Abstract
An important consequence of the discontinuous distribution of insect
populations within their geographic range is phenotypic divergence.
Detection of this divergence can be challenging when it occurs through
subtle shifts in morphological traits with complex geometries, such as
insect wing venation. Here, we used landmark-based wing geometric
morphometrics to investigate the population-level phenotypic variation
of the two subspecies of Glossina morsitans , G. m.
centralis Machado and G. m. morsitans Westwood that occur in
Zambia. Twelve homologous landmarks digitized on the right wings of 720
specimens collected from four and five sites (80 per site with 1:1 sex
ratio) within the G. m. centralis and G. m. morsitansrange respectively, were subjected to generalised Procrustes analysis to
obtain wing centroid size (CS) and wing shape variable. Linear
permutation models were then used to compare CS and wing shape between
male and female G. morsitans , the two subspecies G. m.
centralis and G. m. morsitans , and between sample locations
within each subspecies range. Significant differences in CS and wing
shape were observed between G. morsitans sexes, subspecies and
sample locations within each subspecies range. Neighbour-joining trees
derived from the analysis of Procrustes distances showed that tsetse
within each subspecies range were highly divergent. We conclude thatG. morsitans populations in Zambia exhibit significant
population-level variation in fly size and wing shape which suggests
high levels of population structuring. The main drivers of this
structuring could be adaptation to local climatic condition, especially
temperature and random genetic drift. We therefore recommend molecular
studies to estimate the levels of gene flow between these populations
and determine their levels of genetic isolation.