Abundance and generalisation in mutualistic networks: solving the chicken-and-egg dilemma.
A frequent observation in plant-animal mutualistic networks is that abundant species tend to be more generalised, interacting with a broader range of interaction partners than rare species. Uncovering the causal relationship between abundance and generalisation has been hindered by a chicken-and-egg dilemma: is generalisation a by-product of being abundant, or does high abundance result from generalisation? Here, we analyse a database of plant-pollinator and plant-seed disperser networks, and provide strong evidence that the causal link between abundance and generalisation is uni-directional. Specifically, species appear to be generalists because they are more abundant, but the converse, that is that species become more abundant because they are generalists, is not supported by our analysis. Furthermore, null model analyses suggest that abundant species interact with many other species simply because they are more likely to encounter potential interaction partners.
Physics Department, Faculty of Sciences, Universidad de la República, Igua 4225, Montevideo, 11400, Uruguay.
Hugo
H
Fort
Argentine Institute for Dryland Research, CONICET, CC 507, 5500, Mendoza, Argentina.|Faculty of Exact and Natural Sciences, National University of Cuyo, M5502JMA, Mendoza, Argentina.
Diego P
DP
Vázquez
Electrical and Computer Systems Engineering, School of Engineering, Monash University, 47500, Bandar Sunway, Malaysia.
Boon Leong
BL
Lan
D000818:Animals; D020387:Food Chain; D008954:Models, Biological; D010944:Plants; D054817:Pollination; D011156:Population Density; D058614:Seed Dispersal; D013559:Symbiosis
causality; generalisation; mutualistic networks; plant-animal interactions; pollination; seed dispersal; specialisation