Nonrandom seed dispersal by frugivores and consequences of dispersal loss
We seek to provide new insights to long-lasting questions of what are the impacts of frugivores on plants -- from the individual level to population and community levels, how different frugivore species within a guild may vary in their seed dispersal service, and how frugivore loss affect ecosystem integrity and functioning. These questions have important conceptual implications for understanding the dynamics and functioning of biodiverse plant communities, given that seed dispersal determines ecological and evolutionary patterns of plant diversity. Such knowledge can also help in predicting which species might be most sensitive and what are the ecosystem responses to frugivore loss.
Most of the research we have conducted on this topic has been on seed dispersal by lemur frugivores in biodiverse Malagasy forests, where a majority of plants have traits adapted for seed dispersal by vertebrates and highly diverse plant communities are vying for a limited set of frugivore generalist taxa for seed dispersal services (Razafindratsima 2014, Albert-Daviaud et al. 2020). Previous work by lab members have demonstrated that nonrandom seed dispersal by frugivores could positively affect plant populations, and structure the spatial associations and the interactions between plants within a community. Razafindratsima and Dunham (2015), for instance, demonstrated that nonrandom dispersal of seeds, with respect to forest canopy cover, increased per-seed sapling recruitment fourfold, compared to no dispersal. Additionally, taking a phylogenetic and temporal approach, Razafindratsima and Dunham (2016) showed that by using fruiting trees as seed-dispersal foci, frugivores structure the spatial and phylogenetic patterns of early stage plant-plant associations, setting the template for post-dispersal processes that influence ultimate patterns of plant recruitment. Also, in a recent work, Ramananjato et al. (2020) highlighted the importance of nocturnal omnivores as seed dispersal agents, with a focus on two mouse lemurs. Given their important role in structuring and maintaining diversity, losing these seed dispersers could, therefore, have cascading impacts on ecosystem health. In a previous research, Razafindratsima et al. (2018) developed simulation models under different scenarios of plant community changes, using empirical data on species traits and community composition, to demonstrate that losing large-sized frugivorous primates could result in decrease of a Malagasy forest’s potential to store carbon. Such research findings highlight the needs for considering species interactions into a conservation agenda aimed at reducing carbon emissions and maintaining long-term carbon stocks in tropical forests.
Most of the research we have conducted on this topic has been on seed dispersal by lemur frugivores in biodiverse Malagasy forests, where a majority of plants have traits adapted for seed dispersal by vertebrates and highly diverse plant communities are vying for a limited set of frugivore generalist taxa for seed dispersal services (Razafindratsima 2014, Albert-Daviaud et al. 2020). Previous work by lab members have demonstrated that nonrandom seed dispersal by frugivores could positively affect plant populations, and structure the spatial associations and the interactions between plants within a community. Razafindratsima and Dunham (2015), for instance, demonstrated that nonrandom dispersal of seeds, with respect to forest canopy cover, increased per-seed sapling recruitment fourfold, compared to no dispersal. Additionally, taking a phylogenetic and temporal approach, Razafindratsima and Dunham (2016) showed that by using fruiting trees as seed-dispersal foci, frugivores structure the spatial and phylogenetic patterns of early stage plant-plant associations, setting the template for post-dispersal processes that influence ultimate patterns of plant recruitment. Also, in a recent work, Ramananjato et al. (2020) highlighted the importance of nocturnal omnivores as seed dispersal agents, with a focus on two mouse lemurs. Given their important role in structuring and maintaining diversity, losing these seed dispersers could, therefore, have cascading impacts on ecosystem health. In a previous research, Razafindratsima et al. (2018) developed simulation models under different scenarios of plant community changes, using empirical data on species traits and community composition, to demonstrate that losing large-sized frugivorous primates could result in decrease of a Malagasy forest’s potential to store carbon. Such research findings highlight the needs for considering species interactions into a conservation agenda aimed at reducing carbon emissions and maintaining long-term carbon stocks in tropical forests.
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Lemur frugivores: (a) Eulemur rubriventer, (b) Eulemur rufifrons, and (c) Varecia variegata editorum. These species are the main seed dispersers of (d) Cryptocarya crassifolia in Ranomafana National Park, Madagascar. Photo credits: Coke Smith and Onja Razafindratsima. Photo credits: (a) Coke Smith, (c) Mamy‐Fy Rakotondrainibe, (b and d) O. H. Razafindratsima. Ecology, Volume: 96, Issue: 1, Pages: 24-30, First published: 01 January 2015, DOI: (10.1890/14-0684.1)
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Seed predation and secondary dispersalGround-dwelling vertebrates, such as rodents, could play important roles in post-dispersal predation and movement of large seeds, which may influence patterns of plant recruitment and regeneration. We aim to identify the potential roles of rodents in filling functional gap in the absence of primary seed dispersers, by influencing seed fate.
A recent work by Razafindratsima (2017) showed that the native rodent species, Nesomys rufus, was potentially responsible for seed predation and/or removal in a less-disturbed habitat in Ranomafana National Park. Additionally, lack of seed-hoarding in the area during the study period suggests a limited role of rodents in secondary seed dispersal in this system; however, further studies are needed. |
Forest rat at Ranomafana National Park
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