Abstract
Gaining understanding of food-web processes often requires a simplified representation of natural diversity. One such simplification can be based on functional traits, as functionally similar species may provide a similar contribution to ecosystem level-processes. However, understanding how similarity in functional traits actually translates into similar contributions to ecosystem-level properties remains a challenge due to the complex ways in which traits can influence species' dynamics. Moreover, in many communities, seasonality alters the abiotic and biotic forcing regime, causing ongoing changes to patterns of species' dominance; groups of species do not stay intact but are rather continuously subjected to changes throughout the year. Using long-term high frequency measurements of phytoplankton in Lake Constance, we investigated the effect of seasonal changes on the relationship between functional similarity and temporal dynamics similarity of 36 morphotypes, and the relative contribution of different functional traits during the different parts of the year. Our results revealed seasonal differences in the overall degree of synchronization of morphotypes' temporal dynamics and how combinations of functional traits influence the relationship between functional trait similarity and temporal dynamics similarity, showing that different forcing regimes change how species cope with their environment based on their functional traits. Moreover, we show that the individual functional traits matter at different periods of the year indicating that species which are dynamically similar at certain parts of the year may not be at others. The differential strength of the overall and individual impact of functional traits on species' temporal dynamics makes the cohesion of a pair of functionally similar species dependent on the different forcing. Hence, simplifying food webs based solely on functional traits may not provide consistent estimates of functional groups over all seasons.
Highlights
Investigation into the structure and functioning of natural foodwebs often relies upon the aggregation of a high number of species into fewer ecologically meaningful groups [1,2]
The median values of these distributions were significantly greater than zero (Fig. 2) indicating that an increase in functional similarity is accompanied by a strengthening in the covariation of morphotypes temporal dynamics
Our results demonstrate the capacity for differences among periods without such an a priori knowledge of the importance of traits and we suggest that these differences are driven by the biotic and abiotic factors impacting dynamics
Summary
Investigation into the structure and functioning of natural foodwebs often relies upon the aggregation of a high number of species into fewer ecologically meaningful groups [1,2] Work in this area focused on using information from the food web itself, such as the flow of nutrients or energy, to define trophic roles or groups and their similarity and reduce the complexity of ecosystems [3,4]. Suggested functional characteristics range from e.g. basic adaptive strategies such as the C-R-S concept [5] or a performance trait which is the net result of several morpho-physiological traits [6], to specific morpho-physio-phenological traits which directly or indirectly impact fitness [7] They constitute potentially a valuable source of information for aggregating species into groups responsible for particular ecosystem-level functions such as N fixation and edible primary production. Understanding how similarity in functional traits translates into similarity in the contribution to ecosystemlevel properties remains a challenge, due to the multitude of potential functional characteristics exhibited by a species and the complex, non-linear ways in which these can interact with a variable environment and other species
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
