Temporal Congruence Revisited: Comparison of Mitochondrial DNA Sequence Divergence in Cospeciating Pocket Gophers and their Chewing Lice

A Different Tempo of Mitochondrial DNA Evolution in Birds and Their Parasitic Lice

“…Hafner et al (1994) reported an order of magnitude difference between lice and gophers in the rate of substitution at the third codon position in mitochondrial cytochrome oxidase I and suggested that the more rapid evolution of the lice may reflect their shorter generation time relative to that of their hosts. Subsequent independent reanalyses of these data (Huelsenbeck et al, 1997;Page, 1996a) support Hafner et al's conclusion of a more rapid rate of substitution in lice, but suggest that the disparity in rates is approximately 2.5 rather than an order of magnitude. As this is the only published study of louse DNA to date it is not known whether this disparity applies to other mammalian or bird lice and their hosts.…”

“…The probability of obtaining an observed number of cospeciation events was determined by comparing the actual host tree with 100 random parasite trees generated using a Markovian model (Harding, 1971). The correlation between host and parasite divergence was tested using the randomisation test described in Page (1996a).…”

“…mately constant rate of evolution within each clade, that is, a molecular clock within each. The two clocks may tick at different rates and so be local clocks, but they need to be present, otherwise it is difficult to separate rate variation within lineages from that between hosts and parasites (Page, 1996a). To test for molecular clocks we computed maximum likelihood branch lengths for the host and parasite subtrees shown in Fig.…”

“…Difference in generation time between lice and their hosts has been offered as an explanation for the higher rate of substitution in pocket gopher lice and their hosts (Hafner et al, 1994). However, the apparent correspondence between the magnitudes of the rate difference and generation length in these two organisms is weakened by subsequent analyses suggesting a less pronounced difference in evolutionary rate between gophers and lice (Huelsenbeck et al, 1997;Page, 1996a). These reanalyses suggest that gopher lice are accumulating nucleotide substitutions only two to three times more rapidly than their mammalian hosts.…”

Using parasite databases to identify potential nontarget hosts of biological control organisms

“…Hinkle et al (1994) used morphological and gene sequence data to show congruent cladogenesis between leaf-cutting ants and antine fungi. DNA sequencing studies have convincingly documented coevolution between gophers (e.g., Geomys and Orthogeomys) and their parasitic lice (Page 1996), and between Nesoydne planthoppers and their plant hosts (Roderick 1997).…”