Abstract
BackgroundIncreasing temperatures and changes in precipitation patterns threaten the existence of many organisms. It is therefore informative to identify the functional traits that underlie differences in desiccation resistance to understand the response of different species to changes in water availability resulting from climate change. We used adult dung beetles as model species due to their importance to ecosystem services. We investigated: (i) the effect of physiological (water loss rate, water loss tolerance, body water content), morphological (body mass) and ecological (nesting behaviour) traits on desiccation resistance; (ii) the role of phylogenetic relatedness in the above associations; and, (iii) whether relatively large or small individuals within a species have similar desiccation resistance and whether these responses are consistent across species.ResultsDesiccation resistance decreased with increasing water loss rate and increased with increasing water loss tolerance (i.e. proportion of initial water content lost at the time of death). A lack of consistent correlation between these traits due to phylogenetic relatedness suggests that the relationship is not determined by a shared evolutionary history. The advantage of a large body size in favouring desiccation resistance depended on the nesting behaviour of the dung beetles. In rollers (one species), large body sizes increased desiccation resistance, while in tunnelers and dwellers, desiccation resistance seemed not to be dependent on body mass. The phylogenetic correlation between desiccation resistance and nesting strategies was significant. Within each species, large individuals showed greater resistance to desiccation, and these responses were consistent across species.ConclusionsResistance to desiccation was explained mainly by the dung beetles’ ability to reduce water loss rate (avoidance) and to tolerate water loss (tolerance). A reduction in water availability may impose a selection pressure on body size that varies based on nesting strategies, even though these responses may be phylogenetically constrained. Changes in water availability are more likely to affect dweller species, and hence the ecosystem services they provide.
Highlights
Increasing temperatures and changes in precipitation patterns threaten the existence of many organisms
In the Mediterranean area, characterized by high levels of dung beetle diversity and endemism [14,15,16], increasing temperature due to climate change is expected to induce a northward shift of thermophilous species (e.g. Scarabaeidae), more adapted to live in arid and warm conditions, that may replace the activity of mesophilous dung beetles that live in less extreme conditions (Aphodiidae, Geotrupidae)
Physiological adaptations to desiccation resistance and the underlying traits are suggested to be key traits under selection [25, 26], and their study will allow the understanding of how species will survive dry environments [27] through mechanistic models
Summary
Increasing temperatures and changes in precipitation patterns threaten the existence of many organisms. In the Mediterranean area, characterized by high levels of dung beetle diversity and endemism [14,15,16], increasing temperature due to climate change is expected to induce a northward shift of thermophilous species (e.g. Scarabaeidae), more adapted to live in arid and warm conditions, that may replace the activity of mesophilous dung beetles that live in less extreme conditions (Aphodiidae, Geotrupidae). This rapid replacement of species is especially worrying at the southernmost extremities of Europe (e.g. the Italian peninsula) where the influx of a more thermophilous fauna would be probably more difficult because of the distance from the African continent [17]. The dramatic abandonment of extensive historical grazing land, habitat degradation and use of medical veterinary products represent serious additional threats to dung beetle distribution changes [18]
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