Geographic contrasts between pre- and postzygotic barriers are consistent with reinforcement in Heliconius butterflies.

Identifying the traits causing reproductive isolation and the order in which they evolve isfundamental to understanding speciation. Here, we quantify prezygotic and intrinsicpostzygotic isolation between allopatric, parapatric and sympatric populations of thebutterflies Heliconius elevatus and Heliconius pardalinus. Sympatric populations from theAmazon (H. elevatus and H. p. butleri) exhibit strong prezygotic isolation and rarely mate incaptivity; however, hybrids are fertile. Allopatric populations from the Amazon(H. p. butleri) and Andes (H. p. sergestus) mate freely when brought together in captivity, butthe female F1 hybrids are sterile. Parapatric populations (H. elevatus and H. p. sergestus)exhibit both assortative mating and sterility of female F1s. Assortative mating in sympatricpopulations is consistent with reinforcement in the face of gene flow, where the driving force,selection against hybrids, is due to disruption of mimicry and other ecological traits ratherthan hybrid sterility. In contrast, the lack of assortative mating and hybrid sterility observedin allopatric populations suggests that geographic isolation enables the evolution of intrinsicpostzygotic reproductive isolation. Our results show how the types of reproductive barriersthat evolve between species may depend on geography

Genomic architecture and introgression shape a butterfly radiation

We use twenty de novo genome assemblies to probe the speciation history and architecture of gene flow in rapidly radiating Heliconius butterflies. Our tests to distinguish incomplete lineage sorting from introgression indicate that gene flow has obscured several ancient phylogenetic relationships in this group over large swathes of the genome. Introgressed loci are underrepresented in low recombination and gene-rich regions, consistent with the purging of foreign alleles more tightly linked to incompatibility loci. We identify a hitherto unknown inversion that traps a color pattern switch locus. We infer that this inversion was transferred between lineages via introgression and is convergent with a similar rearrangement in another part of the genus. These multiple de novo genome sequences enable improved understanding of the importance of introgression and selective processes in adaptive radiation

SNAPSHOT USA 2019 : a coordinated national camera trap survey of the United States

This article is protected by copyright. All rights reserved.With the accelerating pace of global change, it is imperative that we obtain rapid inventories of the status and distribution of wildlife for ecological inferences and conservation planning. To address this challenge, we launched the SNAPSHOT USA project, a collaborative survey of terrestrial wildlife populations using camera traps across the United States. For our first annual survey, we compiled data across all 50 states during a 14-week period (17 August - 24 November of 2019). We sampled wildlife at 1509 camera trap sites from 110 camera trap arrays covering 12 different ecoregions across four development zones. This effort resulted in 166,036 unique detections of 83 species of mammals and 17 species of birds. All images were processed through the Smithsonian's eMammal camera trap data repository and included an expert review phase to ensure taxonomic accuracy of data, resulting in each picture being reviewed at least twice. The results represent a timely and standardized camera trap survey of the USA. All of the 2019 survey data are made available herein. We are currently repeating surveys in fall 2020, opening up the opportunity to other institutions and cooperators to expand coverage of all the urban-wild gradients and ecophysiographic regions of the country. Future data will be available as the database is updated at eMammal.si.edu/snapshot-usa, as well as future data paper submissions. These data will be useful for local and macroecological research including the examination of community assembly, effects of environmental and anthropogenic landscape variables, effects of fragmentation and extinction debt dynamics, as well as species-specific population dynamics and conservation action plans. There are no copyright restrictions; please cite this paper when using the data for publication.Publisher PDFPeer reviewe

Drosophila Interspecific Hybrids Phenocopy piRNA- Pathway Mutants

The Piwi-interacting RNA (piRNA) pathway defends the germline of animals from the deleterious activity of selfish transposable elements (TEs) through small-RNA mediated silencing. Adaptation to novel invasive TEs is proposed to occur by incorporating their sequences into the piRNA pool that females produce and deposit into their eggs, which then propagates immunity against specific TEs to future generations. In support of this model, the F1 offspring of crosses between strains of the same Drosophila species sometimes suffer from germline derepression of paternally inherited TE families, caused by a failure of the maternal strain to produce the piRNAs necessary for their regulation. However, many protein components of the Drosophila piRNA pathway exhibit signatures of positive selection, suggesting that they also contribute to the evolution of host genome defense. Here we investigate piRNA pathway function and TE regulation in the F1 hybrids of interspecific crosses between D. melanogaster and D. simulans and compare them with intraspecific control crosses of D. melanogaster. We confirm previous reports showing that intraspecific crosses are characterized by derepression of paternally inherited TE families that are rare or absent from the maternal genome and piRNA pool, consistent with the role of maternally deposited piRNAs in shaping TE silencing. In contrast to the intraspecific cross, we discover that interspecific hybrids are characterized by widespread derepression of both maternally and paternally inherited TE families. Furthermore, the pattern of derepression of TE families in interspecific hybrids cannot be attributed to thei

The pattern of TE derepression in interspecific hybrid ovaries does not correlate with interspecific differences in piRNA abundance and does not match expectations from models of intraspecific hybrid dysgenesis.

