Gombash, B. J. | bioRxiv Science

bioRxiv2025

Contrasting Impacts of the Anthropogenic Environment on the Diet of Long-tailed Macaques (Macaca fascicularis) in Southeast Asia

Human expansion will only increase access to anthropogenic food resources for wildlife species. Access to these resources can have positive and negative impacts on wildlife species. It is generally assumed that access to anthropogenic resources will decrease diet diversity, although recent work questions this. Our research uses metabarcoding to assess the diet detected in fecal samples from long-tailed macaques (Macaca fascicularis) on the islands of Singapore and Bali, Indonesia. We gathered information about multiple parameters to characterize the distinctly different anthropogenic environments on the two islands. Then, we used a leave one out cross validation model selection procedure and linear regressions to determine which environmental parameters impact various diet metrics for the macaques in these two different anthropogenic contexts. Macaques in both island contexts increased their usage of crop diet items with greater anthropogenic access, but with different resulting patterns. We found that as food provisioning of the macaques increases in Bali, multiple measures of diet richness decrease, as generally expected, yet diet stability within a group also decreases, indicating that although diet richness decreases with provisioning, individuals do not experience similar levels of access to these resources. In contrast to Bali, there were no significant differences in diet stability across groups in Singapore with increases in anthropogenic resources. These differing impacts on diet, seen in a single species, highlight the need to consider more closely the details of the spatial and temporal distribution of anthropogenic resource access when making predictions about how a species diet will be impacted.

ecology↗

bioRxiv2025

Diet, Climatic Conditions, and Sex Affect the Mycobiome of Wild Common Marmosets (Callithrix jacchus)

Recent research on the gut mycobiome, or the fungal portion of the gut microbial community, suggests that it interacts with host physiology and impacts host health. However, fundamental questions about how the mycobiome is assembled remain unanswered. It remains unclear whether the fungi detected in the gut are predominantly residents of the gastrointestinal tract or if they are largely transient and pass through. To address this question, we sought to determine whether host factors (e.g., sex) or external environmental factors (e.g., variable climatic conditions and diet) were more strongly correlated with the gut mycobiome of common marmosets (Callithrix jacchus), a primate species living in the semi-arid Caatinga biome of northeastern Brazil. A stronger correlation with host factors, would suggest a more resident mycobiome, while a stronger association with external environmental factors suggests a more transient mycobiome. We collected 52 marmoset fecal samples across a 2-year period and DNA metabarcoding was used to assess both the mycobiome and diet of each sample. We used FUNGuild to assign ecological roles to the fungi, which were sorted into resident (e.g. animal pathogens) and transient (e.g. plant pathogens) groups. We found that mycobiome richness and evenness varied by host sex and correlated with the arthropod component of the diet while mycobiome composition varied between wetter and drier periods and correlated with the plant portion of the diet. The fact that external environmental factors were associated with the presence of specific taxa led us to conclude that the mycobiome is largely made up of transient taxa. ImportanceOther than causing infectious diseases, the function of the mycobiome is poorly understood. There is evidence that the mycobiome can play a positive role, such as training the hosts immune system, and a negative role, such as causing cancer and Alzheimers disease. To fully understand these associations, basic questions about which taxa live in the host and which pass through, must be addressed. We used DNA metabarcoding and a tool that can group fungi based on their ecological roles, to determine whether the mycobiome of Caatinga marmosets was more strongly correlated with host sex or host diet and environment. We found that the marmoset mycobiome was more strongly correlated with diet and environment and most fungi passed through the host rather than lived in the hosts gut.

microbiology↗