Vertical Stratification Increases the Capacity of Morphological Traits to Predict Trophic Position in Neotropical Ants.

Morphology is a key functional trait that influences the ecophysiology of organisms. The use of morphological traits for understanding functional ecology is common in studies of ants, especially relating to their feeding biology. However, there is limited information on the predictive value of these traits in identifying the trophic position of ants. Moreover, although vertical stratification is a common feature of many ant assemblages, with distinct arboreal and ground-active communities, the influence of verticality on the relationship between morphology and trophic position is unknown. We used data from 73 ant species from Brazilian Cerrado to examine the strength of associations between nine morphological traits and trophic position, and to evaluate if this varies between vertical strata. No individual morphological trait explained variation in the trophic position of arboreal species. However, femur length, petiole length, and head width were each individually correlated with the trophic position of ground species, but only weakly so. Predictive capacity increased substantially when data from different traits were combined in multiple regression models, especially when separate equations were derived for the arboreal and ground faunas. The estimation error of these models was below 15% for 70% of the species, with the most informative traits being femur length, petiole length, and head width for ground species and eye length, mandible length, and Weber's length for arboreal species. These results indicate that the use of multiple morphological traits is an effective approach for predicting the trophic position of most ants in our Neotropical system, the efficacy of which is enhanced when the different vertical strata are taken into consideration. We believe that our approach to assessing the predictive capacity of morphological traits, through the use of multiple traits and consideration of different microhabitats, has wide applicability to functional studies not just of ants but to fauna more generally.