Ecological assembly rules on arthropod community inhabiting mistletoes

다국어 초록 (Multilingual Abstract)

1. The colonisation of a new habitat by a community is led by deterministic and stochastic processes at different spatio‐temporal scales. Parasitic plants, such as mistletoe, represent a new habitat within forest canopy that is free to be colonised by many organisms.
2. This study investigates how ecological factors operating at forest and plant scales drive changes in both specialist (mistletoe‐dwelling) and tourist (transient visitors) arthropod communities inhabiting European mistletoe, Viscum album subsp. austriacum, in a Mediterranean pine forest. The influence of elevation along a broad elevational gradient was tested by sampling arthropod communities dwelling in mistletoe plants and host pine branches and the effects of mistletoe plant size, distances to other mistletoes, and temporal variation in arthropod assemblages inhabiting mistletoes.
3. The diversity of the specialist community remained constant along the elevational gradient and over the summer period, while the tourist and pine‐dwelling arthropod communities showed species turnover. Larger mistletoes were occupied by more species and individuals, whereas more isolated mistletoes presented the same equilibrium point as the more aggregated ones. Thus, mistletoe size is key to the composition of the arthropod community.
4. In conclusion, this study's findings indicate contrasting assembly rules for specialised and tourist arthropod communities associated with mistletoe. The specialist community was highly stable and followed a deterministic trophic sequence of colonisation as the assemblage rule: first, colonisation by the main specialist herbivore, Cacopsylla visci, and, second, by its predator Anthocoris visci. Meanwhile, the tourist community, being a subset of the arthropod assemblage of the pine, acts independent of mistletoe presence.

The European mistletoe, Viscum album, represents a new habitat within forest canopy colonised by a highly specialised arthropod community and transient specimens coming from pine host.
Different ecological factors, such as elevational gradient, plant size, distances to others mistletoes, and temporal variation, determine the ecological assembly rules of an arthropod community inhabiting mistletoes.
Specialists and tourists have contrasting assembly rules, where specialists are highly stable under practically all environmental conditions following a trophic sequence of colonisation, and tourists act independent of mistletoe presence.