Evaluating sampling completeness in a desert plant-pollinator network

CHACOFF, NATACHA P.; VÁZQUEZ, DIEGO P.; LOMÁSCOLO, SILVIA B.; STEVANI, ERICA L.; DORADO, JIMENA; PADRÓN, BENIGNO

JOURNAL OF ANIMAL ECOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2012 vol. 81 p. 190 - 200

0021-8790

1. The study of plant--pollinator interactions in a network context is receiving increasing attention. This approach has helped to identify several emerging network patterns such as nestedness and modularity. However, most studies are based only on qualitative information, and some ecosystems, such as deserts and tropical forests, are underrepresented in these datasets.2. We present an exhaustive analysis of the structure of a four-year plant--pollinator network from the Monte desert in Argentina using both qualitative and quantitative tools. We described the structure of this network and evaluate the completeness of our sampling using asymptotic species richness estimators, to assess the extent to which the realized sampling effort allows an accurate description of species interactions and to estimate the minimun number of additional sampling required to detect 90% of the interactions. We evaluated completeness of detection of the community-wide pollinator fauna, of the pollinator fauna associated to each plant species and of the plant--pollinator interactions. We also evaluated whether sampling completeness was influenced by plant characteristics, such as flower abundance, flower phenological span, sampling effort, number of interspecific links (degree) and selectiveness in the identify of their flower visitors.3. We found that this desert plant--pollinator network has a nested structure and that it exhibits modularity and high network-level generalization.4. In spite of our high sampling effort, and although we sampled 80% of the pollinator fauna we recorded only 55% of the interactions. Thus, although a 0.64-fold increase in sampling effort would suffice to detect 90% of the pollinator species, a 5-fold increase in sampling effort would be necessary to detect 90% of the interactions.5. Detection of interactions was incomplete for most plant species, particularly those with a long flowering season, high flower abundance or a high level of specialisation. Our results suggest that to minimize this incompleteness, sampling effort should be adjusted to the length of the flowering season, flower abundance and plant specialisation, with greater effort on specialized plants with a long flowering season and abundant flowers.6. Sampling the diversity of interactions is labor intensive, and most plant--pollinator networks published to date are likely to be undersampled. Our analysis allowed estimating the completeness of our sampling, the additional effort needed to detect most interactions and the plant traits that influence the detection of their interactions.