Biology subjects

Mason, N. A.

Publications and source records attributed to Mason, N. A..

4 recordsLinked to original sources

bioRxiv2021

Plumage balances camouflage and thermoregulation in Horned Larks (Eremophila alpestris)

Animal coloration serves many biological functions and must therefore balance potentially competing selective pressures. For example, many animals have camouflage, in which coloration matches the visual background against which predators scan for prey. However, different colors reflect different amounts of solar radiation and may therefore have thermoregulatory implications as well. In this study, we examined geographic variation in dorsal patterning, color, and solar reflectance among Horned Larks (Eremophila alpestris) of the western United States. We found associations between dorsal plumage brightness, hue, and patterning relative to the soil conditions where specimens were collected. Specifically, brighter dorsal plumage corresponded to brighter soil, while redder, more saturated hues in dorsal plumage corresponded to redder soils. Furthermore, backs with more high-contrast patterning were more common among females and also associated with soil that had coarser soil fragments, suggesting that lark plumage has been selected to optimize background matching in different environments. We also found that larks exhibited higher solar reflectance in hotter and more arid environments, which lowers the water requirements for homeothermy. Taken together, these findings suggest that natural selection has balanced camouflage and thermoregulation in Horned Larks across a wide variety of soil types and abiotic conditions.

zoology↗

bioRxiv2021

Morphology of migration: Associations between wing shape, bill morphology, and migration in kingbirds (Tyrannus)

Morphology is closely linked to locomotion and diet in animals. In animals that undertake long-distance migrations, limb-morphology is under selection to maximize mobility and minimize energy expenditure. Migratory behaviors also interact with diet, such that migratory animals tend to be dietary generalists, while sedentary taxa tend to be dietary specialists. Despite a hypothesized link between migration status and morphology, phylogenetic comparative studies have yielded conflicting findings. We tested for evolutionary associations between migratory status and limb and bill morphology across kingbirds, a pan-American genus of birds with migratory, partially migratory, and sedentary taxa. Migratory kingbirds had longer wings, in agreement with expectations if selection favors improved aerodynamics for long-distance migration. We also found an association between migratory status and bill shape, such that more migratory taxa had wider, deeper, and shorter bills compared to sedentary taxa. However, there was no difference in intraspecific morphological variation among migrants, partial migrants, and residents, suggesting that dietary specialization has evolved independently of migration strategy. The evolutionary links between migration, diet, and morphology in kingbirds uncovered here further strengthen ecomorphological associations that underlie long-distance seasonal movements in animals.

evolutionary biology↗

bioRxiv2021

Dorsal color variation among subspecies of the "Oregon" Dark-eyed Junco complex

Initial descriptions of avian subspecies were based on expert opinions of geographic variation in phenotypes and are inherently subjective. Although best practices for subspecies delimitation continue to be debated, reassessing subspecies limits with current, quantitative methods is important toward refining and improving taxonomic treatments. Plumage coloration is the basis of many subspecies diagnoses, but is potentially problematic because of the historical lack of quantitative methods to quantify color. Recently developed methods, such as colorimetry, provide repeatable measurements of color variation that can be used to reassess subspecies limits. In this study, we reassess color variation among subspecies of the Oregon Dark-eyed Junco (Junco hyemalis [oreganus Group]) complex, in which differences in back and hood color were established as diagnostic characters. We measured back and hood brightness and hue in 206 museum specimens among five Oregon Dark-eyed Junco subspecies using a colorimeter. We then compared mean measurements among subspecies and conducted a discriminant function analysis to assess how well dorsal color predicted subspecies. Our data correctly classified only 67.9% of males and 82.5% of females to their presumed subspecies. Furthermore, no adjacent subspecies pairs passed the "75% rule" due to extensive overlap in plumage characters. Thus, back color alone is not as effective in diagnosing Oregon Dark-eyed Junco subspecies as originally described, suggesting a possible taxonomic revision. Specifically, similarity in phenotypic and genetic data suggests that some combination of thurberi, montanus, and shufeldti may be lumped to recognize broad, clinal variation in dorsal color alongside clinal variation in other phenotypes and extensive gene flow.

zoology↗

bioRxiv2019

Genome Report: De novo assembly of a high-quality reference genome for the Horned Lark (Eremophila alpestris)

The Horned Lark (Eremophila alpestris) is a species of small songbird that exhibits remarkable geographic variation in appearance and habitat across an expansive distribution. While E. alpestris and related species have been the focus of many ecological and evolutionary studies, we still lack a highly contiguous genome assembly for horned larks and related taxa (Alaudidae). Here, we present CLO_EAlp_1.0, a highly contiguous assembly for horned larks generated from blood samples of a wild, male bird captured in the Altiplano Cundiboyacense of Colombia. By combining short-insert and mate-pair libraries with the ALLPATHS-LG genome assembly pipeline, we generated a 1.04 Gb assembly comprised of 2708 contigs with an N50 of 10.58 Mb and a L50 of 29. After polishing the genome, we were able to identify 94.5% of single-copy gene orthologs from an Aves data set and 97.7% of single-copy gene orthologs from a vertebrata data set, indicating that our de novo assembly is near complete. We anticipate that this genomic resource will be useful to the broader ornithological community and those interested in studying the evolutionary history and ecological interactions of a widespread, yet understudied lineage of songbirds.

genomics↗