A molecular view on adaptation on local and continental scales in the Sub-Antarctic and Antarctic bivalve Aequiyoldia

• Main Author: Martinez, Mariano
• Other Authors: Zimmer, Martin, Abele, Doris, Mark, Felix
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Universität Bremen 2021
• Subjects: adaptation; climate change; heteroplasmy; Aequiyoldia eightsii; Antarctica; 570; 570 Life sciences; biology; ddc:570; Antarctic; Antarctic Peninsula; Drake Passage; Southern Ocean; Antarc*
• Online Access: https://media.suub.uni-bremen.de/handle/elib/5393; https://doi.org/10.26092/elib/1142; https://nbn-resolving.org/urn:nbn:de:gbv:46-elib53932

Marine species and populations have three potential responses to climate change: shift their distribution, adapt to the new environmental conditions or go extinct. The persistence of species unable to shift their ranges in response to changing conditions will be determined by their standing phenotypic plasticity or their ability to develop evolutionary adaptive responses. Physiological comparisons of closely related species/populations on latitudinal gradients have proven to be very informative in determining their respective phenotypic plasticity and genetic adaptability. These macro-scale perspectives, however, overlook the role of small-scale environmental variation in the inter-individual physiological and genetic differences. In this thesis, I used the Southern Ocean protobranch bivalve Aequiyoldia cf. eightsii (Jay, 1839) from West Antarctic Peninsula (WAP) and southern South America (SSA) as a “model species” to study the genetic and phenotypic traits that support adaptation to current and future environmental change at small (i.e., local or population scale) and large -scale (i.e., continental or species scale). As recent evidence suggests the possibility of cryptic speciation between Aequiyoldia bivalves from WAP and SSA, Chapter 2 aims at analysing the genetic diversity between and within populations on both sides of the Drake Passage. In this Chapter I report several highly differentiated mitochondrial genomes (h1, h2, h3, h4) within A. cf. eightsii coexisting in Antarctic populations but also inside a subset of the individuals sampled (mitochondrial heteroplasmy). The mitochondrial differentiation pattern is mirrored in nuclear Single Nucleotide Polymorphisms (SNPs) only across the Drake Passage, whilst the equally strongly differentiated mitochondrial lineages in the Southern Ocean are part of the same distribution of SNPs. These results suggest that populations on both sides of the Drake are two reproductively isolated species, and refuted the previous suggestions of cryptic speciation in WAP A. ...