Native fauna interact differently with native and alien trees in a tropical megacity

Area of Science:

• Ecology
• Urban Ecology
• Conservation Biology

Background:

• Invasive alien plants negatively impact ecosystems, but can offer resources in urban areas.
• Urban ecosystems, especially in tropical megacities, face biotic homogenization, impacting native fauna.
• Research on native fauna-alien flora interactions has primarily focused on temperate invertebrate pollinators.

Purpose of the Study:

• To investigate differential interactions of native diurnal birds and mammals with native versus alien trees in Bengaluru, India.
• To understand the role of alien trees as a resource for vertebrate pollinators in a rapidly growing tropical megacity.
• To inform urban ecosystem management in biodiverse regions.

Main Methods:

• Observational study in Bengaluru, India, assessing interactions between native birds/mammals and native/alien trees.
• Quantified bird species richness and abundance in relation to tree origin and characteristics (height, floral display size).
• Recorded feeding behaviors of nectarivorous birds and mammals (squirrels) on native and alien trees, noting pollination facilitation and nectar theft.

Main Results:

• Tree origin was not a primary predictor of bird species richness or abundance.
• Taller native trees with larger floral displays supported higher bird species richness than alien trees.
• Nectarivorous birds showed more pollination-facilitating feeding on native trees but more nectar theft on alien trees.
• Squirrels were more likely to depredate flowers of native trees.

Conclusions:

• Alien trees can serve as significant resources for native fauna in urbanizing landscapes.
• Nectar theft by birds from alien trees may reduce their reproductive success (seed set).
• Understanding these interactions is crucial for managing urban biodiversity and invasive species in highly biodiverse tropical regions.