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Germination Success (germination + success)
Selected AbstractsThe Effect of Seed Mass and Gap Size on Seed Fate of Tropical Rain Forest Tree Species in GuyanaPLANT BIOLOGY, Issue 2 2004L. H. van Ulft Abstract: For eleven tree species, differing in seed mass, germination success (emergence success for two small-seeded species) and the causes of failure to germinate were studied in the forest understorey and in logging gaps in the tropical rain forests of Guyana. In the forest understorey, germination success increased with seed mass. However, as gap size increased the difference between smaller and larger seeded species diminished because germination success of smaller-seeded species increased slightly, while that of larger-seeded species decreased dramatically. The negative effect of gap size on germination success of larger-seeded species was caused by an increased risk of desiccation with gap size, which was a far more important seed mortality agent for larger than for smaller-seeded species. Generally, seeds of smaller-seeded species suffered more from insect predation and were removed at higher rates than larger-seeded species. On the other hand, larger-seeded species were eaten more by mammals than smaller-seeded species. It is concluded that logging can result in shifts in the species composition in the tropical rain forests of Guyana which are dominated by species with large seeds, since germination success of larger-seeded species is dramatically reduced in large logging gaps. [source] Consequences of southern cassowary (Casuarius casuarius, L.) gut passage and deposition pattern on the germination of rainforest seedsAUSTRAL ECOLOGY, Issue 3 2010MATT G. BRADFORD Abstract In Australia's tropical rainforests the endangered southern cassowary, Casuarius casuarius, L., is the largest native frugivore and many plant species, because of the size of their fruits or seeds, are thought to be largely dependent on cassowaries for their dispersal. In this study we asked whether the contribution of cassowaries to plant recruitment extends beyond removing seeds from the vicinity of the parent. To do this we conducted germination trials involving 17 rainforest plant species to test whether cassowary consumption and seed deposition pattern alter germination probability or time to germination. Twenty-four per cent of species showed changed germination probabilities, with one species showing no germination without cassowary consumption, and 35% showed changed time to germination. However these differences did not translate into any significant effects when considered across all species. We examined gut scarification, fruit pulp removal (de-inhibition) and deposition in faecal material as mechanisms for changing germination success; each contributed to the changed success of individual species. There was a negative effect of seed clumping on five species. We conclude that cassowary consumption can modify germination performance in a minority of rainforest plants and that the effect is generally positive. Although the effect on large seeded species was small it is most likely to be important as the cassowary is the only animal in Australia able to internally process large numbers of these seeds. [source] Gut passage effect of the introduced red-whiskered bulbul (Pycnonotus jocosus) on germination of invasive plant species in MauritiusAUSTRAL ECOLOGY, Issue 3 2009JANNIE F. LINNEBJERG Abstract In Mauritius, many of the worst invasive plant species have fleshy fruits and rely on animals for dispersal. The introduced red-whiskered bulbul (Pycnonotus jocosus) feeds on many fleshy-fruited species, and often moves from invaded and degraded habitats into higher quality native forests, thus potentially acting as a mediator of continued plant invasion into these areas. Furthermore, gut passage may influence seed germination. To investigate this, we fed fleshy fruits of two invasive plant species, Ligustrum robustum and Clidemia hirta, to red-whiskered bulbuls. Gut passage times of seeds were recorded. Gut-passed seeds were sown and their germination rate and germination success compared with that of hand-cleaned seeds, as well as that of seeds in whole fruits. Gut passage and hand-cleaning had significant positive effects on germination of both species. Gut-passed seeds of both C. hirta and L. robustum germinated faster than hand-cleaned seeds. However, for L. robustum, this was only true when compared with hand-cleaned seeds with intact endocarp; when compared with hand-cleaned seeds without endocarp, there was no difference. For overall germination success, there was a positive effect of gut passage for C. hirta, but not for L. robustum. For both C. hirta and L. robustum, no seeds in intact fruits geminated, suggesting that removal of pulp is essential for germination. Our results suggest that, first, the initial invasion of native forests in Mauritius may not have happened so rapidly without efficient avian seed dispersers like the red-whiskered bulbul. Second, the bulbul is likely to be a major factor in the continued re-invasion of C. hirta and L. robustum into weeded and restored conservation management areas. [source] Vertebrate Fruit Removal and Ant Seed Dispersal in the Neotropical Ginger Renealmia alpinia (Zingiberaceae),BIOTROPICA, Issue 2 2009Carlos García-Robledo ABSTRACT Plants frequently display fruit characteristics that support multiple seed-dispersal syndromes. These ambiguous characteristics may reflect the fact that seed dispersal is usually a complex process involving multiple dispersers. This is the case for the Neotropical ginger Renealmia alpinia (Zingiberaceae). It was originally suggested that the aromatic fruits of R. alpinia located at the base of the plant are adapted for terrestrial mammal seed dispersal. However, the dark-purple coloration of the fruits and bright orange aril surrounding the seeds suggest that birds may play a role in R. alpinia seed dispersal. At La Selva Biological Station, Costa Rica, we used camera traps to record vertebrate visits to infructescences of R. alpinia. Most visitors were toucans and aracaris (Ramphastidae). However fruits were also removed by terrestrial mammals (coatis and armadillos). In addition to vertebrate fruit removal, some of the fruits dehisce and the seeds that fall on the ground are dispersed by ants. Fruitfall traps showed that 77 percent of fruits are removed by vertebrates. However, 15 percent of fruits fall to the base of parent plants to be potentially dispersed by ants. Experiments using a laboratory ant colony showed that ants are effective seed dispersers of R. alpinia. Ant seed manipulation increased germination success and reduced time to germination. In conclusion, primary seed dispersal in the Neotropical ginger R. alpinia is mostly performed by birds, additionally ants are effective dispersers at short distances. Seed dispersal in R. alpinia is a complex process involving a diverse array of dispersal agents. RESUMEN Los frutos de algunas plantas presentan características que se ajustan a más de un síndrome de dispersión. Es posible que estas características ambiguas reflejen el hecho de que la dispersión de semillas es usualmente un proceso complejo que involucra múltiples organismos dispersores. Ese es el caso de la Zingiberaceae Neotropical Renealmia alpinia. Originalmente se sugirió que los frutos aromáticos y la posición basal de las infrutescencias de R. alpinia son adaptaciones para la dispersión por mamíferos terrestres. Sin embargo, el color morado oscuro del exocarpo y el color anaranjado de los arilos en los frutos maduros sugieren que las aves pueden jugar un papel importante en la dispersión de semillas de R. alpinia. En la estación Biológica La Selva, Costa Rica, usamos cámaras trampa para registrar las visitas por invertebrados a las infrutescencias de R. alpinia. La mayoría de las visitas fueron por tucanes y arasaríes (Ramphastidae). La dispersión de semillas en R. alpinia puede ser aún más compleja pues parte de los frutos maduros liberan semillas en la base de la planta, las cuales son dispersadas por hormigas. Trampas de frutos registraron 77% de los frutos removidos por vertebrados. Sin embargo las semillas de 15% de los frutos cayeron en el suelo para ser potencialmente dispersadas por hormigas. Experimentos en laboratorio demostraron que las hormigas son dispersores efectivos de R. alpinia. Semillas manipuladas por hormigas germinaron en mayor proporción y presentaron una reducción en el tiempo de germinación. En conclusión, los frutos de R. alpinia son principalmente dispersados por aves. Adicionalmente, las hormigas son eficaces dispersoras de semillas a cortas distancias. La dispersión de semillas en R. alpinia es un proceso complejo que involucra un diverso gremio de agentes dispersores. [source] | ||||||||||