DOI: 10.5061/dryad.dv1gq
title: Data from: Why are some plant-pollinator networks more nested than others?

description: 1. Empirical studies have found that the mutualistic interactions forming
 the structure of plant-pollinator networks are typically more nested than
 expected by chance alone. Additionally, theoretical studies have shown a
 positive association between the nested structure of mutualistic networks
 and community persistence. Yet, it has been shown that some
 plant-pollinator networks may be more nested than others, raising the
 interesting question of which factors are responsible for such enhanced
 nested structure. 2. It has been argued that ordered network structures
 may increase the persistence of ecological communities under less
 predictable environments. This suggests that nested structures of
 plant-pollinator networks could be more advantageous under highly seasonal
 environments. While several studies have investigated the link between
 nestedness and various environmental variables, unfortunately, there has
 been no unified answer to validate these predictions. Here, we move from
 the problem of describing network structures to the problem of comparing
 network structures. We develop comparative statistics, and apply them to
 investigate the association between the nested structure of 59
 plant-pollinator networks and the temperature seasonality present in their
 locations. 3. We demonstrate that higher levels of nestedness are
 associated with a higher temperature seasonality. We show that the
 previous lack of agreement came from an extended practice of using
 standardized measures of nestedness that cannot be compared across
 different networks. 4. Importantly, our observations complement theory
 showing that more nested network structures can increase the range of
 environmental conditions compatible with species coexistence in
 mutualistic systems, also known as structural stability. This increase in
 nestedness should be more advantageous and occur more often in locations
 subject to random environmental perturbations, which could be driven by
 highly changing or seasonal environments. This synthesis of theory and
 observations could prove relevant for a better understanding of the
 ecological processes driving the assembly and persistence of ecological
 communities.
description: Data_and_codeThe file contains: - The R-code: (1) to load a plant-pollinator network, (2) to calculate the raw NODF as in Almeida-Neto et al. (Oikos 117, 2008), (3) the maximum NODF value that can be reached by a network with given connectance and size (using a greedy algorithm as explained in the manuscript), and (4) the combined NODF statistic as described in the manuscript (NODF divided by the product of maximum NODF, connectance, and the log of the geometric mean of plants and pollinators). - Note that we are providing a simple example of a binary network. In the manuscript we used the 59 plant-pollinator networks downloaded from the Web of Life database (www.web-of-life.es): M_PL_001 to M_PL_059. - The temperature seasonality (variance of daily temperature) for 43 plant-pollinator networks for which we found information about latitude and longitude. Environmental data were downloaded from the public repository WorldClim version 1.4, release 3, resolution 2.5 min.