Niche differentiation mechanisms among canopy frugivores and zoochoric trees in the northeastern extreme of the Amazon

ABSTRACT Frugivores and zoocoric trees represent an important proportion of tropical rainforest biodiversity. As niche differences favor species coexistence, we aimed to evaluate morphological and temporal niche segregation mechanisms among zoochoric trees and canopy frugivores in a tropical rainforest in the northeastern extreme of the Brazilian Amazon. We tested the effects of fruit morphology, tree size, frugivore body size and time of day on fruit consumption. We recorded the frugivore species that fed on 72 trees (44 species, 22 genera) and whether these frugivores swallowed the seeds. We monitored trees only once from 07:00 to 17:00 h between January and September 2017. We observed fruit consumption in 20 of the 72 trees. Seventy-three frugivore individuals from 22 species visited the trees. Heavier fruits were consumed by larger frugivores, while seed size was inversely correlated with frugivore size. Narrower fruits and fruits with smaller seeds had greater probability of having their seeds ingested, and larger frugivores were more prone to ingest seeds. Trees bearing fruits with smaller seeds were visited by a greater number of frugivores. Taxonomic groups differed in the time of arrival at fruiting trees. None of the evaluated variables (fruit weight and size, and seed size) affected the richness of frugivores that visited the trees. We concluded that, in the studied forest, fruit morphology (weight, size and seed size) is a niche segregation mechanism among zoochoric trees, while body size and time of day are niche segregation mechanisms among frugivores.

摘要 食果动物与动物传播型树木（zoocoric trees）在热带雨林生物多样性中占据重要比例。鉴于生态位分化有利于物种共存，本研究旨在评估巴西亚马逊东北部边缘热带雨林中，动物传播型树木与树冠层食果动物之间的形态与时间生态位分化机制。我们测试了果实形态、树木体量、食果动物体型以及活动时段对果实取食行为的影响。研究记录了取食72株树木（隶属于44个物种、22个属）的食果动物物种，以及这些动物是否吞食了植物种子。2017年1月至9月期间，我们仅在每日7:00至17:00对树木开展单次监测。我们在72株树木中的20株上观测到了果实取食行为，共有隶属于22个物种的73只食果动物个体到访这些树木。结果显示，体型更大的食果动物会取食重量更高的果实，而种子尺寸与食果动物体型呈负相关关系；形态更窄的果实以及种子尺寸更小的果实，其种子被吞食的概率更高，且体型更大的食果动物更易吞食植物种子。结有小尺寸种子果实的树木，会吸引更多数量的食果动物到访。不同分类类群的食果动物，抵达结果树木的活动时段存在显著差异。本研究评估的各项变量（果实重量、果实尺寸以及种子尺寸）均未对到访树木的食果动物物种丰富度产生影响。最终结论表明，在所研究的热带雨林中，果实形态（重量、尺寸与种子尺寸）是动物传播型树木之间的生态位分化机制，而食果动物的体型与活动时段则是食果动物类群间的生态位分化机制。