The atypoid mygalomorphs include spiders from three described families that build a diverse array of entrance web constructs, including funnel-and-sheet webs, purse webs, trapdoors, turrets and silken collars. Molecular phylogenetic analyses have generally supported the monophyly of Atypoidea, but prior studies have not sampled all relevant taxa. Here we generated a dataset of ultraconserved element loci for all described atypoid genera, including taxa (Mecicobothrium and Hexurella) key to understanding familial monophyly, divergence times, and patterns of entrance web evolution. We show that the conserved regions of the arachnid UCE probe set target exons, such that it should be possible to combine UCE and transcriptome datasets in arachnids. We also show that different UCE probes sometimes target the same protein, and under the matching parameters used here show that UCE alignments sometimes include non-orthologs. Using multiple curated phylogenomic matrices we recover a monophyletic Atypoidea, and reveal that the family Mecicobothriidae comprises four separate and divergent lineages. Fossil-calibrated divergence time analyses suggest ancient Triassic (or older) origins for several relictual atypoid lineages, with late Cretaceous/early Tertiary divergences within some genera indicating a high potential for cryptic species diversity. The ancestral entrance web construct for atypoids, and all mygalomorphs, is reconstructed as a funnel-and-sheet web.
For years, the issues related to the origin of the Goths and their early migrations in the Iron Age have been a matter of hot debate among archaeologists. Unfortunately, the lack of new independent data has precluded the evaluation of the existing hypothesis. To overcome this problem, we initiated systematic studies of the populations inhabiting the contemporary territory of Poland during the Iron Age. Here, we present an analysis of mitochondrial DNA isolated from 27 individuals (collectively called the Mas-VBIA group) excavated from an Iron Age cemetery (dated to the 2nd-4th century A.D.) attributed to Goths and located near Masłomęcz, eastern Poland. We found that Mas-VBIA has similar genetic diversity to present-day Asian populations and higher diversity than that of contemporary Europeans. Our studies revealed close genetic links between the Mas-VBIA and two other Iron Age populations from the Jutland peninsula and from Kowalewko, located in western Poland. We disclosed the genetic connection between the Mas-VBIA and ancient Pontic-Caspian steppe groups. Similar connections were absent in the chronologically earlier Kowalewko and Jutland peninsula populations. The collected results seem to be consistent with the historical narrative that assumed that the Goths originated in southern Scandinavia; then, at least part of the Goth population moved south through the territory of contemporary Poland towards the Black Sea region, where they mixed with local populations and formed the Chernyakhov culture. Finally, a fraction of the Chernyakhov population returned to the southeast region of present-day Poland and established the archaeological formation called the “Masłomęcz group”.
Prior to human arrival in the 13th century, two large birds of prey were the top predators in New Zealand. In the absence of non-volant mammals, the extinct Haast’s eagle (Hieraaetus moorei), the largest eagle in the world, and the extinct Eyles’ harrier (Circus teauteensis) the largest harrier in the world, had filled ecological niches that are on other landmasses occupied by animals such as large cats or canines. The evolutionary and biogeographic history of these island giants has long been a mystery. Here we reconstruct the origin and evolution of New Zealand’s giant raptors using complete mitochondrial genome data. We show that both Eyles’ harrier and Haast’s eagle diverged from much smaller, open land adapted Australasian relatives in the late Pliocene to early Pleistocene. These events coincided with the development of open habitat in the previously densely forested islands of New Zealand. Our study provides evidence of rapid evolution of island gigantism in New Zealand’s extinct birds of prey. Early Pleistocene climate and environmental changes were likely to have triggered the establishment of Australian raptors into New Zealand. Our results shed light on the evolution of two of the most impressive cases of island gigantism in the world.
