Phylogeography and population genetics of the maize stalk borer Busseola fusca (Lepidoptera, Noctuidae) in sub‐Saharan Africa

Abstract

The population genetics and phylogeography of African phytophagous insects have received little attention. Some, such as the maize stalk borer Busseola fusca, display significant geographic differences in ecological preferences that may be congruent with patterns of molecular variation. To test this, we collected 307 individuals of this species from maize and cultivated sorghum at 52 localities in West, Central and East Africa during the growing season. For all collected individuals, we sequenced a fragment of the mitochondrial cytochrome b. We tested hypotheses concerning the history and demographic structure of this species. Phylogenetic analyses and nested clade phylogeographic analyses (NCPA) separated the populations into three mitochondrial clades, one from West Africa, and two--Kenya I and Kenya II--from East and Central Africa. The similar nucleotide divergence between clades and nucleotide diversity within clades suggest that they became isolated at about the same time in three different refuges in sub-Saharan Africa and have similar demographic histories. The results of mismatch distribution analyses were consistent with the demographic expansion of these clades. Analysis of molecular variance (amova) indicated a high level of geographic differentiation at different hierarchical levels. NCPA suggested that the observed distribution of haplotypes at several hierarchical levels within the three major clades is best accounted for by restricted gene flow with isolation by distance. The domestication of sorghum and the introduction of maize in Africa had no visible effect on the geographic patterns observed in the B. fusca mitochondrial genome.

Phylogeographic pattern and regional evolutionary history of the maize stalk borerBusseola fusca(Fuller) (Lepidoptera: Noctuidae) in sub-Saharan Africa

“…Th e molecular marker used is a fragment of the gene coding for the cytochrome b for which approximately 1000 bp were amplifi ed by PCR. Th e same primers and PCR protocol as described by Sezonlin et al (2006) were used for all samples. Amplifi ed PCR products were purifi ed with the Quick protocol (Promega Wizard SV Gel and PCR Clean-Up System) and directly sequenced on an automated sequencer ABI prism 377 using the amplifi cation primers in both directions.…”

“…It is more adapted to lowland in West Africa than in East and Southern Africa (Kfi r et al 2002). Previous study on the genetic structure of B. fusca shows that this ecological preference is associated with major diff erences in partial DNA sequence of the cytochrome b mitochondrial gene (Sezonlin et al 2006). According to that study, B. fusca populations are diff erentiated into three major clades of mitochondrial haplotypes, one located in West African region (W), one restricted to East Africa (KI) and one found in Central and East Africa (KII).…”

“…Biogeographic barriers likely corresponding to B. fusca ancient history on wild Poaceae have been shown to be the major factors of diff erentiation of this species. Th ese barriers, namely the Cameroon Volcanic Line (CVL) region between Central and West Africa and the Rift Valley in East Africa, appear to be similar to those that shaped geographic diff erentiation of phytophagous mammals and rodents (Sezonlin et al 2006).…”

“…Partial sequences of the gene coding for cytochrome b, informative at the intrageneric level in Lepidoptera (Simmons & Weller 2001;Sezonlin et al 2006) have been used. A sequential approach combining several phylogeographic and evolutionary methods (Bernatchez 2001) was used to analyse the molecular data and infer the demographic history of B. fusca populations in more details.…”

Genetic hitchhiking and resistance evolution to transgenic Bt toxins: insights from the African stalk borer Busseola fusca (Noctuidae)

“…To a first approximation, the whole population seems close to panmixia at coarse scales (700 km × 400 km). It has been suggested that B. fusca could be characterised by limited dispersal capacities (Sezonlin et al, 2006). However, consistent with Dupas et al (2014), our study did not reveal strong barriers to gene flow.…”