Calculates the fraction of the maximum distance between species occurrences, which can be used as a proxy of species dispersal ability. This fraction can be used as the radius needed to apply the circular buffer method (Rivers et al 2010) to obtain subpopulations for conservation assessments of extinction risk.
subpop.radius(
XY,
factor.div = 10,
quant.max = 1,
mode = "spheroid",
proj_type = "cea"
)a data.frame. containing the geographical coordinates for each taxon.
numeric. denominator value used to obtain the fraction of the maximum distance. Default to 10.
numeric. The upper-quantile of the inter-point distance to be considered as a threshold of maximum distance. Can vary between 0 and 1. Default to 1.
character string either 'spheroid' or 'planar'. By default 'spheroid'
string or numeric
The estimated radius in kilometres for each taxon.
XY as a data.frame should have the following structure:
It is mandatory to respect field positions, but field names do not matter
The first column is contains numeric value i.e. latitude in decimal degrees
The second column is contains numeric value i.e. longitude in decimal degrees
The third column is contains character value i.e. the names of the species
Rivers MC, Bachman SP, Meagher TR, Lughadha EN, Brummitt NA (2010) Subpopulations, locations and fragmentation: applying IUCN red list criteria to herbarium specimen data. Biodiversity and Conservation 19: 2071-2085. doi: 10.1007/s10531-010-9826-9
mydf <- data.frame(ddlat = c(-44.6,-46.2,-45.4,-42.2,-43.7,-45.0,-28.0),
ddlon = c(-42.2,-42.6,-45.3,-42.5,-42.3,-39.0,-17.2),
tax = rep("a", 7),
stringsAsFactors = FALSE)
subpop.radius(mydf)
#> tax radius
#> 1 a 313.759
subpop.radius(mydf, quant.max = 0.95)
#> tax radius
#> 1 a 300.379
subpop.radius(mydf, factor.div = 15)
#> tax radius
#> 1 a 209.173