An approach using ddRADseq and machine learning for understanding
geographic and bathymetric patterns of speciation in Antarctic
gastropods (Mollusca)
Abstract
Sampling impediments and paucity of suitable material for molecular
analyses have precluded the study of speciation and radiation of
deep-sea species in Antarctic ecosystems. This knowledge may serve to
establish the framework for evaluating future anthropogenic alterations,
particularly in a highly susceptible region like Antarctica. Here, we
analyze genome-wide single nucleotide polymorphisms (SNPs) obtained from
double digestion restriction site-associated DNA sequencing (ddRADseq)
for most species in the family Antarctophilinidae and throughout the
geographic distribution and bathymetric ranges of these marine snails.
We also reevaluate the fossil record associated with this taxon. In
light of the new data provided we discuss relevant diversification
processes and biogeographic and bathymetric affinities. Novel approaches
in finding genetic distinctive lineages, including unsupervised machine
learning variational autoencoder (VAE) plots, are further used to
establish species hypothesis frameworks aided by available morphological
data. In this sense, two new species and a complex of cryptic species
are here identified, suggesting allopatric speciation connected to
geographic or bathymetric isolation. We further, observe that the
shallow waters around the Scotia Arc and on the continental shelf in the
Weddell Sea present high endemism and diversity. In contrast, likely due
to the glacial pressure during the Cenozoic, a deep-sea group with fewer
species emerged expanding over great areas in the South-Atlantic
Antarctic Ridge. Our study exemplifies how diachronic paleoclimatic and
current environmental factors shaped Antarctic communities both at the
shallow and deep-sea levels, promoting Antarctica as the center of
origin for numerous taxa such as gastropod mollusks.