Biology subjects

Baumann, M. J.

Publications and source records attributed to Baumann, M. J..

4 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↗

bioRxiv2024

Taxonomy and nomenclature of the giant hummingbirds (Patagona spp.) (Aves: Trochilidae)

Giant hummingbirds (Patagona spp.) are extraordinarily large hummingbirds whose taxonomy has been muddled for two centuries. Patagona systematics were recently redefined in a study of migration, physiology, and genomics, revealing two species: the Southern Giant Hummingbird and Northern Giant Hummingbird. Here, we re-evaluate taxonomy and nomenclature of the genus in light of its newly-clarified biology and species limits, analyzing data from 608 specimens and wild-caught individuals spanning 1864-2023. The forms gigas and peruviana were both described based on multiple syntypes. No adequate syntypes for P. gigas are extant, so we designate a neotype for this taxon. We then critically consider the identity and usage of gigas and peruviana, respectively, and examine identification challenges that have fostered taxonomic uncertainty. We endorse the names Patagona gigas for the Southern Giant Hummingbird and P. peruviana for the Northern Giant Hummingbird. The genetic identity of the peruviana lectotype remains untested, but its plumage appears to match the northern species. We found that [~]33% of Patagona gigas specimens in major museum collections are misidentified as peruviana; we provide this list to correct the historical record. To facilitate identification and future study of these two cryptic species, we provide comprehensive information on plumage, measurements, and seasonal ranges.

zoology↗

bioRxiv2020

Detecting turnover among complex communities using null models: A case study with sky-island haemosporidian parasites

Turnover in species composition between sites, or beta diversity, is a critical component of species diversity that is typically influenced by geography, environment, and biotic interactions. Quantifying turnover is particularly challenging, however, in multi-host, multi-parasite assemblages where undersampling is unavoidable, resulting in inflated estimates of turnover and uncertainty about its spatial scale. We developed and implemented a framework using null models to test for community turnover in avian haemosporidian communities of three sky islands in the southwestern United States. We screened 776 birds for haemosporidian parasites from three genera (Parahaemoproteus, Plasmodium, and Leucocytozoon) by amplifying and sequencing a mitochondrial DNA barcode. We detected infections in 280 birds (36.1%), sequenced 357 infections, and found a total of 99 parasite haplotypes. When compared to communities simulated from a regional pool, we observed more unique, single-mountain haplotypes and fewer haplotypes shared among three mountain ranges than expected, indicating that haemosporidian communities differ to some degree among adjacent mountain ranges. These results were robust even after pruning datasets to include only identical sets of host species, and they were consistent for two of the three haemosporidian genera. The two more distant mountain ranges were more similar to each other than the one located centrally, suggesting that the differences we detected were due to stochastic colonization-extirpation dynamics. These results demonstrate that avian haemosporidian communities of temperate-zone forests differ on relatively fine spatial scales associated with adjacent sky-islands. Null models are essential tools for detecting turnover in complex, undersampled, and poorly known systems.

ecology↗

bioRxiv2018

Ecology, Not Distance, Explains Community Composition in Parasites of Sky-Island Audubon’s Warblers

O_LIHaemosporidian parasites of birds are ubiquitous in terrestrial ecosystems, but their coevolutionary dynamics remain poorly understood. If species turnover in parasites occurs at a finer scale than species turnover in hosts, widespread hosts would encounter diverse parasites and potentially diversify as a result. Previous studies have shown that some wide-ranging hosts encounter varied haemosporidian communities throughout their range, and vice-versa. However, it remains difficult to test spatial patterns of diversity in this complex multi-host multi-parasite system because it remains inadequately surveyed.\nC_LIO_LIWe sought to understand how and why a community of avian haemosporidian parasites varies in abundance and composition across an array of eight sky islands in southwestern North America. We tested whether bird community composition, aspects of the environment, or geographic distance explain parasite species turnover in a widespread, generalist host.\nC_LIO_LIWe sampled 178 Audubons Warblers (Setophaga auduboni) along elevational transects in eight mountain ranges and screened them for haemosporidian mtDNA. We tested predictors of infection using generalized linear models (GLMs) and we tested predictors of bird- and parasite-community dissimilarity using generalized dissimilarity modeling (GDM).\nC_LIO_LIPredictors of infection differed by genus: Parahaemoproteus was predicted by elevation and climate, Leucocytozoon varied idiosyncratically among mountain ranges, and Plasmodium was unpredictable, but rare. Parasite species turnover was nearly three-fold higher than bird species turnover and was predicted by elevation, climate, and bird community composition, but not by geographic distance.\nC_LIO_LIHaemosporidian communities vary strikingly at spatial scales of hundreds of kilometers, across which the bird community varies only subtly. The finer spatial scale of turnover among parasites species implies that their ranges tend to be smaller than those of their hosts. Avian host species should encounter different parasite species in different parts of their ranges, resulting in spatially varying selection on host immune systems. Furthermore, the fact that parasite turnover was predicted by bird turnover implies that different species within a host community affect each others parasites, potentially facilitating indirect antagonistic effects.\nC_LI

ecology↗