Literaturdatenbank
Literaturdatenbank |
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Waibel, E. A. (2009). Mixed effects of ingestion by the aldabran giant tortoise (aldabrachelys gigantea) on the germination of alien plant species on the mascarene islands. Unpublished thesis , University of Zürich, Zürich.
Added by: Sarina Wunderlich (30 Jun 2012 22:02:01 UTC) |
| Resource type: Thesis/Dissertation BibTeX citation key: Waibel2009 View all bibliographic details  |
Categories: General Keywords: Aldabrachelys, Aldabrachelys dussumieri, Ernährung = nutrition, Schildkröten = turtles + tortoises, Testudinidae Creators: Waibel Publisher: University of Zürich (Zürich) |
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| Abstract |
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Testudinidae Dipsochelys dussumieri The use of non-native species as analogue species to restore lost ecological interactions is currently hotly debated. On the Mascarene Islands, the suitability of the Aldabran giant tortoise, Aldabrachelys gigantea as extant ecological replacement for the extinct giant tortoises is currently investigated; to see if they can restore lost grazing and seed dispersal functions. However, tortoises are likely to include not only native species in their diets, but also the numerous alien species, potentially facilitating the germination and dispersal of fleshy-fruited, animal-dispersed species. In a pot experiment that run over four months we investigated the effects of ingestion by A. gigantea on the germination success and the germination rate of five alien, partly invasive, fleshy-fruited species on Rodrigues. Feeding of distinctly coloured plastic pellets together with the fruits of these species allowed us to test for individual tortoise effects on seed germination patterns. Overall, ingestion by A. gigantea increased the probability of germination and germination rate, but reduced the number of germinated seeds in pots in which germination occurred. However, both the sign and the magnitude of these effects differed among the experimental plant species. Furthermore, individual tortoises influenced the percentage and rate of germination differently. Moreover, for germination percentage, these tortoise identity effects varied among plant species. Some, but not all of this variation was explained by tortoise age. Ingestion by sub-adult tortoises increased the germination whereas adult tortoises reduced seed germination compared to that of control seeds. We conclude that the consequences of Aldabran giant tortoise ingestion are contingent on the involved plant species. Our findings also emphasize the importance of considering intraspecific effects of frugivore ingestion on seed germination.
Added by: Sarina Wunderlich |