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Abstract Despite being quite specious (~10,000 extant species), birds have a fairly uniform genome size and karyotype (including the common occurrence of microchromosomes) relative to other vertebrate lineages. Storks (Family Ciconiidae) are a charismatic and distinct group of large wading birds with nearly worldwide distribution but few genomic resources. Here we present an annotated chromosome-level reference genome and chromosome orthology analysis for the wood stork (Mycteria americana), a species that has been federally protected under the Endangered Species Act since 1984. The annotated chromosome-level reference assembly was produced using the blood of a wild female wood stork chick, has a length of 1.35 Gb, a contig N50 of 37 Mb, a scaffold N50 of 80 Mb, and a BUSCO score of 98.8%. We identified 31 autosomal pairs and two sex chromosomes in the wood stork genome, but failed to identify four additional autosomal microchromosomes previously found via karyotyping. Orthology analyses confirmed reported synapomorphies unique to storks and identified the chromosomes participating in these fusions. This study highlights the difficulty and potential problems associated with delineating microchromosomes in reference genome assemblies. It also provides a foundation for studying karyotype evolution in the core water bird clade that includes penguins, albatrosses, storks, cormorants, herons, and ibises. Finally, our reference genome will allow for numerous genomic studies, such as genome-wide association studies of local adaptation, that will aid in wood stork conservation. 

Abstract The enormous population sizes and wide biogeographical distribution of many microbial eukaryotes set the expectation of high levels of intraspecific genetic variation. However, studies investigating protist populations remain scarce, mostly due to limited ‘omics data. Instead, most genetics studies of microeukaryotes have thus far relied on single loci, which can be misleading and do not easily allow for detection of recombination, a hallmark of sexual reproduction. Here, we analyze >40 genes from 72 single-cell transcriptomes from two morphospecies—Hyalosphenia papilio and Hyalosphenia elegans—of testate amoebae (Arcellinida, Amoebozoa) to assess genetic diversity in samples collected over four years from New England bogs. We confirm the existence of cryptic species based on our multilocus dataset, which provides evidence of recombination within and high levels of divergence between the cryptic species. At the same time, total levels of genetic diversity within cryptic species are low, suggesting that these abundant organisms have small effective population sizes, perhaps due to extinction and repopulation events coupled with efficient modes of dispersal. This study is one of the first to investigate population genetics in uncultivable heterotrophic protists using transcriptomics data and contributes towards understanding cryptic species of nonmodel microeukaryotes. 

Abstract Sex determination is a critical element of successful vertebrate development, suggesting that sex chromosome systems might be evolutionarily stable across lineages. For example, mammals and birds have maintained conserved sex chromosome systems over long evolutionary time periods. Other vertebrates, in contrast, have undergone frequent sex chromosome transitions, which is even more amazing considering we still know comparatively little across large swaths of their respective phylogenies. One reptile group in particular, the gecko lizards (infraorder Gekkota), shows an exceptional lability with regard to sex chromosome transitions and may possess the majority of transitions within squamates (lizards and snakes). However, detailed genomic and cytogenetic information about sex chromosomes is lacking for most gecko species, leaving large gaps in our understanding of the evolutionary processes at play. To address this, we assembled a chromosome-level genome for a gecko (Sphaerodactylidae: Sphaerodactylus) and used this assembly to search for sex chromosomes among six closely related species using a variety of genomic data, including whole-genome re-sequencing, RADseq, and RNAseq. Previous work has identified XY systems in two species of Sphaerodactylus geckos. We expand upon that work to identify between two and four sex chromosome cis-transitions (XY to a new XY) within the genus. Interestingly, we confirmed two different linkage groups as XY sex chromosome systems that were previously unknown to act as sex chromosomes in tetrapods (syntenic with Gallus chromosome 3 and Gallus chromosomes 18/30/33), further highlighting a unique and fascinating trend that most linkage groups have the potential to act as sex chromosomes in squamates. 

Cloud applications are increasingly shifting to interactive and loosely-coupled microservices. Despite their advantages, microservices complicate resource management, due to inter-tier dependencies. We present Sinan and PuppetMaster, two cluster managers for interactive microservices that leverages easily-obtainable tracing data instead of empirical decisions, to infer the impact of a resource allocation on end-to-end performance, and allocate appropriate resources to each tier. In a preliminary evaluation of the system with an end-to-end social network built with microservices, we show that the cluster manager's data-driven approach allows the service to always meet its QoS without sacrificing resource efficiency.