STATISTICAL TESTS OF HOST-PARASITE COSPECIATION.

Area of Science:

• Evolutionary Biology
• Phylogenetics
• Molecular Evolution

Background:

• Cospeciation, the synchronous speciation of ecologically linked species, is often indicated by congruent phylogenies.
• Understanding cospeciation requires robust methods to compare evolutionary histories of associated species.

Purpose of the Study:

• To develop and apply phylogenetic tests for cospeciation using maximum-likelihood and Bayesian methods.
• To investigate potential cospeciation between pocket gophers and their parasitic lice.
• To test hypotheses of topological agreement, identical speciation times, and congruent evolutionary rates.

Main Methods:

• Phylogenetic estimation using maximum-likelihood and Bayesian approaches on mitochondrial COI DNA sequences.
• Comparison of phylogenies for pocket gophers and lice to assess topological congruence.
• Analysis of speciation times and evolutionary rates between host and parasite lineages.

Main Results:

• Phylogenetic differences between gopher and louse lineages were significant and not due to sampling error.
• The data suggest a host-switching rate approximately one-third of the host speciation rate.
• Lice exhibited nucleotide substitution rates two to four times higher than those of pocket gophers.

Conclusions:

• While some evidence supports a shared evolutionary history between gophers and lice, host switching is a significant factor.
• Differential evolutionary rates between hosts and parasites can impact the congruence of their phylogenies.
• Phylogenetic methods provide powerful tools for detecting cospeciation and associated evolutionary dynamics.