Using a null hypothesis framework to test expectations of disparity in an adaptive radiation

Area of Science:

• Evolutionary Biology
• Marine Biology
• Herpetology

Background:

• Adaptive radiations are theorized to produce significant species and morphological diversity.
• Testing evolutionary hypotheses, like adaptive radiation, can be challenging using traditional methods.
• Null hypothesis testing provides a framework for evaluating scientific conjectures.

Purpose of the Study:

• To investigate adaptive radiation in Hydrophis sea snakes.
• To compare species richness and morphological disparity between Hydrophis and the Aipysurus-Emydocephalus clade.
• To test for differences in diversification rates and morphological disparity using phylogenetic null models.

Main Methods:

• Phylogenetic null models were employed to assess diversification rates.
• A phylomorphospace approach was used to analyze morphological disparity.
• Comparative analysis between Hydrophis and Aipysurus-Emydocephalus lineages was conducted.

Main Results:

• No significant differences in diversification rates were detected between the two sea snake groups.
• Hydrophis species exhibited significantly greater morphological disparity within their morphospace.
• Species richness was comparable between the Hydrophis and Aipysurus-Emydocephalus lineages.

Conclusions:

• The study supports the adaptive radiation of Hydrophis, driven by ecological specialization.
• Morphological disparity, rather than species richness, is a key indicator of adaptive radiation in this context.
• Phylogenetic null models and morphospace analysis are valuable tools for studying evolutionary radiations.