Estimating the diversity of wood-decaying polypores in tropical lowland rain forests in Malaysia: the effect of sampling strategy

Unlike in temperate regions, few studies have examined the effect of sampling effort on the observed number of wood-decaying polypores in the tropics. We conducted field surveys at Pasoh Forest Reserve and Lambir Hills National Park, two primary lowland dipterocarp forests in Malaysia, to compare the numbers of observed and estimated species for each site. Field surveys included five occasions over 4 years on a 2-ha plot in Pasoh, and two occasions in 1 year in 12 0.1-ha transects in Lambir. From Pasoh, 140 polypore species were recorded and 188 species were estimated (using the Chao2 estimator). From Lambir, 90 species were recorded and 149 estimated. Thus, at both sites the number of species observed comprised <75 % of the estimated number of species. At Pasoh, more than 80 % of the total species were recorded by the end of the third sampling occasion. When sampling effort (area × number of sampling occasions) was constant, more species were recorded by field surveys conducted over larger areas with less frequent sampling than those conducted over smaller areas with more frequent sampling. The numbers of species recorded in the present work were greater than those identified in temperate and boreal regions in previous studies. The species richness of wood-decaying polypores in tropical regions may be largely underestimated without conducting field surveys on at least three occasions. If potential sampling effort is limited, surveying a larger area on fewer occasions is a reasonable compromise to ensure coverage of the majority of polypore species.