Felling the giants: integral projection models indicate adult management to control an exotic invasive palm

Abstract

Population models are helpful for understanding demographic trends in invasive plants and crucial in defining effective management actions. Here, we assessed the dynamics of three populations of the invasive palm Roystonea oleracea on an island in the Atlantic Forest, Brazil. We aimed to verify variations in the life cycle parameters (survival, growth, fecundity) of individuals; to evaluate population growth rates (λ); and to understand which vital rates most impact λ. In 2015, we established plots (40 × 40 m) in areas occupied by R. oleraceae and tagged (numbered aluminum tags) and measured the diameter at ground level (DGL) of all palms in the plots. We conducted an annual census in each population in 2016, 2017, and 2018 where all palms were relocated and measured again. We used Integral Projection Models to verify differences in life cycle parameters and to calculate λ, and prospective analyses of elasticity to verify the contribution of each vital rates on λ. Palms with smaller DGL ( 10 mm) had higher survival rates, increased in size, or reproduced. The λ values were different between populations: Population 1 was decreasing, Population 2 was increasing, and Population 3 was stable. Survival and growth of palms with larger diameters were the vital rates that most impacted λ. Management strategies to eliminate palms with DGL > 400 mm are essential to reduce the λ of the species and to control their spread to new locations.