<p>(A) Widespread misexpression of TEs in interspecific hybrids. Log2 transformed ratio of TE transcripts exhibiting ≥2-fold increased transcript abundance in interspecific F1 hybrids relative to both <i>D. melanogaster</i> (yellow) and <i>D. simulans</i> (blue). Candidate horizontally transferred TE families that are derepressed in interspecific hybrids are highlighted by a red arrow <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001428#pbio.1001428-Bartolom1" target="_blank">[10]</a> and/or a red asterisk <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001428#pbio.1001428-Lerat1" target="_blank">[12]</a>. TE families represented by full-length copies in both genomes, the <i>D. melanogaster</i> genome only, or neither genome are indicated under the green, yellow, and black bars, respectively <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001428#pbio.1001428-Bartolom1" target="_blank">[10]</a>,<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001428#pbio.1001428-Clark1" target="_blank">[49]</a>. (B) No TEs in dysgenic intraspecific hybrids exhibit ≥2-fold increased transcript abundance relative to both parental strains. Log2 transformed fold-change in TE transcript abundance in F1 dysgenic hybrids relative to <i>D. melanogaster w^K</i> (pink) and <i>w¹¹¹⁸</i> (blue) parental strains. (C) Many TE classes have differential abundance of their corresponding piRNAs between <i>D. melanogaster</i> and <i>D. simulans</i>. <i>D. melanogaster</i> biased TEs (≥2-fold higher abundance) are yellow, and <i>D. simulans</i> biased TEs are shaded blue. Red line indicates equivalent expression values in both species. (D) TE derepression in interspecific hybrid ovaries does not correlate with interspecific differences in piRNA abundance. Each bar represents the total number of TE classes with the pattern of interspecific differential abundance for piRNAs from (C), while grey shading indicates the proportion that are misregulated in interspecific hybrids from (A). The proportion of misregulated TEs is not significantly different among the three classes (<i>X²</i> = 2.08, <i>df</i> = 2, <i>p</i> = 0.35). (E and F) Species-specific TE transcripts are equivalently derepressed from the maternal and paternal genomes in interspecific hybrids. Log2 transformed ratio of TE transcripts exhibiting ≥2-fold increased abundance in hybrids relative to <i>D. melanogaster</i> (yellow) or <i>D. simulans</i> (blue) when considering reads that map exclusively to the <i>D. melanogaster</i> or <i>D. simulans</i> genomes. Red arrows and asterisks as in (A).</p

Interspecific hybrids phenocopy piRNA pathway mutants in disrupted piRNA production and nuage mislocalization.

<p>(A and B) Aberrant ping pong fractions in interspecific but not intraspecific hybrids. Ping pong fractions <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001428#pbio.1001428-Brennecke2" target="_blank">[23]</a> for all TE families are compared between intraspecific hybrids and their parents (A) and interspecific hybrids and their parents (B). Only TE families that were represented by >50 small RNA reads and a ping pong fraction >0.1 in at least one of the three libraries are shown. (C) Ping pong fractions for TE classes derepressed in interspecific hybrids (taken from <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001428#pbio-1001428-g001" target="_blank">Figure 1A</a>). (D and E) Increased antisense fraction of group III elements in interspecific hybrids. The antisense fraction of piRNAs derived from individual TE families in interspecific hybrids compared to <i>D. melanogaster</i> (D) and <i>D. simulans</i> (E). Classification of TE groups is from Li et al. <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001428#pbio.1001428-Li1" target="_blank">[45]</a>. Black line indicates equivalent antisense fractions in interspecific hybrids and parental pure species. (F) Anti-Aub and anti-Ago3 staining in <i>D. melanogaster</i> and interspecific hybrids in stage 2–6 egg-chambers. anti-Ago3 cross-reacts with <i>D. simulans</i>, but anti-Aub does not. Scale bars: 10 µm.</p