Basic HTML Version
Journal of Mosquito Research, 2013, Vol.3, No.9, 65
-
70
ISSN 1927-646X
http://jmr.sophiapublisher.com
66
(Harbach et al., 1997).
Phylogenetic reconstruction is a neglected area in
mosquito vector systematics (Munstermann and Conn,
1997). Despite the fact that
A. gambiae
and
A.
arabiensis
are highly efficient vectors, with an almost
worldwide presence and the availability of the genome
sequence (also molecular markers) for
A. gambiae
complex available. The phylogenetic relationships
among the members are not fully delineated (Foley et
al., 1998). The difficulty of determining the direction
of evolution of the genus is made arduous because of
the recent origin of the complex, the considerable
level of sequence similarity, shared genetic elements,
and shared molecular ancestral polymorphisms
(Besansky et al., 1994; Mohanty et al., 2009).
Phylogenic analysis as a tool for taxonomic studies
has proved useful in mosquito sytematics
(Mohanty et al., 2009).
Taxonomic classification of organisms have improved
in light of advances made in DNA sequencing, which
has provided DNA sequence data useful for
reconstructing evolutionary relationships among
several organisms. However, these new genetic
classification often conflict with traditional taxonomy
(Jobst et al., 1998). Thus, a good ideal on the molecular
evolution and phylogenetic of the
A. gambiae
complex
will help to understand the origins, evolution,
classification and epidemiology (Foley et al., 1998;
Thelwell et al., 2000). This has important implication in
the control of malaria (Besansky et al., 2003).
Previous classification of the genus has not been
tested using modern phylogenetics methods (Harbach
et al., 1997), but instead, relies on intuitive taxonomic
interpretations of a limited number of morphological
similarities. Mohanty et al (2009) and Morgan et al
(2009) provided the analysis of the phylogenetic
relationship of
Anopheles
species, however the
phylogenetics
A. gambiae
complex was not
thoroughly investigated. Worked by Besansky et al
(2003), after constructing a molecular phylogenetic
tree of the
A. gambiae
complex with the
A. gambiae
and
A. arabiensis
, determined both species evolved
from the same ancestor. The tree they constructed
was contrary to the general accepted phylogenetics,
which places the two principal vectors on distant
branches. Coluzzi et al (1979) in their work noted
that the
A. gambiae
complex represents one of the
most recently diverged groups of sibling species
studied to date. Thus the ability to infer evolutionary
relationships in this species complex poses a challenge
to all available phylogenetic techniques. Hence
delineating the evolutionary position of
Anopheles
subfamily requires additional data.
In the present study, we explored cytochrome oxidase
subunits I (
COI
) of mitochondrial DNA of the six
member of the
A. gambiae
complex to infer the
evolution and phylogeny of this group. Recently
molecular markers have been used for a variety of
genomic-based taxonomic, phylogenetic, population
and evolutionary investigations in animal species
(Hillis, 1996; Wilkerson et al., 2005; Khan et al.,
2008). One of these DNA markers is the
Mitochondrial DNA (mtDNA) sequence. Although
mtDNA-sequence data have proved valuable in
phylogenetic analysis, the selection of the appropriate
gene for analysis is important. Among the coding
genes in the mitochondrion genome, subunit I of the
cytochrome oxidase (
COI
) gene possesses features
suitable for evolutionary studies (Thompson et al.,
1997). MtDNA posses a relatively fast mutation rate,
which results in significant variation in mtDNA
sequences between species providing an ample within
species variance useful for phylogenetic investigations
(Tamura and Nei, 1993; Mohanty et al., 2009). Our
aim was to test the utility of
COI
genes of the species
of
A. gambiae
complex to resolve the relationships
among these species.
Materials and Methods
We retrieved the nucleotide sequences of individual
mtDNA gene sequences of
COI
, of 6 members of the
A. gambiae
complex from the GenBank database
(www.ncbi.nim.nih.gov). The details of these
sequences are given in Table 1. Sequence alignment
was performed by using CLUSTAL-X software
(http://www.clustal.org), version 2.1 (Saitou and Nei,
1987) through elimination of all positional gaps and
missing data. The sequences were then trimmed to get
their equal lengths for all the species. As a result, a
total of COI was 524 bp used in the final dataset.