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Species concepts are well established and apply across diverse groups of organisms; however, there is no consensus on what defines higher taxonomic groups. The genus rank is important to taxonomists because it comprises part of the scientific name of an organism. A consistent and biologically meaningful method for determining generic status is needed for taxonomic stability and utility. Lasiurine bats are a group for which there is disagreement on how many genera to recognize. Some authors argue for splitting this group into three genera based on morphology, genetic divergence, and time of divergence; others argue that a single genus should be maintained. Here, we use lasiurines to explore generic-level taxonomy and how it is applied. Genetic divergence levels are compared among sister genera and within genera of vespertilionine bats using Cytochrome b ( Cytb ) sequences. We used Cytb because it is the most sequenced mitochondrial gene in mammals, but other genes might be more appropriate for a different taxon. Future methods will eventually use complete mitogenomes and genomes. We conclude that lasiurine bats are most appropriately divided into three genera to maintain taxonomic consistency within their subfamily. Since Linnaeus, the quarter millennium of progress in the science of mammalogy has provided a binomial nomenclatural basis from which can be extracted an acceptable range of genetic diversity upon which to establish generic level taxonomy. We offer a biologically meaningful operational definition of the genus, which we call the 2 Sigma Genus Concept, based on genetic divergence between a genus and its sister genus or lineage and compared to the divergence between sister pairs of established genera in the same higher taxonomic category. Our method is phylogenetic; sister genera are based on the best phylogeny for the higher taxonomic category. Genera must be monophyletic and differ from their closest relatives by not more than two standard deviations above or below the mean value of genetic distance for the larger taxonomic group in which they are contained. There should be genetic-based characters (e.g., morphology, protein structure, behavior) that are diagnostic for each genus. Our method is novel in that it uses the statistical distribution of sister divergences within a higher category to guide the allocation of generic status to monophyletic lineages. Within Vespertilioninae, the mean genetic distance between sister genera is 20.68% ± 3.89% (K2P) for the Cytb gene. Therefore, a proposed new genus should have >12.90% genetic distance to its sister genus. Genera that are > 2 standard deviations above the mean (>28.46%) are candidates to be recognized as a higher category such as tribe or subfamily. The sister-genus divergence for the monophyletic lineage that includes all lasiurine bats is 31.14% ± 1.64% which qualifies it as a higher category (i.e., tribe), and the sister-genus divergences of the three monophyletic lineages within Lasiurini (i.e., red, yellow and hoary bats) are 21.77% and 22.91% which qualifies them for genera. We show the applicability of the method beyond Vespertilioninae by providing a case study where we apply it in a distantly related subfamily of bats.

The muskox ( Ovibos moschatus ), an integral component and iconic symbol of arctic biocultural diversity, is under threat by rapid environmental disruptions from climate change. We report a chromosomal-level haploid genome assembly of a muskox from Banks Island in the Canadian Arctic Archipelago. The assembly has a contig N50 of 44.7 Mbp, a scaffold N50 of 112.3 Mbp, a complete representation (100%) of the BUSCO v5.2.2 set of 9225 mammalian marker genes and is anchored to the 24 chromosomes of the muskox. Tabulation of heterozygous single nucleotide variants in our specimen revealed a very low level of genetic diversity, which is consistent with recent reports of the muskox having the lowest genome-wide heterozygosity among the ungulates. While muskox populations are currently showing no overt signs of inbreeding depression, environmental disruptions are expected to strain the genomic resilience of the species. One notable impact of rapid climate change in the Arctic is the spread of emerging infectious and parasitic diseases in the muskox, as exemplified by the range expansion of muskox lungworms, and the recent fatal outbreaks of Erysipelothrix rhusiopathiae , a pathogen normally associated with domestic swine and poultry. As a genomics resource for conservation management of the muskox against existing and emerging disease modalities, we annotated the genes of the major histocompatibility complex on chromosome 2 and performed an initial assessment of the genetic diversity of this complex. This resource is further supported by the annotation of the principal genes of the innate immunity system, genes that are rapidly evolving and under positive selection in the muskox, genes associated with environmental adaptations, and the genes associated with socioeconomic benefits for Arctic communities such as wool (qiviut) attributes. These annotations will benefit muskox management and conservation.

