Biology subjects

Sorenson, M. D.

Publications and source records attributed to Sorenson, M. D..

6 recordsLinked to original sources

bioRxiv2025

Inbreeding depression and tuberculosis susceptibility in the critically endangered white-winged wood duck Asarcornis scutulata

Captive breeding can be a key component of species conservation strategies, but also exposes these rare species to novel environments including the pathogen landscape. The critically endangered white-winged wood duck (WWWD) Asarcornis scutulata has experienced substantial population declines, local extirpations and fragmentation of its former range in South-East Asia, making it one of the rarest birds in the world. Like other rare species, WWWD declines have led to the initiation of captive breeding programs, but these have been hampered by the WWWDs high susceptibility to Mycobacterium avium, avian tuberculosis (TB). In this study we describe genome-wide patterns of diversity to understand the WWWDs demographic and phylogeographic history, inbreeding in the wild and in captivity, and the causes of TB susceptibility. Captive birds, which originated from northeast India, are genetically differentiated from wild birds sampled in Sumatra, Indonesia, likely reflecting long-standing phylogeographic structure. Demographic analyses revealed that long-term (Pleistocene) population declines preceded anthropogenic declines, a pattern shared with other codistributed, forest-dependent species. All sampled WWWD populations had extremely low genetic diversity but wild-sampled birds retained higher Major Histocompatibility Complex (MHC) diversity, reflecting important functional diversity in the wild. Genetic diversity has eroded over time in captivity and importantly, birds with higher levels of inbreeding succumb earlier to TB infections, suggesting inbreeding depression. Finally, by comparing gene expression between susceptible WWWD and resistant redhead ducks Aythya americana we identify possible mechanisms of TB susceptibility in WWWD. Altogether our study provides genomically-guided objectives for future management and a cautionary tale for ex-situ conservation.

evolutionary biology↗

bioRxiv2025

Genomic resources for comparative analyses of obligate avian brood parasitism

Examples of convergent evolution, wherein distantly related organisms evolve similar traits, including behaviors, underscore the adaptive power of natural selection. In birds, obligate brood parasitism, and the associated loss of parental care behaviors, has evolved independently in seven different lineages, though little is known about the genetic basis of the complex suite of traits associated with this rare life history strategy. We generated genome assemblies for ten brood parasitic species plus eight species representatives of their parental/nesting outgroups. This includes nine long-read chromosome-level assemblies, with scaffold N50 sizes ranging from 38.1 to 72.6 MB, and gene representation completeness measures >97%. Leveraging this new catalog of avian genomes, we constructed clade-level alignments that reveal variation in chromosomal synteny, provide first-time or improved annotations of protein-coding and non-coding genes, and define cross-species ortholog reference sets. We also refine estimates for the timing of the seven independent origins of brood parasitism, ranging from recent events such as 1.6 to 4.5 million years ago in Molothrus cowbirds to much earlier origins over 30 million years ago in two of the three cuckoo lineages. These genomic resources lay the foundation for investigating the genetic and genomic underpinnings of brood parasitism, including the loss of parental care, shifts in mating systems, perhaps resulting in heightened sperm competition, elevated annual fecundity, improved spatial cognition related to nest-finding, and the diverse adaptations shaped by intense coevolution with host species.

genomics↗

bioRxiv2025

Comparative population genomics reveals convergent adaptation across independent origins of avian obligate brood parasitism

Parental care evolved as a strategy to enhance offspring survival at the cost of reduced fecundity. While most birds provide parental care, obligate brood parasites circumvent this tradeoff by exploiting the parental behavior of other species. This radical life history shift has occurred independently seven times in birds, offering an outstanding opportunity to test for convergent patterns of adaptation in the genome. To investigate genomic adaptations underlying this transition, we analyzed population resequencing data from five brood-parasitic species across three independent origins of brood parasitism -- three parasitic finches (family Viduidae), a honeyguide, and a cowbird -- alongside related non-parasitic (parental) outgroups. Using the McDonald-Kreitman framework, we found evidence for repeated adaptation in genes involved in spermatogenesis and sperm function in multiple parasitic clades, but not in the matched outgroup parental species. This is consistent with evidence for increased male-male competition in parasitic lineages as a result of the loss of parental care. In addition, we detected selective sweeps near genes associated with nervous system development in parasitic lineages, perhaps associated with improved spatial cognition that aids brood parasites in locating, monitoring, and laying eggs in host nests. Finally, we found more selective sweeps in host-specific brood parasites as compared to parental outgroups, perhaps reflecting ongoing host-parasite coevolutionary arms races.

evolutionary biology↗

bioRxiv2024

Dietary specialization drives adaptation, convergence, and integration across the cranial and appendicular skeleton in Waterfowl (Anseriformes).

