The spatial pattern and dispersion of Lygodium  microphyllum in the Everglades wetland ecosystem

Since 1958, L. microphyllum (Old World Climbing Fern), which originated from the Old World Tropics, has become a nuisance exotic and has rapidly spread and is being established system-wide in extremely remote and undisturbed areas such as the Florida Everglades. Of particular concern is that L. microphyllum is disrupting, at an alarming rate, the flora and fauna of the native ecosystem at the same time that a major 8.4 billion dollar Everglades restoration program is trying to enhance these same attributes. This research utilized IKONOS satellite data to map L. microphyllum within the 58,000-ha Loxahatchee National Wildlife Refuge wetland in south Florida. Results show that approximately 11.6% of the tree/shrub vegetation within the impoundment has been infected by L. microphyllum. These data were then utilized to explore the spatial spread patterns of L. microphyllum within the Refuge. Results suggest that L. microphyllum is more likely to establish on the southeast side of a tree/shrub island and then spread to the northwest, which corresponds to the prevailing wind direction in south Florida. Spatial pattern analysis of L. microphyllum spread indicated that it is correlated with the density and spatial distribution of tree/shrub island vegetation. It appears that the dispersion of L. microphyllum is density dependent, which can be expressed as a logistic function and has a catastrophic threshold of 160 m of mean distance between tree/shrub islands in the Everglades. It is predicted that 38% (or 1910 ha) of tree/shrub islands in the Refuge will be invaded by L. microphyllum by 2012. Tree islands in the Everglades wetland could be considered similar to oceanic islands throughout the world that are notoriously vulnerable to biological invasions.

[1]  K. Rutchey,et al.  ANALYSIS AND SIMULATIONS OF FRAGMENTATION PATTERNS IN THE EVERGLADES , 1997 .

[2]  R. Wunderlin.  Guide to the Vascular Plants of Central Florida , 1988 .

[3]  N. Shigesada,et al.  Biological Invasions: Theory and Practice , 1997 .

[4]  Thomas Caraco,et al.  Population dispersion and equilibrium infection frequency in a spatial epidemic , 1999 .

[5]  D. Austin,et al.  Spread of the Exotic Fern Lygodium microphyllum in Florida , 1978 .

[6]  D. Gawlik,et al.  AVIAN COMMUNITIES IN BAYHEADS, WILLOWHEADS, AND SAWGRASS MARSHES OF THE CENTRAL EVERGLADES , 1998 .

[7]  James S. Clark,et al.  Ecological and Evolutionary Consequences of Patchiness: A Marine-Terrestrial Perspective , 1993 .

[8]  S. Holbrook,et al.  Spatial and temporal variation in mortality of newly settled damselfish: patterns, causes and co-variation with settlement , 2003, Oecologia.

[9]  A. Suarez,et al.  Patterns of spread in biological invasions dominated by long-distance jump dispersal: Insights from Argentine ants. , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[10]  K. Rutchey,et al.  Spatial Simulations of Tree Islands for Everglades Restoration , 2002 .

[11]  George L. Hunt,et al.  Foraging in a fractal environment: Spatial patterns in a marine predator-prey system , 1992, Landscape Ecology.

[12]  J. Muss,et al.  Predicting rapid invasion of the Florida Everglades by Old World Climbing Fern (Lygodium microphyllum) , 2004 .

[13]  J. Beardsley.  New Immigrant Insects in Hawaii: 1962 through 1976 , 1976 .

[14]  R. Gardner,et al.  Quantitative Methods in Landscape Ecology , 1991 .

[15]  M. Hasebe,et al.  Fern phylogeny based on rbcL nucleotide sequences , 1995 .

[16]  Kenneth M. Nagata.  Early Plant Introductions in Hawai'i , 1985 .

[17]  D. Gawlik,et al.  Habitat-Use Patterns of Avian Seed Dispersers in the Central Everglades , 2002 .

[18]  D. Botstein,et al.  Cluster analysis and display of genome-wide expression patterns. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[19]  K. Rutchey,et al.  Chapter 6: Ecological Effects of Hydrology , 2004 .

[20]  Robert V. O'Neill,et al.  Pattern, process, and predictability: the use of neutral models for landscape analysis , 1991 .

[21]  F. Sklar,et al.  Tree Islands of the Everglades , 2002, Springer Netherlands.

[22]  Alan R. Smith.  Non-Molecular Phylogenetic Hypotheses for Ferns , 1995 .

[23]  G. Panigrahi,et al.  Systematics of genusLygodium Sw. (Lygodiaceae) in India , 1984, Proceedings / Indian Academy of Sciences.

[24]  C. Loveless.  A Study of the Vegetation in the Florida Everglades , 1959 .

[25]  P. J. Clark,et al.  Distance to Nearest Neighbor as a Measure of Spatial Relationships in Populations , 1954 .

[26]  William M. Schaffer,et al.  Plant strategies and the dynamics and structure of plant communities , 1989 .