Revista Chilena de Historia Natural 84 (3): 419-432, 2011
RESEARCH ARTICLE
Why so many apparently rare beetles in Chilean temperate
rainforests?
Species abundance curves were calculated from data sets collected by
fogging 52 trees in Nothofagus forest (~46000 specimens) and 24 trees in Araucaria forest (~15000
specimens) in Chile. Neither data set fitted the standard species abundance models. Like similar data sets collected from
tropical forests, there were too many species represented by single specimens. The proposal that these were vagrants
normally found on other tree species was not supported as, unlike tropical forests, Nothofagus forests are not
diverse, often consisting of single species stands. Examination of three assumptions of the most parsimonious equilibrium
models showed them to be false. Between them the observations of undersampling bias, community disequilibria and
combining data from different feeding guilds with different species abundance curves are likely to be sufficient to explain
the divergence of data for large speciose beetle communities from the predictions of any of the equilibrium models. Until
these three factors can be fully accounted for and residual divergence detected, there is no necessity to propose further,
more complex, mechanisms to explain such data sets. Estimated values of alpha and Simpson D were shown to be strongly
sample size dependent, affecting their value as estimators of biological diversity.
Key words:
species
abundance curves, biodiversity estimation, body size and density
