RESUMO

To properly define ecoregions, specific criteria such as geology, climate, or species composition (e.g., the presence of endemic species) must be taken into account to understand distribution patterns and resolve ecological biogeography questions. Since the studies on insects in Baja California are scarce, and no fine-scale ecoregions based on the region's entomofauna is available, this study was designed to test whether the ecoregions based on vegetation can be used for insects, such as Calliphoridae. Nine collecting sites distributed along five ecoregions were selected, between latitudes 29.6° and 32.0°N. In each site, three baited traps were used to collect blow flies from August 2017 to June 2019 during summer, winter, and spring. A total of 30,307 individuals of blow flies distributed in six genera and 13 species were collected. The most abundant species were Cochliomyia macellaria (Fabricius), Phormia regina (Meigen), and Chrysomya rufifacies (Macquart). The composition of the Calliphoridae community was different between the localities and three general groups have been distinguished, based on the species composition similarity (ANOSIM) results: Gulf-Desert, Mountains, and Pacific-Center. The vegetation-based ecoregions only reflect the blow fly species' distributions to a certain extent, meaning that care must be taken when undertaking ecological biogeographical studies using regionalization based on organisms other than the focal taxa because vegetation does not always reflect fauna species composition.

Assuntos

RESUMO

We investigated functional patterns of fish assemblages of two adjacent basins (Araguaia and Tocantins) to test whether their headwater stream fish assemblages are more functionally (dis)similar than expected by chance and whether these (dis)similarities are related to differences of environmental conditions between basins. We used an analysis of similarities (ANOSIM) on a functional dissimilarity matrix to test for (dis)similarities between fish assemblages of both basins. We performed RLQ and fourth-corner analyses to determine fish species trait-environment relationship. Our results revealed functional dissimilarities between fish assemblages of both basins and significant species trait-environment relationships, suggesting that environmental conditions are driving such dissimilarities. Inter-basin dissimilarities are mainly driven by altitudinal and water temperature gradients, whereas dissimilarities among streams within the basins are influenced by channel depth, turbidity and conductivity. These five environmental variables mostly affected six fish species traits (body mass, water column position, substrate preference, parental care, foraging locality and migration) in different manners. This study is an attempt to understand functional trends of fish assemblages in a tropical region that remains poorly known but severely threatened.(AU)

Nós investigamos os padrões funcionais das assembleias de peixes de duas bacias adjacentes (Araguaia and Tocantins) para testar se as assembleias de peixes de seus riachos de cabeceira são funcionalmente mais (dis)similares do que o esperado ao acaso e se estas (dis)similaridades estão relacionadas a diferenças nas condições ambientais entre as bacias. Nós utilizamos uma análise de similaridades (ANOSIM) sobre uma matriz de dissimilaridade funcional para testar por (dis)similaridades entre as assembleias de peixes das duas bacias. Nós realizamos análises de RLQ e fourth-corner para determinar a relação entre o ambiente e a estrutura funcional das assembleias de peixes. Nossos resultados revelaram dissimilaridades funcionais entre as assembleias de peixes de ambas as bacias e relações significativas entre atributos das espécies e o ambiente, sugerindo que as condições ambientais estão direcionando tais dissimilaridades. As dissimilaridades entre bacias são influenciadas principalmente pelos gradientes de altitude e temperatura da água, enquanto as dissimilaridades entre os riachos na bacia pela profundidade do canal, turbidez e condutividade. Estas cinco variáveis ambientais afetaram principalmente seis atributos das espécies de peixes (massa corporal, posição na coluna de água, preferência por substrato, cuidado parental, local de forrageio e migração) de diferentes maneiras. Este estudo é uma tentativa para entender os padrões funcionais das assembleias de peixes de uma região ainda pouco conhecida, mas, seriamente ameaçada.(AU)

Assuntos

RESUMO

We investigated functional patterns of fish assemblages of two adjacent basins (Araguaia and Tocantins) to test whether their headwater stream fish assemblages are more functionally (dis)similar than expected by chance and whether these (dis)similarities are related to differences of environmental conditions between basins. We used an analysis of similarities (ANOSIM) on a functional dissimilarity matrix to test for (dis)similarities between fish assemblages of both basins. We performed RLQ and fourth-corner analyses to determine fish species trait-environment relationship. Our results revealed functional dissimilarities between fish assemblages of both basins and significant species trait-environment relationships, suggesting that environmental conditions are driving such dissimilarities. Inter-basin dissimilarities are mainly driven by altitudinal and water temperature gradients, whereas dissimilarities among streams within the basins are influenced by channel depth, turbidity and conductivity. These five environmental variables mostly affected six fish species traits (body mass, water column position, substrate preference, parental care, foraging locality and migration) in different manners. This study is an attempt to understand functional trends of fish assemblages in a tropical region that remains poorly known but severely threatened.

