Browsing by Author "Dale J"

Now showing 1 - 7 of 7
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    Contrasting gene flow at different spatial scales revealed by genotyping-by-sequencing in Isocladus armatus, a massively colour polymorphic New Zealand marine isopod
    (PeerJ Inc., 2018-08-22) Wells SJ; Dale J; Prentis P
    Understanding how genetic diversity is maintained within populations is central to evolutionary biology. Research on colour polymorphism (CP), which typically has a genetic basis, can shed light on this issue. However, because gene flow can homogenise genetic variation, understanding population connectivity is critical in examining the maintenance of polymorphisms. In this study we assess the utility of genotyping-by-sequencing to resolve gene flow, and provide a preliminary investigation into the genetic basis of CP in Isocladus armatus, an endemic New Zealand marine isopod. Analysis of the genetic variation in 4,000 single nucleotide polymorphisms (SNPs) within and among populations and colour morphs revealed large differences in gene flow across two spatial scales. Marine isopods, which lack a pelagic larval phase, are typically assumed to exhibit greater population structuring than marine invertebrates possessing a biphasic life cycle. However, we found high gene flow rates and no genetic subdivision between two North Island populations situated 8 km apart. This suggests that I. armatus is capable of substantial dispersal along coastlines. In contrast, we identified a strong genetic disjunction between North and South Island populations. This result is similar to those reported in other New Zealand marine species, and is congruent with the presence of a geophysical barrier to dispersal down the east coast of New Zealand. We also found some support for a genetic basis to colouration evidenced by positive FST outlier tests, with two SNPs in particular showing strong association to the expression of a striped morph. Our study provides one of the first population genomic studies of a marine organism in New Zealand, and suggests that genotyping-by-sequencing can be a good alternative to more traditional investigations based on traditional markers such as microsatellites. Our study provides a foundation for further development of a highly tractable system for research on the evolutionary maintenance of CP.
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    Evolutionary predictors of the specific colors of birds.
    (National Academy of Sciences, 2023-08-14) Delhey K; Valcu M; Muck C; Dale J; Kempenaers B; Losos J
    Animal coloration is one of the most conspicuous aspects of human-perceived organismal diversity, yet also one of the least understood. In particular, explaining why species have specific colors (e.g., blue vs. red) has proven elusive. Here, we quantify for nearly all bird species, the proportion of the body covered by each of 12 human-visible color categories, and test whether existing theory can predict the direction of color evolution. The most common colors are black, white, gray and brown, while the rarest are green, blue, purple, and red. Males have more blue, purple, red, or black, whereas females have more yellow, brown, or gray. Sexual dichromatism is partly due to sexual selection favoring ornamental colors in males but not in females. However, sexual selection also correlated positively with brown in both sexes. Strong social selection favors red and black, colors used in agonistic signaling, with the strongest effects in females. Reduced predation risk selects against cryptic colors (e.g., brown) and favors specific ornamental colors (e.g., black). Nocturnality is mainly associated with brown. The effects of habitat use support the sensory drive theory for camouflage and signaling. Darker colors are more common in species living in wet and cold climates, matching ecogeographical rules. Our study unambiguously supports existing theories of color evolution across an entire class of vertebrates, but much variation remains unexplained.
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    Long-read sequencing reveals atypical mitochondrial genome structure in a New Zealand marine isopod
    (The Royal Society, 2022-01-12) Pearman WS; Wells SJ; Dale J; Silander OK; Freed NE
    Most animal mitochondrial genomes are small, circular and structurally conserved. However, recent work indicates that diverse taxa possess unusual mitochondrial genomes. In Isopoda, species in multiple lineages have atypical and rearranged mitochondrial genomes. However, more species of this speciose taxon need to be evaluated to understand the evolutionary origins of atypical mitochondrial genomes in this group. In this study, we report the presence of an atypical mitochondrial structure in the New Zealand endemic marine isopod, Isocladus armatus. Data from long- and short-read DNA sequencing suggest that I. armatus has two mitochondrial chromosomes. The first chromosome consists of two mitochondrial genomes that have been inverted and fused together in a circular form, and the second chromosome consists of a single mitochondrial genome in a linearized form. This atypical mitochondrial structure has been detected in other isopod lineages, and our data from an additional divergent isopod lineage (Sphaeromatidae) lends support to the hypothesis that atypical structure evolved early in the evolution of Isopoda. Additionally, we find that an asymmetrical site previously observed across many species within Isopoda is absent in I. armatus, but confirm the presence of two asymmetrical sites recently reported in two other isopod species.
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    Social and environmental transmission spread different sets of gut microbes in wild mice.
    (Springer Nature Limited, 2024-05-01) Raulo A; Bürkner P-C; Finerty GE; Dale J; Hanski E; English HM; Lamberth C; Firth JA; Coulson T; Knowles SCL
    Gut microbes shape many aspects of organismal biology, yet how these key bacteria transmit among hosts in natural populations remains poorly understood. Recent work in mammals has emphasized either transmission through social contacts or indirect transmission through environmental contact, but the relative importance of different routes has not been directly assessed. Here we used a novel radio-frequency identification-based tracking system to collect long-term high-resolution data on social relationships, space use and microhabitat in a wild population of mice (Apodemus sylvaticus), while regularly characterizing their gut microbiota with 16S ribosomal RNA profiling. Through probabilistic modelling of the resulting data, we identify positive and statistically distinct signals of social and environmental transmission, captured by social networks and overlap in home ranges, respectively. Strikingly, microorganisms with distinct biological attributes drove these different transmission signals. While the social network effect on microbiota was driven by anaerobic bacteria, the effect of shared space was most influenced by aerotolerant spore-forming bacteria. These findings support the prediction that social contact is important for the transfer of microorganisms with low oxygen tolerance, while those that can tolerate oxygen or form spores may be able to transmit indirectly through the environment. Overall, these results suggest social and environmental transmission routes can spread biologically distinct members of the mammalian gut microbiota.
