Diversidad y control biológico de insectos - CyberTesis UACh ...

Discussion.
In our opinion, the adopted combination of techniques (Althoff and Pellmyr, 2002), is well
suited to deal with topics such as whose studied in this research. Some populations are far
apart (even thousands of kilometers) enough to allow hypothetical vicariant events to occur.
However, when the B fragment phylogeny was overlain on the current geographic
distribution of the isolates, no clear pattern was observed. On the other hand, the AMOVA
analysis do detect a small but significant population structuring, which could be resulted
from more recent events, including human-mediated dispersal of the fungus through
movement of crop plants and soil associated to them.
The demographic analyses proved to be complementary to the phylogenetic approach. As
noted by Althoff and Pellmyr (2002), when the phylogenetic approach reveals a geographic
structure, demographic approach generally agrees. But when the phylogenetic approach
fails to detect such a structure, especially if recent demographic changes has occurred, then
the demographic approaches are useful in that temporal scale. In this particular fungal
population, it seems to be the case and reinforces the use of a combined approach
(Bernatchez, 2001; Althoff and Pellmyr, 2002).
We expected a clear differentiation between Eastern Island and continental Chile, based in
the brief period in which the island has been influenced by the continent (Eastern Island
was anexed to Chile at 1888). The division was clear when AMOVA and pairwise
comparisons were used, but the phylogenetic signal for this division was weak. Eight
Eastern Island’s isolates were grouped closely, but other six isolates were sparsed in a large
cluster including isolates from all remaining populations.
Early studies conducted on B. bassiana did not agree on the putative genetic relatedness
and geographic origin. While some authors reported that they are correlated (Wang et al.,
2003; Yang et al., 2005), others did not support this conclusion (Aquino de Muro et al.,
2003; Aquino de Muro et al., 2005; Berretta et al., 1998; Coates et al., 2002). The studies
differ largely on sample size, molecular methods and statistical analysis, being hard to
properly compare each other. Others authors have suggested that genetic relatedness is
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