Life inside a gall: diversity, phenology and structure of Portuguese gall communities, their hosts, parasitoids and inquilines

Plant galls sustain diverse and complex communities of gallers, parasitoids and inquilines that provide exceptional systems to explore evolutionary, ecological and conservation questions. However, the structure and phenology of such communities are still largely unknown. In order to fill these gaps, we sampled plant galls along the Portuguese coast aiming to (1) characterize the diversity of gall-associated communities (plants, gallers, their parasitoids, and inquilines); (2) evaluate how richness and abundance of gallers are shaped by plant life-form; and (3) explore the phenology (i.e. emergence time) of the different guilds. For 1 year, we collected 31,737 galls from 33 plant species, revealing remarkably diverse communities centred on 49 gallers, 65 parasitoids and 88 inquiline species. The plant families with more galls were Fabaceae, Fagaceae and Cistaceae, while most gallers were Cynipidae and Cecidomyiidae. Regarding parasitoids, Torymidae and Eulophidae were the richest families, and most inquilines belonged to the families Cecidomyiidae, Thripidae, Aphidiidae and Psocoptera. Shrubs hosted a significantly greater abundance and richness of gallers. Overall community composition was highly variable in time, frequently with turnover rates greater than 50% between consecutive months. An asynchrony between life cycles of each guild could be explained by the sequential availability of resources for gallers and parasitoids and by the relaxed physiological constraints between galls and inquilines. This baseline information is vital for revealing a hidden component of biodiversity and shedding light on its community structure and resilience.