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1. Dynamics of reduced genetic diversity in increasingly fragmented populations of Florida scrub jays , Aphelocoma coerulescens

   https://doi.org/10.1111/eva.13421  

   Nguyen, Tram N. ; Chen, Nancy ; Cosgrove, Elissa J. ; Bowman, Reed ; Fitzpatrick, John W. ; Clark, Andrew G. ( June 2022 , Evolutionary Applications)

   Understanding the genomic consequences of population decline is important for predicting species' vulnerability to intensifying global change. Empirical information about genomic changes in populations in the early stages of decline, especially for those still experiencing immigration, remains scarce. We used 7834 autosomal SNPs and demographic data for 288 Florida scrub jays (Aphelocoma coerulescens; FSJ) sampled in 2000 and 2008 to compare levels of genetic diversity, inbreeding, relatedness, and lengths of runs of homozygosity (ROH) between two subpopulations within dispersal distance of one another but have experienced contrasting demographic trajectories. At Archbold Biological Station (ABS), the FSJ population has been stable because of consistent habitat protection and management, while at nearby Placid Lakes Estates (PLE), the population declined precipitously due to suburban development. By the onset of our sampling in 2000, birds in PLE were already less heterozygous, more inbred, and on average more related than birds in ABS. No significant changes occurred in heterozygosity or inbreeding across the 8‐year sampling interval, but average relatedness among individuals decreased in PLE, thus by 2008 average relatedness did not differ between sites. PLE harbored a similar proportion of short ROH but a greater proportion of long ROH than ABS, suggesting one continuous population of shared demographic history in the past, which is now experiencing more recent inbreeding. These results broadly uphold the predictions of simple population genetic models based on inferred effective population sizes and rates of immigration. Our study highlights how, in just a few generations, formerly continuous populations can diverge in heterozygosity and levels of inbreeding with severe local population decline despite ongoing gene flow.

    

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2. Recently Delisted Songbird Harbors Extensive Genomic Evidence of Inbreeding, Potentially Complicating Future Recovery

   https://doi.org/10.1111/eva.70052  

   Calderón, Anna María ; Wood, Andrew W ; Szpiech, Zachary A ; Toews, David PL ( December 2024 , Evolutionary Applications)

   The Kirtland's warbler (Setophaga kirtlandi) is a rare migratory passerine species and habitat specialist of the North American Jack Pine Forests. Their near extinction in the 1970s classified them as endangered and protected under the Endangered Species Act of 1973. After decades of intense conservation management, their population size recovered, and they were delisted from federal protection in 2019. We explore the genomic consequences of this harsh bottleneck and recovery by comparing the genomic architecture of two closely related species whose population sizes have remained large and stable, Hooded Warblers (Setophaga citrina) and American Redstarts (Setophaga ruticilla). We used whole‐genome sequencing to characterize the distribution of runs of homozygosity and deleterious genetic variation. We find evidence that Kirtland's warblers exhibit genetic patterns consistent with recent inbreeding. Our results also show that Kirtland's warblers carry an excess proportion of deleterious variation, which could complicate management for this conservation‐reliant species. This analysis provides a genetically informed perspective that should be thoroughly considered when delisting other species from federal protections. Through the increasing accessibility of genome sequencing technology, it will be more feasible to monitor the genetic landscape of recovering populations to ensure their long‐term survival independent of conservation intervention.

    

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3. Comparative linkage mapping to investigate synteny and recombination in social Vespidae

   https://doi.org/10.1093/aesa/saae029  

   Zarate, Daniela ; Canova, Alyssa ; Wilson_Rankin, Erin_E ; Loope, Kevin ; Purcell, Jessica ; Knolhoff, ed., Lisa ( October 2024 , Annals of the Entomological Society of America)

