Matt Arnegard, Ph.D.

NIH Post-Doctoral Research Fellow

• Ph.D., Neurobiology & Behavior
  Cornell University
  

research interests | peer reviewed publications | curriculum vitae, résumé | video of electric fish behavior | science writing and editorial contributions to Science Spotlight (a science news periodical)

Research Interests

The evolution of biological diversity depends on three interdependent processes: (i) adaptation within lineages; (ii) the splitting of lineages, or speciation; and (iii) the origin of novelty.  While evolutionary biologists have made much progress in understanding the ecological causes of speciation in many different systems, the field has barely begun to uncover the genetic basis of ecological speciation.  I am particularly interested in studying genes underlying sexual signals, mating preferences, and other behaviors related to pre-mating reproductive isolation.  These aspects of animal speciation merge naturally with my broader interests in the evolution of animal communication.  Understanding the origins of new modes of communication requires that we also understand, more generally, how innovative structures and physiological systems evolve de novo.  Investigating genetic changes associated with novelty remains one of evolutionary biology’s greatest challenges, with little insight into this process being offered by well-investigated cases of regressive trait loss.

Radiographs of 'limnetics' (above) and 'benthics' (below) of the Gasterosteus aculeatus species complex. Reproductively-isolated benthics and limnetics have evolved independently in several isolated lakes of British Columbia. Photos by Matt Arnegard.

Currently, my main project with Katie Peichel, Dolph Schluter, and Gina Conte investigates the genetic basis of parallel ecological speciation between benthic and limnetic sticklebacks.  I started this project with Dolph at the University of British Columbia (UBC) in 2007; more recently, I received postdoctoral NRSA funds from NIH to continue this project with Katie at the Fred Hutchinson Cancer Research Center in Seattle, in collaboration with Dolph and Gina at UBC.  In the Schluter lab, Gina and I have created a number of mapping populations of F2 intercross hybrids between sympatric benthic and limnetic sticklebacks endemic to each of two lakes in British Columbia (Paxton and Priest: see above).  The hybrids were reared under fully natural conditions in experimental ponds at UBC.  We are measuring a number of F2 phenotypes related to important ecological differences between the parental species (e.g., morphology, stable isotopes of carbon and nitrogen, habitat choice).  In the summer of 2011, we completed fieldwork needed to measure behaviors contributing to pre-mating reproductive isolation: e.g., nesting habitat choice of F2 males; and F2 female mating preferences for benthic versus limnetic males assessed by genetically fingerprinting offspring.  Recently, our project received additional NIH funds needed to genotype all F2s using an array of 1,536 SNPs.  We aim to determine the genetic architectures underlying ecological speciation for species pairs in both Paxton and Priest Lakes.  We are particularly interested in asking whether the same QTL – either pleiotropic or closely linked genes – simultaneously govern ecological traits under divergent natural selection and behaviors contributing to reproductive isolation.  Such a genetic architecture would favor rapid speciation under gene flow.  We also plan to test whether there is parallelism in the genetic architectures of species differences between the two lakes.

Experimental pond facility at UBC. (Left) Nicole Bedford about to help me and Gina make one of our regular collections of eggs from the nests of territorial males, which we did in 2009 and 2011. (Right) Territorial males guarding their nests, showing the realistic, divergent nesting habitats that we established in these ponds (Paxton benthic male above, Paxton limnetic male below; photos by N. Bedford).

In addition to research on speciation genetics, I also investigate the role of communication in speciation, the origins of novel communication systems, and the effects of neural innovations on the tempo and breadth of species radiation.  I do so using weakly-electric fishes.  In one of the most remarkable cases of convergence in the Animal Kingdom, speciose groups of electric fish (mormyroids and gymnotiforms) arose independently in Africa and South America, respectively.  I recently led an effort to test whether a duplicated voltage-gated sodium channel gene (Scn4aa) directly contributed to independently-derived electric organs in mormyroids and gymnotiforms.  Myogenic electric organs (EOs) produce electrical communication signals in both groups.  EO is composed of cells called electrocytes, which are developmentally derived from skeletal muscle myoblasts and show striking similarities in structure and physiology between groups.  To function, electrocytes require voltage-gated sodium channels (see fig. below), two paralogs of which (Scn4aa and Scn4ab) I and co-authors Derrick Zwickl, Ying Lu, and Harold Zakon investigated in a large number of electrogenic and non-electrogenic fishes.  We tested three predictions of our hypothesis that Scn4aa directly contributed to the parallel origins of this novel organ of communication.  Our findings provide evidence in support of all three predictions, demonstrating that gene duplication can contribute to strikingly similar innovations even after extremely long waiting periods between gene duplication and the origins of novelty.  We also found that amino acid replacements caused by diversifying natural selection on Scn4aa in electric fish occur at the same residues where deleterious substitutions in paralogs cause cardiac or neurological disease in humans (e.g., long QT syndrome).  Read more about these findings in Arnegard et al., 2010 (PNAS 107: 22172-22177). 

