User:Ruijiao/sandbox

Definition
The general definition of functional diversity is understanding the structure of community based on the function of organisms rather than their evolutionary history. A more specific explanation of the word “function” is ‘the value and range of those species and organismal traits that influence ecosystem functioning. Under this context, evaluating functional diversity means measurement of functional traits, a certain type of organisms’ phenotypes which could influence ecosystem functions. Numerous important ecological questions could be driven by evaluating functional diversity, such as resilience and resistance of a certain community, evolution within a system, anthropogenic influence and so forth.

Measurements
Compared with taxonomic diversity, the measurement of functional diversity is still in development. A simple measurement is using the number of functional groups representing functional diversity. However, there is a need to consider the relative richness and the importance of each functional trait. Currently, many measurements are developed to solve this problem. Here, we provide a basic introduction to the measurements according to the summary of Petchey and Gaston’s work (2006).


 * 1) Establish the traits information data set of the focal community. Decide which traits should be used in the present study, which depends on the research interests. The information gathering includes experiments, sampling and in situ measurement.
 * 2) Weighted the traits according to their importance in the present study.
 * 3) Translate the traits dataset into mathematical value which could be analyzed statistically via programming. The traits dataset could include both discontinuous (qualitative) and continuous (quantitative) features.
 * 4) Select a methods to calculate the diversity which make it able to explain the functional dynamics of the community and meet the demand of the focal research interests.

How to choose appropriate functional traits?
Since the major concept of functional diversity is to understand how organisms function on the environment where they exist. It becomes important to choose the functional traits which shows an interaction between biotic and abiotic factors. A general classification could be separating the organisms depends on the way how they assimilate energy and carbon. It is also possible to classify the organisms based on their trophic level which directly correlated with how they access nutrients and resources. Some physiological parameters also have the potential to reflect how organisms interact with abiotic factors. For instance, the wings width of avian species reflects their mobility and determines their foraging efficiency and, at the same time, controls their accessibility to different resources. Another example is that the size of the organism could reflect their consumption rate. The choice of functional traits should also connected with the focal research interests. For instance, to understand how anthropogenic factors influence the succession of a community, scientists should focus on the traits which is sensitive to land use intensification or air pollution.

Why it is necessary to weight the traits?
It is obviously to understand that not all functional traits have equal important to the environment and to the present study. Equally interpret the functional trait will result in trade-off effect and underestimate certain potentially important functional traits. Assigning a weighted value to each functional traits strongly depends on previous background knowledge of scientists.

Discontinuous traits versus continuous traits
Continuous variation is quite simple to be used in discrete measures of functional diversity. Scientists can assign organisms into several group in which organisms have similar trait value on selected traits. The only decision to make is to decide the quantitative amount of difference between each group. Discontinuous measurements are sometimes frequently related with qualitative features. For example, whether the animal is nocturnal or not. It is impossible to assign a continuous value to these kind of variations. Therefore, only “yes” or “no” value could be assigned here. There also exists some discontinuous traits that could be separated into several functional groups. For example, the trophic level of a certain organisms. Special numeric value could be assigned to these kind of categories.

Calculating methods
Several calculating methods are commonly used to generate functional diversity. Rao’s quadratic entropy method and Petchey-Gaston methods are most frequently used.