Polyploid animals have independently evolved from diploids in diverse taxa across the tree of life. We review a few polyploid animal species or biotypes where recently developed molecular and cytogene

Genetic and genomic interactions of animals with different ploidy levels.

Biological complexity is a key component of evolvability, yet its study has been hampered by a focus on evolutionary trends of complexification and inconsistent definitions. Here, we demonstrate the utility of bringing complexity into the framework of epigenetics to better investigate its utility as a concept in evolutionary biology. We first analyze the existing metrics of complexity and explore the link between complexity and adaptation. Although recently developed metrics allow for a unified framework, they omit developmental mechanisms. We argue that a better approach to the empirical study of complexity and its evolution includes developmental mechanisms. We then consider epigenetic mechanisms and their role in shaping developmental and evolutionary trajectories, as well as the development and organization of complexity. We argue that epigenetics itself could have emerged from complexity because of a need to self-regulate. Finally, we explore hybridization complexes and hybrid organisms as potential models for studying the association between epigenetics and complexity. Our goal is not to explain trends in biological complexity but to help develop and elucidate novel questions in the investigation of biological complexity and its evolution.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/ede.12301

Investigating the evolution and development of biological complexity under the framework of epigenetics

Summary
Dispersal is the central mechanism that determines connectivity between populations yet few studies connect the mechanisms of movement with realized dispersal in natural populations. To make such a link, we assessed how physiological variation among individuals predicted dispersal in natural populations of unisexual (all-female) and sexual Ambystoma salamanders on the same fragmented landscape in Ohio.
Specifically, we assessed variation in a trait that influences long-distance animal movement (locomotor endurance) and determined whether variation in endurance matched patterns of realized dispersal assessed using genetic assignment tests. A possible mechanism for why unisexuals would have lower locomotor endurance than a sympatric sexual species (Ambystoma texanum) is the potential energetic cost of evolutionarily mismatched mitochondrial and nuclear genomes within polyploid unisexuals.
We found that sexuals walked four times farther than unisexuals during treadmill endurance trials that mimic the locomotor endurance required for dispersal.
We then applied landscape genetic methods to identify dispersed adults and quantify realized dispersal. We show that the differences in locomotor endurance between unisexual and sexual salamanders scale to realized dispersal: dispersing sexual individuals travelled approximately twice the distance between presumed natal wetlands and the site of capture compared to dispersing unisexuals.
This study links variation in individual performance in terms of endurance with realized dispersal in the field and suggests a potential mechanism (physiological limitation due to mitonuclear mismatch) for the reduced endurance of unisexual individuals relative to sexual individuals although we discuss other possible explanations.
The differences in dispersal between these two types of salamanders also informs our understanding of sexual/unisexual coexistence by suggesting that unisexuals are at a competitive disadvantage in terms of colonization ability under a extinction-colonization model of coexistence.


A lay summary is available for this article.

https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/1365-2435.12813

Locomotor endurance predicts differences in realized dispersal between sympatric sexual and unisexual salamanders

Unisexual Ambystoma are the oldest known unisexual vertebrates and comprise a lineage of eastern North American all female salamanders that reproduce by stealing sperm from as many as five normally...

/pdf/a-family-study-to-examine-clonal-diversity-in-unisexual-4ch0lbfusb.pdf

A family study to examine clonal diversity in unisexual salamanders (genus Ambystoma)

Quantifying introgression between sexual species and polyploid lineages traditionally thought to be asexual is an important step in understanding what drives the longevity of putatively asexual groups. Here, we capitalize on three recent innovations-ultraconserved element (UCE) sequencing, bioinformatic techniques for identifying genome-specific variation in polyploids, and model-based methods for evaluating historical gene flow-to measure the extent and tempo of introgression over the evolutionary history of an allopolyploid lineage of all-female salamanders and two ancestral sexual species. Our analyses support a scenario in which the genomes sampled in unisexual salamanders last shared a common ancestor with genomes in their parental species ∼3.4 million years ago, followed by a period of divergence between homologous genomes. Recently, secondary introgression has occurred at different times with each sexual species during the last 500,000 years. Sustained introgression of sexual genomes into the unisexual lineage is the defining characteristic of their reproductive mode, but this study provides the first evidence that unisexual genomes have undergone long periods of divergence without introgression. Unlike other sperm-dependent taxa in which introgression is rare, the alternating periods of divergence and introgression between unisexual salamanders and their sexual relatives could explain why these salamanders are among the oldest described unisexual animals.

Genome-specific histories of divergence and introgression between an allopolyploid unisexual salamander lineage and two ancestral sexual species.

The Blue-spotted Salamander (Ambystoma laterale) and the Jefferson Salamander (Ambystoma jeffersonianum) are both part of the Jefferson complex that also includes unisexuals of various ploidy levels and genome composition, referred to as genomotypes. Female unisexuals reproduce mainly through gynogenesis, but ploidy elevations, translocations, recombinations, intergenomic exchanges, and genome replacement also have been documented. The objective of this study was to obtain information on the geographical distribution of genomotypes and the distribution of genetic diversity in southern Quebec, Canada. To do so, we examined populations of the Jefferson complex from five sites, including one site from a city and the other sites from protected areas. Genetic analysis using mitochondrial DNA and six microsatellite loci were performed. Results revealed that genomotype frequencies vary greatly, because some populations were mainly composed of A. laterale, whereas unisexuals were clearly predominant in o...

https://bioone.org/journals/Journal-of-Herpetology/volume-45/issue-3/09-151.1/Genomotype-Frequencies-and-Genetic-Diversity-in-Urban-and-Protected-Populations/10.1670/09-151.1.pdf

Genomotype Frequencies and Genetic Diversity in Urban and Protected Populations of Blue-spotted Salamanders (Ambystoma laterale) and Related Unisexuals

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Genomotype Frequencies and Genetic Diversity in Urban and Protected Populations of Blue-spotted Salamanders (Ambystoma laterale) and Related Unisexuals