Biology subjects

Jalinsky, J.

Publications and source records attributed to Jalinsky, J..

4 recordsLinked to original sources

bioRxiv2023

Genome evolution and introgression in the New Zealand mud snails Potamopyrgus estuarinus and Potamopyrgus kaitunuparaoa

We have sequenced, assembled, and analyzed the nuclear and mitochondrial genomes and transcriptomes of Potamopyrgus estuarinus and Potamopyrgus kaitunuparaoa, two prosobranch snail species native to New Zealand that together span the continuum from estuary to freshwater. These two species are the closest known relatives of the freshwater species P. antipodarum--a model for studying the evolution of sex, host-parasite coevolution, and biological invasiveness--and thus provide key evolutionary context for understanding its unusual biology. The P. estuarinus and P. kaitunuparaoa genomes are very similar in size and overall gene content. Comparative analyses of genome content indicate that these two species harbor a near-identical set of genes involved in meiosis and sperm functions, including seven genes with meiosis-specific functions. These results are consistent with obligate sexual reproduction in these two species and provide a framework for future analyses of P. antipodarum--a species comprising both obligately sexual and obligately asexual lineages, each separately derived from a sexual ancestor. Genome-wide multigene phylogenetic analyses indicate that P. kaitunuparaoa is likely the closest relative to P. antipodarum. We nevertheless show that there has been considerable introgression between P. estuarinus and P. kaitunuparaoa. That introgression does not extend to the mitochondrial genome, which appears to serve as a barrier to hybridization between P. estuarinus and P. kaitunuparaoa. Nuclear-encoded genes whose products function in joint mitochondrial-nuclear enzyme complexes exhibit similar patterns of non-introgression, indicating that incompatibilities between the mitochondrial and the nuclear genome may have prevented more extensive gene flow between these two species. Significance StatementNo whole-nuclear genome sequences are currently available for snails of the genus Potamopyrgus, best known for Potamopyrgus antipodarum, an invasive species of rivers and lakes worldwide, and a famous model for the study of the evolution of sex. We have sequenced and analyzed the genome of sexual P. estuarinus and P. kaitunuparaoa, the closest known relatives of P. antipodarum. We show that 1) the genomes are very similar in gene content and size, 2) P. kaitunuparaoa is the closest relative to P. antipodarum, 3) significant introgression has occurred between P. estuarinus and P. kaitunuparaoa; these genomes set the stage for powerful direct analyses of the genomic features, e.g., sex to asexual transitions and invasive success, that make P. antipodarum unique.

evolutionary biology↗

bioRxiv2022

Single-molecule sequencing of animal mitochondrial genomes reveals chloroplast-like architecture and repeat-mediated recombination

Recent advances in long-read sequencing technology have allowed for single-molecule sequencing of entire mitochondrial genomes, opening the door for direct investigation of mitochondrial genome architecture and landscapes of recombination. We used PacBio sequencing to re-assemble mitochondrial genomes from two species of New Zealand freshwater snails, Potamopyrgus antipodarum and Potamopyrgus estuarinus. These assemblies revealed a [~]1.7 kb structure within the mitochondrial genomes of both species that was previously undetected by assembly of short sequencing reads and likely corresponding to a large non-coding region commonly present in mitochondrial genomes. The overall architecture of these Potamopyrgus mitochondrial genomes is reminiscent of the chloroplast genomes of land plants, harboring a large single-copy region (LSC) and a small single-copy region (SSC) separated by a pair of inverted repeats (IRa and IRb). Individual sequencing reads that spanned across the Potamopyrgus IRa-SSC-IRb structure revealed the occurrence of "flip-flop" recombination, apparently mediated by the IRs. We also detected evidence for two distinct IR haplotypes and recombination between them in wild-caught P. estuarinus, as well as extensive inter-molecular recombination between SNPs in the LSC region. Together, these observations suggest that mitochondrial inheritance is not strictly maternal in these snails. The chloroplast-like architecture and repeat-mediated mitochondrial recombination we describe here raise fundamental questions regarding the origins and commonness of such architecture, whether and how recombination mediates mitochondrial genome evolution, and the role of genome architecture in driving cytoplasmic genome biology and the maintenance of cytoplasmic genomes.

evolutionary biology↗

bioRxiv2021

Asexual freshwater snails make poor mate choice decisions

Once-useful traits that no longer contribute to fitness tend to decay over time. Here, we address whether the expression of mating-related traits that increase the fitness of sexually reproducing individuals but are likely less useful or even costly to asexual counterparts seems to exhibit decay in the latter. Potamopyrgus antipodarum is a New Zealand freshwater snail characterized by repeated transitions from sexual to asexual reproduction. The frequent coexistence of sexual and asexual lineages makes P. antipodarum an excellent model for the study of mating-related trait loss. We used a mating choice assay including sexual and asexual P. antipodarum females and conspecific (presumed better choice) vs. heterospecific (presumed worse choice) males to evaluate the loss of behavioral traits related to sexual reproduction. We found that sexual females engaged in mating behaviors with conspecific mating partners more frequently and for a greater duration than with heterospecific mating partners. By contrast, asexual females mated at similar frequency and duration as sexual females, but did not mate more often or for longer duration with conspecific vs. heterospecific males. These results are consistent with a scenario where selection acting to maintain mate choice in asexual P. antipodarum is weak or ineffective relative to sexual females and, thus, where asexual reproduction contributes to the evolutionary decay of mating-related traits in this system.

evolutionary biology↗

bioRxiv2019

Male evolution under relaxed selection: Evidence for degeneration in sperm produced by male snails from asexual lineages

How drastic changes in selective regimes affect trait evolution is an important open biological question. We take advantage of naturally occurring and repeated transitions from sexual to asexual reproduction in a New Zealand freshwater snail species to address how relaxed selection on male-specific traits influences sperm morphology. The occasional production of male offspring by the otherwise all-female asexual lineages allows a unique and powerful opportunity to assess the fate of sperm traits in a context where males are unnecessary. These comparisons revealed that the sperm produced by "asexual" males are markedly distinct from sexual counterparts. In particular, the asexual male sperm harbored markedly higher phenotypic variation and was much more likely to be morphologically abnormal. Together, these data suggest that transitions to asexual reproduction might be irreversible at least in part because male function is likely to be compromised. More broadly, our results are consistent with a scenario where relaxed selection translates into rapid trait degeneration.

evolutionary biology↗