Species diversity and seasonal activity of amphibians at different elevations in Num San Noi Stream at Phuluang Wildlife Sanctuary

Abstract

Seasonal activity of amphibians at Nam San Noi stream, Phuluang Wildlife Sanctuary was studied from May 2006 to May 2007. Night visual encounter surveys were conducted on three 100 m stream transects at each of three elevations, 800, 950, and 1250 m. Each stream transect was surveyed once a month. Species and number of amphibians found in each survey were recorded. A total of 22 species was found during the survey period. The species diversity in the wet season was higher than in the dry season at all three elevations. The similarity index indicated that species composition between seasons at 1250 m were similar whereas at 800 and 950 m they differed. The total abundance of all species and abundance of the 6 most common species had significant differences between the wet and dry season. The abundances of Odorrana aureola and Odorrana chloronota were high during the wet season while the number of Limnonectes gyldenstolpei, Hylarana nigrovittata, Aquixalus bisacculus, and Microhyla berdmorei and total abundance of all species peaked in the dry season. The highest abundances of the most common species were found to be associated with breeding activity. The Canonical Correspondence Analysis (CCA) indicated that the year-round abundances of most amphibians at difference elevations were associated with stream size, water temperature, and substrate temperature whereas the variations in amphibian abundance between season at each elevation were associated with relative humidity, water temperature, air temperature, substrate temperature, and stream width. Species composition and abundance of amphibians at Nam San Noi stream in the Phuluang Wildlife Sanctuary were also observed. Shannon-Wiener’s diversity index indicated that the lowest elevation (800 m) had the highest diversity whereas the highest elevation (1250 m) had the lowest value. Morishita’s similarity index showed that species compositions at 800 and 950 m, were very similar but both were different from the highest elevation, 1250 m. Seven species which had the highest percentage of total abundance had low abundance at the highest elevation with the exception of Limnonectes kuhlii and Odorrana aureola that were most abundant at the highest elevation. Xenophrys major was a species found only at one elevation, 950 m. These results indicated that species diversity of amphibians tended to be higher at the lower elevation. Num San Noi stream also flows across an agricultural area. Therefore, species composition, abundance, oviposition sites and percentage of developing eggs of each species of amphibians were compared between forest and agricultural stream at similar elevations (750-800 m). Six 100 m stream transects, 3 in the forest and 3 in the agricultural area were surveyed once a month. The Shannon-Wienner’s diversity index indicated that the diversity in agricultural stream transects (ASTs) was significantly higher than the FSTs. The Morishita’s similarity index indicated that the species composition of the 1st AST (closest to the forest) was the most similar to the FSTs, 0.744 – 0.867, whereas the species composition of the other 2 ASTs (far from the forest edge) were less similar to FSTs, 0.493 – 0.527. In the ASTs, abundances of each of 5 forest species were significantly lower whereas 6 urban species were significantly higher when compared with the FSTs (p ≤ 0.05). Moreover, during the study period oviposition sites and developing eggs were not found in ASTs. The CCA showed that the abundance of urban species were associated with high solar energy, air temperature, and water temperature whereas the forest species were found associated with high relative humidity and stream water transparency. The results indicated that the agricultural area had a negative effect on the abundance of forest species.