Sotka Erik E.

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Erik E.

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  • Article
    Can diversifying selection be distinguished from history in geographic clines? A population genomic study of killifish (Fundulus heteroclitus)
    (Public Library of Science, 2012-09-26) Strand, Allan E. ; Williams, Larissa M. ; Oleksiak, Marjorie F. ; Sotka, Erik E.
    A common geographical pattern of genetic variation is the one-dimensional cline. Clines may be maintained by diversifying selection across a geographical gradient but can also reflect historical processes such as allopatry followed by secondary contact. To identify loci that may be undergoing diversifying selection, we examined the distribution of geographical variation patterns across the range of the killifish (Fundulus heteroclitus) in 310 loci, including microsatellites, allozymes, and single nucleotide polymorphisms. We employed two approaches to detect loci under strong diversifying selection. First, we developed an automated method to identify clinal variation on a per-locus basis and examined the distribution of clines to detect those that exhibited signifcantly steeper slopes. Second, we employed a classic -outlier method as a complementary approach. We also assessed performance of these techniques using simulations. Overall, latitudinal clines were detected in nearly half of all loci genotyped (i.e., all eight microsatellite loci, 12 of 16 allozyme loci and 44% of the 285 SNPs). With the exception of few outlier loci (notably mtDNA and malate dehydrogenase), the positions and slopes of Fundulus clines were statistically indistinguishable. The high frequency of latitudinal clines across the genome indicates that secondary contact plays a central role in the historical demography of this species. Our simulation results indicate that accurately detecting diversifying selection using genome scans is extremely difficult in species with a strong signal of secondary contact; neutral evolution under this history produces clines as steep as those expected under selection. Based on these results, we propose that demographic history can explain all clinal patterns observed in F. heteroclitus without invoking natural selection to either establish or maintain the pattern we observe today.
  • Article
    Supporting Spartina: Interdisciplinary perspective shows spartina as a distinct solid genus
    (Ecological Society of America, 2019-09-19) Bortolus, Alejandro ; Adam, Paul ; Adams, Janine B. ; Ainouche, Malika L. ; Ayres, Debra ; Bertness, Mark D. ; Bouma, Tjeerd J. ; Bruno, John F. ; Caçador, Isabel ; Carlton, James T. ; Castillo, Jesus M. ; Costa, Cesar S.B. ; Davy, Anthony J. ; Deegan, Linda A. ; Duarte, Bernardo ; Figueroa, Enrique ; Gerwein, Joel ; Gray, Alan J. ; Grosholz, Edwin D. ; Hacker, Sally D. ; Hughes, A. Randall ; Mateos‐Naranjo, Enrique ; Mendelssohn, Irving A. ; Morris, James T. ; Muñoz‐Rodríguez, Adolfo F. ; Nieva, Francisco J.J. ; Levin, Lisa A. ; Li, Bo ; Liu, Wenwen ; Pennings, Steven C. ; Pickart, Andrea ; Redondo‐Gómez, Susana ; Richardson, David M. ; Salmon, Armel ; Schwindt, Evangelina ; Silliman, Brian ; Sotka, Erik E. ; Stace, Clive ; Sytsma, Mark ; Temmerman, Stijn ; Turner, R. Eugene ; Valiela, Ivan ; Weinstein, Michael P. ; Weis, Judith S.
    In 2014, a DNA‐based phylogenetic study confirming the paraphyly of the grass subtribe Sporobolinae proposed the creation of a large monophyletic genus Sporobolus, including (among others) species previously included in the genera Spartina, Calamovilfa, and Sporobolus. Spartina species have contributed substantially (and continue contributing) to our knowledge in multiple disciplines, including ecology, evolutionary biology, molecular biology, biogeography, experimental ecology, biological invasions, environmental management, restoration ecology, history, economics, and sociology. There is no rationale so compelling to subsume the name Spartina as a subgenus that could rival the striking, global iconic history and use of the name Spartina for over 200 yr. We do not agree with the subjective arguments underlying the proposal to change Spartina to Sporobolus. We understand the importance of both the objective phylogenetic insights and of the subjective formalized nomenclature and hope that by opening this debate we will encourage positive feedback that will strengthen taxonomic decisions with an interdisciplinary perspective. We consider that the strongly distinct, monophyletic clade Spartina should simply and efficiently be treated as the genus Spartina.
  • Preprint
    The role of multixenobiotic transporters in predatory marine molluscs as counter-defense mechanisms against dietary allelochemicals
    ( 2010-05-14) Whalen, Kristen E. ; Sotka, Erik E. ; Goldstone, Jared V. ; Hahn, Mark E.
    Multixenobiotic transporters have been extensively studied for their ability to modulate the disposition and toxicity of pharmacological agents, yet their influence in regulating the levels of dietary toxins within marine consumers has only recently been explored. This study presents functional and molecular evidence for multixenobiotic transporter-mediated efflux activity and expression in the generalist gastropod Cyphoma gibbosum, and the specialist nudibranch Tritonia hamnerorum, obligate predators of chemically defended gorgonian corals. Immunochemical analysis revealed that proteins with homology to permeability glycoprotein (P-gp) were highly expressed in T. hamnerorum whole animal homogenates and localized to the apical tips of the gut epithelium, a location consistent with a role in protection against ingested prey toxins. In vivo dye assays with specific inhibitors of efflux transporters demonstrated the activity of P-gp and multidrug resistance-associated protein (MRP) families of ABC transporters in T. hamnerorum. In addition, we identified eight partial cDNA sequences encoding two ABCB and two ABCC proteins from each molluscan species. Digestive gland transcripts of C. gibbosum MRP-1, which have homology to vertebrate glutathione-conjugate transporters, were constitutively expressed regardless of gorgonian diet. This constitutive expression may reflect the ubiquitous presence of high affinity substrates for C. gibbosum glutathione transferases in gorgonian tissues likely necessitating export by MRPs. Our results suggest that differences in multixenobiotic transporter expression patterns and activity in molluscan predators may stem from the divergent foraging strategies of each consumer.