Species distribution is reflected by the observation of species individuals in
different sites of an ecological domain. The distributional size and the range boundary
of the species are measured through the counting of the presence or absence of the
species across different sites. However, as mentioned in previous chapters 9 and 10 and
here, when the individuals of species has been recorded with the geographic coordinates
within some spatial ranges, one common ecological question that we would encounter
would be, are the distribution of all the species individuals present some non-random
patterns? That is, would the species tend to aggregately distribute in some limited areas
across the whole ecological domain, while some areas are not favoured by the species
and thus rarely have the occurrence of the individuals of species? Testing of
distributional randomness could offer insights and address these ecological questions. In
this chapter, I would present only some classical statistical methods for quantifying the
randomness of spatial distribution of species. Readers interested into this subject should
refer to books in the field of spatial statistics.
Keywords: Distribution and diversity, limited sampling, nearest neighbouring,
quadrate-based versus spatial point-based randomness, Riley’s K statistic, spatial
biodiversity patterns, spatial statistics.
