Influence of sampling methods on the description of a Neotropical seed dispersal network

Analysis of ecological networks is a useful approach to investigate species interactions. However, sampling method may influence the observed patterns especially in highly diverse communities. Here we evaluated how sampling decisions influence the characterization of a seed dispersal network between frugivorous birds and plants in a Neotropical community, in Brazil. We found that phytocentric and zoocentric approaches were highly complementary, with only 3.6% of the links in common between both approaches. The phytocentric network was less asymmetric and had higher values for specialization (H-2') and modularity (Q(w)) than the zoocentric, which in turn had more plants, and higher nestedness (NODFc). The network combining both methods was larger and had intermediate values of specialization, modularity and nestedness. Furthermore, species-level metrics: normalized degree, specialization (d') and species strength, were not correlated between the two methods for the bird and plant species in common. Our results indicate that the choice of sampling method may affect the interpretation of network structure and the role species play in the communities. Moreover, while phytocentric sampling may limit the detection of interactions to plants seen by the observer, zoocentric sampling tends to undersample bird species with higher body mass or that do not forage in the understory. We stress that the choice of sampling method requires careful consideration of the most appropriate spatial scales to describe an interaction pattern, as well as their advantages and limitations, to better understand the drivers and consequences of species interactions.

Automated summary

Analysis of ecological networks is a useful approach to investigate species interactions. Sampling method can affect the observed patterns and interpretation of network structure. This study found that sampling approaches based on plants and animals were highly complementary in characterizing a seed dispersal network. The choice of sampling method can impact the assessment of species roles in communities.