Voltage-gated sodium channel alpha-subunit. Each domain contains six transmembrane segments (yellow). The fourth segments (S4) contain positively charged residues that serve as voltage sensors. P-loops between S5 and S6 form the sodium-selective outer pore. An inactivation gate in the linker between domains III and IV mediates fast channel inactivation at the inner pore via a conserved binding particle (IFM across many species).

The origins of electrical communication are examples of ‘key innovations’ that have directly contributed to the independent evolutionary radiations of gymnotiforms and mormyroids.  I also recently led a project showing that electric organ discharges (EODs) have evolved much faster than ecological traits in the Paramormyrops species flock of mormyroid electric fishes radiating in west-Central Africa (see fig. below).  Based on the prior work of myself and others, we know that EODs function as courtship signals underlying mate recognition, and that EODs exhibit dramatic sexual dimorphism in many mormyroids, including Paramormyrops.  Together, these findings implicate sexual selection as a potentially important driver of mormyroid speciation (within specific lineages).  Given certain features of the electrical communication modality, our findings also suggest that ‘opportunity’ in the communication landscape can augment rates of phenotypic divergence and species radiation by sexual selection, analogous to the well established role of ‘ecological opportunity’ in adaptive radiation.  Read more about this research in Arnegard et al., 2010 (Am. Nat. 176: 335-356).  Co-authors: Pete McIntyre, Luke Harmon, Miriam Zelditch, Will Crampton, Justin Davis, John Sullivan, Sébastien Lavoué, and Carl Hopkins.

One of many assemblages of the Paramormyrops species flock of mormyroids from Gabon, Central Africa. Shown here are the six sympatric species/morphs present in the Okano River at the abandoned Village 'Na'. Oscilloscope tracings of their electric signals are shown to the right (time scale = 1 msec). Image by Matt Arnegard and Duncan Reid.©

