Abstract
On an evolutionary time scale, competition for food drives species formation by genetic adaptations to the environment and subsequent niche separation. On a short-term scale, animals use different strategies to meet their nutritional requirements, which ultimately influence their fitness. Understanding these adaptations in herbivores is especially important in temperate climates where animals have adapted both physiologically and behaviorally to seasonal variations in order to meet their nutritional requirements. The aim of this project was to investigate temporal variation in chemical composition of rumen content between two coexisting species of large herbivores, the native roe deer (Capreolus capreolus L.) and the introduced fallow deer (Dama dama L.), as well as a potential effect of competition on niche separation (interspecific differences in rumen nutrient composition). We analyzed 345 rumen samples collected from animals at one 95 km2 estate, Koberg, in southwestern Sweden. Based on samples from all seasons, temporal variation in nutrient composition and interspecific differences between the two deer species were investigated under two contrasting fallow deer population densities. Results revealed that nutrient composition varied between species and across seasons. Roe deer had a higher proportion of rumen protein compared to fallow deer, with the highest proportions in spring. In contrast, fallow deer had a higher proportion of rumen hemicellulose compared to roe deer in spring, while no differences in nutrient composition between species could be found in fall. Overall, there were greater differences between the two species when fallow deer density was high and competition likely more pronounced than when fallow deer density was low. The results from this study can be used to understand interspecific competition and how it fosters niche separation between coexisting large herbivores.
Highlights
On an evolutionary time scale, competition for food drives species formation by genetic adaptations to the environmentCommunicated by: Teresa Abaigar Ancín Communicated by: Teresa Abaigar Ancín (Raubenheimer et al 2012) and subsequent niche separation of the species (Hardin 1960; Schoener 1974; Codron and Clauss 2010)
The Tukey–Kramer test revealed that available protein (AP) was significantly higher for roe deer compared to fallow deer in spring (P = 0.0139), summer (P < 0.0001) and winter (P = 0.0003) by 41%, 36% and 35% percentage points, respectively, but there were no significant differences between species in fall (P ≥ 0.46)
The variation ranged across seasons between 200 and 412 g kg−1 dry matter (DM) for roe deer and 149 and 291 g kg−1 DM for fallow deer
Summary
On an evolutionary time scale, competition for food drives species formation by genetic adaptations to the environmentCommunicated by: Teresa Abaigar Ancín Communicated by: Teresa Abaigar Ancín (Raubenheimer et al 2012) and subsequent niche separation of the species (Hardin 1960; Schoener 1974; Codron and Clauss 2010). On an evolutionary time scale, competition for food drives species formation by genetic adaptations to the environment. On a short-term scale, an overlap in habitat use and diet preferences, together with limited food availability, may increase interspecific competition (Putman 1996; Pan et al 2019; Regmi et al 2020). Interspecific competition may increase due to seasonal changes or when population densities increase (Nicholson et al 2006; Obidziński et al 2013), and this in turn can increase either overlap or niche separation between competing species depending on e.g., resource availability and environmental conditions (Pianka 1974; Schoener 1974; Araujo et al 2011; Redjadj et al 2014). As long as resources are not short in supply, niche segregation may contribute to coexistence to reduce competition at higher
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