Browsing by Author "Razafindratsima, Onja H."
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Item Assessing the impacts of nonrandom seed dispersal by multiple frugivore partners on plant recruitment(Ecological Society of America, 2015) Razafindratsima, Onja H.; Dunham, Amy E.Directed dispersal is defined as enhanced dispersal of seeds into suitable microhabitats, resulting in higher recruitment than if seeds were dispersed randomly. While this constitutes one of the main explanations for the adaptive value of frugivore-mediated seed dispersal, the generality of this advantage has received little study, particularly when multiple dispersers are involved. We used probability recruitment models of a long-lived rainforest tree in Madagascar to compare recruitment success under dispersal by multiple frugivores, no dispersal, and random dispersal. Models were parameterized using a three-year recruitment experiment and observational data of dispersal events by three frugivorous lemur species that commonly disperse its seeds. Frugivore-mediated seed dispersal was nonrandom with respect to canopy cover and increased modeled per-seed sapling recruitment fourfold compared to no dispersal. Seeds dispersed by one frugivore, Eulemur rubriventer, had higher modeled recruitment probability than seeds dispersed randomly. However, as a group, our models suggest that seeds dispersed by lemurs would have lower recruitment than if dispersal were random. Results demonstrate the importance of evaluating the contribution of multiple frugivores to plant recruitment for understanding plant population dynamics and the ecological and evolutionary significance of seed dispersal.Item Chapter 3: Status, trends and future dynamics of biodiversity and ecosystems underpinning nature's contributions to people.(IPBES, 2018) Cormier-Salem, Marie-Christine; Dunham, Amy E.; Gordon, Christopher; Belhabib, Dyhia; Bennas, Nard; Duminil, Jérôme; Egoh, Benis N.; Elahamer, Aisha Elfaki Mohamed; Moise, Bakwo Fils Eric; Gillson, Lindsey; Haddane, Brahim; Mensah, Adelina; Mourad, Ahmim; Randrianasolo, Harison; Razafindratsima, Onja H.; Taleb, Mohammed Sghir; Shemdoe, Riziki; Dowo, Gregory; Amekugbe, Millicent; Burgess, Neil; Foden, Wendy; Niskanen, Leo; Mentzel, Christine; Njabo, Kevin Y.; Maoela, Anicia Malebajoa; Marchant, Robert; Walters, Michele; Yao, Adou Constant; Archer, E.; Dziba, L.; Mulongoy, K.J.; Maoela, M.A.; Walters, M.Item Frugivores bias seed-adult tree associations through nonrandom seed dispersal: a phylogenetic approach(Wiley, 2016) Razafindratsima, Onja H.; Dunham, Amy E.Frugivores are the main seed dispersers in many ecosystems, such that behaviorally driven, nonrandom patterns of seed dispersal are a common process; but patterns are poorly understood. Characterizing these patterns may be essential for understanding spatial organization of fruiting trees and drivers of seed-dispersal limitation in biodiverse forests. To address this, we studied resulting spatial associations between dispersed seeds and adult tree neighbors in a diverse rainforest in Madagascar, using a temporal and phylogenetic approach. Data show that by using fruiting trees as seed-dispersal foci, frugivores bias seed dispersal under conspecific adults and under heterospecific trees that share dispersers and fruiting time with the dispersed species. Frugivore-mediated seed dispersal also resulted in nonrandom phylogenetic associations of dispersed seeds with their nearest adult neighbors, in nine out of the 16 months of our study. However, these nonrandom phylogenetic associations fluctuated unpredictably over time, ranging from clustered to overdispersed. The spatial and phylogenetic template of seed dispersal did not translate to similar patterns of association in adult tree neighborhoods, suggesting the importance of post-dispersal processes in structuring plant communities. Results suggest that frugivore-mediated seed dispersal is important for structuring early stages of plant-plant associations, setting the template for post-dispersal processes that influence ultimate patterns of plant recruitment. Importantly, if biased patterns of dispersal are common in other systems, frugivores may promote tree coexistence in biodiverse forests by limiting the frequency and diversity of heterospecific interactions of seeds they disperse.Item Increasing women's participation in community-based conservation: key to success?(Indian Ocean e-Ink, 2015) Razafindratsima, Onja H.; Dunham, Amy E.Item Simplified Communities of Seed-Dispersers Limit the Composition and Flow of Seeds in Edge Habitats(Frontiers Media S.A., 2021) Razafindratsima, Onja H.; Raoelinjanakolona, Nasandratra Nancia; Heriniaina, Rio R.; Nantenaina, Rindra H.; Ratolojanahary, Tianasoa H.; Dunham, Amy E.Edge effects, driven by human modification of landscapes, can have critical impacts on ecological processes such as species interactions, with cascading impacts on biodiversity as a whole. Characterizing how edges affect vital biotic interactions such as seed dispersal by frugivores is important for better understanding potential mechanisms that drive species coexistence and diversity within a plant community. Here, we investigated how differences between frugivore communities at the forest edge and interior habitats of a diverse tropical rainforest relate to patterns of animal-mediated seed dispersal and early seedling recruitment. We found that the lemur communities across the forest edge-interior gradient in this system showed the highest species richness and variability in body sizes at intermediate distances; the community of birds showed the opposite pattern for species richness. Three large-bodied frugivores, known to be effective dispersers of large seeds, tended to avoid the forest edge. As result, the forest edges received a lower rate of animal-mediated seed dispersal compared to the interior habitats. In addition, we also found that the seeds that were actively dispersed by animals in forest edge habitats were smaller in size than seeds dispersed in the forest interior. This pattern was found despite a similarity in seed size of seasonally fruiting adult trees and shrubs between the two habitats. Despite these differences in dispersal patterns, we did not observe any differences in the rates of seedling recruitment or seed-size distribution of successful recruit species. Our results suggest that a small number of frugivores may act as a potential biotic filter, acting on seed size, for the arrival of certain plant species to edge habitats, but other factors may be more important for driving recruitment patterns, at least in the short term. Further research is needed to better understand the potential long-term impacts of altered dispersal regimes relative to other environmental factors on the successional dynamics of edge communities. Our findings are important for understanding potential ecological drivers of tree community changes in forest edges and have implications for conservation management and restoration of large-seeded tree species in disturbed habitats.