Date Published: June 26, 2019
Publisher: Public Library of Science
Author(s): Martha M. Lyke, Anthony Di Fiore, Noah Fierer, Anne A. Madden, Joanna E. Lambert, Michael Scott Brewer.
Insectivory, or the consumption of insects and other arthropods, is a significant yet cryptic component of omnivorous primate diets. Here, we used high-throughput DNA sequencing to identify arthropods from fecal DNA and assess variation in insectivory by closely-related sympatric primates. We identified arthropod prey taxa and tested the hypothesis that variation in insectivory facilitates niche differentiation and coexistence among closely-related species with high dietary overlap. We collected 233 fecal samples from redtail (Cercopithecus ascanius; n = 118) and blue monkeys (C. mitis; n = 115) and used a CO1 metabarcoding approach to identify arthropod DNA in each fecal sample. Arthropod DNA was detected in 99% of samples (N = 223 samples), and a total of 68 families (15 orders) were identified. Redtails consumed arthropods from 54 families, of which 12 (21.8%) were absent from blue monkey samples. Blue monkeys consumed arthropods from 56 families, of which 14 (24.6%) were absent from redtail samples. For both species, >97% of taxa present belonged to four orders (Araneae, Diptera, Hymenoptera, Lepidoptera). Redtail samples contained more Lepidoptera taxa (p<0.05), while blue monkey samples contained more Araneae (p<0.05). Blue monkeys consumed a greater diversity of arthropod taxa than redtail monkeys (p<0.05); however, the average number of arthropod families present per fecal sample was greater in the redtail monkey samples (p<0.05). These results indicate that while overlap exists in the arthropod portion of their diets, 20–25% of taxa consumed are unique to each group. Our findings suggest that variation in arthropod intake may help decrease dietary niche overlap and hence facilitate coexistence of closely-related primate species.
Understanding the mechanisms of species coexistence is an integral part of community ecology with implications for understanding species interactions at both evolutionary and ecological scales [1–3]. Classical niche theory states that when two or more similar species coexist, one or both must alter some aspect of their niche or one species will outcompete the other [4,5]. Resource competition has been implicated as an important component driving niche partitioning in coexisting species [4,5]. However, it is now widely recognized that, while competition can have a strong influence on species’ interactions, there may be other factors involved [1,3]. When two species evolve via allopatric speciation, divergent adaptations to their respective habitats can facilitate coexistence when the species come in contact . For example, guenons (Cercopithecus spp.) are argued to have undergone allopatric speciation relatively recently (2.1–0.5mya) , and it is thought that divergent dietary adaptations have facilitated coexistence . While there may also be direct resource competition, it is the differences in resource use–i.e., the areas of non-overlap–that are expected to enable species to coexist [3,6].
Out of the 233 fecal samples in total, eight samples (one PCR plate column) failed to amplify, likely due to pipetting error, leaving 225 samples for downstream analyses (redtails n = 118, blues n = 107). Across these 225 fecal samples, we identified 15 arthropod orders, 68 families (Table 1), and 122 genera (S1 Table). Redtails consumed arthropods from 54 arthropod families in 11 orders (Table 1), of which 12 families (21.8%) and 4 orders (36.3%) were absent from blue monkey samples. Blue monkeys consumed arthropods from 56 families in 11 orders (Table 1), of which 14 families (24.6%) and 4 orders (36.3%) were absent from redtail samples.
In this study, we used high-throughput DNA sequencing to identify a large diversity of arthropod taxa consumed by sympatric guenons inhabiting KNP. As very few actual arthropod taxa have been identified previously (but see), we present the first robust report of taxa consumed by these omnivorous primates. Because arthropods make up 20–50% of the diets of blue and redtail monkeys , these data represent an important component of their feeding ecology. We demonstrated that, while there was considerable overlap in arthropod prey, 20–25% of the arthropod taxa consumed were unique to each primate group. Specifically, we identified certain taxa (Table 1) that were more commonly found in the feces of one or the other monkey group, indicating some degree of arthropod prey specificity.