Tropical dung beetle morphological traits predict functional traits and show intraspecific differences across land uses

Abstract

Functional traits and functional diversity measures are increasingly being used to examine land use effects on biodiversity and community assembly rules. Morphological traits are often used directly as functional traits. However, behavioral characteristics are more difficult to measure. Establishing methods to derive behavioral traits from morphological measurements is necessary to facilitate their inclusion in functional diversity analyses. We collected morphometric data from over 1,700 individuals of 12 species of dung beetle to establish whether morphological measurements can be used as predictors of behavioral traits. We also compared morphology among individuals collected from different land uses (primary forest, logged forest, and oil palm plantation) to identify whether intraspecific differences in morphology vary among land use types. We show that leg and eye measurements can be used to predict dung beetle nesting behavior and period of activity and we used this information to confirm the previously unresolved nesting behavior for Synapsis ritsemae. We found intraspecific differences in morphological traits across different land use types. Phenotypic plasticity was found for traits associated with dispersal (wing aspect ratio and wing loading) and reproductive capacity (abdomen size). The ability to predict behavioral functional traits from morphology is useful where the behavior of individuals cannot be directly observed, especially in tropical environments where the ecology of many species is poorly understood. In addition, we provide evidence that land use change can cause phenotypic plasticity in tropical dung beetle species. Our results reinforce recent calls for intraspecific variation in traits to receive more attention within community ecology.

Assessing the functional relationship between dung beetle traits and dung removal, burial, and seedling emergence

“…1) We included an array of morphological traits that, altogether, were able to account for the differences in body design of the species performing each one of the three major dung exploitation strategies (as in Inward et al 2011, Raine et al 2018).…”

“…These different dung exploitation strategies determine where dung-and the seeds embedded in it-is relocated. Several morphological features related to size of front and hind tibiae, head, prothorax, body size, and shape (see Appendix S1: Section S1, Supplementary Material and Methods) have been traditionally regarded as adaptations of dung beetles to coprophagy and, especially, dung burial (Halffter and Matthews 1966, Edmonds 1972, Halffter and Edmonds 1982, Mart ın-Piera and L opez-Col on 2000, Raine et al 2018). These traits have been recently used to analyze the relationship of functional diversity with ecosystem functions (BEF; Griffiths et al 2015Griffiths et al , 2016.…”

“…However, these behavioral traits consider the main dung exploitation strategies (Halffter and Matthews 1966), and are usually included in studies of dung beetle functional diversity. Three main factors could explain this contrasting and relatively unexpected result: 1) We included an array of morphological traits that, altogether, were able to account for the differences in body design of the species performing each one of the three major dung exploitation strategies (as in Inward et al 2011, Raine et al 2018.…”

Trait‐based ecology of terrestrial arthropods

“…In ants, some morphological traits were found to be associated with trophic position, and these associations persisted after correcting for phylogeny (Gibb et al ., ). Likewise, morphological traits were recently shown to predict nesting behaviours and activity periods in dung beetles (Raine et al ., ). However in most cases morphological traits were used without evidence of any associations between morphological traits and higher traits, let alone their effects on performance.…”

A Research Agenda for Microclimate Ecology in Human-Modified Tropical Forests

“…Dung beetles are a widely used indicator group, as they play a key role in driving numerous ecosystems functions-such as nutrient cycling and seed dispersal-and can be easily sampled using pitfall traps (Nichols et al, 2008). Across the SAFE landscape dung beetle diversity, abundance and traits have been extensively surveyed, as has their contribution to nutrient cycling through dung removal (Raine et al, 2018a). By combining these data with existing high-resolution microclimate maps of understorey temperature and vapor pressure deficit , dung beetle abundance and community composition can be extrapolated across the oil palm-forest mosaic landscape.…”