In tropical rainforests, the fruit is a vital food source for numerous birds and mammals. Food availability is a key factor influencing the spatial distribution of vertebrates. Quantifying the relationships between key food resources and animal distribution in structurally complex tropical rainforest ecosystems has relied on time-consuming and labor-intensive methods, such as long-term observations and trap-based surveys.

In a study published in Molecular Ecology Resources, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences and their collaborators demonstrated how fruit resources directly shape the distribution of fruit-eating animals (frugivores) in a tropical rainforest by using airborne environmental DNA (airborne eDNA) technology.

The study was conducted in a 20-ha forest dynamics plot in Xishuangbanna, Yunnan Province, China. By combining airborne environmental DNA sampling which captures genetic materials suspended in the air with comprehensive ground-based tree surveys, researchers detected a total of 89 terrestrial vertebrate species including 71 bird species and 18 mammal species over six days and three rounds of sampling.

Researchers found that the quantity of fruit-producing trees and their fruit sizes significantly influenced the spatial distribution of frugivores, and areas richer in fruit resources showed a higher probability of presence for both fruit-eating birds and mammals. The distribution of small-fruited trees was a key driver for the distribution of small birds and small mammals like squirrels. In contrast, the distribution of non-fruit-eating animal species showed no significant association with fruit resources.

“Airborne eDNA technology is not only an efficient tool for biodiversity monitoring, but it can also reveal fine-scale species interaction patterns. It allows us to simultaneously gather distribution data for multiple animal groups across large areas in a short time," said YANG Jie from XTBG.

This study provides the first direct evidence that the fine-scale distribution of frugivores including birds and mammals is dynamically shaped by the availability of fruit resources, particularly from small-fruited trees.