Is geographic variation within species related to macroevolutionary patterns between species?

Area of Science:

• Evolutionary Biology
• Speciation and Macroevolution
• Climate Change Ecology

Background:

• The link between microevolutionary processes (within-species variation) and macroevolutionary patterns (among-species diversity) is a key, yet understudied, area in evolutionary biology.
• Understanding how geographic variation within species relates to large-scale trait evolution among species is crucial for a comprehensive view of evolution.
• Discrete color polymorphisms, like dorsal stripe presence/absence in Plethodon salamanders, offer a tractable system to investigate these relationships.

Purpose of the Study:

• To investigate the relationship between climate and morphology across and within species in the salamander genus Plethodon.
• To determine if a specific color polymorphism (red dorsal stripe) in Plethodon cinereus is linked to climatic factors and has a long evolutionary history.
• To explore how within-species geographic variation and macroevolutionary trait patterns are interconnected.

Main Methods:

• Comparative analysis of climate and morphological data (dorsal stripe presence/absence) across multiple Plethodon species.
• Phylogenetic reconstruction to assess the evolutionary history of the color polymorphism (>40 million years).
• Statistical modeling to test for climate-morphology correlations at both interspecific and intraspecific levels.

Main Results:

• The red dorsal stripe polymorphism in Plethodon has been evolutionarily variable for over 40 million years.
• A strong correlation exists between climatic variation and intraspecific morph frequencies at the among-species level.
• Contrary to the among-species patterns, significant climate-morphology relationships were largely absent within most individual polymorphic species.

Conclusions:

• The study reveals a complex interplay between climate, geographic variation, and macroevolutionary trait diversification in Plethodon salamanders.
• While climate strongly influences trait distribution across species, its role within species appears more nuanced and context-dependent.
• This research provides foundational insights into the poorly understood links between micro- and macroevolutionary processes.