a1 Molecular Biologyand Biotechnology Unit, International Centre of Insect Physiology and Ecology, PO Box 30772–00100, Nairobi, Kenya
a2 School of Environmental Sciences and Development, North West University, Private Bag X6001, Potchefstroom 2520 South Africa
a3 Biological Control Unit, International Centre of Insect Physiology and Ecology, PO Box 30772–00100, Nairobi, Kenya
The invasive larger grain borer Prostephanus truncatus (Horn) is the most important pest of farm-stored maize in Africa. It was introduced into the continent from Mesoamerica in the late 1970s and by 2008 had spread to at least 18 countries. Classical biological control using two populations of the predator Teretrius nigrescens Lewis achieved long-term and cost effective control in warm-humid areas, but not in cool and hot-dry zones. The present study investigated the phylogenetic relationships between geographical populations of the predator. Ten populations of T. nigrescens were studied using randomly amplified polymorphic DNA polymerase chain reaction (RAPD-PCR), sequence analysis of mitochondrial Cytochrme oxydase 1 (mtCOI) gene and ribosomal internally transcribed spacers (ITS) 1, 5.8S and ITS2. The mtCOI variation revealed two clades associated with geographical regions in Central America. It also reveals a significant isolation by distance between populations and considerable genetic shifts in laboratory rearing. RAPD-PCR did not reveal any potential SCAR diagnostic markers. The ITS variation mainly involved insertions and deletions of simple sequence repeats even within individuals. This study reveals the existence of two different mitochondrial lineages of the predator, associated with the geographical origin of populations distinguishable by fixed mutations on the mtCOI gene. The populations of T. nigrescens released in Africa belonged to two different clades from Meso America, namely south (released in West Africa) and north (released in eastern Africa). However, more polymorphic markers are required to clarify the observations in demographic time scales.
(Accepted February 21 2011)
(Online publication April 15 2011)
p1 Current address: Chemical Ecology Division, Swedish University of Agricultural Sciences, PO Box 102, SE 230 53, Alnarp, Sweden
p2 Current address: Postfach 508-4, 7004 Chur, Switzerland