Showing papers by "Stephen L. Cameron published in 2007"

A mitochondrial genome phylogeny of Diptera: whole genome sequence data accurately resolve relationships over broad timescales with high precision

Abstract: Mitochondrial genomes provide a promising new tool for understanding deep-level insect phylogenetics, but have yet to be evaluated for their ability to resolve intraordinal relationships. We tested the utility of mitochondrial genome data for the resolution of relationships within Diptera, the insect order for which the most data are available. We sequenced an additional three genomes, from a syrphid, nemestrinid and tabanid, representing three additional dipteran clades, 'aschiza', non-heteroneuran muscomorpha and 'basal brachyceran', respectively. We assessed the influence of optimality criteria, gene inclusion/exclusion, data recoding and partitioning strategies on topology and nodal support within Diptera. Our consensus phylogeny of Diptera was largely consistent with previous phylogenetic hypotheses of the order, except that we did not recover a monophyletic Muscomorpha (Nesmestrinidae grouped with Tabanidae) or Acalyptratae (Drosophilidae grouped with Calliphoridae). The results were very robust to optimality criteria, as parsimony, likelihood and Bayesian approaches yielded very similar topologies, although nodal support varied. The addition of ribosomal and transfer RNA genes to the protein coding genes traditionally used in mitochondrial genome phylogenies improved the resolution and support, contrary to previous suggestions that these genes would evolve too quickly or prove too difficult to align to provide phylogenetic signal at deep nodes. Strategies to recode data, aimed at reducing homoplasy, resulted in a decrease in tree resolution and branch support. Bayesian analyses were highly sensitive to partitioning strategy: biologically realistic partitions into codon groups produced the best results. The implications of this study for dipteran systematics and the effective approaches to using mitochondrial genome data are discussed. Mitochondrial genomes resolve intraordinal relationships within Diptera accurately over very wide time ranges (1-200 million years ago) and genetic distances, suggesting that this may be an excellent data source for deep-level studies within other, less studied, insect orders.

The mitochondrial genome of the screamer louse Bothriometopus (phthiraptera: ischnocera): effects of extensive gene rearrangements on the evolution of the genome.

Abstract: Mitochondrial (mt) genome rearrangement has generally been studied with respect to the phenomenon itself, focusing on their phylogenetic distribution and causal mechanisms. Rearrangements have additional significance through effects on substitution, transcription, and mRNA processing. Lice are an ideal group in which to study the interactions between rearrangements and these factors due to the heightened rearrangement rate within this group. The entire mt genome of the screamer louse Bothriometopus was sequenced and compared to previously sequenced louse genomes. The mt genome is 15,564 bp, circular, and all genes are encoded on the same strand. The gene arrangement differs radically from both other louse species and the ancestral insect. Nucleotide composition is A+T biased, but there is no skew which may be due to reversal of replication direction or a transcriptional effect. Bothriometopus has both tRNA duplication and concerted evolution which has not been observed previously. Eleven of the 13 protein-coding genes have 3′ end stem-loop structures which may allow mRNA processing without flanking tRNAs and so facilitate gene rearrangements. There are five candidate control regions capable of forming stem-loop structures. Two are structurally more similar to the control regions of other insect species than those of other lice. Analyses of Bothriometopus demonstrate that louse mt genomes, in addition to being extensively rearranged, differ significantly from most insect species in nucleotide composition biases, tRNA evolution, protein-coding gene structures and putative signaling sites such as the control region. These may be either a cause or a consequence of gene rearrangements.

The complete mitochondrial genome sequence of the Mormon cricket (Anabrus simplex: Tettigoniidae: Orthoptera) and an analysis of control region variability

Abstract: The Anabrus simplex is a swarming plague orthopteran found in western North America The genome is 15 766 bp in length and genome organization follows the ancestral insect gene arrangement atp6 lacked any readily identifiable stop codon Examination of mRNA secondary structure for this gene suggested a stem/loop-mediated mRNA post-transcriptional processing to liberate a mature atp6 mRNA with a complete stop codon produced by polyadenylation Comparison of similar protein with protein gene boundaries in other insect species reveal a general mechanism for mRNA excision and provide further supporting evidence for post-transcriptional mRNA processing in mitochondrial genomes The A + T-rich region, or control region, was sequenced for 55 A simplex individuals from 12 different populations Variance studies between these individuals show that the A + T-rich region contains significant phylogenetic signal to be used in population studies

Mitochondrial genomic comparisons of the subterranean termites from the Genus Reticulitermes (Insecta: Isoptera: Rhinotermitidae)

Abstract: Termites of the genus Reticulitermes are some of the most significant pests of structural timber and tree farming in the northern hemisphere, causing losses in the billions of dollars annually beca...

Save Isoptera: a comment on Inward et al.

Abstract: A number of phylogenetic studies during the last decade have shown that termites—one of the main groups of eusocial insects—are a type of cockroach, whose closest living relative is the wood-feeding genus Cryptocercus (reviewed in [Klass & Meier (2006)][1] and [Inward et al. (2007)][2]). Inward