Browsing by Author "Whelan, Nathan V."

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    Ctenophore relationships and their placement as the sister group to all other animals
    (Nature Portfolio, 2017) Whelan, Nathan V.; Kocot, Kevin M.; Moroz, Tatiana P.; Mukherjee, Krishanu; Williams, Peter; Paulay, Gustav; Moroz, Leonid L.; Halanych, Kenneth M.; Auburn University; United States Department of the Interior; US Fish & Wildlife Service; University of Alabama Tuscaloosa; University of Florida
    Ctenophora, comprising approximately 200 described species, is an important lineage for understanding metazoan evolution and is of great ecological and economic importance. Ctenophore diversity includes species with unique colloblasts used for prey capture, smooth and striated muscles, benthic and pelagic lifestyles, and locomotion with ciliated paddles or muscular propulsion. However, the ancestral states of traits are debated and relationships among many lineages are unresolved. Here, using 27 newly sequenced ctenophore transcriptomes, publicly available data and methods to control systematic error, we establish the placement of Ctenophora as the sister group to all other animals and refine the phylogenetic relationships within ctenophores. Molecular clock analyses suggest modern ctenophore diversity originated approximately 350 million years ago +/- 88 million years, conflicting with previous hypotheses, which suggest it originated approximately 65 million years ago. We recover Eupiokamis duniapae-a species with striated muscles-as the sister lineage to other sampled ctenophores. Ancestral state reconstruction shows that the most recent common ancestor of extant ctenophores was pelagic, possessed tentacles, was bio-luminescent and did not have separate sexes. Our results imply at least two transitions from a pelagic to benthic lifestyle within Ctenophora, suggesting that such transitions were more common in animal diversification than previously thought.
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    Miscues misplace sponges
    (National Academy of the Sciences, 2016) Halanych, Kenneth M.; Whelan, Nathan V.; Kocot, Kevin M.; Kohn, Andrea B.; Moroz, Leonid L.; Auburn University; University of Alabama Tuscaloosa; University of Florida
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    Rediscovery of Leptoxis compacta (Anthony, 1854) (Gastropoda: Cerithioidea: Pleuroceridae)
    (PLOS, 2012) Whelan, Nathan V.; Johnson, Paul D.; Harris, Phil M.; University of Alabama Tuscaloosa
    The Mobile River Basin is a hotspot of molluscan endemism, but anthropogenic activities have caused at least 47 molluscan extinctions, 37 of which were gastropods, in the last century. Nine of these suspected extinctions were in the freshwater gastropod genus Leptoxis (Cerithioidea: Pleuroceridae). Leptoxis compacta, a Cahaba River endemic, has not been collected for > 70 years and was formally declared extinct in 2000. Such gastropod extinctions underscore the imperilment of freshwater resources and the current biodiversity crisis in the Mobile River Basin. During a May 2011 gastropod survey of the Cahaba River in central Alabama, USA, L. compacta was rediscovered. The identification of snails collected was confirmed through conchological comparisons to the L. compacta lectotype, museum records, and radulae morphology of historically collected L. compacta. Through observations of L. compacta in captivity, we document for the first time that the species lays eggs in short, single lines. Leptoxis compacta is restricted to a single location in the Cahaba River, and is highly susceptible to a single catastrophic extinction event. As such, the species deserves immediate conservation attention. Artificial propagation and reintroduction of L. compacta into its native range may be a viable recovery strategy to prevent extinction from a single perturbation event.