Previous studies on genetics of hoary bats produced differing conclusions on the timing of their colonization of the Hawaiian Islands and whether or not North American (Aeorestes cinereus) and Hawaiian (A. semotus) hoary bats are distinct species. One study, using mtDNA COI and nuclear Rag2 and CMA1, concluded that hoary bats colonized the Hawaiian Islands no more than 10,000 years ago based on indications of population expansion at that time using Extended Bayesian Skyline Plots. The other study, using 3 mtDNA and 1 Y-chromosome locus, concluded that the Hawaiian Islands were colonized about 1 million years ago. To address the marked inconsistencies between those studies, we examined DNA sequences from 4 mitochondrial and 2 nuclear loci in lasiurine bats to investigate the timing of colonization of the Hawaiian Islands by hoary bats, test the hypothesis that Hawaiian and North American hoary bats belong to different species, and further investigate the generic level taxonomy within the tribe. Phylogenetic analysis and dating of the nodes of mtDNA haplotypes and of nuclear CMA1 alleles show that A. semotus invaded the Hawaiian Islands approximately 1.35 Ma and that multiple arrivals of A. cinereus occurred much more recently. Extended Bayesian Skyline plots show population expansion at about 20,000 years ago in the Hawaiian Islands, which we conclude does not represent the timing of colonization of the Hawaiian Islands given the high degree of genetic differentiation among A. cinereus and A. semotus (4.2% divergence at mtDNA Cytb) and the high degree of genetic diversity within A. semotus. Rather, population expansion 20,000 years ago could have resulted from colonization of additional islands, expansion after a bottleneck, or other factors. New genetic data also support the recognition of A. semotus and A. cinereus as distinct species, a finding consistent with previous morphological and behavioral studies. The phylogenetic analysis of CMA1 alleles shows the presence of 2 clades that are primarily associated with A. semotus mtDNA haplotypes, and are unique to the Hawaiian Islands. There is evidence for low levels of hybridization between A. semotus and A. cinereus on the Hawaiian Islands, but it is not extensive (<15% of individuals are of hybrid origin), and clearly each species is able to maintain its own genetic distinctiveness. Both mtDNA and nuclear DNA sequences show deep divergence between the 3 groups (genera) of lasiurine bats that correspond to the previously recognized morphological differences between them. We show that the Tribe Lasiurini contains the genera Aeorestes (hoary bats), Lasiurus (red bats), and Dasypterus (yellow bats).

Although many processes of diversification have been described to explain variation of morphological traits within clades that have obvious differentiation among taxa, not much is known about these patterns in complexes of cryptic species. Molossus is a genus of bats that is mainly Neotropical, occurring from the southeastern United States to southern Argentina, including the Caribbean islands. Molossus comprises some groups of species that are morphologically similar but phylogenetically divergent, and other groups of species that are genetically similar but morphologically distinct. This contrast allows investigation of unequal trait diversification and the evolution of morphological and behavioural characters. In this study, we assessed the role of phylogenetic history in a genus of bat with three cryptic species complexes, and evaluated if morphology and behavior are evolving concertedly. The Genotype by Sequence genomic approach was used to build a species-level phylogenetic tree for Molossus and to estimate the ancestral states of morphological and echolocation call characters. We measured the correlation of phylogenetic distances to morphological and echolocation distances, and tested the relationship between morphology and behavior when the effect of phylogeny is removed. Morphology evolved via a mosaic of convergence and stasis, whereas call design was influenced exclusively through local adaptation and convergent evolution. Furthermore, the frequency of echolocation calls is negatively correlated with the size of the bat, but other characters do not seem to be evolving in concert. We hypothesize that slight variation in both morphology and behaviour among species of the genus might result from niche specialization, and that traits evolve to avoid competition for resources in similar environments.

Historical events, habitat preferences, and geographic barriers might result in distinct genetic patterns in insular versus mainland populations. Comparison between these two biogeographic systems provides an opportunity to investigate the relative role of isolation in phylogeographic patterns and to elucidate the importance of evolution and demographic history in population structure. Herein, we use a genotype‐by‐sequencing approach (GBS) to explore population structure within three species of mastiff bats (Molossus molossus, M. coibensis, and M. milleri), which represent different ecological histories and geographical distributions in the genus. We tested the hypotheses that oceanic straits serve as barriers to dispersal in Caribbean bats and that isolated island populations are more likely to experience genetic drift and bottlenecks in comparison with highly connected ones, thus leading to different phylogeographic patterns. We show that population structures vary according to general habitat preferences, levels of population isolation, and historical fluctuations in climate. In our dataset, mainland geographic barriers played only a small role in isolation of lineages. However, oceanic straits posed a partial barrier to the dispersal for some populations within some species (M. milleri), but do not seem to disrupt gene flow in others (M. molossus). Lineages on distant islands undergo genetic bottlenecks more frequently than island lineages closer to the mainland, which have a greater exchange of haplotypes. In this manuscript, we use the genotype‐by‐sequencing approach on three species of Mastiff bats with different ecological histories and geographical distributions to explore population genetics parameters and better understand the role of geographic barriers in the dispersal and gene flow in bats. Our analyses show that the population structure of each species varies according to environmental factors, levels of population isolation, and demographic histories. We show that oceanic straights seem to pose a partial barrier for some species and that more isolated lineages on islands tend to undergo genetic bottlenecks more than connected lineages closer to the mainland.

