Dr. Nicole Valenzuela Department of Ecology, Evolution, and Organismal Biology

Iowa State University

251 Bessey Hall. Ames, IA 50011

(515) 294-1285






Nicole Valenzuela


COPYRIGHT NOTICE: Reprints of published articles are provided as a service to enhance accessibility and the exchange of information. In downloading, you agree to comply with United States copyright law (Title 17, United States Code), such that the reprints are not to be "used for any purpose other than private study, scholarship, or research." All copyrights remain with the original publishers of the articles. Please make only a single copy of any article, for personal use only.



80. Lee LS and Valenzuela N. 2019. Discovery of putative XX/XY male heterogamety in Emydura subglobosa turtles exposes a novel trajectory of sex chromosome evolution in Emydura. Cytogenetic and Genome Research. . In Press.

79. Valenzuela N, R Literman, JL Neuwald, BA Mizoguchi, JB Iverson, JL Riley, and JD Litzgus. Extreme thermal fluctuations from climate change unexpectedly accelerate demographic collapse of vertebrates with temperature-dependent sex determination. Scientific Reports. DOI: 10.1038/s41598-019-40597-4. PDF

78 Lee LS, EE Montiel1, BM Navarro-Domínguez, and N Valenzuela. 2018. Chromosomal Rearrangements During Turtle Evolution Altered the Synteny of Genes Involved in Vertebrate Sex Determination. Cytogenetic and Genome Research. DOI: 10.1159/000497302. In Press.


77. Radhakrishnan S, Literman R, Neuwald JL, and N Valenzuela. 2018. Thermal response of epigenetic genes informs turtle sex determination with and without sex chromosomes Sexual Development. DOI: 10.1159/000492188 . PDF.

76. O’Connor, RE, Romanov MN, Kiazim L, Barrett PM, Farré M, Damas J, Ferguson-Smith M, Valenzuela N, Larkin DM, Griffin DK. 2018. Reconstruction of genome organization in the diapsid common ancestor permits tracing of chromosome evolution in avian and non-avian dinosaurs. Nature Communications 9:1883. PDF

75. Literman R, Burrett A, Bista B, and Valenzuela N. 2018. Putative independent evolutionary reversals from genotypic to temperature-dependent sex determination are associated with accelerated evolution of sex-determining genes in turtles. Journal of Molecular Evolution 86:11–26. PDF.

74. Escalona T, Valenzuela N, Adams DC. 2018. A lengthy solution to the optimal propagule size problem in the large-bodied South American freshwater turtle, Podocnemis unifilis. Evolutionary Ecology 32:29–41. PDF

73. Valenzuela, N. 2018. Causes and consequences of evolutionary transitions in the level of phenotypic plasticity of reptilian sex determination. In Plasticity of Sexual Systems. J. Leonard, Editor. Springer. In press.


72. Radhakrishnan S and Valenzuela N. 2017. Chromosomal context affects the molecular evolution of sex-linked genes and their autosomal counterparts in turtles and other vertebrates. Journal of Heredity 108:720-730. PDF

71. Tang WQ, Mu Y, Valenzuela N, Du WD. Effects of incubation temperature on the expression of sex-related genes in the Chinese pond turtle, Mauremys reevesii. Sexual Development.. PDF

70. Radhakrishnan S, Literman R, Mizoguchi B, and Valenzuela N. 2017. MeDIPseq and nCpG analyses illuminate sexually dimorphic methylation of gonadal development genes with high historic methylation in turtle hatchlings with temperature-dependent sex determination.Epigenetics & Chromatin 10:28. DOI 10.1186/s13072-017-0136-2 PDF

69. Literman R., S. Radhakrishnan, J. Tamplin, R. Burke, C. Dresser, and Valenzuela N. 2017. Development of sexing markers in Glyptemys insculpta and Apalone spinifera turtles uncovers an XX/XY sex-determining system in the critically-endangered bog turtle Glyptemys muhlenbergii.Conservation Genetic Resources. DOI 10.1007/s12686-017-0711-7. Full Text

68. Radhakrishnan S, R Literman, J Neuwald, A Severin, and Valenzuela N. Transcriptomic responses to environmental temperature by turtles with temperature-dependent and genotypic sex determination assessed by RNAseq inform the genetic architecture of embryonic gonadal development. 2017. PLoS ONE 12(3): e0172044. PDF

