Article review written by: Jennifer Groover
Biologists have long been under the impression that larger areas tend to have more species. A new study from Universidade Federal de Pemambuco and Instituto National de Pesquisas da Amazonia (INPA) shows that composition of preferential habitats of an area may play a larger role than overall size of land. This study titled, “Low Primate Diversity and Abundance in Northern Amazonia and its Implications for Conservation” was published in the November issue of Biotropica. The finding of this study that large areas of the Rio Negro basin in Amazonia are covered by continuous forest, but have correspondingly few primate species show the potential need to reevaluate how land is chosen to be conserved.
Researchers Antonio Rossano Mendes Pontes and Mateus Dantas de Paula of the Brazil University and William Magnusson of the INPA worked in conjunction with the Brazilian Ministry of Science to collect data for this research. The Ministry initiated the Program for Biodiversity Research in Amazonia that installed several 25-km2 transects for research in untouched Amazonia forest. The scientists of this article collected data by surveying primates between May and September 2006 using the line-transect method. They conducted both daytime and night transects, recording the following from two daytime and one nighttime line-transects per day: species, group size, encounter distance, location along the trail of the sighted animals, forest type, date, start and stop times, trail surveyed, total distance walked, and height of each encounter.
The results showed the number of primate encounters as well as species diversity in the terra firme forests were significantly higher than in inundated forests and scrublands. Terra firme forests compose 9.2% (210.5 km2) of the Virua National Park (VNP) while scrubland and inundated forest cover 91% (2081.2 km2), yet the total estimated number of primates respectively was 6916 individuals from 8 species and 26,621 of mostly 1 species. This would imply conservation of primate diversity in large tropical areas would depend more on habitat composition of the land than continuous size of the land. This knowledge is essential in planning conservation zones to efficiently conserve the most biodiversity possible and in this case places a focus on preserving terra firma forests for primates.
Prior research of sympatric primates of Amazonia has emphasized habitat segregation that allows the spreading out of species to occupy different niches. Prior studies show an increase in land area reduces extinction probability, offers more diverse habitats, and can result in speciation. However, the results of this study show a pattern of aggregation, rather than the segregation prior studies predict. This study suggests that given a lack of hunting pressure, this difference in observed pattern is a result of conducting large-scale integrated ecological studies that look at primate populations. This is opposed to the currently more prominent intra-habitat studies that look at primate behavior within one type of habitat or satellite landscape evaluations of plant biodiversity.
Since all areas surveyed were within a few kilometers of terra firme forest, the researchers suspect some overestimation in primate count numbers. They also concluded extrapolation of results would far overestimate primate abundance due to the variation in habitat. Lastly, they suspect some error in the night counts due to fewer transects and difficulty in spotting the primates in the dark. Further transects during many years and in several different tropical forests could help improve the definitiveness of this study’s results.
By conducting future large-scale research on tropical forests, more efficient conservation efforts can be made to protect primate biodiversity. The results of this study show that parks and reserves of northwestern Amazonia will need to be very large to maintain viable populations of primates. Having broad habitat categories may not be sufficient since only some are suitable to primates, leading to aggregation.
Current parks and reserves commonly attempt to maintain connectivity of habitats so animals can spread to occupy different niches. This study suggests that primates have preferential habitats and will disperse into different niches within that habitat rather than between unpreferential habitats. Thus, learning what makes that habitat preferential to increased biodiversity and maximizing the area will be more important when determining conservation zones instead of just conserving a large array of continuous habitats as current practice suggests. This study suggests maximizing conservation efforts on terra firme forests in the Virua National Park may help preserve primate biodiversity. If future research supports this study’s findings, broadening this research to other endangered animals may be useful in developing parks and reserves that maximize biodiversity by maximizing conservation of that animal’s preferential habitat.
Pontes, A. R. M., de Paula, M. D. and Magnusson, W. E. (2012), Low Primate Diversity
and Abundance in Northern Amazonia and its Implications for Conservation. Biotropica, 44: 834–839. doi: 10.1111/j.1744-7429.2012.00873.x