The response of frog communities to forest disturbance and fragmentation in Papua New Guinea

A project undertaken at the New Guinea Binatang Research Center, and supervised by Chris Dahl

Background

Papua New Guinea is one of the last three remaining tropical biodiversity hotspot areas of the world (Mittermeier et al. 2003). It has extremely high and endemic flora and fauna diversity representing only 5% of the global diversity; however this biodiversity hotspot region is poorly known and studied. This is true for frog diversity (Dahl et al. 2009 and Dahl et al. 2013). Its biodiversity is increasingly being threatened from logging and slash-and-burn agriculture, which has led to the development of secondary forests (Shearman et al. 2009, Shearman and Bryan 2011). Despite these trends, the conservation value of small primary forest reserves and secondary forests has not been studied. We see this as an important conservation priority and suggest using frogs as a suitable focal taxon for such study.

Aims
  • To surveyed lowland rain forest sites in order to quantify frog communities and assessed frog diversity response to primary rainforest fragmentation.
  • To understand whether the frog diversity is equally represented in rainforest fragmentation in village base 200-300 ha reserves?
  • To understand whether the frog diversity is influence by forest fragments, between secondary to large primary forest fragments.
  • Determine whether frogs in these forest types are more susceptible to chytrid fungus.
  • To investigate other important ecological information on the distribution and habitat preference of frog species and describe species new to science.

Major results

A total of 82 nights used to survey primary forests and 58 nights for secondary forests spanning across six lowland sites (Figure 1). We observed 16,945 individual frogs and identified 45 species consist of 16 genera and six families. The number of frog diversity varied considerably among our surveyed sites. We found that few genera in five frog families have less number of species (<10 species) in lowland forests than the species of frogs in the family Microhylidae. These frog families appeared to be well established with high number of individuals in lowland rainforest (Figure 2). Interestingly, we found that large continuous primary forest in lowland forests of Papua New Guinea may not necessarily maintain a high animal diversity. Our Ohu site which is a small village reserved of 200 ha forest fragment had 34 frog species, compared to Rai Coast and Wanang sites are 10,000 ha of large continuous forests had <30 frog species (Figure 3). Our sampling effort per site shown by the species accumulative curve nearly reached asymptote. This suggest that we found most frog species at this study sites (Figure 4). Our result showed small village reserve forest fragments may appear important reservoir for protection of frogs and other animal taxa. Inclusion, we identified the size of forest fragments provide suitable micro-habitats for different frog species. These habitats are increasingly important to study for long term monitoring and observe frog community response to habitat modifications and climate change.

Training achievement

Elizah Nagombi was awarded the second class honours degree at the University of Papua New Guinea and received a scholarship to further his studies at the James Cook University (Figure 5). George Dahl was appointed as a frog specialist for the New Guinea Bintang Research Center to carry on frog activities and surveys (Figure 6). 

References

Dahl, C., V. Novotny, J. Moravec, and S. J. Richards. 2009. Beta diversity of frogs in the forests of New Guinea, Amazonia and Europe: contrasting tropical and temperate communities. Journal of Biogeography 36:896-904.

Dahl, C., S.J.Richards, and V. Novotny, 2013. The Sepik River (Papua New Guinea) is not a dispersal barrier for lowland rainforest frogs. Journal of Tropical Ecology 29:477-483

Mittermeler, R.A., C.G.Mittermeler, T.M.Brooks, J.D.Pilgrim, W.R.Konstant, G.A.B.d.Fonseca, and C.Kormos. 2003. Wilderness and biodiversity conservation. PNAS 100 10309-10313.

Shearman, P and Bryan, J. 2011. A bioregional analysis of the distribution of rainforest
cover, deforestation and degradation in Papua New Guinea. Austral Ecology, 36, 9-
24.

Shearman, P.l., J.Ash, B.Mackey, J.E.Bryan, and B.Lokes. 2009. Forest conversion and degradation in Papua New Guinea 1972-2002. Biotropica: 1744-7429.

 


Figure 1. Map of lowland forest sampling sites.

Figure 2. The number of frog genera, species and individuals in the six families of frogs encountered in the study.

Figure 3. Species richness of frogs in the six sampling sites. Sites arranged in order of increasing primary forest fragment size.

Figure 4. Individual based rarefaction curve for the six different sampling sites. The species accumulation in all sites were levelled off indicating an adequatte sampling effort.

Figure 5. Elizah Nagombi (left) and a colleague at Elizah's graduation.

Figure 6. George Dahl at work.