Common assumption is that interspecific trait variation (ITV) contributes more to functional variability than intraspecific variation. Yet recent studies have shown that ITV can play significant role as well – affecting community assembly and species interactions. But despite the significance of ITV emphasized in reviews, and analyzed in studies, general patterns are yet to emerge. Further research is necessary to search for the mechanisms how ITV affects community and ecosystem processes.
Majority of ITV-studies with plants have so far focused on measuring key functional traits for many species in conjunction in one or few communities. Our study examined ITV from a hitherto unexplored angle, proposing that ITV dynamics could be explained by modularity concept. We propose that phenotypic plasticity in plants, which is the main source of ITV is usually expressed in subindividual level, creating complex interplay between local responses and systemic control.
We tested the modularity of ITV on one species: Phacelia secunda – common herbaceous perennial plant endemic to Chile. It has a wide climatic niche, occurring in habitats ranging from sandy beaches to mountain forests. It´s also known to be morphologically variable along climatic gradients. We measured numerous generative and vegetative traits throughout the whole range of its distribution.
Results/Conclusions
ITV responses of Phacelia secunda to abiotic and biotic factors showed differentiating patterns. Whereas abiotic factors (climate) predominantly influenced vegetative traits of the structures that are responsible for resource gathering, biotic factors (surrounding vegetation) influenced generative organs, which translate acquired resources into fitness.
These results strongly indicate that ITV has modular nature and different abiotic and biotic variables affect different plant organs differently. Here climatic factors affected predominately the vegetative traits of Phacelia secunda, but biotic interactions from surrounding vegetation affected the generative traits. It remains to be tested whether this contrasting pattern is to be found with other species as well.
Our study widens the perspective of ITV studies in several ways: Firstly, it´s based on measurements taken from populations from the entire distribution range of one broad-niched species, which gives the opportunity to assess ITV dynamics throughout a species´ full bioclimatic amplitude. Secondly, our approach was to measure as many functionally meaningful traits as possible. Thus, instead of trying to relate specific functional traits to specific environmental gradients, we were able to seek more general patterns in ITV. Thirdly, we measured both generative and vegetative traits, and tested ITV separately against abiotic and biotic factors.