Biology subjects

Dornburg, A.

Publications and source records attributed to Dornburg, A..

23 records · Page 2Linked to original sources

bioRxiv2021

Reevaluating claims of ecological speciation in Halichoeres bivittatus

Understanding the role of ecological processes in speciation has become one of the most active areas of research in marine population biology in recent decades. The traditional view was that allopatry was the primary driver of speciation in marine taxa, but the geography of the marine environment and the dispersal capabilities of many marine organisms render this view somewhat questionable. One of the earliest and most highly cited empirical examples of ecological speciation with gene flow in marine fishes is that of the slippery dick wrasse, Halichoeres bivittatus. Evidence for this cryptic or incipient speciation event was primarily in the form of a deep north-south divergence in a single mitochondrial locus, combined with a finding that these two haplotypes were associated with different habitat types in the Florida Keys and Bermuda, where they overlap. Here we examine habitat assortment in the Florida Keys using a broader sampling of populations and habitat types than were available for the original study, and find no evidence to support the claim that haplotype frequencies differ between habitat types, and little evidence to support any differences between populations. These results severely undermine claims of ecological speciation with gene flow in Halichoeres bivittatus. We argue that future claims of this type should be supported by multiple lines of evidence that illuminate potential mechanisms and allow researchers to rule out alternative explanations for spatial patterns of genetic differences.

evolutionary biology↗

bioRxiv2020

What makes Hemidactylus invasions successful? A case study on the island of Curacao.

Hemidactylus spp. (House geckos) rank among the most successful invasive reptile species worldwide. Hemidactylus mabouia in particular has become ubiquitous across tropical urban settings in the Western Hemisphere. H. mabouia’s ability to thrive in close proximity to humans has led to the rapid displacement of native geckos in urban areas, however the mechanisms driving this displacement remain understudied. Here we combine data from nitrogen and carbon stable isotopes, stomach contents, and morphometric analyses of traits associated with feeding and locomotion to test alternate hypotheses of displacement between H. mabouia and a native gecko, Phyllodactylus martini, on the island of Curaçao. Consistent with expectations of direct food resource competition, we demonstrate substantial overlap of invertebrate prey resources between the species. Additionally, we found strong evidence from both diet content and stable isotope analyses that H. mabouia acts as a vertebrate predator, preying upon P. martini as well as other native and non-native reptiles. Finally, we show that H. mabouia possesses several morphological advantages, including larger sizes in feeding-associated traits and limb proportions that could offer a propulsive locomotor advantage on vertical surfaces. Together, these findings suggest the successful establishment of H. mabouia likely involves a combination of both exploitative interspecific competition and predation. Given the ubiquity of H. mabouia, illuminating the role of this species as both a competitor and a predator casts new concerns on the ecological and demographic impacts of this widespread urban invader.Competing Interest StatementThe authors have declared no competing interest.View Full Text

zoology↗

bioRxiv2020

Infestation dynamics between parasitic Antarctic fish leeches (Piscicolidae) and their crocodile icefish hosts (Channichthyidae)

An understanding of host-parasite interactions represents an important, but often overlooked, axis for predicting how marine biodiversity may be impacted by continued environmental change over the next century. For host and parasite communities in the Southern Ocean, investigations of many major groups of parasites have largely been limited to taxonomic and phylogenetic studies, creating an urgent need for the collection of baseline ecological data if we are to detect changes in host-parasite interactions in the future. Here, we survey three species of Crocodile icefish (Notothenioidei: Channichthyidae) collected from two island archipelagos in Antarcticas South Scotia Arc region for evidence of leech infestations. Specifically, we report on infestation prevalence and intensity of three leech species (Trulliobdella bacilliformis, Trulliobdella capitis, and Nototheniobdella sawyeri) on the host fish species Chaenocephalus aceratus, Champsocephalus gunnari, and Chionodraco rastrospinosus. Additionally, we characterize spatial patterns of relative abundances of each leech species across the Elephant and South Orkney Islands, size distribution of parasitized fish, and patterns of host and attachment site specificity. Our results reveal high levels of attachment area fidelity for each leech species. These results suggest skin thickness and density of the vascular network constrain leech attachment sites and further suggest trophic transmission to be an important axis of parasitization. We also demonstrate that, while leech species appear to be clustered spatially, this clustering does not appear to be correlated with fish biomass. This study illuminates the complex interactions among fish hosts and leech parasites in the Southern Ocean and lays the groundwork for future studies of Antarctic marine leech ecology that can aid in forecasting how host-parasite interactions may shift in the face of ongoing climate change.