   Genetic linkage maps are valuable resources for investigating chromosomal structure, quantifying karyotype, estimating recombination rates, and improving preexisting genome assemblies. Comparative linkage mapping, in turn, broadens our understanding of the phylogenetic history of these genomic features. Through an assessment of synteny (the conservation of gene order on homologous chromosomes in different species) and variation in recombination rate, we can begin to understand how genomic features change during the evolution of distinct species. Here, we construct high-density genetic linkage maps for 3 Vespidae wasp species from the Vespula genus: Vespula consobrina, Vespula pensylvanica, and Vespula vidua to investigate shared genomic architecture between these 3 yellowjacket wasp species. We show that these species exhibit high levels of collinearity, often in chromosome-length blocks of synteny, with some evidence for small interchromosomal rearrangements. We also identify 2 “inversions” in all 3 species that are likely artifacts from the genome assembly process. In addition, we map genome-wide recombination rates and reveal the recombination landscape to be highly variable on intrachromosomal, interchromosomal, and interspecific scales. Genome-wide recombination rates are high for all three Vespula species, (V. pensylvanica: 22.7 cM/Mb, V. consobrina: 24.3 cM/Mb, and V. vidua: 24.7 cM/Mb), which is consistent with findings of high recombination rates for other eusocial species. Our high-quality linkage maps will be resources for ongoing evolutionary genetics studies interested in the genome evolution of social wasps.

    

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4. How Veeries vary: Whole genome sequencing resolves genetic structure in a long-distance migratory bird

   https://doi.org/10.1093/ornithology/ukad061  

   Kimmitt, Abigail_A ; Pegan, Teresa_M ; Jones, Andrew_W ; Winker, Kevin ; Winger, Benjamin_M ( December 2023 , Ornithology)

   In high-latitude species with high dispersal ability, such as long-distance migratory birds, populations are often assumed to exhibit little genetic structure due to high gene flow or recent postglacial expansion. We sequenced over 120 low-coverage whole genomes from across the breeding range of a long-distance migratory bird, the Veery (Catharus fuscescens), revealing strong evidence for isolation by distance. Additionally, we found distinct genetic structure between boreal, western montane U.S., and southern Appalachian sampling regions. We suggest that population genetic structure in this highly migratory species is detectable with the high resolution afforded by whole-genomic data because, similar to many migratory birds, the Veery exhibits high breeding-site fidelity, which likely limits gene flow. Resolution of isolation by distance across the breeding range was sufficient to assign likely breeding origins of individuals sampled in this species’ poorly understood South American nonbreeding range, demonstrating the potential to assess migratory connectivity in this species using genomic data. As the Veery’s breeding range extends across both historically glaciated and unglaciated regions in North America, we also evaluated whether contemporary patterns of structure and genetic diversity are consistent with historical population isolation in glacial refugia. We found that patterns of genetic diversity did not support southern montane regions (southern Appalachians or western U.S. mountains) as glacial refugia. Overall, our findings suggest that isolation by distance yields subtle associations between genetic structure and geography across the breeding range of this highly vagile species even in the absence of obvious historical vicariance or contemporary barriers to dispersal.

    

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5. A Genomic Perspective on the Evolutionary Diversification of Turtles

   https://doi.org/10.1093/sysbio/syac019  

   Gable, Simone M. ; Byars, Michael I. ; Literman, Robert ; Tollis, Marc ; Hahn, ed., Matthew ( March 2022 , Systematic Biology)

   To examine phylogenetic heterogeneity in turtle evolution, we collected thousands of high-confidence single-copy orthologs from 19 genome assemblies representative of extant turtle diversity and estimated a phylogeny with multispecies coalescent and concatenated partitioned methods. We also collected next-generation sequences from 26 turtle species and assembled millions of biallelic markers to reconstruct phylogenies based on annotated regions from the western painted turtle (Chrysemys picta bellii) genome (coding regions, introns, untranslated regions, intergenic, and others). We then measured gene tree-species tree discordance, as well as gene and site heterogeneity at each node in the inferred trees, and tested for temporal patterns in phylogenomic conflict across turtle evolution. We found strong and consistent support for all bifurcations in the inferred turtle species phylogenies. However, a number of genes, sites, and genomic features supported alternate relationships between turtle taxa. Our results suggest that gene tree-species tree discordance in these data sets is likely driven by population-level processes such as incomplete lineage sorting. We found very little effect of substitutional saturation on species tree topologies, and no clear phylogenetic patterns in codon usage bias and compositional heterogeneity. There was no correlation between gene and site concordance, node age, and DNA substitution rate across most annotated genomic regions. Our study demonstrates that heterogeneity is to be expected even in well-resolved clades such as turtles, and that future phylogenomic studies should aim to sample as much of the genome as possible in order to obtain accurate phylogenies for assessing conservation priorities in turtles. [Discordance; genomes; phylogeny; turtles.]

    

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