Background: 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. Method: 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. Results: 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. Conclusions: 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.

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The integrative taxonomy approach has recently been widely suggested in systematic studies.  Lines of evidence such as the geometric morphometrics and ecological analyses have been useful for discriminating between genetically well-differentiated species.  Within the genus Reithrodontomys, R. mexicanus is one of the more taxonomically complex species, being considered a cryptic species complex.  R. cherrii was considered a subspecies of R. mexicanus, until molecular evidence raised it to the species-level.  Herein, we evaluate these two forms using morphological and ecological data based on the premise that they constitute genetically differentiated species.  We carried out geometric morphometric analyses on dorsal and ventral views of the skull.  Landmark and semi-landmark configurations for both views of the skull were selected based on previous studies of cricetid rodents.  We tested the presence of sexual dimorphism, and the skull shape and size differences between species on both cranial views.  Additionally, we characterized the environmental space of each species habitat using bioclimatic variables, elevation, and the Normalized Difference Vegetation Index (NDVI).  Females and males of R. mexicanus and R. cherrii did not show sexual dimorphism in shape or size of both skull views.  We found significant differences between the two species in both shape and size of the skull.  Cranial structures of the ventral view were more useful to differentiate both species.  R. mexicanus exhibited a broader environmental space than R. cherrii, with relatively similar values of temperature and elevation, but not of precipitation.  The pairwise comparison showed significant differences in the majority of the environmental variables analyzed.  Although for each view, we found statistical differences in the skull shape of R. cherrii and R. mexicanus, the ventral side showed major resolutive power differentiating both species. Our findings suggest that R. cherrii tends to have a larger skull than R. mexicanus.  However, the morphological and pelage coloration similarity between these species reported in the past, could explain the previous inclusion of R. cherrii as a subspecies of R. mexicanus.  R. mexicanus occurs in a variety of vegetation-types coinciding with the broader environmental space that it occupies compared to that of R. cherrii. The natural areas where both species are distributed were associated with high NDVI values.  Our results complement the molecular evidence and, under an integrative taxonomy approach, support R. cherrii as a different species from R. mexicanus.

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.

Al ser la vegetación uno de los principales elementos de los ecosistemas terrestres, e indicadora de diferentes procesos biofísicos, es importante contar con herramientas adecuadas para su monitoreo. Los índices espectrales de vegetación han sido una de las formas más efectivas de evaluar las propiedades de la cobertura vegetal a grandes escalas y el Índice de Vegetación de Diferencia Normalizada (NDVI) ha sido uno de los más empelados. Nuestro objetivo fue describir las diferencias espaciales y temporales del NDVI en Cuba, según tipos de vegetación o cobertura del suelo. El análisis temporal se dividió en plurianual y anual. Los valores del índice se muestrearon mediante 10 000 puntos aleatorios, clasificados según el uso del suelo, la formación de plantas y la altitud. Se tomaron muestras de las 23 áreas naturales protegidas con mayor representación de área terrestre. El índice tuvo un promedio global de 0.702 ± 0.198, con un 71% de los valores superiores a 0.60. Las áreas de usos antropogénicos mostraron valores de índice 10% más bajos que la vegetación natural. Las formaciones boscosas tuvieron valores superiores a 0.8, excepto los manglares. No se detectó asociación significativa entre la altitud y los valores de NDVI. Las áreas protegidas mostraron diferentes valores de índice, en relación con su gestión y categoría de extensión. Las coberturas utilizadas pueden servir de base para otros estudios sobre la distribución de vegetación y fauna cubana.

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La información espacial, los productos satelitales y sus derivados son fuentes importantes de información ambiental. Sin embargo, la precisión de las mediciones de áreas y distancias está sacrificada al emplearse proyecciones planas e ignorar conscientemente las irregularidades del relieve. Esto es esencial en estudios ecológicos donde el área que importa medir es la percibida por los organismos y de la que dependen los recursos del hábitat y no su proyección a un plano desde una vista superior. En este trabajo se evalúan las diferencias en las estimaciones de áreas geográficas teniendo en cuenta e ignorando la topografía del terreno, en aplicaciones de estudios ecológicos o de modelación de distribuciones, tomando el archipiélago cubano como referencia. Mediante parcelas y distribuciones de especies virtuales simuladas se evaluó la magnitud de los sesgos en estas estimaciones al ignorarse la información del relieve, empleando un mapa de área topológica derivado de un modelo digital de elevación con resolución espacial de 26.8 m. Los valores de subestimación alcanzaron un máximo de 1598 m2, equivalente a 45% de error, y son notables en regiones montañosas. Parcelas de igual área planimétrica pueden tener diferencias de hasta un 15% en las áreas reales, según su ubicación y las proporciones entre tipos de relieve que incluyen. Los cambios en los modelos de áreas de distribución potencial en dos especies virtuales creadas tuvieron errores en la estimación de las áreas superiores a 700 km2. Al emplear valores de áreas relativizadas a porcentajes, el error disminuye. Más estudios sobre el impacto metodológico de estos sesgos son necesarios, sobre todo en términos de sus implicaciones para las conclusiones ecológicas de los estudios o sobre su influencia potencial en decisiones de manejo de recursos naturales.

Background: Spots and coloring patterns evaluated quantitatively can be used to discrimination and identify possible cryptic species. Triatoma dimidiata (Reduviidae: Triatominae) is one of the main complexes of Chagas disease vector species. Phylogenetic studies have defined three haplogroups for Mexico and part of Central America. In this work, we evaluate the possibility of correctly discriminating among these T. dimidiata haplogroups using the pattern of dorsal spots.Results: A distinctive spot pattern was found for each haplogroup. The most differentiated pattern was presented by haplogroup 2, mainly apparent in the 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 the variables analyzed, these differences being greater in relative spot area, mean relative area of central spots, central spots Feret diameters, lateral spots Feret diameters and aspect ratio. Both the DFA and the neural network had correct discrimination values above 90%. Conclusions: We conclude that the spot pattern can be reliably used to discriminate among haplogroups, and possibly among triatomine species.