ecology↗

bioRxiv2019

Evolutionary analyses guide selection of model systems to investigate proto-oncogene function in ALK and LTK

Model systems to investigate oncogene-driven cancer have played an essential role in the development of therapies for cancer. However, not all systems are appropriate for all therapeutic targets. Knowing where and when proto-oncogenes and their interactors originated in evolutionary history is key to understanding which organisms can serve as models. Here we investigate two tyrosine kinase receptors that underlie tumorigenesis in cancer: anaplastic lymphoma kinase (ALK) and leukocyte tyrosine kinase (LTK). In Drosophila melanogaster, Caenorhabitis elegans, and Homo sapiens, the discovery of putative ligands Jeb, Hen-1, and AUG has the potential to accelerate the development of novel therapeutics. However, homology of these ligands and receptors is unclear. We performed an exhaustive search for their homologs spanning the metazoan tree of life. Jeb and Hen-1 were restricted to species that diverged prior to the origin of all vertebrates. No non-vertebrate species had ligands orthologous to AUG. Instead, an ancestral receptor tyrosine kinase and AUG gene were present in early vertebrates and are still solitary in lamprey; we demonstrate that the early embryonic expression of AUG in lamprey parallels its expression in model mammal systems. The presence of ALK and LTK in jawed vertebrates is an evolutionary innovation, as is a previously unrecognized functional convergence within ALK and LTK occurring between actinopterygians and sarcopterygians. Our results provide the phylogenetic context necessary for the selection of model organisms that will provide informative investigations of the biology of these critically important tyrosine kinase receptors, enabling successful therapeutic development.\n\nSignificanceThe anaplastic lymphoma kinase ALK can be oncogenically altered to become a driver of several malignancies, including non-small-cell lung cancer and anaplastic large-cell lymphomas. The development of therapeutics targeting this gene depend on the discovery of its interacting partner ligands in relevant model organisms. ALK is found across most major animal groups including mammals, fishes, and invertebrates. Correspondly, several candidate ligands for ALK and its duplicate LTK have been advanced by research in model species. However their homology to the human ligands and therefore their potential to guide therapeutic development is unknown. Our comparative evolutionary analysis revealed which model organisms had functional receptor-ligand pairings that are informative regarding the role of these genes in human tumorigenesis.

cancer biology↗

bioRxiv2018

Historical contingency shapes adaptive radiation in Antarctic fishes

Adaptive radiation illustrates the links between ecological opportunity, natural selection, and the generation of biodiversity (1). Central to adaptive radiation is the association between a diversifying lineage and the evolution of key traits that facilitate the utilization of novel environments or resources (2, 3). However, is not clear whether adaptive evolution or historical contingency is more important for the origin of key phenotypic traits in adaptive radiation (4, 5). Here we use targeted sequencing of >250,000 loci across 46 species to examine hypotheses concerning the origin and diversification of key traits in the adaptive radiation of Antarctic notothenioid fishes. Contrary to expectations of adaptive evolution, we show that notothenioids experienced a punctuated burst of genomic diversification and evolved key skeletal modifications before the onset of polar conditions in the Southern Ocean. We show that diversifying selection in pathways associated with human skeletal dysplasias facilitates ecologically important variation in buoyancy among Antarctic notothenioid species, and demonstrate the sufficiency of altered trip11, col1a2 and col1a1 function in zebrafish (Danio rerio) to phenocopy skeletal reduction in Antarctic notothenioids. Rather than adaptation being driven by the cooling of the Antarctic (6), our results highlight the role of exaptation and historical contingency in shaping the adaptive radiation of notothenioids. Understanding the historical and environmental context for the origin of key traits in adaptive radiations provides context in forecasting the effects of climate change on the stability and evolvability of natural populations.

evolutionary biology↗