67 Montiel EE, D Badenhorst, J Tamplin, R Burke, and N Valenzuela. 2017. Discovery of youngest sex chromosomes reveals first case of convergent co-option of ancestral autosomes in turtles. Chromosoma 126:105–113. PDF


66. Twyman H, Valenzuela N, Literman R, Andersson S, Mundy NI. 2016. Seeing red to being red: conserved genetic mechanism for red cone oil droplets and co-option for red coloration in birds and turtles.Proceedings of The Royal Society B. 283: 20161208. PDF

65. Sabath N, Itescu Y, Feldman A, Meiri S., Mayrose I., and N Valenzuela. 2016. Sex determination and the birth and death of species. Ecology and Evolution . DOI 10.1002/ece3.2277. PDF

64. Montiel EE, D Badenhorst, LS Lee, R Literman, V Trifonov, N Valenzuela. 2016. Cytogenetic insights into the evolution of chromosomes and sex determination reveal striking homology of turtle sex chromosomes to amphibian autosomes. Cytogenetic and Genome Research 148:292-304 . PDF

63. Mizoguchi BA and N Valenzuela. 2016. Ecotoxicological perspectives of sex determination. Sexual Development 10:45-57. DOI:10.1159/000444770. PDF

62. Gómez-Saldarriaga C, N Valenzuela, and C.P. Ceballos. 2016. Effects of the incubation temperature on the onset and duration of the thermosensitive period for sex determination in the Magdalena River Turtle, Podocnemis lewyana. Chelonian Conservation and Biology 15 (1): 43-53 PDF


61. Badenhorst D, LD Hillier, R Literman, EE Montiel, S Radhakrishnan, P Minx, DE Janes, WC Warren, SV Edwards, and N Valenzuela. 2015. Physical mapping and refinement of the painted turtle genome (Chrysemys picta) inform amniote genome evolution and challenges turtle-bird chromosomal conservation. Genome Biology and Evolution 7(7):2038–2050. PDF

60. Pennell M, Kirkpatrick M, Otto S, Vamosi J, Peichel C, Valenzuela N, Kitano J. 2015. Y fuse? Sex chromosome fusions in fishes and reptiles. PLoS Genetics 11(5): e100523. PDF

59. Mu Y., Zhao B., Tang W., Sun B., Zeng Z., Valenzuela N., Du W. 2015. Temperature-dependent sex determination ruled out in the Chinese soft-shelled turtle (Pelodiscus sinensis) via molecular cytogenetics and incubation experiments across populations. Sexual Development 9:111-117. PDF.


58. Janes DE, Organ CL, Stiglec R, O’Meally D, Sarre SD, Georges A, Graves JAM, Valenzuela N, Literman R, Rutherford K, Gemmell N, Iverson JB, Tamplin JW, Edwards SV, Ezaz T. Molecular evolution of Dmrt1 accompanies change of sex-determining mechanisms in Reptilia. Biology Letters 10: 20140809. PDF

57. Literman R, D Badenhorst, and N Valenzuela. 2014. QPCR-based molecular sexing by copy number variation in rRNA genes and its utility for sex identification in soft-shell turtles. Methods in Ecology and Evolution 5: 872-880. PDF.

56. The Tree of Sex Consortium 2014. TL Ashman, D Bachtrog, H Blackmon, EE Goldberg, MW Hahn, M Kirkpatrick, J Kitano, JE Mank, I Mayrose, R Ming, SP Otto , CL Peichel, MW Pennell, N Perrin, L Ross, N Valenzuela, JC Vamosi. Tree of Sex: A database of sexual systems. Nature Scientific Data 1:140015. DOI: 10.1038/sdata.2014.15. PDF.

55. Valenzuela N, D Badenhorst, EE Montiel, R. Literman. 2014. Molecular cytogenetic search for cryptic sex chromosomes in painted turtles Chrysemys picta. Cytogenetic and Genome Research 144: 39-46. PDF.

54. The Tree of Sex Consortium: Bachtrog D, Mank JE, Peichel CL, Kirkpatrick M, Otto S, Ashman TL, Hahn M, Kitano J, Mayrose I, Ming R, Perrin N, Ross L, N Valenzuela, Vamosi J. 2014. Sex determination: Why so many ways of doing it? PLoS Biology 12(7): e1001899. doi:10.1371/journal.pbio.1001899. PDF.

