Traits of aphidophagous coccinellids and landscape variables

Coccinellids are important biocontrol agents and are threatened by
agricultural intensification and landscape change. Their responses to the
landscape are inconsistent, which may be due to a taxonomic focus of
studies that misses the traits that drive the differences in species
responses to the landscape. In this study, we investigated how
coccinellids in alfalfa respond to environmental variables in terms of
their traits. We examined five traits: body size, activity period, habitat
specialization, spatial ubiquity and dispersal habits, and analysed how
single and multiple traits (syndromes) are affected by local variables
(aphid density), and landscape compositional (diversity of land uses) and
configurational heterogeneity (edge density), at two spatial scales (500
and 1500 m). The community weighted mean of all traits, except body size,
was affected by landscape heterogeneity, mostly at the smaller spatial
scale. Coccinellid communities break into two groups of trait syndromes in
their response to landscape heterogeneity. Smaller species, uncommon in
alfalfa, mostly native, were negatively associated with compositional and
configurational heterogeneity at both spatial scales, while the remaining
species were associated with increased landscape heterogeneity. This
latter group of species splits into two groups at the smaller spatial
scale, composed by large exotic and natives, distributed along a gradient
of landscape configurational heterogeneity. The response of ladybeetles to
landscape composition and configuration depends more on their traits than
on their origin (native vs. exotics). These responses should be considered
when designing policies for agricultural landscape management, depending
on the conservation aims.