Hydrological modification drives century-scale eutrophication and invasion increasing invertebrate assemblage...

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.