Species with narrow environmental tolerances are often distributed within fragmented patches of suitable habitat, and dispersal among these subpopulations can be difficult to directly observe. Genetic data can help quantify gene flow between localities, which is especially important for vulnerable species with a disjunct range. The Shenandoah salamander (Plethodon shenandoah) is a federally endangered species known only from three mountaintops in Virginia, USA. To reconstruct the evolutionary history and population connectivity of this species, we generated both mitochondrial and nuclear data using sequence capture from individuals collected across all three mountaintops. Applying population and landscape genetic methods, we found strong population structure that was independent of geographic distance. Both the nuclear markers and mitochondrial genomes indicated a deep split between the most southern population and the genetically similar central and northern populations. Although there was some mitochondrial haplotype‐splitting between the central and northern populations, there was admixture in nuclear markers. This is indicative of either a recent split or current male‐biased dispersal among mountain isolates. Models of landscape resistance found that dispersal across north‐facing slopes at mid‐elevation levels best explain the observed genetic structure among populations. These unexpected results highlight the importance of incorporating landscape features in understanding and predicting the movement and fragmentation of this range‐restricted salamander species across space.
DNA analyses of Mesolithic and Neolithic individuals indicates the British Neolithic transition was mediated by incoming continental farmers, with little gene flow from local hunter-gatherers.
Summary Stochastic activation of clustered Protocadherin (Pcdh) α, β, and γ genes generates a cell-surface identity code in individual neurons that functions in neural circuit assembly. Here, we show that Pcdhα gene choice involves the activation of an antisense promoter located in the first exon of each Pcdhα alternate gene. Transcription of an antisense long noncoding RNA (lncRNA) from this antisense promoter extends through the sense promoter, leading to DNA demethylation of the CTCF binding sites proximal to each promoter. Demethylation-dependent CTCF binding to both promoters facilitates cohesin-mediated DNA looping with a distal enhancer (HS5-1), locking in the transcriptional state of the chosen Pcdhα gene. Uncoupling DNA demethylation from antisense transcription by Tet3 overexpression in mouse olfactory neurons promotes CTCF binding to all Pcdhα promoters, resulting in proximity-biased DNA looping of the HS5-1 enhancer. Thus, antisense transcription-mediated promoter demethylation functions as a mechanism for distance-independent enhancer/promoter DNA looping to ensure stochastic Pcdhα promoter choice.
Ecosystem engineering species alter the physical structure of their environment and can create or modify habitats, having a massive impact on local biodiversity. Coralligenous reefs are highly diverse habitats endemic to the Mediterranean Sea built by calcareous benthic organisms among which Crustose Coralline Algae are the main engineering species. We analyzed the diversity of Lithophyllum stictiforme or L. cabiochiae in coralligenous habitats combining a multiple barcode and a population genomics approach with seascape features. Population genomics allowed disentangling pure spatial effects from environmental effects. We found that these taxa form a complex of eight highly divergent cryptic species that are easily identifiable using classic barcode markers (psbA, LSU, COI). Three factors have a significant effect on the relative abundances of these cryptic species: the location along the French Mediterranean coast, depth and Photosynthetic Active Radiation (PAR). The analysis of around 5000 SNPs for the most abundant species revealed genetic differentiation among localities in the Bay of Marseille but no differentiation between depths within locality. Thus, the effect of depth and PAR on cryptic species communities is not a consequence of restricted connectivity but rather due to differential settlement or survival among cryptic species. This differential is more likely driven by irradiance levels rather than by pressure or temperature. Both the genetic and species diversity patterns are congruent with the main patterns of currents in the Bay. Ecological differentiation among these engineering cryptic species, sensitive to ocean warming and acidification, could have important consequences on the diversity and structure of the coralligenous communities.
Mosses are a highly diverse lineage of land plants. Here, the authors provide a detailed phylogeny of 29 orders of moss, using nuclear and organelle data to provide robust hypotheses for most of the ordinal moss relationships.
The Cas12a nuclease from Acidaminococcus sp. (AsCas12a) can recognize a wider set of protospacer-adjacent motif (PAM) sequences, expanding the targeting range f
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