Evaluación de la Variación Espacial de la Riqueza y Abundancia en las Especies de Pulgas (Siphonaptera) en Abrothrix Olivacea (Waterhouse, 1839).
Loading...
Date
2023
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Universidad de Concepción
Abstract
Conocer la distribución de los parásitos es relevante desde el punto de vista de la salud pública. Aunque, existen diversas hipótesis para explicar la distribución de la riqueza y abundancia de las especies (ej. “hipótesis del centro de abundancia”, “hipótesis de óptimo de abundancia”, “hipótesis latitudinal”, “gradiente latitudinal de diversidad”, entre otras), la mayoría de ellas han sido evaluadas en vertebrados de vida libre, mientras que para invertebrados no se ha encontrado evidencias suficientes que sustenten estas hipótesis y menos aún para las especies parásitas. En las hipótesis señaladas, los factores ambientales serían los que determinan la
distribución de las especies, sin embargo, para el caso de las especies parásitas, cobran importancia la disponibilidad de recursos representados por las distintas especies de hospedadores que estos parasitan. Dado el comportamiento generalista o especialista de las especies de parásitos, se podrían generar diferencias en la distribución de la riqueza de especies parásitas a través de la distribución de los hospedadores. Las pulgas son parásitos que habitan en todo el mundo, incluso en desiertos y la Antártica, son muy importantes epidemiológicamente, ya que transmiten microorganismos patógenos responsables de cerca de 45 enfermedades, afectando tanto a humanos, como a animales, formando parte de ciclos zoonóticos. Parasitan al 95% de los mamíferos, entre ellos roedores cricétidos los que cuentan con una mayor riqueza de pulgas. En la presente investigación utiliza como modelo de estudio la
especie Abrothrix olivacea (Waterhouse, 1839) y sus pulgas, para evaluar los factores que determinan la distribución de la abundancia y riqueza de especies de pulgas en este roedor a lo largo de su distribución en Chile. A. olivacea es uno de los roedores con más amplia distribución en Chile, abarcando desde el límite con Perú hasta Tierra del Fuego. A través de esta amplia distribución, este roedor habita distintas regiones ecológicas y tiene interacciones estrechas con otras especies de roedores que pueden influir en la distribución de la abundancia y riqueza de pulgas que posee. Como hipótesis se planteó que: 1) La riqueza de pulgas en A. olivacea se encuentra determinada por el número de especies de roedores con los que cohabita a lo largo de
su distribución geográfica, esperando encontrar que A. olivacea presente mayor riqueza de pulgas en localidades donde cohabita con un mayor número de especies, 2) La reproducción de las pulgas está determinada por la humedad y la temperatura, donde a menor temperatura y humedad la reproducción disminuye, por lo tanto, se espera encontrar menor abundancia en ambientes donde estos parámetros ambientales sean menores; y 3) Existe competencia interespecífica entre pulgas que cohabitan en un hospedador, por lo que se espera que las especies que conforman una comunidad co ocurran menos de lo esperado por azar. La primera hipótesis fue evaluada a nivel de comunidades componentes, para ello se estimó la riqueza y abundancia de las pulgas en cada una de las localidades, adicionando datos de temperatura y humedad (mínima y máxima) de cada una de ellas, y la riqueza de especies de roedores que viven en simpatría con A. olivacea. Las variables se relacionaron a través de un modelo lineal generalizado aplicando la función de Poisson. Para la segunda hipótesis se realizó un análisis estadístico de MLG utilizando la función de Poisson, relacionando temperatura y humedad de las localidades donde se distribuyeron las 5 especies más abundantes y con más amplia distribución en el muestreo. Para la tercera hipótesis se evaluó la existencia de
patrones de co ocurrencia de especies de pulgas a nivel de infracomunidades, a través del índice C-score. Los resultados indican que no hay una relación estadísticamente significativa entre el
número de especies de roedores que cohabitan con A. olivacea y la riqueza de pulgas. La distribución de la riqueza de especies de pulgas no mostró asociación con los factores ambientales a lo largo de la distribución geográfica de A. olivacea. Se encontró una relación positiva entre abundancia de pulgas y riqueza. Para C-score se obtuvo un valor observado mayor al esperado, lo que indicaría que las especies no interactúan de una manera positiva ni negativa, sino que la estructura de las comunidades es al azar. Por lo tanto, se rechazan las tres hipótesis. Este estudio contribuyó a evaluar los factores que podrían determinar la distribución de estos ectoparásitos en A. olivacea e insta a investigar los efectos de otros factores no considerados en este estudio.
