Arita HT, Robinson JG, Redford KH. 1990. Rarity in Neotropical Forest Mammals and Its Ecological Correlates. Conservation Biology 4:181-192.
Blog author: Alex Shupinski
Authors:
Hector T. Arita
PhD from University of Florida
Research:Looking at patterns and structures of animal communities at a local and macroecological scale and relating it to conservation. Since 1992 he is a researcher in the National University Autónoma de México.
John G. Robinson
PhD from University of North Carolina in Zoology
Research: My interests are in the application of ecological and behavioral theory to conservation planning. My research has focused on neotropical forestry, with an increasing emphasis on the consequences of forest fragmentation and subsistence hunting on wildlife populations. This has led me to evaluate the mutual dependencies of humans and the natural world, and specifically to analyze the concept of sustainable use. Primates in particular are vulnerable to human induced disturbance, both directly and through landscape changes. My primatological research focuses on the determinants of reproductive success in primates, and relies on long-term field studies of primates in Venezuela, Colombia and Brazil.
Kent H. Redford
PhD from Harvard University
Career: In 1997 he joined the Wildlife Conservation Society to work in the International Program on conservation strategy. He worked with colleagues and established and helped run interdisciplinary graduate programs in conservation and development for students from tropical countries. Leading a series of focused horizon-scanning workshops on key issues confronting the practice of conservation and was a member of the Conservation Committee that developed a conservation mission for the whole organization.
Background
-Distribution is number of sites or area of distribution
-Abundance is local population density/# of individuals in a site
-Lower populations correlate with higher extinction probability
-Terborgh listed six traits increasing proneness to extinction. Low local density it not listed as one of the six . Looking at Neotropical forest mammals from Robinson and Redford (1986)
Goals:
1. How well distribution and abundance characterize rarity
2. Examine ecological correlates of these variables and the importance in conservation
Methods
Relationship between Rarity, Abundance, and Distribution
-Rabinowitz (1981) classified forms of rarity. Rejected in 1986 that the three ways were correlated
-Low local density and restricted distributional range may be correlated (MacNaughton & Wolf 1970, Brown 1984).
-Positive correlation between local density and number of sites found
Rarity in Neotropical Mammals
-Data on body mass, diet and density of forest species, 100 total
-Plotted ranges on a grid map of dots, tallied the number of dots included in the range for each species
Relationship Between the Variables
-Logged the data for a better fit. Correlated area of distributional range to local density
-Correlation coefficients found for entire data set, then broken down by taxonomic and trophic groups. A negative correlation found between distribution and abundance with all species.
-Taxonmically, the groups varied from positive to negative except for carnivores, showed no correlation
-Negative association between distribution and abundance of Neotropical forest mammals is seen only when comparing different taxonomic groups
Types of Rarity
-Divided into groups; locally rare, locally abundance, widespread, restricted distribution
-Type A (restricted and locally abundant) and Type D (widespread and locally rare) showed slight negative correlation (distribution and abundance) but not statistically significant
-Saw patterns taxonomically, looked at taxonomical groups. Primates, rodents, carnivores and artiodactyls showed significant deviation from null, demonstrating taxonomic group plays a role in rarity.
The Effect of Body Size
-Negative correlation between body mass and average local density found, body mass and distribution area were positively correlated. Bigger animals have wider distributional ranges and lower local densities
-Body size influenced the correlation between density and distribution area because body size is related to many ecological parameters
-Larger animals are more likely to be more widespread with low local density. Smaller animals will be locally abundance and restricted in distribution.
Implications for Conservation and Conclusions
-artificial ceiling placed on ranges. Did not investigate the ranges of these species in other parts of the world.
-Protection of species as a whole or protecting individual species will vary classification of a species
-Rarity classification can prove useful in conservation efforts and where those efforts should be concentrated.
Main Points/Conclusions
-Negative correlation between distribution and abundance was found
-Distributional range plotted against local density demonstrated species clustering according to trophic and taxonomic groups because diet and phylogenetic history influence rarity
-Distribution and abundance are independent estimators of rarity when comparing species with similar body size and ecological traits.
-Larger animals have lower densities and wider distributional ranges so rarity is associated with body size
-Require different conservation management based on what category of rarity the species falls into
My Thoughts:
I thought it was very important that they recognized the difference between protecting a species as a whole and protecting individual populations of a species. The goal in mind will influence how that species is characterized in the realm of rarity. I think that characterizing rarity could prove very important in the future of conservation. I think this could be a great tool used in individual locations especially, for instance, parks or preserves. It allows them to be aware of individual species risk of extinction but I believe it provides another tool by looking at species in category B (widespread and locally abundant). In areas of conservation, it may prove beneficial to monitor category B numbers. If those numbers show decline or decrease in range then the area itself may be having issues and more rare species need to be addressed quickly.
I like that they present their results but seem to be also cautious of the limitations of their analyses. I agree with Alex that this seem like a potentially useful tool for conservation and planing. I wonder if this work has been considered in the posterior managing of reserves and endangered species.
ReplyDeleteI think adaptability and behavioral plasticity/flexibility play a critical role in determining whether a species is common or rare. Ultimately, human behavior is affecting all species. We're very good at driving common species to extinction, and those that cannot adapt to human activity will become rare, regardless of whether their distribution and density is large/high or small/low.
ReplyDeleteI agree with Maria, probably rarity today for many species results from anthropogenic factors. This add more difficulty to the goal of understanding the causes of rarity, as the current patterns we observe, are probably the result of combined "natural" and human causes.
ReplyDeleteI like the idea of using this classification to identify conservation targets and actions (e.g. local conservation of A species vs. widespread connectivity or reserve network for species in category D)
After reading the classic/book paper first, I appreciate the approach for mammals. However, I would have liked to see more discussion on the importance of body mass. The authors show that it is linked to the other traits and to distribution, but some more in-depth evaluation on why that is would have been interesting. That discussion is also beneficial to conservation, as determining why or how body size affects mammals' traits and distributions.
ReplyDeleteI like this article because it gave an in-depth background explanation of how endangered species are determined. I also enjoy the relation of body mass to abundance as well. The tests used to determine what categories each species belong to was brilliant. The fact that conservation efforts were stated as well was also a plus. Overall, enjoyed reading this.
ReplyDeleteI really like how this paper involve mammals and the correlation between body mass and local density. I also like how the paper distinguish that there should be different ways to conserve species based on the category of rarity.
ReplyDeleteAn example of a systematically categorized rarity of the species status database is International Union for Conservation Nature (IUCN). The branch is known as the Redlist of Threatened Species which has reasonably accurate information (except sometimes over or underestimated because of lack of information) about species taxonomy and distribution. I am sure this uses the criteria of extinction risk based on the rarity and abundance in their distribution. But I don't know which ones they take account of the criteria. It is an interesting logical observation between body mass of species and area distribution and density.
ReplyDeleteI thought this was interesting and wonder how applicable it is to other biomes. Since they only analyze forest dwellin species, would the resulting nomogram be similar in grassland species? Perhaps it would be more stretched out for fewer geographic barriers?
ReplyDeleteLike Devra, I also wish they talked more about body size since they seem to say many things are controlled by it.
One of my thoughts from the first paper was how it was received in later years, interesting that just five years later the correlation between Deborah's proposed rarity categories was rejected. Liked to see the conservation implications of where we should be focusing protection effort.
ReplyDelete