Understanding why some species succeed in naturalizing and invading ecosystems, while others do not, has intrigued scientists since Darwin’s time. The Pre-Adaptation Hypothesis posits that introduced species closely related to natives, and thus ecologically similar, are more likely to establish. This concept aligns with the Climate Matching Hypothesis, which emphasizes environmental similarity between native and invaded regions as a key factor in invasion success. However, conflicting evidence leaves the role of biogeographic origin and climatic affinity in predicting invasion risk unresolved. Here, we examine how biogeographical origin, climatic matching, and inter- and intraspecific pre-adaptation influence the success of congeneric plant species introduced to the Canary Islands, an oceanic archipelago with Mediterranean climatic affinities. We integrated phylogenetic, climatic and occurrence data at two levels: (i) interspecific comparisons of phylogenetic distances and climatic similarity between each introduced species and its closest native counterpart; and (ii) intraspecific analysis of climatic niche dynamics between native and introduced ranges. Most introduced congeneric species originate from the Mediterranean Basin and temperate Europe, with a notable contribution from the Neotropics. While Mediterranean and temperate European introduced taxa were phylogenetically closer to native Canarian species, we found no consistent evidence of pre-adaptation when climatic similarity among congeneric species pairs was also considered. In contrast, intraspecific analyses revealed widespread niche expansion, regardless of origin. However, species from the Mediterranean and Neotropical origin displayed a greater effect on climatic niche stability, suggesting stronger climatic matching. Overall, our findings highlight the prevalence of niche shifts among introduced plant species and underscore the role of climatic niche expansion in facilitating biological invasions. These results have key implications for assessing invasion risks in increasingly disturbed insular regions worldwide.

Most of our understanding of island diversity comes from the study of aboveground systems, while the patterns and processes of diversification and community assembly for belowground biotas remain poorly understood. Here we take advantage of a relatively young and dynamic oceanic island to advance our understanding of eco-evolutionary processes driving community assembly within soil mesofauna. Using whole organism community DNA (wocDNA) metabarcoding and the recently developed metaMATE pipeline, we have generated spatially explicit and reliable haplotype-level DNA sequence data for soil mesofaunal assemblages sampled across the four main habitats within the island of Tenerife. Community ecological and metaphylogeographic analyses have been performed at multiple levels of genetic similarity, from haplotypes to species and supraspecific groupings. Broadly consistent patterns of local-scale species richness across different insular habitats have been found, whereas local insular richness is lower than in continental settings. Our results reveal an important role for niche conservatism as a driver of insular community assembly of soil mesofauna, with only limited evidence for habitat shifts promoting diversification. Furthermore, support is found for a fundamental role of habitat in the assembly of soil mesofauna, where habitat specialism is mainly due to colonisation and the establishment of preadapted species. Hierarchical patterns of distance decay at the community level and metaphylogeographical analyses support a pattern of geographic structuring over limited spatial scales, from the level of haplotypes through to species and lineages, as expected for taxa with strong dispersal limitations. Our results demonstrate the potential for wocDNA metabarcoding to advance our understanding of biodiversity.