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    The evolution of carotenoid-based plumage colours in passerine birds
    (John Wiley and Sons Ltd on behalf of British Ecological Society, 2023-01-04) Delhey K; Valcu M; Dale J; Kempenaers B; Willink B
    1. Many birds use carotenoids to colour their plumage yellow to red. Because birds cannot synthesise carotenoids, they need to obtain these pigments from food, although some species metabolise dietary carotenoids (which are often yellow) into derived carotenoids (often red). 2. Here, we study the occurrence of yellow and red carotenoid-based plumage colours in the passerines, the largest bird radiation and quantify the effects of potential ecological and life-history drivers on their evolution. 3. We scored the presence/absence of yellow and red carotenoid-based plumage in nearly 6,000 species and use Bayesian phylogenetic mixed models to assess the effects of carotenoid-availability in diet, primary productivity, body size, habitat and sexual selection. We also test the widespread assumption that red carotenoid-based colours are more likely to be the result of metabolization. Finally, we analyse the pattern of evolutionary transitions between yellow and red carotenoid-based plumage colours to determine whether, as predicted, the evolution of yellow carotenoid-based colours precedes red. 4. We show that, as expected, both colours are more likely to evolve in smaller species and in species with carotenoid-rich diets. Yellow carotenoid-based plumage colours, but not red, are more prevalent in species that inhabit environments with higher primary productivity and closed vegetation. In general, females were more likely to have yellow and males more likely to have red carotenoid-based plumage colours, closely matching the effects of sexual selection. Our analyses also confirm that red carotenoid-based colours are more likely to be metabolised than yellow carotenoid-based colours. Evolutionary gains and losses of yellow and red carotenoid-based plumage colours indicate that red colours evolved more readily in species that already deposited yellow carotenoids, while the reverse was rarely the case. 5. Our study provides evidence for a general, directional evolutionary trend from yellow to red carotenoid-based colours, which are more likely to be the result of metabolization. This may render them potentially better indicators of quality, and thus favoured by sexual selection.
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    What drives our aesthetic attraction to birds?
    (Springer Nature Limited, 2023-09-27) Santangeli A; Haukka A; Morris W; Arkkila S; Delhey K; Kempenaers B; Valcu M; Dale J; Lehikoinen A; Mammola S
    In the Anthropocene, the era when the imprint of humans on nature is pervasive across the planet, it is of utmost importance to understand human relationships with other species. The aesthetics of nature, and of species, is one of the values that plays a role in shaping human-nature relationships. Birds are ubiquitous across the world. The beauty of birds exerts a powerful tug on human emotions, and bird-rich areas attract scores of eco-tourists. People naturally find some birds more beautiful or interesting than others, but we currently lack a global understanding of the specifics of what makes a species aesthetically attractive. Here, we used a global citizen-science database on bird attractiveness covering nearly all extant bird species, to show that there are specific visual features that drive our aesthetic appeal for some bird species over others. First, our aesthetic attraction is highest for smaller birds with specific, vivid colors (e.g., blue and red, and departing from brown-grey) and extreme ornaments (a long crest or tail). Second, our aesthetic attraction is highest for species with broad ranges, possibly because such species may be more familiar to us. The features that make us attracted to a particular bird strongly align with broad human visual aesthetic preferences in modern society. Unveiling the visual features underpinning our aesthetic attraction to birds is a critical step towards optimizing conservation (e.g., via conservation marketing) and education campaigns, and leverage the cultural ecosystem service potential of birds.
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    Wildlife trade targets colorful birds and threatens the aesthetic value of nature
    (Elsevier Inc, 2022-10-10) Senior RA; Oliveira BF; Dale J; Scheffers BR
    A key component of nature's contribution to people is aesthetic value. Charismatic species rally public support and bolster conservation efforts. However, an insidious aspect to humanity's valuation of nature is that high value also drives wildlife trade, which can spearhead the demise of prized species. Here, we explore the antagonistic roles of aesthetic value in biodiversity conservation by using novel metrics of color to evaluate the aesthetics of the most speciose radiation of birds: passerines (i.e., the perching birds). We identify global color hotspots for passerines and highlight the breadth of color in the global bird trade. The tropics emerge as an epicentre of color, encompassing 91% and 65% of the world's most diverse and most uniquely colored passerine assemblages, respectively. We show that the pet trade, which currently affects 30% of passerines (1,408/5,266), traverses the avian phylogeny and targets clusters of related species that are uniquely colored. We identify an additional 478 species at risk of future trade based on their coloration and phylogenetic relationship to currently traded species-together totaling 1,886 species traded, a 34% increase. By modeling future extinctions based on species' current threat status, we predict localized losses of color diversity and uniqueness in many avian communities, undermining their aesthetic value and muting nature's color palette. Given the distribution of color and the association of unique colors with threat and trade, proactive regulation of the bird trade is crucial to conserving charismatic biodiversity, alongside recognition and celebration of color hotspots.