Grant-funded Project Nr. 152/2005/B-BIO/PřF Final Report
Project title:
Population ecology of the genus Clusia on the inselberg in French Guaiana
Research leader:
Mgr. Blanka Vlasáková, 2003
Co-researcher:
RNDr. Petr Sklenář, PhD.
Period of project:
2005-2006
Overall grant:
416 000 CZK
Project Results
New species identified on the Nouragues inselberg Originally, the research should focus on two species of the genus Clusia: C. minor and C. nemorosa. During the course of the study I have discovered that the first species had been identified wrong, i.e. it was not C. minor. In collaboration with dr. Mats Gustafsson (University of Aarhus, Denmark) ITS sequencing was run to find out the true identity of this plant. According to the analyses the plant under study belongs to a new and almost certainly unnamed species, which closest relative is C. sellowiana that is distributed in northern Brazil. Preliminary, the plant is termed C. sp. aff. sellowiana. Plant-pollinator interactions The two plant species are involved in very different pollinations systems. Clusia nemorosa produces floral resins – a clear adaptation for bee pollination. However, pollen as a form of reward is heavily exploited, which has a profound effect on the process of pollination. Therefore the specialization and the strength of the bee-plant interaction is far lower that it was expected from the presence of a specialized floral reward. Clusia sp. aff. sellowiana flowers at night and produces no resins. Pollinators are rewarded with a floral secret produced by spongy tissues at the base of stamens and staminodes. The composition of the secret is unclear. It contains no sugars. The plant is pollinated by a cockroach Amazonina platystylata. This mode of pollination is absolutely unique and has been recorded only once before. The floral scent contains a high percentage of acetoin, a compound unusual for floral scents. Acetoin is present in sex pheromones of other cockroach taxa. Field and laboratory experiments confirmed positive reaction of the cockroaches when the acetoin is present in the environment. Primary and secondary dispersal, predation and the pattern of the seed rain The seeds of both species are dispersed by a guild of small frugivorous passerines. Smaller seeds of Clusia sp. aff. sellowiana (0.4 cm) are swallowed and the aril is removed in the course of digestion. The seeds are released intact in the droppings. Larger seeds of C.nemorosa (0.8 cm) are processed in the beak where the aril is removed and seeds are dropped onto the ground. Predispersal predation by invertebrates is nearly nonexistent. Granivorous birds remove less than 10% of the ripen seeds. The final pattern of the seed rain is influenced by secondary dispersal that is mainly mediated by ants. Due to different handling techniques and preferences of primary and secondary dispersers the final pattern of seed distribution differs considerably between the two plant species. Seeds under a fruiting Clusia sp. aff. sellowiana are usually conspecific but their mother plant can be situated tens of meters away. On the contrary, seeds under C. nemorosa are either conspecific, originating from tree above or they belong to Clusia sp. aff. sellowiana and have been transferred to this place by birds. Germination, seedling survival and plant establishment Clusia sp. aff. sellowiana gains control over the space by clonal horizontal growth. It dominates the places of the inselberg where litter can accumulate. On a local scale it does not reproduce sexually. However, the colonization of new habitats is possible only via sexual reproduction. The conditions needed for successful establishment of a new individual are not clear. Seed germination and seedling survival is extremely low. Seedlings are rarely encountered on the inselberg. Clusia nemorosa usually occurs as a tree either solitary or mixed into the shrubs of Clusia sp. aff. sellowiana. In that case it overgrows the shrub vegetation to reach to its most important source, which is light. This species get control over the space vertically and occupies a different niche than C. sp. aff. sellowiana. Due to the limitations of its horizontal growth it is not likely that C. nemorosa can replace C. sp. aff. sellowiana Presentation of results The data have been presented at the International Conference of the Society for Tropical Ecology (gtö), which took place in Feb 2007 in Bonn, Germany. The poster was entitled: „Reproduction of selected Clusia species on the Nouragues inselberg in French Guiana” (http://www.zfmk.de/web/Forschung/Kongresse/2007/200702_gtoe/index.de.html There are 3 scientific publications being prepared: 1) Cockroaches as pollinators of Clusia sp. aff. sellowiana, a new species from an inselberg in French Guiana (shortly before finishing), 2) Pollen versus resin – pollination of Clusia nemorosa and 3) Seed dispersal and regeneration of dominant Clusia species on an inselberg in French Guiana.