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Indiana University Bloomington

Department of Biology

Faculty & Research

Faculty Profile

Eric Knox

Photo of Eric Knox
Director, IU Herbarium; Senior Scientist

IU Affiliations
Center for Biological Research Collections

Contact Information
By telephone: 812-855-9601
JH A313

IU Herbarium

Evolution, Ecology & Behavior
Research Areas
  • Evolution
  • Genomics and Bioinformatics
  • Plant Molecular Biology

Ph.D., University of Michigan, 1993


George R. Cooley Award, American Society of Plant Taxonomists

Fellow, Indiana Academy of Science

Research Description

Our work focuses on three broad areas: Evolution of the Lobeliaceae and Cyphiaceae; Horizontal gene transfer in Amborella trichopoda; Documenting the flora of Indiana.

The Lobeliaceae and Cyphiaceae are closely related, mid-sized families of flowering plants.  The Lobeliaceae (1200 species in 31 genera) are nearly cosmopolitan and are particularly diverse in temperate and high-altitude tropical areas.  The Cyphiaceae (75 species in the genus Cyphia) are restricted to Africa.  Biogeographic reconstruction indicates that both families originated in Southern Africa, with repeated patterns of diversification from the winter-rainfall areas of the Western Cape to the summer-rainfall areas to the east, then north to the highlands of eastern Africa, with repeated dispersal to the West African highlands, Madagascar, and (for the Lobeliaceae) elsewhere in the world.  Lobelia is the 'core genus' of the Lobeliaceae, from which the remaining segregate genera evolved.  The DNA-based phylogenetic estimate for these two families now includes over 700 samples, but additional work is needed to complete the sampling of all major groups.  In addition to the biogeographic reconstruction, this phylogenetic estimate permits reconstruction of morphological evolution, particularly the derivation of giant lobelias from herbaceous ancestors, and evolution of the reproductive features used to delimit the segregate genera.  These families also show extensive rearrangements in their chloroplast genomes, which is unusual in angiosperms.  We have completely sequenced 50 of these chloroplast genomes and are currently analyzing the results in order to understand the molecular basis of this structural instability.  Certain groups of Lobeliaceae also show accelerated rates of mitochondrial DNA sequence evolution, and we are sequencing the mitochondrial genomes from representatives of the fast and slow groups.

Amborella trichopoda is a small tree that grows in the rainforest of New Caledonia.  The sole member of its genus and family, A. trichopoda has long been recognized as an unusual plant with several morphological features thought to be primitive in the evolution of flowering plants.  Although several other groups of plants were similarly regarded as 'relics' of early angiosperm evolution, Amborella is evidently the single surviving species of a lineage that is sister to all other flowering plants.  Even more surprising, the mitochondrial genome of Amborella is more than eight times the normal size and contains many foreign copies of mitochondrial genes that were acquired by horizontal gene transfer from various donors that include other angiosperms, mosses, and green algae.  We have sequenced the mitochondrial genome of Amborella, and we completed fieldwork in New Caledonia in order to collect the potential donors of these horizontally transferred genes.

The Indiana University Herbarium (IND) is the main repository for the specimens collected by Charles Deam, upon which he based his 1940 book The Flora of Indiana.  We are working to update the taxonomy and distribution information for the native and naturalized species of vascular plants in Indiana, and to make this information widely available through a fully searchable website known as the Indiana Botanical Information System (IBIS).  Once IBIS is implemented, a variety of research and educational modules will be developed to help make this information accessible to a wide range of potential users.

