Specialisation and modularity of plant-pollinator networks

Modularity is the tendency of certain species to consistently interact with each other. It is a ubiquitous and important property of ecological networks that can determine the level of specialisation of species within those networks. Watts et al. investigate modularity and specialisation of plant-pollinator communities in the Peruvian Andes, a biodiverse region where no work in this area has hitherto been carried out.

Plant species and habitats surveyed in the Sacred Valley: (A) Barnadesia horrida (Asteraceae); (B) Baccharis salicifolia (Asteraceae); (C) Passiflora tripartita var. mollissima (Passifloraceae); (D) Polylepis (Rosaceae) woodlands 3700–4200 m; (E) subtropical montane dry forest (3000–3400 m), characterized by steep rocky slopes with spiny shrubs such as Duranta mandonii (Verbenaceae) and many Puya sp.; (F) Lupinus mutabilis (Fabaceae); (G) Oreocallis grandiflora (Proteaceae). Photographs: (A, C, F, G) Stella Watts, (D, E) Jeff Ollerton, (B) Lynn Watson. Full details in Watts *et al*.(2016)

They find that species at the centre of the modular structure of the plant–pollinator network tend to be the most abundant, with long phenologies. Additionally, they show that generalist plant species with open-access flowers dominate the plant-pollinator network. They conclude by cautioning that measuring specialisation requires careful consideration of how one defines a ‘specialist’.