How to define a 'trait' objectively?

Question

I'm coming across an increasing number of papers that use trait-based approaches for risk assessment, like this one . This paper defines a trait as follows:

Traits are the physiological, morphological, and ecological attributes of species or other taxonomic entities, which describe their physical characteristics, ecological niche, and functional role within an ecosystem.

I've wondered about using this sort of approach during some analyses of invasiveness potential in vector insects before and it's likely to come up during a systematic literature review I'm coordinating, but I'm concerned that devising my own trait classification system is likely to introduce confirmation bias into a study. Is there either a recognised methodology for trait definition, or alternatively some sort of accepted list or classification of traits that I could use, to minimise the chances of this? Is there a generally-accepted method to correct for phylogenetic correlation?

I've tried Google but the results mostly appear to be about trait theory, which is an approach used in psychology to study human personality.

Answer 1

I think you this paper is what you need. The many concepts of trait are discussed in the functional ecology background. But basically, a "trait" can be defined as

" 'Functional traits’ are defined as morpho-physiophenological traits which impact fitness indirectly via their effects on growth, reproduction and survival, the three components of individual performance." (Violle et al. 2007)

Which are not so different from the definition you posted. Some organisms have an improved methodology to collect and measure traits, like plants. But this is not common to all organisms. As for the method to correct for phylogenetic correlation, this is a whole different field called Phylogenetic Comparative Methods. To choose the method you need to know the kind of data you have and the question being asked.