o_19ko2dt161ng2j4e1tgnoqv1s45a.pdf

RESEARCH ON THE DIVERSITY OF MOTHS AND BUTTERFLIES IN MALAYSIA AND THEIR USE AS
BIODIVERSITY INDICATORS
BIODIVERSITY INDICES
Species abundance models are commonly used to indicate the level of biodiversity in a habitat,
with the log normal and the log series being the main models. They are based on an assumption
that for a very large sample that closely reflects the population structure, it will result in a bellshaped
log normal curve. But a typical smaller annual sample is one-tailed and usually fits
equally well to the log series and the log normal, with the rarer species having been missed.
Species abundance curves usually have the log abundance plotted against species rank. A
shallower curve means higher diversity while a steeper curve means lower diversity.
Moth samples are usually annual samples, which fit into the log series. Based on the log
series, a diversity index known as Williams Alpha is derived (Fisher et al. 1943). This index
is independent of sample size, which allows cross-comparison of most samples. The log series
gives a diversity value less subject to the vagaries of the non-resident species, and is more
dependent on the mid-range species resident at the site, and hence more representative (Taylor
1978). For these reasons, most moth samples are compared using Williams Alpha. A higher
value means higher diversity.
For butterfly samples, which are normally smaller, non-parametric indices with no assumption
on the underlying species abundance distribution are commonly used. These include the popular
Shannon index, as well as Simpson’s index (Magurran 1988). They are diversity indices based
on the proportional abundances of species.
SIMILARITY COEFFICIENTS
Biodiversity indices alone may tell us the levels of diversity but they don’t show the composition
of the underlying species assemblages. The ‘coefficient of association’ is a R-mode measure
of percentage dissimilarity showing the pattern in species distributions and, hence, species
associations, among the sampling sites. Based on the percentage dissimilarity, numerical singlelink
dendrograms as well as linkage diagrams can be drawn in which species indicative of a
habitat are clustered together. This technique has been applied in biodiversity studies in
Malaysia, for example, by Chey (1994).
Similarity coefficients can also be used in the R-mode to identify associations of species of
moths that show correlations with particular vegetation zones and altitude zones (e.g., Holloway
1989b; Chey et al. 1997; Intachat et al. 2005). These associations offer particularly good
suites of indicator species.
Preston’s coefficient of faunal resemblance (1962), a simpler Q-mode measure of similarity
based on presence or absence of species, is commonly used. The number of species present in
each of any two sites and the number of shared species between them are used to calculate the
Preston’s coefficient. Based on the coefficient values, single-link dendrograms can be drawn
clustering similar sites together.
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