Cryptic diversity within the major trypanosomiasis vector Glossina fuscipes revealed by molecular markers

Area of Science:

• Genetics
• Entomology
• Parasitology

Background:

• The tsetse fly Glossina fuscipes s.l. transmits human African trypanosomiasis (HAT), commonly known as sleeping sickness.
• Three subspecies of G. fuscipes s.l. have been described based on morphological differences, particularly in genitalia.
• Understanding the genetic structure of G. fuscipes s.l. is crucial for effective vector control strategies.

Purpose of the Study:

• To evaluate whether molecular evidence from nuclear DNA, mitochondrial DNA, and symbiont DNA supports the distinct taxonomic status of the described G. fuscipes s.l. subspecies.
• To investigate the genetic diversity and population structure across the geographic range of G. fuscipes s.l.

Main Methods:

• Analysis of nuclear DNA markers, including microsatellites and gene sequences (Internal Transcribed Spacer 1 - ITS1).
• Analysis of mitochondrial DNA (mtDNA) and symbiont DNA.
• Comparison of molecular data with existing morphological classifications.

Main Results:

• Nuclear ribosomal ITS1 sequences supported the three described subspecies.
• However, nuclear and mitochondrial sequence data did not support the monophyly of the morphological subspecies G. f. fuscipes and G. f. quanzensis.
• A distinct monophyletic group comprising flies from Ethiopia was identified, as were maternally inherited loci suggesting monophyly in the Lake Victoria basin and Tanzania, though not supported by nuclear loci.
• Microsatellite data revealed significant population structuring across the G. fuscipes s.l. range.

Conclusions:

• Morphological classification alone is insufficient for classifying G. fuscipes populations for control purposes.
• The Ethiopian population exhibits notable genetic discreteness, which has implications for the planned sterile insect release (SIT) program.
• High genetic differentiation in the Ethiopian population could potentially impact the effectiveness of SIT if reproductive isolation exists with released flies.