Hydrological modification drives century-scale eutrophication and invasion increasing invertebrate assemblage heterogeneity in Lake Fúquene, Colombia.

Hydrological alteration, eutrophication and macrophyte invasion generate novel ecological states and biotic homogenization in shallow lakes. As these stressors increasingly co-occur and unfold over decades to centuries, disentangling their combined effects on invertebrate assemblages remains however challenging. To assess their long-term (decades-centuries) interactions on driving aquatic invertebrates, we analysed three ²¹⁰Pb-dated sediment cores spanning contrasting dominance of the invasives Egeria densa (submerged), Pontederia crassipes (floating) and Azolla filiculoides (floating) in Fúquene, a largely drained, eutrophic Andean shallow lake (Colombia). Eighteen invertebrate taxa were recorded with multivariate analyses explaining 51% of assemblage variation and identified a pre-1800 mesotrophic phase; a drainage phase (ca 1800-late 1980s) marked by shifts towards eutrophic taxa; and a post-perimeter canal phase (post-1990) characterized by invasive expansion and distinct macrophyte-associated invertebrate assemblages. Despite restructuring, invertebrate assemblages did not homogenize but became more heterogeneous among cores post-1990. Variation partitioning revealed strong coupled hydro-chemical-macrophyte effects at the assemblage and taxon level explaining 13-56% of the variation, with invasive growth forms uniquely accounting for 5-40%. E. densa stands supported aquatic insects, whereas floating species favoured Oribatidae, bryozoans and semi-terrestrial chironomids. Invasion-eutrophication-driven homogenization is therefore not inevitable but contingent on hydrology, environmental variation and growth-form diversity.