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Basic research in the species composition of the order Anura of two Indonesian island areas and the influence of human activities on biodiversity in this area
Johánková, Klára ; Masopustová, Renata (advisor) ; Jan, Jan (referee)
Amphibians are the most threatened of all vertebrates. Alarming declines of amphibian species is considered to be a direct consequence of extreme vulnerability associated with specific requirements of the micro - environmental conditions. Disruption of these conditions causes irreversible changes in species composition of amphibians, affected area tends to have lower diversity and abundance of native species. The most threatened amphibian species are those with narrow habitat preferences, living in specific areas where any intervention can lead to rapid decrease or complete disappearance of species. Habitat loss, intensive land use, fragmentation, invasive species, diseases, pesticides and climate change are the main causes of dramatic decline in amphibian species richness worldwide. Habitat loss, endangering many species worldwide, is considered the biggest threat to amphibians.
Southeast Asia is currently experiencing one of the largest global deforestations. Many factors are involved in forest losses, e.g. Population growth, logging, changes in cultivation practices, infrastructure growth, politics, forest fires and global environmental factors. At least half of the forest loss is associated with human activity. Deforestation due to agriculture or livestock expansion causes degradation and loss of soil, microclimate changes and loss of biodiversity. An extent reduction in space required for preservation and development of biodiversity is the result of devastation of the environment. This process particularly affects the presence and abundance of native amphibian species. It has been proven that even low to moderate levels of anthropogenic disturbance have a measurable and profound impact on tropical species. Examples are conversion of rainforests to oil palm monoculture plantations, destroying the entire ecological niche, disrupting complex food chains and natural migration corridors of animals. Compare to forests or other woody crops plantations, significantly fewer species are found in areas with oil palm.
The main aim of the practical part of this thesis is a field research carried out in two different island areas in Indonesia. The research was primarily focused on frog species composition in different habitats. Selected target areas were the islands of Simeulue and Bangkaru that are a part
of a chain of islands on the west coast of Sumatra. These research areas were chosen for various types of biomes represented on them. Biotope of the first of the islands was largely affected by human activity hence a significant part of it is used for agriculture. The second island was never affected by human activity and is entirely covered with primary rainforest. On the base of research performed in farm area of the island of Simeulue, following frog species were confirmed to occure: Duttaphrynus melanostictus (Schneider, 1799), Odorrana hosii (Boulenger, 1891), Limnonectes macrodon (Duméril a Bibron, 1841) and Amnirana nicobariensis (Stoliczka, 1870). Presence of two frog species not described on Simeulue yet was proven - Microhyla fissipes Boulenger, 1884 and Rhacophorus margaritifer (Schlegel, 1837). Presence of Hylarana parvacola (Inger, Stuart & Iskandar, 2009) was confirmed on the island of Bangkaru. Furthermore one, on Bangkaru previously undescribed species, Limnonectes macrodon (Duméril a Bibron, 1841) was discovered.
Richer frog species diversity was found in economically utilized areas on inhabited island of Simeulue. Frog diversity in the primary forest on Bangkaru, which has never been colonized, was lower. The results may collide with literature, indicating that a greater diversity of species is occurring in less disturbed areas. This proves that the abundance of species can be influenced not only by environment disturbance but also by other factors. In this case, different sizes and levels of isolation of the islands are probably involved. These findings are supported by the theory of island biogeography, which states that large islands have more species than small ones and islands close to the mainland have more species than isolated ones.
The objective of this work was only a basic research; its findings should be supported by more detailed studies carried out in the area.
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