Rastro evolutivo del cambio climático del Pleistoceno en el gasterópodo del Pacífico Sureste Fissurella picta (Gmelin, 1791)
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2018
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es
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Universidad Andrés Bello
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Los periodos glaciales han influenciado en gran medida los actuales patrones genéticos de las poblaciones marinas. Durante los ciclos glaciales, una extensa capa de hielo habría cubierto el extremo sur de Sudamérica, donde habría alcanzado la costa del Pacífico sureste, causando el desplazamiento de hábitats costeros. Especies como la lapa Fissurella picta, podría mostrar evidencia de haber sido afectada diferencialmente al habitar en porciones de la costa cubierta y no cubierta por la capa de hielo durante las glaciaciones. Muestreamos F. picta de catorce localidades a lo largo del Sureste del Pacífico, y secuenciamos una región del gen mitocondrial Citocromo Oxidasa Subunidad 1 (COI) y la unidad ribosomal Espaciador Transcrito Interno 1 (ITS1) para realizar análisis genéticos de poblaciones. Adicionalmente, para complementar los análisis genéticos se desarrolló un modelamiento de nicho (ENM) para configurar la disponibilidad potencial de hábitats desde el pasado al presente. La diversidad haplotípica y nucleotídica fue muy alta con COI, y baja con ITS1. Por su parte la inferencia demográfica reveló una historia antigua, la cual se habría expandido en los últimos 125 mil años, coincidiendo con el final del Interglacial Eemiense. La conectividad entre poblaciones de F. picta sería más alta de lo esperada. En conjunto los análisis de diferenciación, estructuración genética y migración apoyan la presencia de sólo una unidad poblacional a lo largo de la distribución de F. picta. El ENM mostró una expansión distribucional hacia hábitats en la porción sur de la distribución desde las glaciaciones hacia el presente. Se discuten posibles explicaciones para la inesperada conectividad estimada.
The glacial periods greatly influenced the present-day genetic patterning of marine populations. During the glacial cycles an extended ice sheet covered the southern tip of South America, reaching the eastern Pacific coast, causing shifts of coastal habitats. Species such as the keyhole limpet Fissurella picta, may show evidence of having been differentially affected, since it lives in areas that were covered and not covered by the ice sheet during the glacial periods. We sampled F. picta from fourteen localities along the Southeastern Pacific coast and sequenced a partial region of the mitochondrial gene Cytochrome Oxidase Subunit I (COI) and the small ribosomal subunit Internal Transcriber Spacer 1 (ITS1) for population genetic analyses. Additionally, to complement the genetic analyses, Environmental Niche Modelling (ENM) was used to model the potential habitat availability from the past to present days. Haplotype and nucleotide diversity were very high with COI, and low with ITS1. The demographic inference revealed an ancient history, starting the expansion around 125 thousand years ago, matching the end of the Eemian interglacial period. The connectivity between F. picta populations was higher than expected. Together, the genetic differentiation, structuring and migration analyses support the presence of only one genetic unit throughout F. picta distribution. The ENM showed a distributional expansion towards habitats in the southern portion of the continent glaciations to present days. A few possible explanations for the unexpected connectivity are discussed.
The glacial periods greatly influenced the present-day genetic patterning of marine populations. During the glacial cycles an extended ice sheet covered the southern tip of South America, reaching the eastern Pacific coast, causing shifts of coastal habitats. Species such as the keyhole limpet Fissurella picta, may show evidence of having been differentially affected, since it lives in areas that were covered and not covered by the ice sheet during the glacial periods. We sampled F. picta from fourteen localities along the Southeastern Pacific coast and sequenced a partial region of the mitochondrial gene Cytochrome Oxidase Subunit I (COI) and the small ribosomal subunit Internal Transcriber Spacer 1 (ITS1) for population genetic analyses. Additionally, to complement the genetic analyses, Environmental Niche Modelling (ENM) was used to model the potential habitat availability from the past to present days. Haplotype and nucleotide diversity were very high with COI, and low with ITS1. The demographic inference revealed an ancient history, starting the expansion around 125 thousand years ago, matching the end of the Eemian interglacial period. The connectivity between F. picta populations was higher than expected. Together, the genetic differentiation, structuring and migration analyses support the presence of only one genetic unit throughout F. picta distribution. The ENM showed a distributional expansion towards habitats in the southern portion of the continent glaciations to present days. A few possible explanations for the unexpected connectivity are discussed.
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Tesis (Biólogo Marino)
Palabras clave
Fissurella, Investigaciones, Pacífico Sureste, Cambios Climáticos