Linking population, ecosystem, and landscape ecology through biological invasions: Syzygium jambos invasion in Puerto Rico

This study focused on the invasion of Syzygium jambos (L.) Alston (Myrtaceae) in a sub-tropical wet forest of the Caribbean National Forest, the Luquillo Long Term Ecological Research (LTER) station in northeastern Puerto Rico. S. jambos, a native of southeast Asia, is a pan-tropical invasive tree that occurs throughout Puerto Rico, where it is most common as a riparian or an understory species in moist and wet secondary forests. I used a combination of experimental and modeling approaches to investigate S. jambos invasion.; The experimental work examined how establishment of S. jambos affects ecosystem processes along an invasion gradient. S. jambos seedlings in uninvaded sites grew significantly more than those in high invasion sites, but growth differences between sites with no and medium invasion were not significant. Invasion intensity did affect growth, with seedlings able to grow better in the no invasion sites, where conspecifics were absent. Habitats lacking S. jambos plants exhibited different ecosystem properties than sites where the plant was present. Relative to sites where S. jambos was absent, those where the plant was present produced litter lower in carbon and higher in nitrogen concentrations, which can potentially lead to faster rates of decomposition. S. jambos seedlings allocated more resources to root growth, relative to shoot growth, under circumstances where conspecifics were absent. Allocation patterns for the plant were significantly affected by invasion density. However, these experiments could not definitively show that Syzygium jambos was driving the observed differences.; I integrated metapopulation and spatial spread models to explore questions about the future expansion potential of S. jambos, the habitats most susceptible to invasion, and which life history stages most influenced population fluctuations. I examined how pre-industrial forest cover percentage, current vegetation distribution, and proximity to rivers influenced S. jambos invasion.; S. jambos metapopulation were most likely to spread to habitats that underwent intense anthropogenic land use in 1936. The spatial distribution and metapopulation models indicated that targeting juvenile or small adult survival rates in sites that were subjected to intense land use in 1936 would most effectively control S. jambos populations.