Quantitative imagery analysis of spot patterns for the three-haplogroup classification of Triatoma dimidiata (Latreille, 1811) (Hemiptera: Reduviidae), an important vector of Chagas disease

Background

Spots and coloring patterns evaluated quantitatively can be used to discriminate and identify possible cryptic species. Species included in the Triatoma dimidiata (Reduviidae: Triatominae) complex are major disease vectors of Chagas disease. Phylogenetic studies have defined three haplogroups for Mexico and part of Central America. We report here our evaluation of the possibility of correctly discriminating these three T. dimidiata haplogroups using the pattern of the dorsal spots.

Methods

Digital images of the dorsal region of individuals from the three haplogroups were used. Image processing was used to extract primary and secondary variables characterizing the dorsal spot pattern. Statistical analysis of the variables included descriptive statistics, non-parametric Kruskal–Wallis tests, discriminant function analysis (DFA) and a neural classification network.

Results

A distinctive spot pattern was found for each haplogroup. The most differentiated pattern was presented by haplogroup 2, which was characterized by its notably larger central spots. Haplogroups 1 and 3 were more similar to each other, but there were consistent differences in the shape and orientation of the spots. Significant differences were found among haplogroups in almost all of the variables analyzed, with the largest differences seen for relative spot area, mean relative area of central spots, central spots Feret diameter and lateral spots Feret diameter and aspect ratio. Both the DFA and the neural network had correct discrimination values of > 90%.

Conclusions

Based on the results of this analysis, we conclude that the spot pattern can be reliably used to discriminate among the three haplogroups of T. dimidiata in Mexico, and possibly among triatomine species.

Patterns of morphological diversification in giant Berberomeloe blister beetles (Coleoptera: Meloidae) reveal an unexpected taxonomic diversity concordant with mtDNA phylogenetic structure

Delimiting species boundaries is a complex challenge usually hindered by overlooked morphological diversification or misinterpretation of geographically structured phenotypic variability. Independent molecular data are extremely useful to characterize and understand such morphological diversity. Morphological and molecular variability of the non-phoretic and apterous, widely distributed, giant blister beetles of the genus Berberomeloe, were investigated within and between lineages across most of the distributional range of the genus. We used two mtDNA gene fragments to characterize genetic variability and to produce a time-calibrated phylogeny of the genus. Our results reveal several mitochondrial lineages, allopatrically, parapatrically and sympatrically distributed. Most clades are not distinguishable between each other based on morphometrics. However, no morphometric overlap is observed between two closely related clades, one of them occurring in sympatry with a distantly congeneric species (B. insignis), suggesting that sympatry could trigger morphological diversification. Although most species share a morphometric space, they can be morphologically identified by a combination of easily observed characteristic qualitative features. Based on the concordance between mtDNA clades and morphological units, we describe six new species of Berberomeloe (B. castuo sp. nov., B. comunero sp. nov., B. indalo sp. nov, B. yebli sp. nov., B. payoyo sp. nov. and B. tenebrosus sp. nov.), revalidate two taxa (B. maculifrons comb. nov. and B. laevigatus comb. nov.) and redefine B. majalis.