Spatial distribution and performance of native and invasive Ardisia (Myrsinaceae) species in Puerto Rico: the anatomy of an invasion
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Comparisons between native and invasive congeners are potentially useful approaches for identifying characteristics that promote invasiveness. Those traits for which an invasive exhibits superior ecological performance are likely to contribute to its invasiveness. We tested the hypothesis that invasive tree species have better ecological performance in early life cycle stages than native species in forests where they coexist. We studied locally sympatric populations of the invasive Ardisia elliptica and the native A. obovata (Myrsinaceae) in Puerto Rico. We compared spatial distribution, herbivory and growth in seedlings, seed germination in the field and under controlled conditions, and fruit production. We found the distribution of each species was aggregated in the three categories of size (seedlings, juveniles and adults) and the populations partially overlapped. The invasive species was the most abundant species in every category of size. The two species did not differ in percentage of leaf area consumed and seedlings of both species had the same relative growth rate (RGR) in the forest. However, the invasive species had higher germination success in the field, faster mean germination time in the lab and higher fruit production. It appears that the success of A. elliptica is not through escape from pathogens or herbivores, but by a better performance in fruiting and seed germination in the forest.
KeywordsInvasive species Ardisia Spatial relationships Early growth Seed germination Fruit production
We thank the staff of Julio Enrique Monagas National Park for permission to conduct research within the Park. We also thank Eliezer Nieves from the Centro Ambiental Santa Ana for providing logistic support in Monagas. We are grateful to all our field assistants: Calip, Francisco Amundaray, Eddie Rosas, Mariyoan Guzman, Estephania Uriarte, Luis Pereira, Nestor Arias and Mariolga Mendoza. We also thank Brenda Betancourt for statistical advice. We also thank Ernesto Medina, Tomas Carlo, Elvira Cuevas, Denny Fernandez del Viso and Jess Zimmerman for their advice throughout this project. This research was funded in part by the Department of Biology, Dean of Graduate Studies and Research, and the Center for Tropical Ecology and Conservation of the University of Puerto Rico, and a grant from the USA National Science Foundation (Elvira Cuevas, project director; HRD-0734826). This work represents part of a thesis by MCM presented to the Department of Biology, University of Puerto Rico, in partial fulfillment of requirements of a M.S. degree.
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