More Like this

1. Incorporating the speciation process into species delimitation

   https://doi.org/doi.org/10.1371/journal.pcbi.1008924  

   Sukumaran, Jeet (May 2021, PLoS computational biology)

   Barraclough, Timothy G. (Ed.)

   The “multispecies” coalescent (MSC) model that underlies many genomic species-delimitation approaches is problematic because it does not distinguish between genetic structure associated with species versus that of populations within species. Consequently, as both the genomic and spatial resolution of data increases, a proliferation of artifactual species results as within-species population lineages, detected due to restrictions in gene flow, are identified as distinct species. The toll of this extends beyond systematic studies, getting magnified across the many disciplines that rely upon an accurate framework of identified species. Here we present the first of a new class of approaches that addresses this issue by incorporating an extended speciation process for species delimitation. We model the formation of population lineages and their subsequent development into independent species as separate processes and provide for a way to incorporate current understanding of the species boundaries in the system through specification of species identities of a subset of population lineages. As a result, species boundaries and within-species lineages boundaries can be discriminated across the entire system, and species identities can be assigned to the remaining lineages of unknown affinities with quantified probabilities. In addition to the identification of species units in nature, the primary goal of species delimitation, the incorporation of a speciation model also allows us insights into the links between population and species-level processes. By explicitly accounting for restrictions in gene flow not only between, but also within, species, we also address the limits of genetic data for delimiting species. Specifically, while genetic data alone is not sufficient for accurate delimitation, when considered in conjunction with other information we are able to not only learn about species boundaries, but also about the tempo of the speciation process itself. 

   more » « less
2. Interspecific competition affects resource use by three cryptic freshwater species of Hyalella Smith, 1874 (Amphipoda: Hyalellidae)

   https://doi.org/10.1093/jcbiol/ruab019  

   Mercer, Arissa A; Cothran, Rickey D (June 2021, Journal of Crustacean Biology)

   null (Ed.)

   Abstract Species that use the same resources present a paradox for understanding their coexistence. This is especially true for cryptic species because they are phenotypically similar. We examined how competition affects food-resource use in three cryptic species of Hyalella Smith, 1874, a freshwater-amphipod genus. We hypothesized that competitively inferior species would use high-quality algae patches when alone and competitively superior species would displace inferior species to low-quality patches. We compared use of foraging patches varying in algal content (i.e., quality) when species were alone or with another species. Our results showed that the competitively inferior species spent more time on the low-quality patch in the presence of the competitively superior species, but the behavior of the competitively superior species was independent of heterospecifics. This study provides insight into the role of interspecific competition in shaping resource use and patterns of coexistence in nature. 

   more » « less
3. A revision of the wilsoni species group in the millipede genus Nannaria Chamberlin, 1918 (Diplopoda, Polydesmida, Xystodesmidae)

   https://doi.org/10.3897/zookeys.1096.73485  

   Hennen, Derek A.; Means, Jackson C.; Marek, Paul E. (April 2022, ZooKeys)

   Although many new species of the millipede genus Nannaria Chamberlin, 1918 have been known from museum collections for over half a century, a systematic revision has not been undertaken until recently. There are two species groups in the genus: the minor species group and the wilsoni species group. In this study, the wilsoni species group was investigated. Specimens were collected from throughout its distribution in the Appalachian Mountains of the eastern United States and used for a multi-gene molecular phylogeny. The phylogenetic tree recovered Nannaria and the two species groups as monophyletic, with Oenomaea pulchella as its sister group. Seventeen new species were described, bringing the composition of the wilsoni species group to 24 species, more than tripling its known diversity, and increasing the total number of described Nannaria species to 78. The genus now has the greatest number of species in the family Xystodesmidae. Museum holdings of Nannaria were catalogued, and a total of 1,835 records used to produce a distribution map of the species group. Live photographs, illustrations of diagnostic characters, ecological notes, and conservation statuses are given. The wilsoni species group is restricted to the Appalachian region, unlike the widely-distributed minor species group (known throughout eastern North America), and has a distinct gap in its distribution in northeastern Tennessee and adjacent northwestern North Carolina. The wilsoni species group seems to be adapted to mesic microhabitats in middle to high elevation forests in eastern North America. New species are expected to be discovered in the southern Appalachian Mountains. 

   more » « less
4. Comparing single- and mixed-species groups in fruit flies: differences in group dynamics, but not group formation

   https://doi.org/10.1093/jhered/esab041  

   Girardeau, Anna R; Foley, Brad R; Saltz, Julia B (August 2021, Journal of Heredity)

   Hughes, Kim (Ed.)

   Abstract Mixed-species groups describe active associations among individuals of 2 or more species at the same trophic level. Mixed-species groups are important to key ecological and evolutionary processes such as competition and predation, and research that ignores the presence of other species risks ignoring a key aspect of the environment in which social behavior is expressed and selected. Despite the defining emphasis of active formation for mixed-species groups, surprisingly little is known about the mechanisms by which mixed-species groups form. Furthermore, insects have been almost completely ignored in the study of mixed-species groups, despite their taxonomic importance and relative prominence in the study of single-species groups. Here, we measured group formation processes in Drosophila melanogaster and its sister species, Drosophila simulans. Each species was studied alone, and together, and one population of D. melanogaster was also studied both alone and with another, phenotypically distinct D. melanogaster population, in a nested-factorial design. This approach differs from typical methods of studying mixed-species groups in that we could quantitatively compare group formation between single-population, mixed-population, and mixed-species treatments. Surprisingly, we found no differences between treatments in the number, size, or composition of groups that formed, suggesting that single- and mixed-species groups form through similar mechanisms of active attraction. However, we found that mixed-species groups showed elevated interspecies male–male interactions, relative to interpopulation or intergenotype interactions in single-species groups. Our findings expand the conceptual and taxonomic study of mixed-species groups while raising new questions about the mechanisms of group formation broadly. 

   more » « less
5. Comparative Microbiome Profiles of Sympatric Tick Species from the Far-Western United States

   https://doi.org/10.3390/insects10100353  

   Chicana, Betsabel; Couper, Lisa I.; Kwan, Jessica Y.; Tahiraj, Enxhi; Swei, Andrea (October 2019, Insects)

   Insight into the composition and function of the tick microbiome has expanded considerably in recent years. Thus far, tick microbiome studies have focused on species and life stages that are responsible for transmitting disease. In this study we conducted extensive field sampling of six tick species in the far-western United States to comparatively examine the microbial composition of sympatric tick species: Ixodes pacificus, Ixodes angustus, Dermacentor variabilis, Dermacentor occidentalis, Dermacentor albipictus, and Haemaphysalis leporispalustris. These species represent both common vectors of disease and species that rarely encounter humans, exhibiting a range of host preferences and natural history. We found significant differences in microbial species diversity and composition by tick species and life stage. The microbiome of most species examined were dominated by a few primary endosymbionts. Across all species, the relative abundance of these endosymbionts increased with life stage while species richness and diversity decreased with development. Only one species, I. angustus, did not show the presence of a single dominant microbial species indicating the unique physiology of this species or its interaction with the surrounding environment. Tick species that specialize in a small number of host species or habitat ranges exhibited lower microbiome diversity, suggesting that exposure to environmental conditions or host blood meal diversity can affect the tick microbiome which in turn may affect pathogen transmission. These findings reveal important associations between ticks and their microbial community and improve our understanding of the function of non-pathogenic microbiomes in tick physiology and pathogen transmission. 

   more » « less