Centro de Investigación en Biodiversidad y Conservación (CIByC), UAEM, Cuernavaca, Morelos, México.
Departamento de Biología Animal y Humana, Facultad de Biología, Universidad de La Habana, Havana, Cuba.
Parasit Vectors. 2020 Jul 1;13(1):332. doi: 10.1186/s13071-020-04202-2.
Triatoma dimidiata (Reduviidae: Triatominae) is an important vector of Chagas disease in various countries in the Americas. Phylogenetic studies have defined three lineages in Mexico and part of Central America. While there is a marked genetic differentiation, methods for identifying them using morphometric analyses with landmarks have not yet been fully resolutive. Elliptical Fourier descriptors (EFDs), which mathematically describe the shape of any closed two-dimensional contours, could be a potentially useful alternative method. Our objective was to validate the use of EFDs for the identification of three lineages of this species complex.
A total of 84 dorsal view images of individuals of the three lineages were used. Body contours were described with EFDs using between 5 and 30 harmonics. The number of obtained coefficients was reduced by a principal components analysis and the first axis scores were used as shape variables. A linear discriminant function analysis and an ordination plot of the discriminant analysis were performed using the shape variables. A confusion matrix of the ordination plot of the discriminant analysis was obtained to estimate the classification errors, the first five PC scores were statistically compared, and a neural network were then performed using the shape variables.
The first principal component explained 50% of the variability, regardless the number of harmonics used. The results of discriminant analysis get improved by increasing the number of harmonics and components considered. With 25 harmonics and 30 components, the identification of haplogroups was achieved with an overall efficiency greater than 97%. The ordering diagram showed the correct discrimination of haplogroups, with only one error of discrimination corroborated by the confusion matrix. When comparing the first five PC scores, significant differences were found among at least two haplogroups. The 30 multilayer perceptron neural networks were also efficient in identification, reaching 91% efficiency with the validation data.
The use of EFD is a simple and useful method for the identification of the main lineages of Triatoma dimidiata, with high values of correct identification.
Triatoma dimidiata（Reduviidae：Triatominae）是美洲多个国家中查加斯病的重要传播媒介。系统发育研究在墨西哥和中美洲部分地区定义了三个谱系。虽然存在明显的遗传分化，但使用具有地标形态计量分析来识别它们的方法尚未完全解决。椭圆傅里叶描述符（EFD）可以数学描述任何封闭二维轮廓的形状，可能是一种有用的替代方法。我们的目标是验证使用 EFD 识别该物种复合体的三个谱系。
共使用了三个谱系的 84 个背面视图个体的图像。使用 EFD 描述身体轮廓，使用 5 到 30 个谐波。通过主成分分析减少获得的系数数量，并将第一轴分数用作形状变量。使用形状变量进行线性判别函数分析和判别分析的排序图。获得判别分析排序图的混淆矩阵以估计分类错误，统计比较前五个 PC 分数，然后使用形状变量进行神经网络。
无论使用的谐波数量如何，第一主成分均解释了 50％的可变性。通过增加考虑的谐波和分量数，判别分析的结果得到了改善。使用 25 个谐波和 30 个分量，可以实现总体效率大于 97％的单倍型组识别。排序图正确地区分了单倍型组，只有一个混淆矩阵证实的鉴别错误。当比较前五个 PC 分数时，发现至少两个单倍型组之间存在显著差异。30 层多层感知器神经网络在识别方面也很有效，验证数据的效率达到 91％。
EFD 的使用是一种简单而有用的方法，可用于识别 Triatoma dimidiata 的主要谱系，具有较高的正确识别率。
