Phenotypic Quantitative Divergence Across Heterogeneous Environments in a Widespread Southern South American Tree

Area of Science:

• Ecology
• Evolutionary Biology
• Genetics

Background:

• Broadly distributed species often exhibit local adaptation, with phenotypic and genetic divergence influenced by environmental gradients.
• The Fabaceae family, particularly diverse in South America, includes versatile species adapted to arid and disturbed environments.
• Vachellia caven, a taxonomically complex native tree, possesses ecological breadth, making it a suitable model for studying adaptive divergence.

Purpose of the Study:

• To investigate adaptive phenotypic divergence in Vachellia caven populations across environmental gradients.
• To assess the interplay of geographic distance, environmental heterogeneity, and genetic differentiation in shaping phenotypic variation.
• To determine if observed trait variations are a result of local adaptation or other evolutionary forces.

Main Methods:

• Quantified phenotypic differentiation of quantitative traits using Analysis of Variance (ANOVA).
• Examined neutral genetic differentiation (FST) among six V. caven varieties across Argentinian populations.
• Performed PST-FST comparisons to identify traits under diversifying selection.
• Assessed correlations between phenotypic variation, environmental variables, genotypic variation, and geographic distances.

Main Results:

• Significant genetic differentiation (FST = 0.329) was observed, consistent with isolation by distance and environmental heterogeneity.
• PST-FST comparisons indicated that all studied traits were under diversifying selection, supporting adaptive divergence.
• Fruit width and length showed significant correlations with environmental variables such as precipitation and temperature.
• Phenotypic divergence in V. caven is shaped by both geographic and environmental factors.

Conclusions:

• Phenotypic and genetic divergence in V. caven populations is driven by local adaptation to diverse environmental conditions.
• Morphological and genetic differentiation facilitates V. caven's success in varied habitats.
• Findings provide insights into the adaptive strategies of V. caven, relevant for conservation and climate change adaptation planning.