Browsing by Author "Ramos-Jiliberto, Rodrigo"

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    Decadal trends in the pollinator assemblage of Eucryphia cordifolia in Chilean rainforests
    (2014) Smith-Ramirez, Cecilia; Ramos-Jiliberto, Rodrigo; Valdovinos, Fernanda S.; Martinez, Paula; Castillo, Jessica A.; Armesto, Juan J.
    Long-term studies of plant-pollinator interactions are almost nonexistent in the scientific literature. The objective of the present study was to determine changes and trends in the pollinator assemblage of ulmo (Eucryphia cordifolia; Cunoniaceae), a canopy-emergent tree found in Chilean temperate rainforests. We assessed the temporal variability of the pollinator assemblage and identified possible modulators of the observed temporal shifts. We sampled insect visitors to the flowers of 16 individual trees of E. cordifolia during 10 consecutive flowering seasons (2000-2009), recording a total of 137 pollinator species with a mean number of species per year of 44. Only three pollinator species (2.2 %) were recorded every year. Two bee species accounted for 50 % of all insect visits to flowers. One bee species, Bombus dahlbomii (native), was dominant in one season, whereas Apis mellifera (exotic) dominated during the next season. These interannual shifts in population abundances presented first-order dynamics that were characterized by oscillations with a period of 2 years. Changes in the abundances of the dominant pollinators, as well as differences in temperature and precipitation during insect emergence and flowering, led to a nested temporal structure of pollinator composition. Furthermore, the abundances of less common pollinators were sensitive to the abundance of the dominant bee species and to monthly maximum temperatures and the average precipitation during spring and summer. Based on our results and those from other studies, we predict a decline in the numbers of Bombus dahlbomii and nondominant native pollinators in response to new exotic arrivals.
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    Osmoregulatory and demographic responses to salinity of the exotic cladoceran Daphnia exilis
    (2010) Heine-Fuster, Inger; Vega-Retter, Caren; Sabat, Pablo; Ramos-Jiliberto, Rodrigo
    Daphnia exilis is a halophylic species that was recently found in Chile, distant from its natural range. In this study, we analyze the osmoregulatory and life-history responses to salinity exhibited by Daphnia exilis, as a first step towards understanding the ecology of this exotic species whose invasion potential has been related to its ability to tolerate saline environments. A set of laboratory experiments were carried out, in which we exposed organisms to a salinity gradient, and measured internal and environmental osmolality, assessed the effect of acclimation time and measured life-history traits that were used to perform a demographic retrospective analysis. Our results showed that (i) D. exilis exhibited a hyper-osmoconformer response, (ii) acclimation time did not exert effects on the osmoregulatory response, (iii) salinity up to 6 g L-1 did not alter the population growth rate, (iv) at 8 g L-1 population growth rate declined, mainly due to a delayed age at maturity and reduced fertility. Based on this information, we suggest that the responses to salinity exhibited by the exotic D. exilis confer an advantage over its natural enemies and may facilitate colonization through exploiting disturbed places as chemical refuges.