“… Figure 5 Posterior plot of the estimated diet composition of devils living in four habitats with differing anthropogenic impacts (cleared land, wet eucalypt-other, wet eucalypt-rainforest, rainforest). Five potential food groups were included in the mixing model based on Lewis et al 54 : Tasmanian pademelon/European hare; brushtail possum; red-necked wallaby; green rosella; and other birds (black currawong; laughing kookaburra; and masked lapwing). Mean proportions, standard deviations and 95% CIs are included in Supplementary Table 5 .…”
Section: Resultsmentioning
confidence: 99%
“…Rainforest-living devils had a comparatively broad isotopic niche and showed some evidence of partitioning, with heavier individuals having higher nitrogen stable isotope values than their smaller counterparts. Primary consumers in the Tasmanian isoscape do not all feed at the same nitrogen isotope ratio 54 . Instead, the higher nitrogen values found in heavier devils indicate that they were feeding primarily on medium-sized herbivorous mammals, while the lower values of smaller devils imply a diet of herbivorous birds 54 .…”
Section: Discussionmentioning
confidence: 98%
“…Raw δ 15 N and δ 13 C values for each individual devil were entered as consumer data, nested within habitat. Five likely prey groups collected from the same region and time period were chosen from Lewis et al 54 based on isotopic values and the raw values for each prey individual were added to the model. These groups were: (1) Tasmanian pademelon and European hare ( Lepus europaeus ); (2) brushtail possum; (3) red-necked wallaby ( Notamacropus rufogriseus ); (4) green rosella ( Platycercus caledonicus ); and (5) other birds (black currawong ( Strepera fuliginosa ); laughing kookaburra ( Dacelo novaeguineae ); and masked lapwing ( Vanellus miles )).…”
Section: Methodsmentioning
confidence: 99%
“…They were limited however, by their ability to only use short-term dietary data from scat or stomach contents containing food that had been consumed over approximately one day 65 . Bulk stable isotope analysis of nitrogen and carbon in whiskers has more recently been used for longer-term analysis of devil diets based on differences in age 66 , DFTD status 67 , and body size and intraspecific competition 54 over several weeks or months. While nitrogen isotopic composition is frequently used to provide an indication of trophic position within the food web, as nutrients from food items are assimilated into the body tissue of consumers in a predictable manner 68 – 70 , carbon isotopic composition can differ significantly at the vegetation baseline of the ecosystem depending on the characteristics of plant species and environmental conditions 71 – 74 .…”
Anthropogenic impacts on carnivores can be complex, posing numerous threats to many species, yet also benefits to those able to exploit certain resources. This balancing act is particularly precarious for those adapters that exploit dietary resources provided by humans, but still require other resources only available in native habitat. Here we measure the dietary niche of one such species, the Tasmanian devil (Sarcophilus harrisii), a specialised mammalian scavenger, across an anthropogenic habitat gradient stretching from cleared pasture to undisturbed rainforest. Populations inhabiting areas of greater disturbance showed restricted dietary niches, suggesting that all individuals fed on similar food items, even within regenerated native forest. Populations in undisturbed rainforest habitats had comparatively broad diets and showed evidence of niche partitioning by body size, which may reduce intraspecific competition. Despite the potential benefits of reliable access to high-quality food items in anthropogenically-modified habitats, the constrained niches we observed may be harmful, indicating altered behaviours and potentially increasing the rate of fights between individuals over food. This is of particular concern for a species at risk of extinction due to a deadly cancer primarily transmitted through aggressive interactions. The lack of diversity in devil diets within regenerated native forest compared to those in old-growth rainforest also indicates the conservation value of the latter for both the devil and the species which they consume.
“… Figure 5 Posterior plot of the estimated diet composition of devils living in four habitats with differing anthropogenic impacts (cleared land, wet eucalypt-other, wet eucalypt-rainforest, rainforest). Five potential food groups were included in the mixing model based on Lewis et al 54 : Tasmanian pademelon/European hare; brushtail possum; red-necked wallaby; green rosella; and other birds (black currawong; laughing kookaburra; and masked lapwing). Mean proportions, standard deviations and 95% CIs are included in Supplementary Table 5 .…”
Section: Resultsmentioning
confidence: 99%
“…Rainforest-living devils had a comparatively broad isotopic niche and showed some evidence of partitioning, with heavier individuals having higher nitrogen stable isotope values than their smaller counterparts. Primary consumers in the Tasmanian isoscape do not all feed at the same nitrogen isotope ratio 54 . Instead, the higher nitrogen values found in heavier devils indicate that they were feeding primarily on medium-sized herbivorous mammals, while the lower values of smaller devils imply a diet of herbivorous birds 54 .…”
Section: Discussionmentioning
confidence: 98%
“…Raw δ 15 N and δ 13 C values for each individual devil were entered as consumer data, nested within habitat. Five likely prey groups collected from the same region and time period were chosen from Lewis et al 54 based on isotopic values and the raw values for each prey individual were added to the model. These groups were: (1) Tasmanian pademelon and European hare ( Lepus europaeus ); (2) brushtail possum; (3) red-necked wallaby ( Notamacropus rufogriseus ); (4) green rosella ( Platycercus caledonicus ); and (5) other birds (black currawong ( Strepera fuliginosa ); laughing kookaburra ( Dacelo novaeguineae ); and masked lapwing ( Vanellus miles )).…”
Section: Methodsmentioning
confidence: 99%