Select Publications
Knox, E. B. 2014. The dynamic history of plastid genomes in the Campanulaceae sensu lato is unique among angiosperms. Proc. Natl. Acad. Sci. USA 111: 11097-11102.
Rice, D. W., A. J. Alverson, A. O. Richardson, G. J. Young, M. V. Sanchez-Puerta, J. Munzinger, K. Barry, J. L. Boore, Y. Zhang, C. W. dePamphilis, E. B. Knox, and J. D. Palmer.  2013.  Horizontal transfer of entire genomes via mitochondrial fusion in the angiosperm AmborellaScience 342: 1468-1473.
Walsh, N. G., D. E. Albrecht, and E. B. Knox.  2010.  Notes and new taxa in Lobelia sect. Holopogon (Campanulaceae: Lobelioideae).  Muelleria 28: 146-162.
Janssens, S. B., E. B. Knox, S. Dessein, and E. F. Smets.  2009.  Impatiens msisimwanensis (Balsaminaceae): Description, pollen morphology, and phylogenetic position of a new East African species.  S. Afr. J. Bot. 75: 104–109.
Janssens, S. B., E. B. Knox, S. Huysmans, E. F. Smets, and V. S. F. T. Merckx.  2009.  Rapid radiation of Impatiens (Balsaminaceae) during Pliocene and Pleistocene: result of a global climate change.  Molec. Phylog. Evol. 52: 806–824.
Cron, G. V., K. Balkwill, and E. B. Knox.  2008.  Phylogenetic evidence for the generic circumscription of Cineraria L. (Asteraceae-Senecioneae).  Taxon 57: 1–20.
Heenan, P. B., E. B. Knox, S. P. Courtney, P. N. Johnson, and M. I. Dawson.  2008.  Generic placement in Lobelia and revised taxonomy for New Zealand species previously in Hypsela and Isotoma (Lobeliaceae).  New Zealand J. Bot. 46: 87–100.
Knox, E. B., A. M. Muasya, and N. Muchhala.  2008.  The predominantly South American clade of Lobeliaceae.  Syst. Bot. 33: 462–468.
Knox, E. B., P. B. Heenan, A. M. Muasya, and B. G. Murray.  2008.  Phylogenetic position and relationships of Lobelia glaberrima (Lobeliaceae), a new alpine species from southern South Island (New Zealand).  New Zealand J. Bot. 46: 77–85.
Cron, G. V., K. Balkwill, and E. B. Knox.  2007.  Multivariate analysis of morphological variation in Cineraria deltoidea (Asteraceae, Senecioneae).  Bot. J. Linn. Soc. 154: 497–521.
Knox, E. B., A. M. Muasya, and P. B. Phillipson.  2006.  The Lobeliaceae originated in southern Africa.  Pp. 215–227 in S. A. Ghazanfar & H. J. Beentje (eds.), Taxonomy and Ecology of African Plants, their Conservation and Sustainable Use.  Proceedings of the 17th AETFAT Congress, Addis Ababa, Ethiopia.  Royal Botanic Gardens, Kew, U.K.
Knox, E. B.  2005.  Dendrosenecio.  Pp. 548-563 in H. J. Beentje, C. Jeffrey & D. J. N. Hind (eds.), Flora of Tropical East Africa, Compositae (part 3, pp. 547–869).  Royal Botanic Gardens, Kew, U.K.
Knox, E. B., Q. Luke, and M. Thulin.  2004.  A new giant Lobelia from the Eastern Arc Mts, Tanzania.  Kew Bull. 59: 189–194.
Knox, E. B.  2004.  Adaptive radiation of African montane plants.  Pp. 345–361 in U. Dieckmann, M. Doebeli, J. A. J. Metz, and D. Tautz (eds.), Adaptive Speciation.  Cambridge University Press, Cambridge.
Phillipson, P. B., and E. B. Knox.  2003.  Lobeliaceae.  Pp. 604-612 in G. Germishuizen and N. L. Meyer (eds.), Plants of southern Africa: an annotated checklist.  Strelitzia 14.  National Botanical Institute, Pretoria.
Knox, E. B., and J. D. Palmer.  1999.  The chloroplast genome arrangement of Lobelia thuliniana (Lobeliaceae): expansion of the inverted repeat in an ancestor of the Campanulales.   Pl. Syst. Evol. 214: 49–64.
Knox, E. B.  1999.  Reconstruction of adaptive radiation in insular habitats using integrated biogeographic information.  J. Biogeogr. 26: 983–992.
Knox, E. B., and J. D. Palmer.  1998.  Chloroplast DNA evidence on the origin and radiation of the giant lobelias in eastern Africa.  Syst. Bot. 23: 109–149.
Knox, E. B.  1998.  The use of hierarchies as organizational models in systematics.  Biol. J. Linn. Soc. 63: 1–49.
Knox, E. B., and J. D. Palmer.  1995.  Chloroplast DNA variation and the recent radiation of the giant senecios (Asteraceae) on the tall mountains of eastern Africa.  Proc. Natl. Acad. Sci. USA 92: 10349–10353.
Knox, E. B., S. R. Downie, and J. D. Palmer.  1993.  Chloroplast genome rearrangements and the evolution of giant lobelias from herbaceous ancestors.  Molec. Biol. Evol. 10: 414–430.

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