This study investigated the mechanisms determining macrophyte species composition in 23 Andalusian Mediterranean mountain wetlands (southern Spain). We employed a methodology combining two approaches: a pattern-based approach utilizing Elements of Metacommunity Structure (EMS) and a mechanistic approach involving Redundancy Analysis (RDA) and variance partitioning. This allowed us to identify the relevance of interactions between environmental and spatial factors. Data collection in these wetlands included macrophyte samples and physicochemical variables, alongside spatial variables generated using Moran’s Eigenvector Maps (MEMs). To refine the analysis of metacommunity structuring, the species matrix was partitioned based on macrophyte dispersal strategy (charophytes by spores and macrophyte vascular plants by seeds). Our results reveal that the macrophyte metacommunity in these wetlands exhibits quasi-clumped species loss for the total community, while charophytes and vascular plants showed quasi-random species loss. In conclusion, this study demonstrates that macrophyte communities in Mediterranean mountain wetlands do not follow a simple species replacement pattern. Instead, they are organized in a quasi-nested pattern, strongly shaped by environmental filters and, to a lesser extent, by spatial connectivity, with a prominent role for random processes. Understanding these mechanisms is crucial for predicting species responses to environmental changes and for designing effective conservation strategies within these vulnerable ecosystems.

Aquatic macrophytes constitute essential bioindicators of the ecological status of Mediterranean wetlands. We evaluated 136 Andalusian wetlands across four biogeographical regions (Sierra Morena, Betic Ranges, Guadalquivir Valley, and Coastal Zone) by contrasting two methodological approaches. We compared a standard biological valuation index, based on hydrophyte valuation and total species richness, with a biogeographical assessment focused strictly on the originality, singularity, and integrity of hydrophyte assemblages. Results revealed a critical nonlinear decoupling between both metrics. Traditional valuation prioritized the Coastal and Guadalquivir zones, inflating the value of communities saturated by widespread taxa and masking their lower structural integrity. Conversely, the biogeographical analysis identified Sierra Morena as the reservoir of highest structural stability despite its natural species poverty. Furthermore, residual analysis exposed highly original hidden jewels systematically undervalued by standard protocols. Since richness-dependent metrics risk neglecting unique hydrophyte components, we propose a dual conservation strategy integrating irreplaceability and structural integrity. Ultimately, this framework provides actionable insights for the sustainable management of Mediterranean aquatic biodiversity, aligning conservation practices with global ecological sustainability goals. We caution that management decisions based solely on richness thresholds may inadvertently prioritize common habitats over functionally unique but species-poor refugia.