Non-Native Conifer Plantations Restructure Multitaxon Biodiversity in an Andean Cloud-Forest Landscape

We evaluated how Pinus patula and Cupressus sempervirens plantations affect woody plants, ants, and orb-weaving spiders from the families Araneidae and Tetragnathidae in a protected cloud-forest landscape in the Colombian Andes. Using standardized field surveys conducted during a short intensive sampling campaign, we compared native forest and conifer plantations. We quantified alpha diversity with Hill numbers (q = 0, 1, 2), estimated sampling completeness, assessed community composition with NMDS and PERMANOVA, partitioned beta diversity into turnover and nestedness components, and identified habitat-associated taxa using indicator species analysis. Alpha-diversity responses were taxon-specific. Woody plants showed consistently higher diversity in native forest across all diversity orders. Ant diversity tended to be higher in native forest, although confidence intervals overlapped between habitats. Spider responses differed by family: Araneidae showed relatively similar alpha diversity between habitats, whereas Tetragnathidae exhibited strong reductions in plantations. In contrast, beta diversity was high across all taxa and was dominated by species turnover, indicating that native forest and conifer plantations support compositionally distinct assemblages rather than subsets of the same communities. Indicator species analysis further identified habitat-associated species in both spider families, as well as among woody plants and ants, with distinct indicator taxa associated with native forest and conifer plantations. Exotic conifer plantations substantially reorganize multitaxon biodiversity in tropical montane ecosystems and do not function as ecological substitutes for native cloud forest. Conservation efforts in Andean montane landscapes should prioritize the protection, restoration, and connectivity of native forest remnants. Short, intensive and standardized multitaxon biodiversity assessments can provide useful ecological baselines in poorly sampled tropical mountain systems and help guide future monitoring and restoration planning.