Episodic chromosomal evolution in Planipapillus (Onychophora: Peripatopsidae): A phylogenetic approach to evolutionary dynamics and speciation

Matthew Rockman, David M. Rowell

Research output: Contribution to journalArticle

Abstract

Planipapillus, a clade of onychophorans from southeastern Australia, exhibits substantial chromosomal variation. In the context of a robust phylogeny based on nuclear and mitochondrial sequence data, we evaluate models of chromosomal evolution and speciation that differ in the roles assigned to selection, mutation, and drift. Permutation tests suggest that all chromosome rearrangements in the clade have been centric fusions and, on the basis of parsimony and maximum-likelihood methods with independent estimates of branch lengths, we conclude that at least 31 centric fusions have been fixed in Planipapillus. A likelihood-ratio test approach, which is independent of our point estimates of ancestral states, rejects an evolutionary model in which the mutation rate is constant and centric fusions are effectively neutral. In contrast to the nucleotide sequence data, which are consistent with neutrality and rate constancy, centric fusions in Planipapillus are underdominant, spontaneous fusion rates vary among lineages, or both. We predict an inverse relationship between rates of chromosomal evolution and historical population size. Chromosomal evolution may play a role in speciation in Planipapillus, both by interactions between centric fusions with monobrachial homology and by the accumulation of multiple weakly underdominant fusions.

Original languageEnglish (US)
Pages (from-to)58-69
Number of pages12
JournalEvolution
Volume56
Issue number1
StatePublished - 2002

Fingerprint

Peripatopsidae
Onychophora
Mutation Rate
Phylogeny
Population Density
Chromosomes
phylogenetics
Mutation
phylogeny
mutation
constancy
population size
homology
testing
chromosomes
nucleotide sequences
chromosome
rate
methodology

Keywords

  • Centric fusion
  • Character-state reconstruction
  • Chromosomal evolution
  • Chromosomal speciation
  • Neutrality
  • Onychophora
  • Underdominance

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Agricultural and Biological Sciences (miscellaneous)
  • Ecology, Evolution, Behavior and Systematics
  • Genetics
  • Ecology
  • Genetics(clinical)

Cite this

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abstract = "Planipapillus, a clade of onychophorans from southeastern Australia, exhibits substantial chromosomal variation. In the context of a robust phylogeny based on nuclear and mitochondrial sequence data, we evaluate models of chromosomal evolution and speciation that differ in the roles assigned to selection, mutation, and drift. Permutation tests suggest that all chromosome rearrangements in the clade have been centric fusions and, on the basis of parsimony and maximum-likelihood methods with independent estimates of branch lengths, we conclude that at least 31 centric fusions have been fixed in Planipapillus. A likelihood-ratio test approach, which is independent of our point estimates of ancestral states, rejects an evolutionary model in which the mutation rate is constant and centric fusions are effectively neutral. In contrast to the nucleotide sequence data, which are consistent with neutrality and rate constancy, centric fusions in Planipapillus are underdominant, spontaneous fusion rates vary among lineages, or both. We predict an inverse relationship between rates of chromosomal evolution and historical population size. Chromosomal evolution may play a role in speciation in Planipapillus, both by interactions between centric fusions with monobrachial homology and by the accumulation of multiple weakly underdominant fusions.",
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