Nós investigamos os padrões funcionais das assembleias de peixes de duas bacias adjacentes (Araguaia and Tocantins) para testar se as assembleias de peixes de seus riachos de cabeceira são funcionalmente mais (dis)similares do que o esperado ao acaso e se estas (dis)similaridades estão relacionadas a diferenças nas condições ambientais entre as bacias. Nós utilizamos uma análise de similaridades (ANOSIM) sobre uma matriz de dissimilaridade funcional para testar por (dis)similaridades entre as assembleias de peixes das duas bacias. Nós realizamos análises de RLQ e fourth-corner para determinar a relação entre o ambiente e a estrutura funcional das assembleias de peixes. Nossos resultados revelaram dissimilaridades funcionais entre as assembleias de peixes de ambas as bacias e relações significativas entre atributos das espécies e o ambiente, sugerindo que as condições ambientais estão direcionando tais dissimilaridades. As dissimilaridades entre bacias são influenciadas principalmente pelos gradientes de altitude e temperatura da água, enquanto as dissimilaridades entre os riachos na bacia pela profundidade do canal, turbidez e condutividade. Estas cinco variáveis ambientais afetaram principalmente seis atributos das espécies de peixes (massa corporal, posição na coluna de água, preferência por substrato, cuidado parental, local de forrageio e migração) de diferentes maneiras. Este estudo é uma tentativa para entender os padrões funcionais das assembleias de peixes de uma região ainda pouco conhecida, mas, seriamente ameaçada.

Assuntos

RESUMO

El análisis de componentes principales (PCA), escalamiento multidimensional no-métrico (MDS) y el análisis de similaridad (ANOSIM) son técnicas estadísticas multivariadas, las dos primeras representan gráficamente de manera simultánea las unidades estadísticas y las variables que las caracterizan, evaluando similaridades entre las unidades y correlaciones entre las variables, la última técnica dota de un test estadístico no paramétrico para comparar agrupaciones de las unidades. Este trabajo evaluó la aplicabilidad de estas técnicas para valorar la calidad nutricional de la dieta, utilizando el bioensayo del gorgojo de arroz. Las dietas ensayadas fueron: almidón de maíz; almidón de papa; 5% glucosa; arvejas; ayuno y ayuno con agua. Se estudiaron las variables supervivencia, variación de peso y composición corporal. El PCA y MDS mostraron relaciones positivas de la supervivencia y variación de peso con los parámetros corporales grasa y carbohidratos, siendo mayor para dietas de almidón, similares al control positivo. En el PCA se observaron diferencias en las poblaciones mantenidas con las diferentes dietas; el MDS no distingue claramente entre ellas, aún cuando logra diferenciar la dieta definida por el ayuno de las restantes. Ambos estudios definieron un gradiente del valor nutritivo de las dietas, en el eje de las abscisas. El ANOSIM indicó diferencias significativas (p<0,05) entre grupos de insectos sustentados con estas dietas. Esta prueba refuerza los resultados obtenidos en el PCA y MDS. La aplicación de estas herramientas estadísticas son promisorias para analizar procesos complejos, como la interacción de distintas variables que midan la calidad nutricional de diferentes dietas.

The principal component analysis (PCA), non-metric multidimensional scaling (MDS) and analysis of similarity (ANOSIM) are multivariate statistical techniques that graphically represent numerical measures of several factors and display multiple relationships that may exist between them. In this study, we evaluated the applicability of these techniques to analyze the nutritional quality of diet, using as model, the bioassay rice weevil. The diets tested were: corn starch, potato starch, 5% glucose, peas, starved and starved with water supply. The variables studied were: survival, weight change and body composition. The PCA and MDS showed positive relationships of survival and weight change with body fat and carbohydrate parameters. Fat and carbohydrates were greater in starches diets, similar to the positive control. The PCA showed differences between populations fed with different diets, whereas the MDS showed similarity between diets. Both studies defined a gradient of the nutritive value of diets in the x-axis. The ANOSIM indicate significant (p<0, 05) differences between groups. This test is necessary to support the results obtained in the PCA and MDS. The application of these statistical tools is promising to analyze complex processes such as interaction of differents variables to measure the nutritional quality of diets.

Assuntos