Food Webs Prelim Arthropod Data
Description
Morphospecies and environmental data for macroarthropod and microarthropod collections from leaf litter in the Liko Na Pilina experiment. In February 2019, we collected single leaf litter samples under canopies of 19 studied plant species to examine macroarthropod populations. This collection was the first of eight collections to be conducted on a quarterly basis and rotated across the four blocks twice. Collections per species were standardized by volume (i.e., one approximately 27 cm x 27 cm bag per species) and distributed spatially as evenly as possible across individuals planted per species in the four plots per block; small collections were made from beneath several individuals per species. We identified 74 macroarthropod morphospecies, ranging between 17 and 35 per plant species. We also performed microarthropod collections as part of a June-July 2017 pilot study focusing on oribatid mites. Litter was collected from 11 tree species. We used four 25-cm2 quadrats placed on the ground at the underneath the plant canopies and found 13 morphospecies of mites. We investigated relationships among the arthropod community (both micro- and macro-arthropods) and the plant functional traits using Redundancy Analyses (RDA) in R (R Development Core, 2018). RDA ordinates invertebrate species using axes that are constrained to be linear combinations of the plant functional traits, in such a way that the relationship between the invertebrate species and the plant functional traits can be clearly seen. We started with the 15 functional traits data that were used to design the experimental treatments (Ostertag et al., 2015) and then ran Variance Inflation Factor (VIF) analyses to look for collinearity. We eliminated all variables with a VIF>10. Functional trait variables included in the RDA were foliar C and P concentrations, foliar δ13C (a measure of integrated water-use efficiency), maximum plant height, seed mass, altitudinal range (a measure of habitat breadth), and shade ratio (a measure of the canopy architecture). While the taxonomic details of the arthropod data sets are still being worked out, RDA shows that the macroarthropod (Figure 5a) and microarthropod (Figure 5b) communities depend on the functional traits of the plant species and thus that primary consumers' functional traits affect the arthropod community. For macroarthropods, C concentration was the only significant variable (P = 0.002), which was tested by the distribution-free Monte Carlo test (999 permutations), in which the distribution of the test statistics under the null hypothesis is generated by random permutations of cases. For microarthropods, only height was significant (P = 0.026) and shade ratio was marginally not significant but potentially important (P = 0.098).