53. Ceballos CP, OE Hernández and N Valenzuela. 2014. Divergent sex-specific plasticity in long-lived vertebrates with contrasting sexual dimorphism. Evolutionary Biology 41:81–98. PDF.


52. Weiner SA, DA Galbraith, DC Adams, N Valenzuela, FB Noll, CM Grozinger, and AL Toth. 2013. A survey of DNA methylation across social insect species, life stages, and castes reveals abundant and caste-associated methylation in a primitively social wasp. Naturwissenschaften 100: 795-799 PDF.

51. Shaffer HB, P Minx, DE Warren, AM Shedlock, RC Thomson, N Valenzuela, J Abramyan, D Badenhorst, KK Biggar, GM Borchert, CW Botka, RM Bowden, EL Braun, AM Bronikowski, BG Bruneau, LT Buck, B Capel, TA Castoe, M Czerwinski, KD Delehaunty, SW Edwards, CC Fronick, MK Fujita, L Fulton, TA Graves-Lindsey, RE Green, W Haerty, R Hariharan, LW Hillier, AK Holloway, D Janes, FJ Janzen, C Kandoth, L Kong, APJ de Koning, Y Li, R Literman, SE McGaugh, L Mork, M O’Laughlin, RT Paitz, DD Pollock, CP Ponting, S Radhakrishnan, BJ Raney, JM Richman, J StJohn, T Schwartz, A Sethuraman, PQ Spinks, KB Storey, N Thane, T Vinar, LM Zimmerman, WC Warren, ER Mardis, and RK Wilson. 2013. The western painted turtle genome, a model for the evolution of extreme physiological adaptations in a slowly evolving lineage. Genome Biology. DOI:10.1186/gb-2013-14-3-r28. PDF

50. Janes DE, Elsey RM, Langan EM, Moore B, Edwards SV and N Valenzuela. 2013. Sex-biased expression of sex-differentiating genes Foxl2 and Fgf9 in American alligators, Alligator mississippiensis. Sexual Development. 7: 253–260 PDF.

49. Badenhorst, D., R. Stanyon, T. Engstrom, and N. Valenzuela.2013. A ZZ/ZW microchromosome system in the spiny softshell turtle, Apalone spinifera reveals an intriguing sex chromosome conservation in Trionychidae. Chromosome Research. 12(2): 137-147. DOI 10.1007/s10577-013-9343-2 PDF.

48. Valenzuela N., J. Neuwald, and R. Literman. 2013. Transcriptional evolution underlying vertebrate sexual development. Developmental Dynamics. 242:307–319. DOI: 10.1002/dvdy.23897 PDF.

47. Ceballos C.P., Adams D.C., Iverson J.B., and Valenzuela N. 2013. Phylogenetic patterns of sexual size dimorphism in turtles and their implications for Rensch´s rule. Evolutionary Biology 40: 194-208. DOI: 10.1007/s11692-012-9199-y. PDF.


46. Valenzuela N. and Ceballos C.P. 2012. Evolución y mecanismos de determinación sexual en tortugas. In: Biología y Conservación de las Tortugas Continentales de Colombia. Paez V.P. Editor. Serie Editorial “Recursos Hidrobiológicos y Pesqueros de Colombia”, Instituto de Investigación de Recursos Biológicos Alexander von Humboldt, Bogotá, Colombia. PDF.



45. Bachtrog D., Kirkpatrick M, Mank, J.E., McDaniel S.F., Pires J.C., Rice W. and Valenzuela N. 2011. Are all sex chromosomes created equal? Trends in Genetics 27 (9): 350-357. PDF.

44. Ceballos, C. and Valenzuela, N. The role of sex-specific plasticity in shaping sexual dimorphism in a long-lived vertebrate, the snapping turtle Chelydra serpentina. Evolutionary Biology 38: 163-181. PDF

43. Neuwald J.L. and Valenzuela N. 2011. The Lesser Known Challenge of Climate Change: Thermal Variance and Sex-Reversal in Vertebrates with Temperature-Dependent Sex Determination PloS ONE 6(3): e18117. doi:10.1371/journal.pone.0018117. PDF

42. Valenzuela N. and Adams D.C. 2011. Chromosome number and sex determination co-evolve in turtles Evolution 65: 1808-1813. PDF

41. Janes, D.E., Valenzuela N., Ezaz T., Amemiya C., and Edwards S.V. 2011. Sex chromosome evolution in Amniotes: applications for bacterial artificial chromosome libraries. Journal of Biomedicine and Biotechnology Vol 2011, doi:10.1155/2011/132975 PDF.


