No abstract

Metarhizium anisopliae is an insect pathogenic fungus with a worldwide distribution. It is being developed and used as a biocontrol agent against a wide range of insect pests but relatively little is known of the life history of this fungus. We tested hypotheses concerning reproductive isolation and recombination in a sample of heat-active (ability to grow at 37 degrees C) and cold-active (ability to grow at 8 degrees C) sympatrically occurring isolates of M. anisopliae from Ontario, Canada by assaying nucleotide sequence variation at six polymorphic loci: the internally transcribed spacer (ITS) region of the nuclear ribosomal DNA repeat, and portions of calmodulin (CAL), chitin synthase (CHS), subtilisin-like protease (PR1), neutral trehalase (NTL) and actin (ACT)-encoding genes. The most parsimonious trees constructed showed a topology consistent with the heat-active and cold-active isolates as two monophyletic groups. We then applied Genealogical Concordance Phylogenetic Species Recognition (GCPSR) to the genealogical trees and concluded that the transition from concordance among branches to incongruity among branches delimited two species of M. anisopliae within Ontario. The GCPSR of two species was supported by intraspecific incongruity within each species when tested using the Partition Homogeneity test, indicating recombination. The GCPSR of two species also corresponded to the heat-active and cold-active groups. As the groups are morphologically indistinguishable we applied the term 'cryptic species'. Therefore, the sympatrically occurring heat-active and cold-active isolates represent different cryptic species with a history of recombination among isolates within each species.

We investigated species limits and phylogenetic relationships among chromosomally distinct North American members of the Simulium malyschevi speciesgroup. Maximum parsimony and Bayesian analyses were conducted based on 12S, COII, cyt b and ITS-1 gene sequences. In terms of species limits, monophyly was highly supported for each chromosomally and morphologically distinct taxon analysed (S. decimatum, S. defoliarti, S. malyschevi, and S. murmanum). In contrast, support for monophyly of morphologically homogeneous S. arcticum complex members was significant only in one case (S. saxosum) and not the other (S. negativum).Considering the overall topology, three principal conclusions were drawn: (i) the status of S. subvariegatum as a member of the S. malyschevi species-group remains uncertain. This species either was excluded from the malyschevi -group or formed a sister group with S. malyschevi at the base of the tree; (ii) although S. murmanum and S. decimatum branch after S. malyschevi, the position of the two species relative to each other remains unresolved; and (iii) the structurally homogeneous S. arcticum species complex was not monophyletic due to the inclusion of S. defoliarti. Further investigation may warrant changes to current malyschevi -group classification. Molecular datasets alone may be insufficient for resolving relationships among particular lineages of black flies.