E. Karadimou

Understanding the ecological mechanisms behind biological invasions remains a major focus of conservation biology and ecosystem management. Several hypotheses highlight that different facets of native biodiversity affect the establishment and spread of alien species. Here, we approach this question by examining the spatiotemporal relationship between alien bird species richness and different facets of biodiversity (taxonomic, functional, and phylogenetic) using breeding bird atlases for three U.S. states and for two time periods in each state. We associated native species richness, and functional and phylogenetic diversity with alien species richness, using generalized least squares models. Our results show that, consistently, across the three states and two time periods examined, alien species richness is positively associated with native diversity, and particularly with phylogenetic diversity. The relative importance of biodiversity metrics reflecting the functional or phylogenetic range occupied by the assemblage seems to advocate in favor of the importance of resource diversity as a main driver of both native and alien diversity. The secondary importance of biodiversity facets reflecting species functional or phylogenetic similarity, along with the lack of importance of functional or phylogenetic clustering or overdispersion, implies that if this relationship is shaped by biotic interactions, then biotic interactions facilitating coexistence (including even processes like predator‐mediated coexistence) are far more important than adversarial interactions like competition, at least at the scale of our analysis. Finally, the dominance of phylogenetic metrics over functional ones highlights the adaptive potential of a community accumulated over long lineage history may play an additional role as a source of information on evolutionary processes driving diversity patterns.

Changes in species diversity following volcanic eruptions have been studied extensively, but our knowledge on functional diversity and community assembly under such conditions is very limited. Here, we study the processes following the destruction of vegetation after a volcanic eruption. Specifically, we investigate (1) the temporal patterns of taxonomic and functional diversity over time since a previous eruption (alpha diversity) and beta diversity, (2) the temporal patterns of 26 individual traits (vegetative characteristics, plant taxa ecological preferences, and regenerative characteristics) providing more detailed information on species strategies at the initial and later stages of succession, and (3) the processes driving species assembly and whether they changed over time since the eruption an eruption. We analyzed data recorded during five floristic censuses that took place between 1911 and 2011, calculated alpha and beta facets of taxonomic and functional diversity and examined how community structure changed over time, using 26 functional characteristics, based on their ability to discern primary from later colonists, including longevity, growth form, Ellenberg's indicator values, seed production and weight, flower size and sex, pollination type, and dispersal mode. Null model analysis was used to test whether the observed functional diversity deviates from random expectations. Alpha diversity, both taxonomic and functional, increased over time after an eruption, while beta diversity did not display a clear trend. This finding indicates that mainly abiotic processes determine species assembly over time after an eruption (at least for the time span studied here), contrary to theoretical expectations. It is most interesting that, simultaneously, some aspects of diversity indicated the effect of biotic interactions (facilitation and competition) on the assembly of species a few years after an eruption. This finding implies a legacy effect, since a high percentage of perennial species was noticed in the assemblage right after the eruption, as well as the effect of the harsh environmental conditions on the assembly of the plant communities. In conclusion, our results indicate the role of legacy effects in succession (most probably through the survival of underground plant parts) and underline the importance of disturbance history in providing the context needed for understanding effects of past events on succession.