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International Journal of Environment Science and Technology
Center for Environment and Energy Research and Studies (CEERS)
ISSN: 1735-1472 EISSN: 1735-1472
Vol. 13, No. 8, 2016, pp. 2037-2044
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Bioline Code: st16186
Full paper language: English
Document type: Research Article
Document available free of charge
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International Journal of Environment Science and Technology, Vol. 13, No. 8, 2016, pp. 2037-2044
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Methods for geographic profiling of biological invasions with multiple origin sites
Santosuosso, U. & Papini, A.
Abstract
Geographic profiling is a method that proved to be
useful also in order to investigate the point of origin of a
biological invasion. K-means clustering and Voronoi diagrams can partition a data set of geographic positions of
populations invading a defined area and are, therefore, useful
in cases in which an invasion had more introduction events as
points of origin. One critical point of the method is to identify
the right number of clusters in which to divide the starting
data set formed by groups of points on a map. The Silhouette
method proved to be capable of identifying the best number
of subsets (clusters) of the general set of observations by
providing different values for different subdivisions of the
set of observations in clusters. For each cluster, the corresponding Voronoi tessellation was built on the starting map.
To test the method, we did a simulation of clusters of data
(points) on a map and we verified whether the proposed
methods worked efficiently with the simulated data set with
hundred repeats and using a varying number of clusters on
the same map. The used techniques revealed to be efficient in
finding the highest probability area of the map that would
include the starting points for each cluster. A case study
consisted in a known data set, that is, the spreading pattern of
Caulerpa racemosa var. cylindracea (sea grapes), that was
compatible (highest probability) with an original point of
introduction in southern Italy and long distance (thousands
of kilometers) secondary spreads via anthropic dispersal.
The proposed techniques may also be applied to other kinds
of data sets of biological data distributed on a map or in
general on a geometrical surface.
Keywords
Biological invasions; Caulerpa; Geographic profiling; K-means; Silhouette; Voronoi tesselletion
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