The Atlantic forest was one of the largest South American rainforests and intensive forest clearing reduced its original area to thousands of small fragments. Human modifications of animal species distributions lead to substantially underestimating the strength of the Bergmann’s rule and few studies have examined the effects of these activities on body size variation at species (phenotypic downsizing) and population level (community downsizing). We first hypothesize that (i) creation of a mosaic of natural (contiguous old growth) and anthropogenic (corridors, fragments, second growth, and clearcuts) habitats has altered the body size variables (body mass and body length) of resident mammals in the Atlantic forest and (ii) the body size variables may differ belong latitudinal gradients. We compared body mass of mammal community analyzed at the interspecific level using data of 279 mammal species from 39,850 individuals that occur in the 388 communities inhabiting forest patches varying from 0.15 to 791,652 ha (average = 11,886 ha, median = 390 ha) that were directly measured from surveys along a gradient of -5.83 to -29.75 of latitude (decimal degrees) in the Atlantic forest of Brazil, Argentina and Paraguay.
Results/Conclusions
We found significantly different body size variables between old growth forest and areas influenced by anthropogenic activities. Individuals from fragments were smaller than those in old growth forest and there is no difference between individuals from lower latitudes area (nearby equator) and higher latitudes areas (distant from equator). Nearly all physiological and ecological processes are strongly influenced by an organism’s body size variables and, in turn, influence its ability to survive in a diversity of habitats including those modified by human. Body size variables is perhaps the most important traits of an organism, affecting all of its physiological and ecological processes and fundamentally influencing its ability to survive and reproduce in different environments, including those that have been modified by human activities. To our knowledge, this study is the first to investigate the influence of anthropogenic fragmentation and geographical gradients on one of the most fundamental and defining characteristics of native species-their body size variables. Assessments of potential anthropogenic shifts in body size variables should, therefore, provide important insights into the sensitivity of particular species to these activities and the likelihood that they may retain their natural character into the future.