Are mangroves in the tropical Atlantic ripe for invasion? Exotic mangrove trees in the forests of South Florida

Authors

James W. Fourqurean, Department of Biological Sciences, Marine Science Program and Southeast Environmental Research Center, Florida International University; Center for Tropical Plant Conservation, Fairchild Tropical Botanic GardenFollow
Thomas J. Smith III, Southeastern Ecological Science Center, United States Geological SurveyFollow
Jennifer Possley, Center for Tropical Plant Conservation, Fairchild Tropical Botanic GardenFollow
Timothy M. Collins, Department of Biological Sciences, Florida International University; Division of Environmental Biology, National Science FoundationFollow
David W. Lee, Department of Biological Sciences, Florida International UniversityFollow
Sandra Namoff, Department of Biological Sciences, Florida International University; Center for Tropical Plant Conservation, Fairchild Tropical Botanic GardenFollow

Date of this Version

8-2010

Document Type

Article

Abstract

Abstract Two species of mangrove trees of Indo- Pacific origin have naturalized in tropical Atlantic mangrove forests in South Florida after they were planted and nurtured in botanic gardens. Two Bruguiera gymnorrhiza trees that were planted in the intertidal zone in 1940 have given rise to a population of at least 86 trees growing interspersed with native mangrove species Rhizophora mangle, Avicennia germinans and Laguncularia racemosa along 100 m of shoreline; the population is expanding at a rate of 5.6% year-1. Molecular genetic analyses confirm very low genetic diversity, as expected from a population founded by two individuals. The maximumnumber of alleles at any locus was three, and we measured reduced heterozygosity compared to native-range populations. Lumnitzera racemosa was introduced multiple times during the 1960s and 1970s, it has spread rapidly into a forest composed of native R. mangle, A. germinans, Laguncularia racemosa and Conocarpus erectus and now occupies 60,500 m2 of mangrove forest with stem densities of 24,735 ha-1. We estimate the population growth rate of Lumnitzera racemosa to be between 17 and 23% year-1. Populations of both species of naturalized mangroves are dominated by young individuals. Given the long life and water-dispersed nature of propagules of the two exotic species, it is likely that they have spread beyond our survey area. We argue that the species-depauperate nature of tropical Atlantic mangrove forests and close taxonomic relatives in the more species-rich Indo-Pacific region result in the susceptibility of tropical Atlantic mangrove forests to invasion by Indo-Pacific mangrove species.

Recommended Citation

Fourqurean, J. W., Collins, T. M., Lee, D., Namoff, S., Possley, J., & Smith, I. I. I. T. J. (January 01, 2010). Are mangroves in the tropical Atlantic ripe for invasion? Exotic mangrove trees in the forests of South Florida. Biological Invasions, 12, 8, 2509-2522.