In this paper we discuss possible ecological causes of the
latitudinal pattern of species richness in Southeast Asia against
the alternative explanation of a sampling artefact. By
analyzing distribution data and quantitative local samples,
we will confirm the existence of the mapped pattern and
evaluate various hypotheses as to its ecological causes: (1)
An overlap of temperate and tropical faunas (possibly
mediated by elevational stratification), (2) the existence of
special habitat conditions, or (3) a ‘peninsular effect’ (Brown
& Opler, 1990) could allow the occurrence of more species
in the northern than in the southern part of Southeast Asia