University of Vermont

The College of Arts and Sciences

Department of Biology

Faculty - Ingi Agnarsson

Ingi Agnarsson

Ingi Agnarsson,

Assistant Professor
  • Ph.D., George Washington University, 2004
  • Research Associate (2004-present) Smithsonian Institution
  • Assistant Professor (2008-2012) University of Puerto Rico
  • Assistant Professor (2012-present) University of Vermont
Area of expertise


Contact Information
Email: Ingi Agnarsson

Office Hours: Tue 2:15-4:00, or by appointment
Marsh Life Science Building, Rm 316
Phone: (802) 656-0460

Dr. Agnarsson's LAB

Island Biogeography Link


I’m an evolutionary biologist working on various fronts. My main research applies phylogenetics, and population genetics to address evolutionary questions with a focus on spiders. Current topics include evolution of sociality in spiders, evolutionary biomechanical of spider silk, and a large project on the biogeography of the Caribbean and the role of dispersal in diversification.

Selected Publications

  • Agnarsson I, Cheng R-C, Kuntner M. 2014. A multi-clade test supports the intermediate dispersal model of biogeography. PLoS One9(1) e86780.
  • Rheims CA, Agnarsson I, Alayón Garcia G. 2014. Description of the male of Yabisi guaba (Araneae: Eresoidea: Hersiliidae). Zoologia 31: 405-407.
  • Cala-Riquelme F, Agnarsson I. 2014. New species of Otiothops MacLeay (Araneae: Palpimanidae: Otiothiopinae) from Cuba. Arachnology 16: 193-194.
  • Bloom T, Binford G, Alayon G, Esposito L, **Peterson I, **Nishida A, **Loubet-Senear K, Agnarsson I. 2014. Discovery of two new species of eyeless spiders within a single Hispaniola cave. Journal of Arachnology 42: 148-154. [0.73; 43/74 (Entomology)]
  • Bond JE, *Garrison NL, *Hamilton CA, Godwin RL, Hedin M, Agnarsson I. 2014. Phylogenomics resolves a spider backbone phylogeny and rejects a prevailing paradigm for orb web evolution. Current Biology 24: 1765–1771. [9.49; 19/289 (Biochemistry and Molecular Biology)].
  • Agnarsson I. 2014. Félagslyndar köngulær á þróunarfræðilegum blindgötum. Náttúrufræðingurinn 84: 132-140. [invited peer-reviewed public science paper, in Icelandic with English abstract: ‘Social spiders on evolutionary blind alleys’]
  • Lopez-Osorio, Pickett KM, Carpenter JM, Ballif BA, Agnarsson I. 2014. Phylogenetic relationships of yellowjackets inferred from nine loci (Hymenoptera: Vespidae, Vespinae, Vespula and Dolichovespula). Molecular Phylogenetics and Evolution73: 190-201
  • McHugh A, Yablonsky A, Binford G, Agnarsson I. 2014. Molecular phylogenetics of Caribbean Micrathena (Araneae: Araneidae) suggests multiple colonization events and single island endemism. Invertebrate Systematics, OnlineEarly.
  • Agnarsson I, Rayor L. 2013. A molecular phylogeny of the Australian huntsman spiders (Sparassidae, Deleninae): implications for taxonomy and social behaviour. Molecular Phylogenetics and Evolution 69: 895-905
  • Majer M, Agnarsson I, Svenning JC, BildeT. 2013. Social species in the spider genus Anelosimus occur in wetter, more productive habitats than non-social species. Naturwissenschaften 100:1031-1040
  • Kuntner M, Arnedo M, Trontelj P, Lokovšek T, Agnarsson I. 2013. A molecular phylogeny of nephilid spiders: Evolutionary history of a model lineage. Molecular Phylogenetics and Evolution 69: 961-979
  • Peng P, Blamires SJ, Agnarsson I, Lin HC, Tso I-M. 2013. A colour-mediated mutualism between two arthropod predators. Current Biology 23: 1-5
  • Agnarsson I, Coddington JA, Kuntner M. 2013. Systematics – progress in the study of spider diversity and evolution. In: Spider Research in the 21st Century (Ed. Penney D) chapter 2, pp 58-111.
  • Agnarsson I, Avilés L, Maddison WP. 2013. Loss of genetic variability in social spiders: genetic and phylogenetic consequences of population subdivision and inbreeding. Journal of Evolutionary Biology 26: 27-37
