Variabilidad espacial de ensambles bentónicos intermareales en Bahía Yendegaia, Canal Beagle, ecorregión subantártica de Magallanes.

La ecorregión subantártica de Magallanes posee una heterogénea costa de fiordos y canales, con una gran extensión de ecosistemas intermareales sujetos al efecto de condiciones climáticas extremas características de zonas de altas latitudes. Estudios recientes sugieren que la estructura de los ensambles intermareales que habitan en ambientes extremos, como subantárticos y antárticos, presentan altas variaciones horizontales y verticales que se acentúan a escalas espaciales finas. Este podría ser un patrón general en hábitats intermareales de altas latitudes del hemisferio sur, y en este este trabajo evaluamos la hipótesis que la variabilidad horizontal y vertical de los ensambles bentónicos intermareales en ambientes extremos subantárticos es mayor a escalas finas. En marzo-abril 2017 analizamos la variabilidad espacial sobre los ensambles bentónicos intermareales de Bahía Yendegaia, Reserva de la Biosfera Cabo de Hornos, como modelo de estudio con un diseño anidado con diferentes escalas espaciales que van desde centímetros a kilómetros. El análisis de los componentes de varianza y pseudo-varianza mostró una significativa variación horizontal y vertical a escalas finas. Identificamos seis comunidades con una marcada zonación vertical. Las especies más representativas fueron el molusco Perumytilus purpuratus y las algas Porphyra/Pyropia sp1. y Ulva flexuosa. Estas especies tuvieron una alta variación vertical en escalas finas. Estos patrones apoyan la hipótesis testeada, sin embargo, es probable que factores físicos locales del hábitat relacionados con cambios abióticos también influyan significativamente sobre las variaciones espaciales a pequeñas escalas en las comunidades de Bahía Yendegaia. Para evaluar el papel de factores físicos, proponemos extender este tipo de estudios incorporando la variabilidad temporal y datos ambientales en bruto. Estos estudios permitirán detectar los factores locales más influyentes sobre la variación espacial de los ensambles bentónicos intermareales subantárticos. Este estudio aporta información de base valiosa sobre patrones de distribución a escala espacial fina y propone factores ecológicos adicionales que podrían incidir sobre la distribución y abundancia de especies y ensambles bentónicos intermareales en ecosistemas subantárticos de Magallanes.

Phenotypic plasticity at fine-grained spatial scales: the scorched mussel Perumytilus purpuratus growing on Patagonian rocky salt-marshes

Understanding phenotypic plasticity of species at different spatial scales is vital in the current context of an increasing pace of environmental changes. Through this knowledge, it is possible to predict their potential to adapt and/or evolve in face of new environmental conditions such as climate change, and/or to understand their ecological range expansion. In Patagonian rocky salt-marshes, one of the most abundant invertebrate species is the scorched mussel Perumytilus purpuratus. In this system, this mussel can be found inhabiting both vegetated and non-vegetated patches, which differ in critical environmental conditions. We performed a field study evaluating whether mussels growing in vegetated patches differ in shell shape from those growing in adjacent non-vegetated patches. We sampled individuals from both patch types and assessed their shell shape and size using geometric morphometrics. The results showed that mussels from vegetated patches had shells that were more dorsoventrally expanded, anterodorsally restricted and globose in shape than those from non-vegetated patches, which showed the opposite traits resulting in a more elongated shell. The differences found could be driven by the different conditions of temperature, desiccation rate, wave action and population density to which mussels are exposed in each patch type. These results revealed the striking phenotypic plasticity of shell form of this native species at a fine-grained scale, which could be one of the explanations for its success in its ecological range expansion.

Mitogenomics of Perumytilus purpuratus (Bivalvia: Mytilidae) and its implications for doubly uniparental inheritance of mitochondria

Animal mitochondria are usually inherited through the maternal lineage. The exceptional system allowing fathers to transmit their mitochondria to the offspring exists in some bivalves. Its taxonomic spread is poorly understood and new mitogenomic data are needed to fill the gap. Here, we present for the first time the two divergent mitogenomes from Chilean mussel Perumytilus purpuratus. The existence of these sex-specific mitogenomes confirms that this species has the doubly uniparental inheritance (DUI) of mitochondria. The genetic distance between the two mitochondrial lineages in P. purpuratus is not only much bigger than in the Mytilus edulis species complex but also greater than the distance observed in Musculista senhousia, the only other DUI-positive member of the Mytilidae family for which both complete mitochondrial genomes were published to date. One additional, long ORF (open reading frame) is present exclusively in the maternal mitogenome of P. purpuratus. This ORF evolves under purifying selection, and will likely be a target for future DUI research.