Journal Articles
Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915
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Item 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 SCLGut 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.Item 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 JAnimal 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.Item 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 B1. 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.Item Wildlife trade targets colorful birds and threatens the aesthetic value of nature(Elsevier Inc, 2022-10-10) Senior RA; Oliveira BF; Dale J; Scheffers BRA 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.