Peer-Reviewed Publications

Lavoué, S., M. Miya, M. E. Arnegard, J. P. Sullivan, C. D. Hopkins, and M. Nishida. In Revision. Comparable ages for the independent origins of electrogenesis in African and South American weakly electric fishes. In Revision for PLoS ONE.
Carlson, B. A. and M. E. Arnegard. 2011. Neural innovations and the diversification of African weakly electric fishes. Communicative & Integrative Biology 4: 720-725.
Carlson, B. A., S. M. Hasan, M. Hollmann, D. B. Miller, L. J. Harmon, and M. E. Arnegard. 2011. Brain evolution triggers increased diversification of electric fishes. Science 332: 583-586.
Gallant, J. R., M. E. Arnegard, J. P. Sullivan, B. A. Carlson, and C. D. Hopkins. 2011. Signal variation and its morphological correlates in Paramormyrops kingsleyae provide insight into the evolution of electrogenic signal diversity in mormyrid electric fish. J. Comp. Physiol. A 197: 799-817.
Lavoué, S., M. Miya, M. E. Arnegard, P. B. McIntyre, V. Mamonekene, and M. Nishida. 2011. Remarkable morphological stasis in an extant vertebrate despite tens of millions of years of divergence. Proc. R Soc. B 278: 1003-1008.
Arnegard, M. E., D. J. Zwickl, Y. Lu, and H. H. Zakon. 2010. Old gene duplication facilitates origin and diversification of an innovative communication system—twice. Proc. Natl. Acad. Sci. USA 107: 22172-22177. (Selected by the Faculty of 1000 and PNAS featured article: Brodie, E.D., III. 2010. How an ancient genome duplication electrified modern fish. PNAS 107: 21953-21954.)
Oliver, M. K. and M. E. Arnegard. 2010. A new genus for Melanochromis labrosus, a problematic Lake Malawi cichlid with hypertrophied lips (Teleostei: Cichlidae). Ichthyol. Explor. Freshwaters 21: 209-232.
Arnegard, M. E., P. B. McIntyre, L. J. Harmon, M. L. Zelditch, W. G. R. Crampton, J. K. Davis, J. P. Sullivan, S. Lavoué, and C. D. Hopkins. 2010. Sexual signal evolution outpaces ecological divergence during electric fish species radiation. Am. Nat. 176: 335-356.  (featured in Nature: Leal, M. and J. B. Losos. 2010. Communication and speciation. Nature 467: 159-160.)
Lavoué, S., J. P. Sullivan, and M. E. Arnegard. 2010. African weakly electric fishes of the genus Petrocephalus (Osteoglossomorpha: Mormyridae) of Odzala National Park, Republic of the Congo (Lékoli River, Congo River basin) with description of five new species. Zootaxa 2600: 1-52.
Arnegard, M. E. 2009. Ongoing ecological divergence in an emerging genomic model. Mol. Ecol. 18: 2926-2929.
Lavoué*, S., M. E. Arnegard*, J. P. Sullivan, and C. D. Hopkins. 2008. Petrocephalus of Odzala offer insights into evolutionary patterns of signal diversification in the Mormyridae, a family of weakly electrogenic fishes from Africa. J. Physiol.—Paris 102: 322-339.
Lavoué, S., J. P. Sullivan, M. E. Arnegard, and C. D. Hopkins. 2008. Differentiation of morphology, genetics and electric signals in a region of sympatry between sister species of African electric fish (Mormyridae). J. Evol. Biol. 21: 1030-1045.
Markert*, J. A. and M. E. Arnegard*. 2007. Size-dependent use of territorial space by a rock-dwelling cichlid fish. Oecologia 154: 611-621.
Arnegard, M. E., B. S. Jackson, and C. D. Hopkins. 2006. Time-domain signal divergence and discrimination without receptor modification in sympatric morphs of electric fishes. J. Exp. Biol. 209: 2182-2198.
Arnegard, M. E. and B. A. Carlson. 2005. Electric organ discharge patterns during group hunting by a mormyrid fish. Proc. R. Soc. B 272: 1305-1314.
Arnegard, M. E., S. M. Bogdanowicz, and C. D. Hopkins. 2005. Multiple cases of striking genetic similarity between alternate electric fish signal morphs in sympatry. Evolution 59: 324-343.
Sullivan, J. P., S. Lavoué, M. E. Arnegard, and C. D. Hopkins. 2004. AFLPs resolve phylogeny and reveal mitochondrial introgression within a species flock of African electric fish (Mormyroidea: Teleostei). Evolution 58: 825-841.
Arnegard, M. E. and A. S. Kondrashov. 2004. Sympatric speciation by sexual selection alone is unlikely. Evolution 58: 222-237.
Arnegard, M. E. and C. D. Hopkins. 2003. Electric signal variation among seven blunt-snouted Brienomyrus species (Teleostei: Mormyridae) from a riverine species flock in Gabon, Central Africa. Environ. Biol. Fishes 67: 321-339.
Arnegard, M. E. and J. Snoeks. 2001. New three-spotted cichlid species with hypertrophied lips (Teleostei: Cichlidae) from the deep waters of Lake Malawi/Nyasa, Africa. Copeia 2001: 705-717.  (With a Chichewa Abstract, translated from English, by Dalitso Richard Kafumbata.)
Markert, J. A., P. D. Danley, and M. E. Arnegard. 2001. New markers for new species: microsatellite loci and the East African cichlids. Trends Ecol. Evol. 16: 100-107.
Danley, P. D., J. A. Markert, M. E. Arnegard, and T. D. Kocher. 2000. Divergence with gene flow in the rock-dwelling cichlids of Lake Malawi. Evolution 54: 1725-1737.
Markert, J. A., M. E. Arnegard, P. D. Danley, and T. D. Kocher. 1999. Biogeography and population genetics of the Lake Malawi cichlid Melanochromis auratus: habitat transience, philopatry and speciation. Mol. Ecol. 8: 1013-1026.
Arnegard, M. E., J. A. Markert, P. D. Danley, J. R. Stauffer, Jr., A. J. Ambali, and T. D. Kocher. 1999. Population structure and colour variation of the cichlid fish Labeotropheus fuelleborni Ahl along a recently formed archipelago of rocky habitat patches in southern Lake Malawi. Proc. R. Soc. Lond. B 266: 119-130.
Arnegard, M. E., P. V. McCormick, and J. Cairns, Jr. 1998. Effects of copper on periphyton communities assessed in situ using chemical-diffusing substrates. Hydrobiologia 385: 163-170.
Stauffer, J. R. Jr., M. E. Arnegard, M. Cetron, J. J. Sullivan, L. A. Chitsulo, G. F. Turner, S. Chiotha, and K. R. McKaye. 1997. Controlling vectors and hosts of parasitic diseases using fishes: a case history of schistosomiasis in Lake Malawi. BioScience 47: 41-49.
Cairns, J. Jr., J. R. Bidwell, and M. E. Arnegard. 1996. Toxicity testing with communities: microcosms, mesocosms, and whole-system manipulations. Rev. Environ. Contam. Tox. 147: 45-69.

*The first two authors contributed equally to these studies.

Video of Electric Fish Behavior — filmed under natural conditions in Africa.

Arnegard, M. E. 2011. Greater focus for fuzzy epigenomes. Dec-12 issue of Science Spotlight: Henikoff lab devises a new strategy for characterizing epigenomes at single base-pair resolution, promising to yield many insights into nucleosome dynamics.

Arnegard, M. E. 2011. Certain beta-HPVs target p300 for degradation, likely disrupting many cellular signaling pathways. Nov-14 issue of Science Spotlight: Galloway lab study suggests that beta-human papillomaviruses may induce skin cancer by a slightly different route than their better-known alpha-cousins.

Arnegard, M. E. 2011. Mathematical model for controllability of dynamic genome networks. Nov-14 issue of Science Spotlight: Development of a systems theory framework for cell differentiation sheds light on dynamic network control, in general, and may one day help to redirect cancer cells along non-pathological trajectories.