Morphological Stasis in Time? A Triatoma brasiliensis brasiliensis Study Using Geometric Morphometrics in the Long Run

Abstract

Triatoma brasiliensis brasiliensis Neiva, 1911 is one of the most important vectors of Chagas disease in the Brazilian semiarid regions in the north-east. The risk imposed by T. b. brasiliensis to the human populations, due to frequent invasions and/or colonization of the domiciles, demands constant monitoring and control actions as well as an understanding of its evolutionary process. In this context, the following research studies the pattern of shape adaptation over time using a large dataset from 102 years of specimen collections in order to identify the morphological plasticity of this vector in Brazil. This dataset was analyzed using geometric morphometrics tools and the timescale was divided into eight different groups, containing specimens from 1912 to 2014. Geometric morphometrics analysis showed an interesting morphological stasis in the wing shape of T. b. brasiliensis, which allowed us to understand the high capacity of adaptation to changes in climate condition through time, and the invasive status which Triatoma species have around the world. Moreover, these results showed novel findings as an interesting phenotypic pattern, with no modifications in more than 100 years, leading us to understand the shape evolution in Triatominae as a vector species of diseases.

Keywords: Chagas disease; morphology; vectors; wing shape.

Figure 1

Image of the left wing of a male of Triatoma brasiliensis brasiliensis Neiva, 1911 showing the selected 10 landmarks: 1. Intersection of Pcu and Pcu (postocubitus) + first anal vein; 2. Intersection of Cu (cubitus) and Cu–postocubitus (Cu–Pcu); 3. Intersection of Cu and M–Cu; 4. Intersection of media and cubitus (M–Cu); 5. Bifurcation of the radius (R) and median (M) veins; 6. Membrane portion on radius vein; 7. First intersection of R + M and Pcu (postocubitus); 8 Second intersection of R + M and Pcu; 9. Intersection of M and extension of Cu–Pcu veins; 10. Intersection of Pcu and Cu.

Figure 2

Canonical variate analysis showing the wing shape influence of the of Triatoma brasiliensis brasiliensis females from various states and years (1912–2014) Canon represents the canonical variate dimension.

Figure 3

UPGMA dendrogram of the Triatoma brasiliensis brasiliensis females, from various states and years (1912–2014) showing the phylogenetic distances among the groups. Groups: 1, 3, 4, 5, 6, 7, 8.

Figure 4

Canonical variate analysis showing the wing shape influence of Triatoma brasiliensis brasiliensis males from several states and years (1912–2014). Groups: 1, 2, 3, 4, 5, 6, 7, 8 Canon represents the canonical variate dimension.

Figure 5

UPGMA Dendrogram of the Triatoma brasiliensis brasiliensis males, from various states and years (1912–2014), showing the phylogenetic distances between the groups.

Figure 6

Canonical variate analysis showing the conformation influence in males and females of Triatoma brasiliensis brasiliensis from different states and years (1912–2014). among the groups Canon represents the canonical variate dimension.

Figure 7

UPGMA dendrogram of the male and female populations of Triatoma brasiliensis brasiliensis from different states and years (1912–2014), showing the phylogenetic distances among the groups.

Figure 8

Canonical variate analysis showing the conformation influence in males and females of Triatoma brasiliensis brasiliensis from several states and years (1912–2014). Groups: 1, 2, 3, 4, 5, 6, 7, 8, and an external group T. infestans Canon represents the canonical variate dimension.