Spatial sorting drives morphological variation in the invasive bird, Acridotheris tristis

Area of Science:

• Ecology
• Evolutionary Biology
• Invasive Species Management

Background:

• Invasive species range expansion often accelerates due to spatial sorting, where individuals with superior dispersal abilities colonize new areas.
• The Common myna (Acridotheris tristis) is an invasive bird species whose rapid range expansion in South Africa warrants investigation into its dispersal mechanisms.

Purpose of the Study:

• To determine if spatial sorting is influencing the range expansion of the invasive Common myna in South Africa.
• To examine the relationship between morphological traits, dispersal ability, and environmental factors in this invasive bird population.

Main Methods:

• Sampling of Common mynas across their invasive range in South Africa.
• Comparison of morphometric measurements related and unrelated to dispersal ability.
• Analysis of environmental factors (vegetation, urbanization) influencing morphological variations.

Main Results:

• Dispersal-relevant traits showed significant correlation with distance from the range core, indicating spatial sorting.
• Strong sexual dimorphism was observed, with females exhibiting significant variations in wing and head traits, suggesting female-biased dispersal.
• Non-dispersal traits (foraging-related) were not spatially sorted but were influenced by environmental variables like vegetation and urbanization.

Conclusions:

• Spatial sorting plays a significant role in the accelerated range expansion of the Common myna in South Africa.
• Female Common mynas appear to be the primary dispersing sex, driving the invasion's spatial dynamics.
• Environmental factors interact with morphology to shape the invasive spread of this species.