Glossina palpalis palpalis populations from Equatorial Guinea belong to distinct allopatric clades

Abstract

BackgroundLuba is one of the four historical foci of Human African Trypanosomiasis (HAT) on Bioko Island, in Equatorial Guinea. Although no human cases have been detected since 1995, T. b. gambiense was recently observed in the vector Glossina palpalis palpalis. The existence of cryptic species within this vector taxon has been previously suggested, although no data are available regarding the evolutionary history of tsetse flies populations in Bioko.MethodsA phylogenetic analysis of 60 G. p. palpalis from Luba was performed sequencing three mitochondrial (COI, ND2 and 16S) and one nuclear (rDNA-ITS1) DNA markers. Phylogeny reconstruction was performed by Distance Based, Maximum Likelihood and Bayesian Inference methods.ResultsThe COI and ND2 mitochondrial genes were concatenated and revealed 10 closely related haplotypes with a dominant one found in 61.1% of the flies. The sequence homology of the other 9 haplotypes compared to the former ranged from 99.6 to 99.9%. Phylogenetic analysis clearly clustered all island samples with flies coming from the Western African Clade (WAC), and separated from the flies belonging to the Central Africa Clade (CAC), including samples from Mbini and Kogo, two foci of mainland Equatorial Guinea. Consistent with mitochondrial data, analysis of the microsatellite motif present in the ITS1 sequence exhibited two closely related genotypes, clearly divergent from the genotypes previously identified in Mbini and Kogo.ConclusionsWe report herein that tsetse flies populations circulating in Equatorial Guinea are composed of two allopatric subspecies, one insular and the other continental. The presence of these two G. p. palpalis cryptic taxa in Equatorial Guinea should be taken into account to accurately manage vector control strategy, in a country where trypanosomiasis transmission is controlled but not definitively eliminated yet.

Contrasting Effects of Historical Sea Level Rise and Contemporary Ocean Currents on Regional Gene Flow of Rhizophora racemosa in Eastern Atlantic Mangroves

“…However, the isolation of Bioko Island may be a remnant of range fragmentation of mangroves, at least if we assume that mangrove forests were ubiquitous in this region during glacial times. This is for example the case for the insect Glossina palpalis palpalis , where Bioko populations have been isolated, resulting in a unique clade, different from mainland populations [ 58 ]. Therefore, future studies should consider mangrove samples from Bioko to assess the full impact of the IBC corridor on genetic connectivity and potential range fragmentation of Central African mangrove populations.…”

“…40 km from the edge of the continental shelf at less than 60 m below sea level [ 56 , 57 ]. It was repeatedly connected to mainland Cameroon during glacial times [ 56 – 58 ]. Following glacial retreat ca .…”

“…Following glacial retreat ca . 12 ka BP, sea level rose and covered these lowlands, separating Bioko from the mainland [ 56 – 58 ] and forming the Inter-Bioko-Cameroon (IBC) corridor. In addition to the many rivers flowing into the coastal waters of Cameroon, the isolation of Bioko Island from the mainland has caused ocean swells around the coast of Cameroon to be weak [ 59 ].…”

Diversity and phylogenetic relationships of Glossina populations in Nigeria and the Cameroonian border region

“…Several studies have indicated that tsetse populations are genetically structured [ 21 , 22 ]. Especially G. p. palpalis, clustering has been observed with distinct West African and Central African clades [ 8 , 15 , 23 , 24 ], however, very few of such data are available on tsetse populations in Nigeria [ 15 , 17 , 18 , 25 , 26 ], where these two clades could meet as the country links West and Central Africa.…”

Ecotype Evolution in Glossina palpalis Subspecies, Major Vectors of Sleeping Sickness

“…palpalis , the very high bootstrap values observed between Central and West Africa and between Cameroon and RDC subsamples suggest subspeciation, if not more, in the ecological sense of it (adaptively divergent but not necessarily sexually isolated entities, see [ 40 , 54 ]). The existence of three subspecies (or even species) separating flies from West Africa (Ivory Coast), South of Cameroon, Equatorial Guinea and DRC has already been suggested, based on mtDNA (COI) [ 13 ] and there are probably more than that [ 55 ]. Here, our seven microsatellite loci provide a strong confirmation that G .…”