  • Agnarsson I, Gregorič M, Blackledge TA, Kuntner M. 2013. The phylogenetic placement of Psechridae and the convergent origin of orb-like spider webs. Journal of Zoological Systematics and Evolutionary Research 51: 100-106
  • Grinsted L, Agnarsson I, Bilde T. 2012. Mixed-species colonies of theridiid spiders show extended maternal care and interspecific brood adoption. Naturwissenschaften­ 99: 1021-1030
  • Blackledge TA, Kuntner M, Agnarsson I. 2012. Biomaterial evolution parallels behavioral innovation in the origin of orb-like spider webs. Scientific Reports 2: 833
  • Agnarsson I, Kuntner M. 2012. The Generation of a Biodiversity Hotspot: Biogeography and Phylogeography of the Western Indian Ocean Islands. In Kesara Anamthawat-Jonsson (Ed.): Current Topics in Phylogenetics and Phylogeography of Terrestrial and Aquatic Systems. Rijeka: In Tech Publishers, pp. 33-82. ISBN 978-953-51-0217-5
  • Agnarsson I. 2012. Systematics of new subsocial and solitary Australasian Anelosimus species (Araneae, Theridiidae). Invertebrate Systematics 26: 1-16.
  • Agnarsson I, Kuntner M, Blackledge TA. Darwin’s bark spider. 2012. In: McGraw-Hill Encyclopedia of Science and Technology. V. 11. New York, McGraw-Hill, pp. 52-54.
  • Blackledge TA, Kuntner M, Agnarsson I. 2011. The form and function of spider orb webs: evolution from silk to ecosystems. In Jérôme Casas, editor: Advances in Insect Physiology 41: 175-262, Burlington: Academic Press.
  • Kuntner M, Agnarsson I. 2011. Phylogeography of a successful aerial disperser: the golden orb spider Nephila on Indian Ocean islands. BMC Evolutionary Biology 11: 119.
  • May-Collado LJ, Agnarsson I. 2011. Phylogenetic analysis of conservation priorities for aquatic mammals and their terrestrial relatives. PLoS One 6(7): 1-10, e22562. doi:10.1371/journal.pone.0022562
  • Kuntner M, Agnarsson I. 2011. Biogeography and diversification of hermit spiders on Indian Ocean islands (Nephilidae: Nephilengys). Molecular Phylogenetics and Evolution 59: 477-488
  • Agnarsson I, Zambrana-Torrelio CM, Flores Saldaña NP, May-Collado LJ. 2011. A time-calibrated species-level phylogeny of bats (Chiroptera, Mammalia). PLoS Currents: Tree of Life. Version 44. 2011 Jan 4 [revised 2011 Feb 4]. Available from:
  • Gregorič M, Agnarsson I, Blackledge TA, Kuntner M. 2011. Darwin's bark spider: giant prey in giant orb webs (Araneidae: Caerostris darwini)? Journal of Arachnology 39: 287-295. *Featured in Nature 479: 152-153
  • Kuntner M, May-Collado L, Agnarsson I. 2011. Phylogeny and conservation priorities of afrotherian mammals (Afrotheria, Mammalia). Zoologica Scripta 40: 1-15.
  • Vélez-Zuazo X, Agnarsson I. 2011. Shark tales: A molecular species level phylogeny of sharks (Selachimorpha, Chondrichthyes). Molecular Phylogenetics and Evolution 58: 207-217
  • Agnarsson I, Avilés L, Maddison WP. 2010. Complete separation along matrilines in a social spider metapopulation inferred from hypervariable mitochondrial DNA region. Molecular Ecology 19: 3052-3063
  • Agnarsson I, Kuntner M, May-Collado LJ. 2010. Dogs, cats, and kin: a molecular species-level phylogeny of Carnivora. Molecular Phylogenetics and Evolution 54: 726–745
  • Agnarsson I, Kuntner M, Blackledge TA. 2010. Bioprospecting finds the toughest biological material: extraordinary silk from a giant riverine orb. PLoS One 5(9): 1-9. *Featured in Science 330: 21.
  • Martén-Rodríguez S, Fenster CB, Agnarsson I, Skog LE, Zimmer EA. 2010. Evolutionary breakdown of pollination specialization in a Caribbean plant radiation. New Phytologist 188: 403-417
  • Sensenig A, Agnarsson I, Blackledge TA. 2010. Behavioral and biomaterial coevolution in spider orb webs Journal of Evolutionary Biology 23: 1839-1856
  • Agnarsson I, Blackledge T. 2009. Can a spider web be too sticky? Tensile mechanics constrain the evolution of capture spiral stickiness in orb weaving spiders. Journal of Zoology 277: 134-140
  • Agnarsson I, Boutry C, Wong S-C, Baji A, Dhinojwala A, Sensenig AT, Blackledge TA. 2009. Supercontraction forces in spider dragline silk depend on hydration rate. Zoology 112: 325-331