Knowing the distribution of parasites is relevant from the point of view of public health. Although, there are various hypotheses to explain the distribution of richness and abundance of species (eg "center of abundance hypothesis", "optimum abundance hypothesis", "latitudinal hypothesis", "latitudinal diversity gradient", among others). ), most of them have been evaluated in free-living vertebrates, while insufficient evidence has been found to support these hypotheses for invertebrates, and even less so for parasitic species. In the hypotheses indicated, the environmental factors would be those that determine the distribution of the species, however, in the case of the parasitic species, the availability of resources represented by the different host species that they parasitize become important. Given the generalist or specialist behavior of parasite species, differences in the distribution of parasite species richness could be generated through the distribution of hosts. Fleas are parasites that inhabit the entire world, including in deserts and Antarctica, they are very important epidemiologically, since they transmit pathogenic microorganisms responsible for about 45 diseases, affecting both humans and animals, forming part of zoonotic cycles. They parasitize 95% of mammals, including cricetid rodents, which have a greater wealth of fleas. In the present investigation, the species Abrothrix olivacea (Waterhouse, 1839) and its fleas are used as a study model to evaluate the factors that determine the distribution of abundance and richness of flea species in this rodent throughout its distribution in Chile. . A. olivacea is one of the rodents with the widest distribution in Chile, ranging from the border with Peru to Tierra del Fuego. Through its wide distribution, this rodent inhabits different ecological regions and has close interactions with other rodent species that may influence the distribution of abundance and richness of fleas it possesses. As a hypothesis, it was proposed that: 1) The richness of fleas in A. olivacea is determined by the number of species of rodents with which it cohabits throughout its geographical distribution, hoping to find that A. olivacea presents a greater richness of fleas in localities where it cohabits with a greater number of species, 2) The reproduction of fleas is determined by humidity and temperature, where at lower temperatures and humidity reproduction decreases, therefore, it is expected to find less abundance in environments where these parameters environmental are minor; and 3) There is interspecific competition between fleas that cohabit in a host, so it is expected that the species that make up a community co-occur less than expected by chance. The first hypothesis was evaluated at the level of component communities, for which the richness and abundance of fleas in each of the localities was estimated, adding data on temperature and humidity (minimum and maximum) of each of them, and the richness of rodent species that live in sympatry with A. olivacea. The variables were related through a generalized linear model applying the Poisson function. For the second hypothesis, a statistical analysis of GLM was carried out using the Poisson function, relating temperature and humidity of the localities where the 5 most abundant species were distributed and with the widest distribution in the sampling. For the third hypothesis, the existence of patterns of co-occurrence of flea species at the infracommunity level was evaluated through the C-score index. The results indicate that there is no statistically significant relationship between the number of rodent species that cohabit with A. olivacea and flea richness. The distribution of flea species richness showed no association with environmental factors along the geographic distribution of A. olivacea. A positive relationship was found between abundance of fleas and richness. For C-score, an observed value higher than expected was obtained, which would indicate that the species do not interact in a positive or negative way, but that the structure of the communities is random. Therefore, all three hypotheses are rejected. This study contributed to assess the factors that could determine the distribution of these ectoparasites in A. olivacea and encourages to investigate the effects of other factors not considered in this study.
Knowing the distribution of parasites is relevant from the point of view of public health. Although, there are various hypotheses to explain the distribution of richness and abundance of species (eg "center of abundance hypothesis", "optimum abundance hypothesis", "latitudinal hypothesis", "latitudinal diversity gradient", among others). ), most of them have been evaluated in free-living vertebrates, while insufficient evidence has been found to support these hypotheses for invertebrates, and even less so for parasitic species. In the hypotheses indicated, the environmental factors would be those that determine the distribution of the species, however, in the case of the parasitic species, the availability of resources represented by the different host species that they parasitize become important. Given the generalist or specialist behavior of parasite species, differences in the distribution of parasite species richness could be generated through the distribution of hosts. Fleas are parasites that inhabit the entire world, including in deserts and Antarctica, they are very important epidemiologically, since they transmit pathogenic microorganisms responsible for about 45 diseases, affecting both humans and animals, forming part of zoonotic cycles. They parasitize 95% of mammals, including cricetid rodents, which have a greater wealth of fleas. In the present investigation, the species Abrothrix olivacea (Waterhouse, 1839) and its fleas are used as a study model to evaluate the factors that determine the distribution of abundance and richness of flea species in this rodent throughout its distribution in Chile. . A. olivacea is one of the rodents with the widest distribution in Chile, ranging from the border with Peru to Tierra del Fuego. Through its wide distribution, this rodent inhabits different ecological regions and has close interactions with other rodent species that may influence the distribution of abundance and richness of fleas it possesses. As a hypothesis, it was proposed that: 1) The richness of fleas in A. olivacea is determined by the number of species of rodents with which it cohabits throughout its geographical distribution, hoping to find that A. olivacea presents a greater richness of fleas in localities where it cohabits with a greater number of species, 2) The reproduction of fleas is determined by humidity and temperature, where at lower temperatures and humidity reproduction decreases, therefore, it is expected to find less abundance in environments where these parameters environmental are minor; and 3) There is interspecific competition between fleas that cohabit in a host, so it is expected that the species that make up a community co-occur less than expected by chance. The first hypothesis was evaluated at the level of component communities, for which the richness and abundance of fleas in each of the localities was estimated, adding data on temperature and humidity (minimum and maximum) of each of them, and the richness of rodent species that live in sympatry with A. olivacea. The variables were related through a generalized linear model applying the Poisson function. For the second hypothesis, a statistical analysis of GLM was carried out using the Poisson function, relating temperature and humidity of the localities where the 5 most abundant species were distributed and with the widest distribution in the sampling. For the third hypothesis, the existence of patterns of co-occurrence of flea species at the infracommunity level was evaluated through the C-score index. The results indicate that there is no statistically significant relationship between the number of rodent species that cohabit with A. olivacea and flea richness. The distribution of flea species richness showed no association with environmental factors along the geographic distribution of A. olivacea. A positive relationship was found between abundance of fleas and richness. For C-score, an observed value higher than expected was obtained, which would indicate that the species do not interact in a positive or negative way, but that the structure of the communities is random. Therefore, all three hypotheses are rejected. This study contributed to assess the factors that could determine the distribution of these ectoparasites in A. olivacea and encourages to investigate the effects of other factors not considered in this study.
Description
Tesis presentada para optar al grado académico de Magíster en Ciencias con mención en Zoología.
Keywords
Rodentia, Siphonaptera, Medio ambiente