary 1.Vertebrates are important seed dispersers for many plants, particularly those inhabiting naturally fragmented habitats such as lakes and wetlands. Such dispersal often takes place through the transport of ingested seeds (endozoochory). 2. Endozoochorous passage of seeds is likely to vary among both disperser and dispersed species. We hypothesized that seed retention time and survival of gut passage varies among disperser species (here Anas ducks) and is influenced by intraspecific differences in seed size. 3. Wigeongrass ( Ruppia maritima ) seeds were ingested by five duck species; Teal, Wigeon, Shoveler, Pintail and Mallard. Defecated seeds were recovered and germinated. 4. Total retrieval and germination of seeds, patterns of retrieval over time and seed weight before and after gut passage did not differ among duck species. Hence interspecific differences among Anas ducks and intraspecific differences in seed weight do not affect seed retention time or the response of seeds to gut passage. 5. Germination of retrieved seeds was influenced by the retention time in the gut, with seeds voided earlier more likely to germinate than those voided later. 6. The probability of dispersal at different retention times by any given duck was low. However, when considering the thousands of ducks moving among wetlands, the dispersal probabilities of seeds become significant. 7. Estimation of seed dispersal distance as a function of retention time suggested higher dispersal probabilities for seeds voided earlier. Based on average flight speeds ranging from 10 to 70 km h − 1 , most probable dispersal distances range from 40 to 280 km. Dispersal over greater distances is possible, but less likely.

The role of avian frugivores in germination of seeds of fleshy-fruited invasive alien plants

“…Some studies show increased seed germination success associated with longer seed retention times (Barnea et al 1991), while others show a decrease (Murray et al 1994;Charalambidou et al 2003) or no effect (Barnea et al 1990(Barnea et al , 1991. In such cases frugivores are primarily seed dispersers.…”

Ingestion by an invasive parakeet species reduces germination success of invasive alien plants relative to ingestion by indigenous turaco species in South Africa

“…This may be due to excessive abrasion of seeds or the toxicity and hydrophobic nature of excreta (VivianSmith and Gosper 2010; Reid and Armesto 2011). The germination response of ingested seeds can be influenced by several factors (Charalambidou et al 2003). These include seed retention time, seed coat structure and seed sizes (Greenberg et al 2001;Guix 2007).…”

“…Seed retention time in frugivores' guts is the most important factor for some species in determining their germination success (Traveset 1998;Cain et al 2000). Small seeds tend to have longer retention times and are less likely to be damaged during gut passage compared with large seeds (Charalambidou et al 2003). However, in some species shorter transit times are observed and these fruits are preferred by avian frugivores (Wilson and Downs 2011).…”

Functional implications of changes in seagrass species composition in two shallow coastal lagoons

“…They quickly reach sexual maturity and produce large amounts of seeds (Bonis et al 1995). In the case of R. maritima, these seeds can remain dormant for extended periods of time (Kantrud 1991) and are able to survive passage through the digestive system of waterfowl and fish, which favors long-distance dispersal of the plants (Agami & Waisel 1988, Charalambidou et al 2003.…”