Browsing by Autor "Maria Elisa Mendiwelso"

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Nest location and architecture as primary drivers of variation in UV reflectance in avian eggs
(Royal Society, 2025) Maria Elisa Mendiwelso; Carlos Daniel Cadena; David Ocampo
Two main hypotheses have been proposed to explain the function of ultraviolet (UV) reflection in avian eggs. The UV resistance hypothesis suggests that high UV reflectance protects embryos against solar exposure in open nests, whereas the egg detectability hypothesis posits that higher UV reflectance helps eggs stand out against the dark background of the nest, making them easier for parents to locate in enclosed nests. Therefore, eggshell reflection in the UV spectrum may serve multiple (possibly even opposing) forces, including UV protection and visual signalling. We tested these two hypotheses using large-scale comparative analyses of eggshell UV reflection for over 500 avian species while considering the influence of various ecological, life history and environmental traits associated with light exposure. We did not find strong support for either of the two hypotheses across all birds. However, in two clades exhibiting notably high levels of UV reflectance (Passeriformes and Charadriiformes), species with higher UV reflectance values predominantly nest in open nests, suggesting a stronger effect of the UV resistance hypothesis. This research contributes to a deeper understanding of the mechanisms driving UV coloration in avian eggs and unravels the interplay between life history traits potentially associated with UV reflectance in specific clades under variable nesting conditions.
New genomic resources and the historical demography of the Tourmaline Sunangel (Trochilidae, <i>Heliangelus exortis</i> ) in the Colombian Andes
(Oxford University Press, 2026) Carlos Daniel Cadena; Laura Pabón; Andrés Felipe Díaz-Salazar; Maria Elisa Mendiwelso; Natalia Ocampo-Peñuela; Nelsy Niño-Rodríguez; Juliana Soto-Patiño; Glenn F. Seeholzer; Suzette G. A. Flantua; Linelle Abueg
Understanding the demographic history of tropical montane species offers insights into how climate-driven habitat dynamics shape genetic diversity and population structure. The Tourmaline Sunangel (Heliangelus exortis), a hummingbird endemic to the Northern Andes of Colombia and Ecuador, inhabits high-elevation ecosystems that were repeatedly impacted by Pleistocene glacial-interglacial cycles. To enable genomic and evolutionary studies in this system, we generated a high-quality, chromosome-level reference genome using PacBio HiFi long reads and Hi-C scaffolding. The resulting 1.05 Gb assembly has contig and scaffold N50s of 8.4 Mb and 73.9 Mb, respectively, with >94 % BUSCO completeness. Using this reference, we analyzed whole-genome resequencing data from ten individuals collected at a single locality in the Eastern Andes of Colombia and reconstructed demographic history with pairwise sequentially Markovian coalescent models. Our results indicate a pronounced population expansion between ~1 Mya and ~300 kya, likely driven by increased habitat connectivity during glacial periods when highland vegetation was displaced downslope, followed by a decline likely associated with interglacial fragmentation. These trends broadly align with paleoecological records, suggesting that populations of forest-associated species such as H. exortis responded to Pleistocene climatic oscillations, though demographic patterns did not strictly mirror known glacial-interglacial dynamics. This work establishes a foundation for future genomic studies in Andean birds, and highlights the potential of combining genomic and paleoecological data to unravel how biodiversity responds to environmental change.
Seasonal neurogenomic changes provide genetic links between male song and testosterone-mediated neurogenesis in a wild songbird
(2025) Maria Elisa Mendiwelso; Timothy A Liddle; Nora H. Prior; Anna K. Magnaterra; Chelsea M. Haakenson; Katherine A. Stennette; Catalina Palacios; Cara A. Krieg; Gregory F. Ball; Tyler J. Stevenson
Abstract Seasonal changes in testosterone mediate the transition from reduced singing in the non-breeding season to high song rates in the early breeding season in male temperate songbirds, a process accompanied by marked neurogenesis in song control regions of the brain. However, the resulting genetic changes and their association with the subsequent behavioral, neuroanatomical and reproductive changes remain poorly understood. Here, we compared gene expression in HVC, a major song control nucleus, between the non-breeding and breeding season in male northern house wrens ( Troglodytes aedon ) and we examined associations with HVC volume, plasma testosterone concentrations, and testes size. Differential gene expression analysis identified three genes (CLIP4, FAM169A, and TTR) consistently linked to seasonal transitions from non-breeding to three breeding stages (pre-laying, egg-laying and incubation). Notably, TTR, which transports thyroid hormone (TH), was highly expressed in the nonbreeding season, consistent with a possible role of TH in regulating seasonal shifts in song output and structure. We also identified seasonal changes in networks of genes related to neural connectivity, cellular restructuring, and cell migration. Weighted gene co-expression network analysis (WGCNA) revealed gene clusters specifically correlated with testosterone and HVC volume. Testosterone-associated genes included genes involved in neural circuit remodeling, chromatin organization, and cytoskeletal dynamics, consistent with testosterone-mediated regulation of these neuroanatomical changes. Genes linked to seasonal increases in HVC volume were involved in neuronal restructuring and neuron migration, implicating these genes in seasonal neurogenesis. Together, our findings link novel gene expression patterns to hormone regulation and neurogenesis underlying seasonal transitions in birdsong.