Plant-pollinator networks show nested structure — specialists share partners with generalists
Nestedness means: if a specialist plant (few pollinators) interacts with a pollinator, that pollinator also visits the generalist plants. The interaction matrix, when rows and columns are sorted by degree, fills the upper-left corner — like a staircase pattern.
NODF = (Σ paired_overlap / n_pairs) × 100 — ranges 0 (random) to 100 (perfectly nested)
Why nested? Generalists act as a core backbone. Specialists exploit a subset of this core. Nestedness
stabilizes mutualistic communities: generalists buffer against specialist extinction, and rare specialists can coexist because their niche is "supported" by the core. Theoretical result (Bastolla 2009, Nature): nestedness minimizes effective competition and maximizes biodiversity.
NODF metric (Almeida-Neto 2008): counts the fraction of links in a less-connected row/column that are also present in more-connected rows/columns — averaged over all pairs.