Table 1.
Specialization indices obtained for plant species studied in each site and degree of plant dependence on insect pollination (IPD).
Figure 1.
Plant dependence on interactions in pollination networks.
Bipartite representation of networks only including plant species whose seed set was studied: (a) SB site (27 plants x 126 insects) and (b) PM site (11 plants x 54 insects). Green nodes represent plant species, red nodes represent pollinator species and links are weighted by interaction frequency (visits per flower/min). Plant nodes are ordered by linkage level (L) from the most specialist (bottom) to the most generalist (top). Within each network plant node size is proportional to the insect pollination dependence (IPD) (be aware size of nodes cannot be compared among subnetworks because they have been rescaled to fit in the figure). In SB network, the smallest green nodes are mainly concentrated in the bottom of the figure, indicating plants with a small linkage level were those with the lowest dependences on insect interactions. This trend is not observed in PM network where plants with just a few interactions (low L) were relatively highly dependent. Phylogenetic relationships between plants are not considered here.
Figure 2.
Relationships between plant dependence on insect pollination and plant specialization.
Regressions obtained for the coastal community (SB). The degree of plant dependence on insect pollination (IPD) is the percentage of actual seed set attributed to pollinator interactions, i.e. excluding seed set caused by wind and self-pollination. Plant specialization is measured as: (a) linkage level (L), (b) diversity of interactions (H), and (c) closeness centrality (CC). Plotted lines are the fitted GEE models.
Table 2.
Results for simple linear regression analyses (LM) and phylogenetic linear regression analysis using GEE in the coastal community (SB) (dfP = 11.33, phylogenetic degrees of freedom as defined in Paradis & Claude 2002 [36]) and in the mountain community (PM) (dfP = 5.7).