Biology subjects

Burns, K. J.

Publications and source records attributed to Burns, K. J..

3 recordsLinked to original sources

bioRxiv2026

Asymmetric gene flow across a desert contact zone in a riparian songbird

Secondary contact is a key point in the speciation process, and fine-scale geography can shape its outcomes. This is especially true for species restricted to fragmented habitats, such as riparian corridors through arid regions. Here we examine the role of disjunct riparian habitat in shaping secondary contact in Bells Vireo (Vireo bellii), a North American songbird species that contains distinct eastern and western forms. We recovered a unique, discontinuous contact zone along the Rio Grande in New Mexico, where two populations with greater nuclear and mitochondrial genetic affinity for the eastern lineage are separated by a population with an affinity for the western lineage. This point of primarily western ancestry on the Rio Grande corresponded with a stretch where several intermittently flowing tributaries join from the west and may have acted as gene flow corridors. Using a combination of empirical analyses of divergence and diversity across the genome and population genetic simulations, we uncovered evidence of neutral, genome-wide admixture driving the genomic architecture of divergence, rather than evidence for local adaptation or selective sweeps. In sum, this genomic study showed us how fine-scale dispersal corridors can cause idiosyncratic patterns of admixture when habitat is limiting in zones of secondary contact.

evolutionary biology↗

bioRxiv2025

The effects of post-divergence gene flow on simultaneous divergence time (SDT) testing

Estimating simultaneous divergence across multiple taxonomic groups from genetic data is a common approach in phylogeographical studies, providing insight into the historical and evolutionary factors shaping species diversification. However, the robustness of divergence time estimates across multiple co-distributed species or population pairs in the face of post-divergence gene flow is often left unaddressed. Here, we use a simulation-based approach to test the robustness of estimating simultaneous divergence within a full-likelihood Bayesian framework when the model assumptions of no gene flow are violated. We generated simulated datasets of multiple population pairs with varying migration rates and estimate shared divergence times with the software package Ecoevolity, comparing them with estimates from population pairs experiencing no migration. Our goal was to identify the threshold at which migration rates begin to bias divergence time estimates, providing insight into the robustness of full-likelihood Bayesian methods under more complex demographic scenarios. We found that simultaneous divergence is incorrectly supported across a broad range of parameters space when assumptions are violated. We suggest that future empirical studies that use simultaneous divergence testing explicitly test for gene flow, or at the very least, explicitly consider the presence, absence, and implications of gene flow in their systems as part of their investigations. We assert that this result--biased support for simultaneous divergence--is just a specific example of a general behavior when the statistical assumptions of the model are not met or there is insufficient power given the data. We additionally recommend that future studies reorient their research framework to focus on trying to demonstrate non-simultaneous divergence in systems. As such, support for simultaneous divergence between groups should be interpreted as failure to resolve non-simultaneous divergence rather than evidence of true simultaneous divergence.

evolutionary biology↗

bioRxiv2023

Constraint and innovation in color evolution among species and among plumage patches in five avian radiations

Understanding the causes and limits of phenotypic diversification remains a key challenge in evolutionary biology. Color patterns are some of the most diverse phenotypes in nature. In birds, recent work within families has suggested that plumage complexity might be a key innovation driving color diversity. Whether these patterns hold at larger taxonomic scales remains unknown. Here, we assemble a large database of UV-Vis spectral data across five diverse clades of birds (45791 spectra, 1135 species). Using multivariate phylogenetic comparative methods, we compare evolutionary rates and color space occupancy (i.e., quantification of observed colors) among these clades. Novel color-producing mechanisms have enabled clades to occupy new regions of color space, but using more coloration mechanisms did not result in overall more color space occupancy. Instead, the use of more color-producing mechanisms resulted in faster rates of color evolution and less integrated color among plumage regions. Flexible Bayesian modeling further allowed us to assess the relationship between interpatch and interspecific directions of color variation. We find that interpatch variation generally diverges from interspecies cladewise trends in males but not females, suggesting developmental or selective constraints operating in females across evolutionary scales. By comparing rates among clades and assessing both interpatch and interspecies color variation, we reveal how innovations and constraints operate across evolutionary and developmental scales.

evolutionary biology↗