Knowledge of genetic diversity and structure is essential for developing conservation strategies for endangered species. Blue whales were hunted to near extinction in the mid-twentieth century. Not-withstanding almost 380,000 animals killed globally, much remains unknown about their population structure and migration patterns. Herein, we use whole genome sequencing to elucidate the poorly understood population genetics of North Atlantic (NA) blue whales. We generated a de novo genome assembly for a NA blue whale to analyze 19 other whole genomic sequences and 31 complete mitochondrial genomes. Present-day and historical samples (earliest from 1876) from the Atlantic and Antarctic Oceans were included to understand the impact of whaling on the genetic diversity of this species. We found low but statistically significant population structuring and high genetic diversity. Demographic modeling using fastsimcoal2 rejected an absence of gene flow between eastern and western NA blue whales and suggested an asymmetric west to east gene flow. Introgression estimated using D-statistics between blue and fin whales (Balaenoptera physalus), was observed in all present-day samples. This gene flow was found to be unidirectional from fin whales to blue whales and accounts for ~ 3.5% of the NA blue whale’s genome. Our sequencing and population structure analyses provide a genomic baseline to inform ongoing conservation strategies for this iconic species.

We report a chromosomal-level genome assembly of a male North American wolverine (Gulo gulo luscus) from the Kugluktuk region of Nunavut, Canada. The genome was assembled directly from long-reads, comprising: 758 contigs with a contig N50 of 36.6 Mb; contig L50 of 20; base count of 2.39 Gb; and a near complete representation (99.98%) of the BUSCO 5.2.2 set of 9,226 genes. A presumptive chromosomal-level assembly was generated by scaffolding against two chromosomal-level Mustelidae reference genomes, the ermine and the Eurasian river otter, to derive a final scaffold N50 of 144.0 Mb and a scaffold L50 of 7. We annotated a comprehensive set of genes that have been associated with models of aggressive behavior, a trait which the wolverine is purported to have in the popular literature. To support an integrated, genomics-based wildlife management strategy at a time of environmental disruption from climate change, we annotated the principal genes of the innate immune system to provide a resource to study the wolverine’s susceptibility to new infectious and parasitic diseases. As a resource, we annotated genes involved in the modality of infection by the coronaviruses, an important class of viral pathogens of growing concern as shown by the recent spillover infections by severe acute respiratory syndrome coronavirus-2 to naïve wildlife. Tabulation of heterozygous single nucleotide variants in our specimen revealed a heterozygosity level of 0.065%, indicating a relatively diverse genetic pool that would serve as a baseline for the genomics-based conservation of the wolverine, a rare cold-adapted carnivore now under threat.

We examined spectral features that characterize the highly stereotyped, repetitive vocalizations of New World baiomyine rodents. Although stereotyped vocal signaling, described as “song,” has been documented in Scotinomys (singing or brown mice), its occurrence was unknown in the sister taxon Baiomys (pygmy mice). We also recorded vocalizations of females, about which little information was previously available. Although examination of morphological and molecular data supports a close relationship between the 2 baiomyine genera, we identified song as a complex behavior that further underpins the monophyly of the Baiomyini. Both spectral and temporal features render these songs highly localizable, a characteristic of possible utility for courtship and other social behavior. The song of Baiomys is confined entirely to the ultrasonic spectrum, unlike that of Scotinomys, which uses a broader range of frequencies. The intensity, identity, and predictability of vocalization suggest that these songs are purposeful and carry information important for species identification.

Peromyscine mice of the cricetid subfamily Neotominae comprise the most common and speciose assemblage of North American rodents. The composition and phylogenetic relationships within this group have been addressed using multiple character systems but remain unresolved, particularly the branching pattern of deeply rooted lineages. The relationships and status of several taxa formerly included within Peromyscus also are controversial. We present a new phylogenetic hypothesis based on combined mitochondrial and nuclear sequences using cytochrome b, interphotoreceptor retinoid-binding protein, and growth hormone receptor gene sequences, and include all major peromyscine lineages. Bayesian and parsimony approaches recover a congruent, well-resolved phylogeny, wherein Peromyscus forms a monophyletic assemblage only if a number of putative genera are included within it. Onychomys rather than Reithrodontomys is the sister taxon to Peromyscus (within which are included Habromys, Osgoodomys, Megadontomys, Podomys, and Neotomodon). Reithrodontomys in turn is the sister taxon to Isthmomys, and these 2 genera are the nearest outlier to Onychomys plus an expanded concept of Peromyscus, consistent with the recent recognition of this entire group as the tribe Reithrodontomyini. The Baiomyini, Ochrotomyini, and Neotoma (Neotomini) appear as successive outgroups to this clade. Based on these results, we present a systematic review of higher-level relationships among peromyscine rodents.