A molecular perspective on the invasibility of the southern ocean benthos: The impact of hypoxia and temperature on gene expression in South American and Antarctic Aequiyoldia bivalves

Abstract

When an organism makes a long-distance transition to a new habitat, the associated environmental change is often marked and requires physiological plasticity of larvae, juveniles, or other migrant stages. Exposing shallow-water marine bivalves (Aequiyoldia cf. eightsii) from southern South America (SSA) and the West Antarctic Peninsula (WAP) to changes in temperature and oxygen availability, we investigated changes in gene expression in a simulated colonization experiment of the shores of a new continent after crossing of the Drake Passage, and in a warming scenario in the WAP. Bivalves from SSA were cooled from 7°C (in situ) to 4°C and 2°C (future warmed WAP conditions), WAP bivalves were warmed from 1.5°C (current summer in situ) to 4°C (warmed WAP), gene expression patterns in response to thermal stress by itself and in combination with hypoxia were measured after 10 days. Our results confirm that molecular plasticity may play a vital role for local adaptation. Hypoxia had a greater effect on the transcriptome than temperature alone. The effect was further amplified when hypoxia and temperature acted as combined stressors. The WAP bivalves showed a remarkable ability to cope with short-term exposure to hypoxia by switching to a metabolic rate depression strategy and activating the alternative oxidation pathway, whilst the SSA population showed no comparable response. In SSA, the high prevalence of apoptosis-related differentially expressed genes especially under combined higher temperatures and hypoxia indicated that the SSA Aequiyoldia are operating near their physiological limits already. While the effect of temperature per se may not represent the single most effective barrier to Antarctic colonization by South American bivalves, the current distribution patterns as well as their resilience to future conditions can be better understood by looking at the synergistic effects of temperature in conjunction with short-term exposure to hypoxia.

Mitochondrial Heteroplasmy and PCR Amplification Bias Lead to Wrong Species Delimitation with High Confidence in the South American and Antarctic Marine Bivalve Aequiyoldia eightsii Species Complex

“…This wide distribution range on both sides of the Drake Passage has given rise to several revisions of its taxonomic status [ 25 ]. Recently, Muñoz-Ramírez et al [ 26 ] highlighted the role of the Antarctic circumpolar current as a biogeographic barrier between the Antarctic Peninsula and South America, confirming the existence of two different species across the Drake Passage, which, according to Martínez et al [ 27 ], have different levels of susceptibility to two major climate change stressors, namely, temperature shifts and hypoxia. González-Wevar et al [ 28 ] suggested the presence of several cryptic species comprising two lineages along the Antarctic Peninsula (5.78% COI p-distance), a third linage in South America (6.5–7.5% COI and 1.2% ITS p-distances) with respect to the Antarctic peninsula, and two additional mitochondrial lineages on Kerguelen Island and the Falkland/Malvinas Islands.…”

Machine learning applied to global scale species distribution models (SDMs)

“…As environmental conditions continue to change, marine species must adapt and potentially shift their distributions to areas with more suitable conditions for their survival and reproduction 1,[5][6][7][8][9][10][11] . Therefore, understanding the present spatio-temporal distribution of marine species and accurately predicting their future is a critical challenge in the current context of global warming 12,13 .…”

“…These approaches provide a broader perspective by focusing on large-scale patterns and processes, allowing for the prediction of species distribution and abundance at regional and global scales 22 . Therefore, this global perspective is essential for the evaluation of climate change and biodiversity 12,13,23 . The results of large-scale predictions can contribute to the development of effective management strategies with global policy objectives, enabling decision-makers to prioritize conservation efforts, implement sustainable practices, and mitigate the impacts of climate change on marine ecosystems 14,24 .…”