Towards precision ecology: Relationships of multiple sampling methods quantifying abundance for comparisons among studies

ABSTRACTBecause different sampling techniques will provide different abundance values, it is currently difficult to compare results among many studies to form holistic understandings of how abundance influences ant ecology. Using three sampling methods in the same location we found pitfall traps best confirmed A. gracilipes presence recording the fewest zero values (9.1%), card counts were the least reliable (67.1%), and tuna lures were intermediate (30.1%). The abundance of A. gracilipes from card counts ranged from 0 to 20, in pitfall traps from 0 to 325, and the full range of tuna lure abundance scores (0-7) were sampled. We then determined the relationships between these three standard ant sampling techniques for the abundance of yellow crazy ant Anoplolepis gracilipes. Irrespective of the data transformation method, the strongest relationship was between pitfall traps and tuna lures, and the least strong was between pitfall traps and card counts. We then demonstrate the utility of this knowledge by analysing A. gracilipes abundance reported within published literature to show where the populations in those studies sit on an abundance spectrum. We also comment on insights into the relative utility of the three methods we used to determine A. gracilipes abundance among populations of varying abundance. Pitfall traps was the most reliable method to determine if the species was present at the sample level. Tuna lures were predominantly reliable for quantifying the presence of workers, but were limited by the number of workers that can gather around a spoonful of tuna. Card counts were the quickest method, but were seemingly only useful when A. gracilipes abundance is not low. Finally we discuss how environmental and biological variation needs to be accounted for in future studies to better standardise sampling protocols to help progress ecology as a precision science.

Vision-Linked Traits Associated With Antenna Size and Foraging Ecology Across Ants

Visual systems in animals often conspicuously reflect the demands of their ecological interactions. Ants occupy a wide range of terrestrial microhabitats and ecological roles. Additionally, ant eye morphology is highly variable; species range from eyeless subterranean-dwellers to highly visual predators or desert navigators. Through a comparative approach spanning 64 species, we evaluated the relationship between ecology and eye morphology on a wide taxonomic scale. Using worker caste specimens, we developed two- and three-dimensional measurements to quantify eye morphology and position, as well as antennal scape length. Surprisingly, we find limited associations between ecology and most eye traits, however, we recover significant relationships between antennal scape length and some vision-linked attributes. While accounting for shared ancestry, we find that two- and three-dimensional eye area is correlated with foraging niche and ommatidia density is significantly associated with trophic level in our sample of ant taxa. Perhaps signifying a resource investment tradeoff between visual and olfactory or tactile acuity, we find that ommatidia density is negatively correlated with antennal scape length. Additionally, we find that eye position is significantly related to antennal scape length and also report a positive correlation between scape length and eye height, which may be related to the shared developmental origin of these structures. Along with previously known relationships between two-dimensional eye size and ant ecology, our results join reports from other organismal lineages suggesting that morphological traits with intuitive links to ecology may also be shaped by developmental restrictions and energetic trade-offs.