Characterisation of species and diversity of Anopheles gambiae Keele Colony

Anopheles gambiae sensu stricto was recently reclassified as two species, An. coluzzii and An. gambiae s.s., in wild-caught mosquitoes, on the basis of the molecular form, denoted M or S, of a marker on the X chromosome. The An. gambiae Keele line is an outbred laboratory colony strain that was developed around 12 years ago by crosses between mosquitoes from 4 existing An. gambiae colonies. Laboratory colonies of mosquitoes often have limited genetic diversity because of small starting populations (founder effect) and subsequent fluctuations in colony size. Here we describe the characterisation of the chromosomal form(s) present in the Keele line, and investigate the diversity present in the colony using microsatellite markers on chromosome 3. We also characterise the large 2La inversion on chromosome 2. The results indicate that only the M-form of the chromosome X marker is present in the Keele colony, which was unexpected given that 3 of the 4 parent colonies were probably S-form. Levels of diversity were relatively high, as indicated by a mean number of microsatellite alleles of 6.25 across 4 microsatellites, in at least 25 mosquitoes. Both karyotypes of the inversion on chromosome 2 (2La/2L+a) were found to be present at approximately equal proportions. The Keele colony has a mixed M- and S-form origin, and in common with the PEST strain, we propose continuing to denote it as an An. gambiae s.s. line

Allele frequencies (freq.) for least and most common alleles at each locus for the Keele colony.

<p>Allele frequencies (freq.) for least and most common alleles at each locus for the Keele colony.</p

Frequency of 2La/2l+^a genotypes in the Keele colony (n = 161).

<p>Frequency of 2La/2l+^a genotypes in the Keele colony (n = 161).</p

PCR primers used to type the chromosome 2 inversion 2La/2L+^a [41].

<p>PCR primers used to type the chromosome 2 inversion 2La/2L+^a [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0168999#pone.0168999.ref041" target="_blank">41</a>].</p

Microsatellite markers on chromosome 3.

<p>Distance represents the cumulative genetic distances from the most distal markers, and is taken from [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0168999#pone.0168999.ref039" target="_blank">39</a>].</p