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The missing part of seed dispersal networks: structure and robustness of bat-fruit interactions.

Mello MA, Marquitti FM, Guimarães PR, Kalko EK, Jordano P, de Aguiar MA - PLoS ONE (2011)

Bottom Line: Primary frugivores interacted with a larger proportion of the plants available and also occupied more central positions; furthermore, their extinction caused larger changes in network structure.We conclude that bat-fruit networks are highly cohesive and robust mutualistic systems, in which redundancy is high within modules, although modules are complementary to each other.Dietary specialization seems to be an important structuring factor that affects the topology, the guild structure and functional roles in bat-fruit networks.

View Article: PubMed Central - PubMed

Affiliation: Institute of Experimental Ecology, University of Ulm, Ulm, Germany. marmello@gmail.com

ABSTRACT
Mutualistic networks are crucial to the maintenance of ecosystem services. Unfortunately, what we know about seed dispersal networks is based only on bird-fruit interactions. Therefore, we aimed at filling part of this gap by investigating bat-fruit networks. It is known from population studies that: (i) some bat species depend more on fruits than others, and (ii) that some specialized frugivorous bats prefer particular plant genera. We tested whether those preferences affected the structure and robustness of the whole network and the functional roles of species. Nine bat-fruit datasets from the literature were analyzed and all networks showed lower complementary specialization (H(2)' = 0.37±0.10, mean ± SD) and similar nestedness (NODF = 0.56±0.12) than pollination networks. All networks were modular (M = 0.32±0.07), and had on average four cohesive subgroups (modules) of tightly connected bats and plants. The composition of those modules followed the genus-genus associations observed at population level (Artibeus-Ficus, Carollia-Piper, and Sturnira-Solanum), although a few of those plant genera were dispersed also by other bats. Bat-fruit networks showed high robustness to simulated cumulative removals of both bats (R = 0.55±0.10) and plants (R = 0.68±0.09). Primary frugivores interacted with a larger proportion of the plants available and also occupied more central positions; furthermore, their extinction caused larger changes in network structure. We conclude that bat-fruit networks are highly cohesive and robust mutualistic systems, in which redundancy is high within modules, although modules are complementary to each other. Dietary specialization seems to be an important structuring factor that affects the topology, the guild structure and functional roles in bat-fruit networks.

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Related in: MedlinePlus

Robustness to cumulative species removal.The simulations of cumulative removals of species showed that bat-fruit networks are very robust both to removals of bats and plants, as extinction curves declined slowly on average.
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pone-0017395-g003: Robustness to cumulative species removal.The simulations of cumulative removals of species showed that bat-fruit networks are very robust both to removals of bats and plants, as extinction curves declined slowly on average.

Mentions: The robustness of bat-fruit networks to cumulative extinctions was relatively high, both for bats (R = 0.55±0.10, range 0.41–0.69) and plants (R = 0.68±0.09, range 0.58–0.84) (Fig. 3). There was also a high robustness to the removal of single species. Proportional change in nestedness (NODFr) varied from 0 to 3.7%, and was lower than 1% in most cases. Furthermore, there were hardly any secondary losses (SLr = 0.0/0.00: median/quartiles, varying from 0 to 3.7%, most cases = 0). Removal of species which interacted with a higher proportion of available partners caused larger changes in nestedness in both bats (N = 87, r = −0.46, P<0.001) and plants (N = 198, r = −0.44, P<0.001) (Fig. 4). The removal of primary frugivores caused larger decreases in nestedness than the removal of secondary or occasional frugivores (N = 87, df = 2, K = 6.87, P = 0.03) (Fig. 4).


The missing part of seed dispersal networks: structure and robustness of bat-fruit interactions.

Mello MA, Marquitti FM, Guimarães PR, Kalko EK, Jordano P, de Aguiar MA - PLoS ONE (2011)

Robustness to cumulative species removal.The simulations of cumulative removals of species showed that bat-fruit networks are very robust both to removals of bats and plants, as extinction curves declined slowly on average.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3046224&req=5

pone-0017395-g003: Robustness to cumulative species removal.The simulations of cumulative removals of species showed that bat-fruit networks are very robust both to removals of bats and plants, as extinction curves declined slowly on average.
Mentions: The robustness of bat-fruit networks to cumulative extinctions was relatively high, both for bats (R = 0.55±0.10, range 0.41–0.69) and plants (R = 0.68±0.09, range 0.58–0.84) (Fig. 3). There was also a high robustness to the removal of single species. Proportional change in nestedness (NODFr) varied from 0 to 3.7%, and was lower than 1% in most cases. Furthermore, there were hardly any secondary losses (SLr = 0.0/0.00: median/quartiles, varying from 0 to 3.7%, most cases = 0). Removal of species which interacted with a higher proportion of available partners caused larger changes in nestedness in both bats (N = 87, r = −0.46, P<0.001) and plants (N = 198, r = −0.44, P<0.001) (Fig. 4). The removal of primary frugivores caused larger decreases in nestedness than the removal of secondary or occasional frugivores (N = 87, df = 2, K = 6.87, P = 0.03) (Fig. 4).

Bottom Line: Primary frugivores interacted with a larger proportion of the plants available and also occupied more central positions; furthermore, their extinction caused larger changes in network structure.We conclude that bat-fruit networks are highly cohesive and robust mutualistic systems, in which redundancy is high within modules, although modules are complementary to each other.Dietary specialization seems to be an important structuring factor that affects the topology, the guild structure and functional roles in bat-fruit networks.

View Article: PubMed Central - PubMed

Affiliation: Institute of Experimental Ecology, University of Ulm, Ulm, Germany. marmello@gmail.com

ABSTRACT
Mutualistic networks are crucial to the maintenance of ecosystem services. Unfortunately, what we know about seed dispersal networks is based only on bird-fruit interactions. Therefore, we aimed at filling part of this gap by investigating bat-fruit networks. It is known from population studies that: (i) some bat species depend more on fruits than others, and (ii) that some specialized frugivorous bats prefer particular plant genera. We tested whether those preferences affected the structure and robustness of the whole network and the functional roles of species. Nine bat-fruit datasets from the literature were analyzed and all networks showed lower complementary specialization (H(2)' = 0.37±0.10, mean ± SD) and similar nestedness (NODF = 0.56±0.12) than pollination networks. All networks were modular (M = 0.32±0.07), and had on average four cohesive subgroups (modules) of tightly connected bats and plants. The composition of those modules followed the genus-genus associations observed at population level (Artibeus-Ficus, Carollia-Piper, and Sturnira-Solanum), although a few of those plant genera were dispersed also by other bats. Bat-fruit networks showed high robustness to simulated cumulative removals of both bats (R = 0.55±0.10) and plants (R = 0.68±0.09). Primary frugivores interacted with a larger proportion of the plants available and also occupied more central positions; furthermore, their extinction caused larger changes in network structure. We conclude that bat-fruit networks are highly cohesive and robust mutualistic systems, in which redundancy is high within modules, although modules are complementary to each other. Dietary specialization seems to be an important structuring factor that affects the topology, the guild structure and functional roles in bat-fruit networks.

Show MeSH
Related in: MedlinePlus