Evaluación del dimorfismo sexual en roedores sigmodontinos en un gradiente altitudinal.
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Date
2024
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Universidad de Concepción
Abstract
El dimorfismo sexual está ampliamente generalizado en el reino animal. En el caso de los mamíferos, los machos suelen ser más grandes que las hembras y estas diferencias morfológicas son atribuidas a la competencia por el acceso a hembras y la fecundidad. A su vez, el dimorfismo sexual está muy relacionado con el sistema de apareamiento poligínico de la mayoría de los mamíferos. Aunque se atribuye la evolución del dimorfismo sexual en tamaño (DST) a la selección sexual y la fecundidad, es probable que las relaciones comunitarias donde se desarrollan las especies también estén afectando en los rasgos morfológicos que se presumen resultado de selección sexual. Pero en este caso, las diferencias en atributos son resultado de la competencia por los recursos locales a nivel interespecífico manifestándose intraespecíficamente. En la vertiente occidental de los Andes en Perú, se ha descrito que la riqueza de especies de roedores sigmodontinos se encuentra correlacionada positivamente con el gradiente altitudinal por lo que se puede encontrar comunidades con baja y elevada riqueza de especies. Interesantemente, los roedores muestran un patrón de apareamiento poligínicos muy relacionado al DST. Es probable que, en estas comunidades de abundante riqueza de especies por las interacciones de la comunidad mediante la competencia de los recursos, exista un desplazamiento de los fenotipos a nivel intraespecífico reflejado en el tamaño del cráneo debido a que esta estructura esta más relacionado con la alimentación y en comunidades con una riqueza baja, el DST este ausente. Por lo que se plantea como objetivo evaluar el dimorfismo sexual en las comunidades presentes en un gradiente altitudinal. Utilizando especímenes depositados en una colección científica, se construyó una base de datos para organizar las comunidades de roedores en base a las coberturas distribuidas en un gradiente altitudinal desde donde fueron colectados y posteriormente se tomaron medidas craneométricas. Se obtuvieron datos de seis comunidades: lomas, desierto, cactáceas, matorral, queñual y pajonal. Encontramos que no hay dimorfismo sexual en ninguna de las comunidades. Lo que indica que no hay una relación positiva entre la riqueza de especies y el DST. Es probable que a través de sus historias de vida de las comunidades se refleje un proceso microalopátrico de las especies de roedores de manera que coexistan segregando sus horarios de actividad, el uso del espacio, la dieta y el comportamiento y de este modo reducir la competencia y que estas hayan evolucionado en conjunto en la comunidad y no como unidades separadas. Posiblemente, entre los sexos también se esté dando este mecanismo microalopátrico sumado a que sus conductas están relacionadas con la etapa reproductiva, esto debido a una necesidad alimentaria diferenciada entre los sexos, como en las hembras en la época de lactancia o el cuidado parental, así mismo la eficacia por conseguir alimento no depende del tamaño corporal sino de otros factores relacionados al tipo de requerimiento de la especie, por cual se segregan sexualmente.
Sexual dimorphism is widely generalized in the animal kingdom. In the case of mammals, males are often larger than females, and these morphological differences are attributed to competition for access to females and fertility. Furthermore, sexual dimorphism is closely related to the polygynous mating system of most mammals. Although the evolution of sexual dimorphism in size (SDS) is attributed to sexual selection and fertility, it is likely that the community relationships where the species develop are also influencing the morphological traits that are presumed to be the result of sexual selection. In this case, however, differences in attributes result from competition for local resources at the interspecific level, manifesting intra-specifically. In the western foothills of the Andes in Peru, it has been described that the species richness of sigmodontine rodents is positively correlated with the altitudinal gradient, allowing for communities with both low and high species richness. Interestingly, rodents show a polygynous mating pattern closely related to SDS. It is likely that in these communities, with abundant species richness due to community interactions through resource competition, there is a shift in phenotypes at the intra-specific level reflected in skull size, as this structure is more related to feeding. In communities with low richness, SDS may be absent. Therefore, the objective is to evaluate sexual dimorphism in the communities present along an altitudinal gradient. Using specimens deposited in a scientific collection, a database was constructed to organize the rodent communities based on the cover types distributed along the altitudinal gradient from which they were collected, and cranial measurements were subsequently taken. Data were obtained from six communities: lomas, desert, cacti, scrubland, quena, and pajonal. We found that there is no sexual dimorphism in any of the communities, indicating that there is no positive relationship between species richness and SDS. It is likely that through the life histories of the communities, a micro-allopatric process of rodent species is reflected in such a way that they coexist by segregating their activity schedules, space use, diet, and behavior, thus reducing competition and evolving together in the community rather than as separate units. Possibly, this micro-allopatric mechanism is also occurring between sexes, combined with behaviors related to the reproductive stage due to nutritional needs, as in females during lactation or parental care. Moreover, the efficiency in obtaining food does not which is why they segregate sexually. depend on body size but on other factors related to the species' requirements, which is why they segregate sexually.
Sexual dimorphism is widely generalized in the animal kingdom. In the case of mammals, males are often larger than females, and these morphological differences are attributed to competition for access to females and fertility. Furthermore, sexual dimorphism is closely related to the polygynous mating system of most mammals. Although the evolution of sexual dimorphism in size (SDS) is attributed to sexual selection and fertility, it is likely that the community relationships where the species develop are also influencing the morphological traits that are presumed to be the result of sexual selection. In this case, however, differences in attributes result from competition for local resources at the interspecific level, manifesting intra-specifically. In the western foothills of the Andes in Peru, it has been described that the species richness of sigmodontine rodents is positively correlated with the altitudinal gradient, allowing for communities with both low and high species richness. Interestingly, rodents show a polygynous mating pattern closely related to SDS. It is likely that in these communities, with abundant species richness due to community interactions through resource competition, there is a shift in phenotypes at the intra-specific level reflected in skull size, as this structure is more related to feeding. In communities with low richness, SDS may be absent. Therefore, the objective is to evaluate sexual dimorphism in the communities present along an altitudinal gradient. Using specimens deposited in a scientific collection, a database was constructed to organize the rodent communities based on the cover types distributed along the altitudinal gradient from which they were collected, and cranial measurements were subsequently taken. Data were obtained from six communities: lomas, desert, cacti, scrubland, quena, and pajonal. We found that there is no sexual dimorphism in any of the communities, indicating that there is no positive relationship between species richness and SDS. It is likely that through the life histories of the communities, a micro-allopatric process of rodent species is reflected in such a way that they coexist by segregating their activity schedules, space use, diet, and behavior, thus reducing competition and evolving together in the community rather than as separate units. Possibly, this micro-allopatric mechanism is also occurring between sexes, combined with behaviors related to the reproductive stage due to nutritional needs, as in females during lactation or parental care. Moreover, the efficiency in obtaining food does not which is why they segregate sexually. depend on body size but on other factors related to the species' requirements, which is why they segregate sexually.
Description
Tesis presentada para optar al grado de Magíster en
Ciencias con Mención en Zoología
Keywords
Roedores, Variación (genética), Adaptación (Biología)