“…They were limited however, by their ability to only use short-term dietary data from scat or stomach contents containing food that had been consumed over approximately one day 65 . Bulk stable isotope analysis of nitrogen and carbon in whiskers has more recently been used for longer-term analysis of devil diets based on differences in age 66 , DFTD status 67 , and body size and intraspecific competition 54 over several weeks or months. While nitrogen isotopic composition is frequently used to provide an indication of trophic position within the food web, as nutrients from food items are assimilated into the body tissue of consumers in a predictable manner 68 – 70 , carbon isotopic composition can differ significantly at the vegetation baseline of the ecosystem depending on the characteristics of plant species and environmental conditions 71 – 74 .…”
Anthropogenic impacts on carnivores can be complex, posing numerous threats to many species, yet also benefits to those able to exploit certain resources. This balancing act is particularly precarious for those adapters that exploit dietary resources provided by humans, but still require other resources only available in native habitat. Here we measure the dietary niche of one such species, the Tasmanian devil (Sarcophilus harrisii), a specialised mammalian scavenger, across an anthropogenic habitat gradient stretching from cleared pasture to undisturbed rainforest. Populations inhabiting areas of greater disturbance showed restricted dietary niches, suggesting that all individuals fed on similar food items, even within regenerated native forest. Populations in undisturbed rainforest habitats had comparatively broad diets and showed evidence of niche partitioning by body size, which may reduce intraspecific competition. Despite the potential benefits of reliable access to high-quality food items in anthropogenically-modified habitats, the constrained niches we observed may be harmful, indicating altered behaviours and potentially increasing the rate of fights between individuals over food. This is of particular concern for a species at risk of extinction due to a deadly cancer primarily transmitted through aggressive interactions. The lack of diversity in devil diets within regenerated native forest compared to those in old-growth rainforest also indicates the conservation value of the latter for both the devil and the species which they consume.
“…As Bolnick et al (2003) and a number of more recent studies on various animals ( Bolnick et al, 2007 ; Araújo, Bolnick & Layman, 2011 ; Lucas et al, 2018 ; Szigeti et al, 2019 ; Lewis, Hughes & Rogers, 2022 ) demonstrated, there are two fundamentally different ways to be a dietary generalist. Either all individuals in a population are generalised, or different individuals specialise on different resources, as we found in Ceratina bees.…”
It is increasingly recognised that intraspecific variation in traits, such as morphology, behaviour, or diet is both ubiquitous and ecologically important. While many species of predators and herbivores are known to display high levels of between-individual diet variation, there is a lack of studies on pollinators. It is important to fill in this gap because individual-level specialisation of flower-visiting insects is expected to affect their efficiency as pollinators with consequences for plant reproduction. Accordingly, the aim of our study was to quantify the level of individual-level specialisation and foraging preferences, as well as interspecific resource partitioning, in three co-occurring species of bees of the genus Ceratina (Hymenoptera: Apidae: Xylocopinae), C. chalybea, C. nigrolabiata, and C. cucurbitina. We conducted a field experiment where we provided artificial nesting opportunities for the bees and combined a short-term mark-recapture study with the dissection of the bees’ nests to obtain repeated samples from individual foraging females and complete pollen provisions from their nests. We used DNA metabarcoding based on the ITS2 locus to identify the composition of the pollen samples. We found that the composition of pollen carried on the bodies of female bees and stored in the brood provisions in their nests significantly differed among the three co-occurring species. At the intraspecific level, individual females consistently differed in their level of specialisation and in the composition of pollen carried on their bodies and stored in their nests. We also demonstrate that higher generalisation at the species level stemmed from larger among-individual variation in diets, as observed in other types of consumers, such as predators. Our study thus reveals how specialisation and foraging preferences of bees change from the scale of individual foraging bouts to complete pollen provisions accumulated in their nests over many days. Such a multi-scale view of foraging behaviour is necessary to improve our understanding of the functioning of plant-flower visitor communities.
The consequences of biological invasions and habitat degradation for native biodiversity depend on how species cope with the individual and synergetic challenges these processes present. To assess the impact of anthropogenic land‐use on the food web architecture of an invaded community, we examine the diets of nine native and two highly invasive mammal species at different trophic levels, inhabiting different land‐uses across six biogeographic regions in Tasmania, Australia. We use two complementary methods, environmental DNA metabarcoding analysis (eDNA) of faeces and stable isotope analysis (SIA) of nitrogen (N) and carbon (C) in whole blood, to account for the high interindividual and temporal variability in the diets of multiple species simultaneously. eDNA showed regionalisation in the diet of smaller species, with land‐use further defining dietary taxa within each region. SIA revealed that bioregion and land‐use influence the δ13C values of all carnivore species and omnivores, whereas the δ15N values of these species are influenced only by land‐use and not bioregion. Including multiple species showed that native rats are changing their diet in response to the presence of invasive rats, an impact that would have otherwise been attributed to land‐use. Our findings demonstrate that human activities and invasive species are moulding the diets of invaded communities, raising questions about the potential impacts that dietary modifications will have on the life‐history traits and the evolutionary consequences these modifications might have on the survival of native species. This highlights the urgency of including human activities in ecological studies and the importance of targeting multispecies assemblages to gain a better understanding of synergetic impacts on native biodiversity.
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