Aim: Understanding the causes and consequences of biological invasions remains a challenge for several disciplines, including biogeography. One major issue in overcoming this challenge is disentangling the confounding mechanisms of species invasiveness and community invasibility. Here, we tackle this issue by applying a novel approach based on the phylogenetic affinities between exotic species and natives in the recipient community to elucidate naturalization and pre-adaptation processes. Location: Japan. Taxon: Seed plants. Methods: Geographical co-occurrence data for 1,094 exotics and 4,869 native species (including 1,676 endemics) were created at the 10-km grid-cell and vegetation-plot levels. For individual exotic species, standardized effect size of phylogenetic species variability (PSVSES) of the recipient native assemblage (i.e. phylogenetic fields) was calculated and its clustering/over-dispersion was tested, representing exotic invasiveness in relation to invasibility of native recipients. To identify drivers of species invasiveness, the correlation of PSVSES with species attributes, involving phylogenetic distance between each exotic and native species, was explored. Results: Phylogenetic fields (PSVSES) showed significant over-dispersion (~16% exotics) or clustering (~14% exotics). Interspecific variation of PSVSES among exotics was substantially explained by species ecological attributes. Geographical extent and climatic niche widths were negatively correlated with PSVSES. Preference for human influence was positively correlated with PSVSES at the 10-km grid-cell level, but negatively at the vegetation-plot level. Exotics colonized from the Palearctic and Indo-Malay regions, which belong to the same biogeographical region as East Asia, tended to have clustered phylogenetic fields. Main conclusions: Environmental filtering and biotic sorting both played a key role in exotic plant colonization, supporting both of Darwin's contradictory hypotheses of naturalization versus pre-adaptation. Clustered phylogenetic fields indicated that an exotic colonizes its recipient assemblage through abiotic filtering (i.e. pre-adaptation); at the same time, phylogenetic over-dispersion was indicative of naturalization for exotics that occupied a biotic niche space among native recipients (i.e. naturalization). Phylogenetic field patterns depended on species’ ecological attributes, including phylogenetic relatedness between exotics and recipient natives, especially reflecting invasibility at the local-community level.
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