Abstract
The activity of the litter-feeding macrofauna affects litter decomposition rates at the local scale, and their preference for particular litter types is mediated by litter traits. Environmental changes such as invasion by exotic plants may change the characteristics of the litter at a local scale, with consequences to ecosystem processes. Here we evaluated the feeding preferences of four detritivores (terrestrial isopods) from two biogeographic regions (neotropical and palearctic), offering them native or non-native litter in cafeteria experiments. Our results show that isopods from different geographical regions exhibit essentially the same food preference, irrespective of whether or not they previously had encountered the litter tested. Combining the isopods' preference ranks with the principal component analysis of nine litter traits, we show that preference increases with increasing nitrogen and calcium contents and decreases with increasing toughness, C:N ratio and thickness, irrespective of the geographical origin of both litter and detritivores. We conclude that the palatability of a non-native litter to the native detritivore community can be predicted from their respective litter traits and thus, native detritivores will feed on a particular non-native litter type as likely as do detritivores in the native range of the plant. As the combination of traits that indicates palatability to the isopods also indicates litter decomposability, it could be possible to predict ecosystem responses in terms of litter decomposition rates upon changes in litter composition.
Highlights
Decomposition of plant litter is shaped by environmental factors, among which climatic conditions, soil properties, litter characteristics and microbial and faunal activity have been considered pivotal (Swift et al, 1979; Wall et al, 2008)
We investigate this relationship, and we hypothesize that (1) feeding preferences of different detritivores species are governed by the same suite of traits and (2) the litter traits that govern food preferences of detritivores are independent of whether detritivores had previously contact with a particular litter type to acclimate with or adapt to
By crossing the preference ranks obtained in the multi-choice experiments with the ordination of plant traits, we show that the feeding preferences of both palearctic and neotropical isopods were negatively correlated to the position of plants along principal component analysis (PCA) axis 1 (Pearson r = -0.43, P = 0.0037) (Fig. 3A) and positively correlated with axis 2 (Pearson r = 0.57, P = 0.0001) (Fig. 3B)
Summary
Decomposition of plant litter is shaped by environmental factors, among which climatic conditions, soil properties, litter characteristics and microbial and faunal activity have been considered pivotal (Swift et al, 1979; Wall et al, 2008). While there is a substantial amount of research using litter traits to explain decomposability (Tian et al, 1992; Cornelissen et al, 1999; PérezHarguindeguy et al, 2000; Cornwell et al, 2008), which litter traits determine litter palatability to detritivores and its generality is less understood We investigate this relationship, and we hypothesize that (1) feeding preferences of different detritivores species are governed by the same suite of traits and (2) the litter traits that govern food preferences of detritivores are independent of whether detritivores had previously contact with a particular litter type to acclimate with or adapt to. With this set-up we expected to simulate the introduction of non-native plant species to a native community of detritivores
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