Convergence provides strong evidence for adaptive evolution as it reflects shared adaptive responses to the same selection pressures. The waterfowl (order Anseriformes) are an ideal group in which to study convergent evolution as they have repeatedly evolved morphotypes putatively correlated with diet (i.e., dabbler, grazer, diver). Here, we construct the most robust evolutionary hypothesis to date for waterfowl and reveal widespread morphological convergence across the order. We quantified the shape of the skull and hindlimb elements (femur, tibiotarsus, and tarsometatarsus) of 118 species of extant waterfowl using geometric morphometrics. Multivariate generalized evolutionary models provide strong support for a relationship between dietary ecology and skull shape, and evidence for convergent evolution across lineages that share dietary niches. Foraging behavior better explained the evolution of hindlimb shape, but diet still contributed significantly. We also find preliminary evidence for integration across all three measured hindlimb elements with each other and with the skull. We demonstrate that dietary ecology drives morphological convergence within waterfowl, that this convergent evolution involves multiple integrated skeletal structures, and that morphological changes are associated with shifts in the rate of phenotypic evolution.

evolutionary biology↗

bioRxiv2022

Patterns of lineage-specific genome evolution in the brood parasitic black-headed duck (Heteronetta atricapilla)

Occurring independently at seven separate origins across the avian tree of life, obligate brood parasitism is a unique suite of traits observed in only approximately 1% of all bird species. Obligate brood parasites exhibit varied physiological, morphological, and behavioural traits across lineages, but common among all obligate brood parasites is that the females lay their eggs in the nest of other species. Unique among these species is the black-headed duck (Heteronetta atricapilla), a generalist brood parasite that is the only obligate brood parasite among waterfowl. This provides an opportunity to assess evolutionary changes in traits associated with brood parasitism, notably the loss of parental care behaviours, with an unspecialized brood parasite. We generated new high-quality genome assemblies and genome annotations of the black-headed duck and three related non-parasitic species (freckled duck, African pygmy-goose, and ruddy duck). With these assemblies and existing public genome assemblies, we produced a whole genome alignment across Galloanserae to identify conserved non-coding regions with atypical accelerations in the black-headed duck and coding genes with evidence of positive selection, as well as to resolve uncertainties in the duck phylogeny. To complement these data, we sequenced a population sample of black-headed ducks, allowing us to conduct McDonald-Kreitman tests of lineage-specific selection. We resolve the existing polytomy between our focal taxa with concordance from coding and non-coding sequences, and we observe stronger signals of evolution in non-coding regions of the genome than in coding regions. Collectively, the new high-quality genomes, comparative genome alignment, and population genomics provide a detailed picture of genome evolution in the only brood parasitic duck.

evolutionary biology↗

bioRxiv2019

Phylogenomics clarifies biogeographic and evolutionary history, and conservation status of West Indian tremblers and thrashers (Aves: Mimidae)

The West Indian avifauna has provided fundamental insights into island biogeography, taxon cycles, and the evolution of avian behavior. Our interpretations, however, rely on robust hypotheses of evolutionary relationships and consistent conclusions about taxonomic status in groups with many endemic island populations. Here we present a phylogenetic study of the West Indian thrashers, tremblers, and allies, an assemblage of at least 5 species found on 29 islands, which is considered the archipelagos only avian radiation. We improve on previous phylogenetic studies of this group by using double-digest restriction site-associated DNA sequencing (ddRAD-seq) to broadly sample loci scattered across the nuclear genome. A variety of analyses, based on either nucleotide variation in 2,223 loci that were recovered in all samples or on 13,282 loci that were confidently scored as present or absent in all samples, converged on a single well-supported phylogenetic hypothesis. In contrast to previous studies, we found that the resident West Indian taxa form a monophyletic group, exclusive of the Neotropical-Nearctic migratory Gray Catbird Dumetella carolinensis, which breeds in North America. Earlier studies indicated that the Gray Catbird was nested within a clade of island resident species. Instead, our findings imply a single colonization of the West Indies without the need to invoke a subsequent reverse colonization of the mainland by West Indian taxa. Furthermore, our study is the first to sample both endemic subspecies of the endangered White-breasted Thrasher Ramphocinclus brachyurus. We find that these subspecies have a long history of evolutionary independence with no evidence of gene flow, and are as genetically divergent from each other as other genera in the group. These findings support recognition of R. brachyurus (restricted to Martinique) and the Saint Lucia Thrasher R. sanctaeluciae as two distinct, single-island endemic species, and indicate the need to re-evaluate conservation plans for these taxa. Our results demonstrate the utility of phylogenomic datasets for generating robust systematic hypotheses.

evolutionary biology↗