DOI: 10.5061/dryad.s7h44j13f
title: The Cryptic impacts of invasion: functional homogenization of tropical ant communities by invasive fire ants

description: The diversity and distribution of traits in an ecological community shapes
 its responses to change and the ecosystem processes it modulates. This
 ‘functional diversity’, however, is not necessarily a direct outcome of
 taxonomic diversity. Invasions by exotic insects occur in ecosystems
 worldwide, but there is limited understanding of how they impact
 functional diversity. We present the first comprehensive trait-based
 investigation of the impacts of an ant invasion, and the first
 incorporating intraspecific polymorphisms in species-level functional
 diversity. The fire ant Solenopsis invicta is an invasive species with a
 global distribution. Focusing on invaded and uninvaded plots in tropical
 grasslands of Hong Kong, we investigated how the presence of S. invicta
 affects the diversity and distribution of ant species and traits within
 and across communities, the functional identities of communities, and
 functionally unique species. Using trait probability density functions, we
 built trait spaces for 29 species, and scaled up these components to
 calculate functional diversity at community and landscape levels. We found
 that invasion had limited effects on species and functional richness but
 pronounced effects on functional composition. Specifically, invaded
 communities had fewer functionally-unique individuals, and were
 characterized by species with narrower heads and bodies and shorter
 mandibles. Moreover, invaded communities showed substantially higher
 levels of functional redundancy (+56%) due to a clustering of trait
 values. Consequently, across the landscape, invaded communities displayed
 23% less functional turnover than uninvaded communities despite showing
 comparable levels of taxonomic turnover – a result confirming theoretical
 predictions of the effects of high local functional redundancy. In sum,
 the presence of S. invicta alters the functional properties of multiple
 local communities selectively, resulting in functional homogenization
 across the landscape. The disparities between taxonomic and functional
 impacts of invasion highlight the need to consider how trait diversity
 across ecological scales shapes biodiversity and its responses to change.
description: Attached data files: 
 "matrix.freq": A species by site matrix. Cells report
 the frequencies of occurrence for each of the 29 ant species in each of
 the 61 plots. Species names are presented as abbreviations; refer to
 Supporting Information of the original publication for full species
 names.  "traits.ind": Seven morphological
 trait measurements for 319 individuals across 29 ant species. All
 measurements were performed in accordance with the standards specified in
 the Global Ants Trait Database. Note: "leg.length" is the combined length of the femur and tibia of the hind leg. The column "caste" records whether an individual is a minor worker (w) or a major worker (m). Species names are presented as abbreviations; refer to Supporting Information of the original publication for full species names.