Disparidad morfológica a través del tiempo : cambios morfológicos de los ammonites durante la transición jurásico-cretácico en Chile central
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Fecha
2020
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Profesor/a Guía
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Idioma
es
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Universidad Andrés Bello
Nombre de Curso
Licencia CC
Licencia CC
Resumen
Los cambios en la diversidad de especies se pueden observar a distintas escalas
espaciales y temporales. A escala geológica, además de los cambios en la
diversidad, se han observado cambios en la diversidad morfológica
(morfodisparidad) al representarse en el espacio tridimensional las posibles formas
o estructuras de los organismos (morfo espacio) entre especies asociado a eventos
alterantes. En este estudio se analizarán a los ammonites; cefalópodos extintos que
en su registro fósil muestran una diversidad morfológica y de especie muy amplia.
Esto se realizará, con motivo de determinar los cambios morfológicos que se
pudieron originar tras un recambio faunístico en la transición del Jurásico-Cretácico
(J/K). Para lograr estudiar y estimar la morfodisparidad, junto a inferir el
morfoespacio de los ammonites de la transición J/K entre las etapas Titoniano al
Valanginiano, se compararán 158 ammonites de diferentes géneros y especies
entre cuatro localidades de Chile central. Esto mediante siete medidas morfológicas
que serán tomadas por medio de morfometría lineal y además por medio de 17
“semilandmarks” de la vista lateral, junto a otros nueve de la vista frontal por medio
de morfometría geométrica. Las que luego serán analizadas usando estadística
multivariada. Además, la diversidad de especie se analiza por medio del uso de
estadígrafos y dado a que la abundancia de los ammonites es incalculable se
utilizarán los datos de frecuencia relativa de cada especie en cada localidad. Se
compararán los cambios morfológicos observados en los ensambles, de acuerdo a
su rango estratigráfico, con tal de observar la morfodisparidad y su variación en el
morfoespacio, con el fin de dilucidar si estaría relacionado con el cambio faunístico
y si hay indicios de que haya algún evento que lo propició. Los resultados sugieren
que dentro de la transición J/K, entre el Berriasiano inferior y el Berriasiano superior,
hubo un recambio faunístico a raíz de la distribución y área de los morfoespacios
con respecto a las formas de las conchas donde se observan grupos asociados
tanto a un periodo u otro.
Changes in species diversity can be observed at different spatial and temporal scales. At the geological scale, in addition to changes in diversity, changes in morphological diversity (morphodisparity) have also been observed, by representing in three-dimensional space the possible forms or structures of organisms (morphospace), between species associated with altering events. In this study, ammonites will be analyzed; extinct cephalopods that in their fossil registry show a very wide morphological and species diversity. The main objective is to analise morphological changes that could be originated after a faunistic change in the transition from Jurassic-Cretaceous (J/K). In order to study and estimate the morphodisparity, along with inferring the morphospace of the ammonites of the J/K transition between the Titonian and Valanginian stages, 158 ammonites of different genera and species will be compared in four localities of central Chile. The methodology consists of seven morphological measurements which will be obtained by means of linear morphometry and by 17 "semilandmarks" from the lateral view, along with another nine from the frontal view by means of geometric morphometry. Subsequently, these measurements will then be analyzed using multivariate statistics. In addition, the diversity of species is analyzed by means of the use of statisticians and since the abundance of ammonites is impossible to be estimated, the relative frequency data of each species in each location will be used. The morphological changes observed in the assemblages, will be compared according to the corresponding geological age, in order to observe the morphodisparity and its variation in the morphospace. This comparison aims at elucidating the relation between the faunistic change and any possible event that could have caused it. The results suggest that within the J/K transition, between the Lower Berriasian and the Upper Berriasian, there was a faunistic change due to the distribution and area of the morphospace regarding to the forms of the shells where groups associated with one period or another are observed.
Changes in species diversity can be observed at different spatial and temporal scales. At the geological scale, in addition to changes in diversity, changes in morphological diversity (morphodisparity) have also been observed, by representing in three-dimensional space the possible forms or structures of organisms (morphospace), between species associated with altering events. In this study, ammonites will be analyzed; extinct cephalopods that in their fossil registry show a very wide morphological and species diversity. The main objective is to analise morphological changes that could be originated after a faunistic change in the transition from Jurassic-Cretaceous (J/K). In order to study and estimate the morphodisparity, along with inferring the morphospace of the ammonites of the J/K transition between the Titonian and Valanginian stages, 158 ammonites of different genera and species will be compared in four localities of central Chile. The methodology consists of seven morphological measurements which will be obtained by means of linear morphometry and by 17 "semilandmarks" from the lateral view, along with another nine from the frontal view by means of geometric morphometry. Subsequently, these measurements will then be analyzed using multivariate statistics. In addition, the diversity of species is analyzed by means of the use of statisticians and since the abundance of ammonites is impossible to be estimated, the relative frequency data of each species in each location will be used. The morphological changes observed in the assemblages, will be compared according to the corresponding geological age, in order to observe the morphodisparity and its variation in the morphospace. This comparison aims at elucidating the relation between the faunistic change and any possible event that could have caused it. The results suggest that within the J/K transition, between the Lower Berriasian and the Upper Berriasian, there was a faunistic change due to the distribution and area of the morphospace regarding to the forms of the shells where groups associated with one period or another are observed.
Notas
Tesis (Licenciado en Biología)
Palabras clave
Ammonites, Morfología, Chile, Jurásico, Cretácico