  • Agnarsson I, Dhinojwala A, Sahni V, Blackledge TA. 2009. Spider silk as a novel high performance biomimetic muscle driven by humidity. Journal of Experimental Biology 212: 1990-1994
  • Blackledge TA, Boutry C, Wong S-C, Baji A, Dhinojwala A, Sahni V, Agnarsson I. 2009. How super is supercontraction? Permanent versus cyclic responses to humidity in spider dragline silk. Journal of Experimental Biology 212: 1981-1989
  • Blackledge TA, Coddington J, Scharff N, Szuts T, Wenzel J, Hayashi C, Agnarsson I. 2009. Reconstructing web evolution and spider diversification in the molecular era. Proceedings of the National Academy of Sciences of the United States of America 106: 5229-5234
  • Coddington JA, Agnarsson I, Miller J, Kuntner M, Hormiga G. 2009. Undersampling bias: the null hypothesis for singleton species in tropical arthropod biodiversity surveys. Journal of Animal Ecology 78: 573–584
  • Kuntner M, Agnarsson I. 2009. Phylogeny accurately predicts behavior in Indian Ocean Clitaetra spiders (Araneae: Nephilidae) Invertebrate Systematics 23: 193-204
  • Agnarsson I, Coddington JA. 2008. Quantitative tests of primary homology. Cladistics 24: 51-61.
  • Agnarsson I, May-Collado L. 2008. The phylogeny of Cetartiodactyla: the importance of dense taxon sampling, missing data, and the remarkable promise of Cytochrome b to provide reliable species-level phylogenies. Molecular Phylogenetics and Evolution 48: 964–985
  • Agnarsson I, Miller J. 2008. Is ACCTRAN better than DELTRAN? Cladistics 24: 1032-1038
  • Eberhard WG, Agnarsson I, Levi HW. 2008. Web forms and phylogeny of theridiid spiders (Araneae: Theridiidae): chaos from order? Systematics and Biodiversity 6: 415-475
  • Agnarsson I, Kuntner M. 2007. Taxonomy in a changing world: seeking solutions for a science in crisis. Systematic Biology 56: 531-539.
  • Agnarsson I, Maddison WP, Avilés L. 2007. The phylogeny of the social Anelosimus spiders (Araneae: Theridiidae) inferred from six molecular loci and morphology. Molecular Phylogenetics and Evolution 43: 833-851
  • Avilés L, Agnarsson I, Salazar P, Purcell J, Iturralde G, Yip E, Powers KS, Bukowski T. 2007. Altitudinal pattern of sociality in the spider genus Anelosimus and the biology of a new mid-elevation social species in Ecuador. American Naturalist 170: 783-792.
  • May-Collado LJ, Agnarsson I, Wartzok D. 2007b. A phylogenetic review of tonal sound production in whales. BMC Evolutionary Biology 7: 136.
  • Agnarsson I. 2006a. A revision of the New World eximius lineage of Anelosimus (Araneae, Theridiidae) and a phylogenetic analysis using worldwide exemplars. Zoological Journal of the Linnean Society 146: 453-593.
  • Agnarsson I, Avilés L, Coddington JA, Maddison WP. 2006. Social theridiid spiders – repeated origins of an evolutionary dead-end. Evolution 60: 2342-2351
  • Kuntner M, Agnarsson I. 2006. Are the Linnean and phylogenetic nomenclatural systems combinable? Recommendations for Biological Nomenclature. Systematic Biology 55: 774-784.
  • May-Collado L, Agnarsson I. 2006. Cytochrome b and Bayesian inference of whale phylogeny. Molecular Phylogenetics and Evolution 38: 344–354.
  • Agnarsson I. 2004. Morphological phylogeny of cobweb spiders and their relatives (Araneae, Araneoidea, Theridiidae). Zoological Journal of the Linnean Society 141: 447-626.
  • Arnedo MA, Coddington J, Agnarsson I, Gillespie RG. 2004. From a comb to a tree: Phylogenetic relationships of the comb-footed spiders (Araneae, Theridiidae) inferred from nuclear and mitochondrial genes. Molecular Phylogenetics and Evolution 31: 225-245.
  • Agnarsson I. 2002. Sharing a web - on the relation of sociality and kleptoparasitism in theridiid spiders (Theridiidae, Araneae). Journal of Arachnology 30: 181-188.
  • Agnarsson I. 1996. Icelandic spiders. Fjölrit Náttúrufræðistofnunar 31, 175 pages, 169 figures.