40. Valenzuela, N. 2010. Co-evolution of genomic structure and selective forces underlying sexual development and reproduction. Cytogenetics nd Genome Research 127:232–241PDF.

39. Valenzuela, N. 2010. Multivariate expression analysis of the gene network underlying sexual development in turtle embryos with temperature-dependent and genotypic sex determination. Sexual Development 4 (1-2): 39-49 PDF.



38. Valenzuela, N. 2009. The painted turtle, Chrysemys picta: A model system for vertebrate evolution, ecology, and human health. Cold Spring Harbor Protocols 2009: DOI:10.1101/pdb.emo124 PDF.

37. Valenzuela, N. 2009. Egg incubation and collection of painted turtle embryos. Cold Spring Harbor Protocols 2009 DOI:10.1101/pdb.prot5238 PDF.

36. Escalona, T., Adams, D.C., and Valenzuela, N. 2009. Nesting ecology in the freshwater turtle Podocnemis unifilis: spatiotemporal patterns and inferred explanations. Functional Ecology 23: 826-835 PDF.

35. Escalona, T., Engstrom T.N., Hernandez O.E., Bock B.C., Vogt R.C. and Valenzuela N. 2009. Population genetics of the endangered South American freshwater turtle, Podocnemis unifilis, inferred from microsatellite DNA data. Conservation Genetics 10: 1683–1696 PDF.



34. Chinsamy, A. and Valenzuela, N. 2008. Skeletochronology of the endangered side-neck turtles Podocnemis expansa. South African Journal of Science 104(7/8): 311-314 PDF

33. Martinez, P., Ezaz T., Valenzuela, N., Georges, A., and Graves J.A.M. 2008. An XX/XY heteromorphic sex chromosome system in the Australian chelid turtle Emydura macquarii, a new piece in the puzzle of sex chromosome evolution in turtles. Chromosome Research 16(6): 815-825 PDF

32. Valenzuela, N. 2008. Sexual development and the evolution of sex determination. Sexual Development 2(2): 64-72. PDF

31. Valenzuela, N. 2008. Evolution of the gene network underlying gonadogenesis in turtles with temperature-dependent and genotypic sex determination. Integrative and Comparative Biology 48 (4): 476-485. PDF Full Text

30. Janes D.E., Organ C., and Valenzuela N. 2008. New resources inform study of genome size, content and organization in non-avian reptiles. Integrative and Comparative Biology 48(4): 447-453. PDF Full Text

29. Valenzuela, N. 2008. Relic thermosensitive gene expression in a turtle with genotypic sex determination. Evolution 62-1: 234-240. PDF


 28. McGaugh, S.E., Alacs E.A., Edwards S.V., Feldman C.R., Georges A., Sites, J.R.Jr., Valenzuela N. 2007. From molecules to organisms: Research applications of modern genetic tools for turtle biology and conservation. Chelonian Research Monographs 4: 47-72. PDF

27. Valenzuela, N. and Shikano T. 2007. Embryological ontogeny of Aromatase gene expression in Chrysemys picta and Apalone mutica turtles: comparative patterns within and across temperature-dependent and genotypic sex-determining mechanisms. Development, Genes and Evolution 217: 55–62. PDF



 26. Valenzuela, N., LeClere A., and Shikano T. 2006. Comparative expression of steroidogenic factor 1 in Chrysemys picta and Apalone mutica turtles with environmental and genotypic sex determination. Evolution and Development 8 (5): 424-432 PDF

25. Ezaz T., Valenzuela, N., Gruetzner F., Miura I., Burke R., Georges, A. and Graves J.M. 2006. An XX/XY sex microchromosome system in a freshwater turtle, Chelodina longicollis (Testudines : Chelidae) with genetic sex determination. Chromosome Research 14:139-150 PDF

24. Pearse, D.E., A.D. Arndt, N. Valenzuela, B.A. Miller, V. Cantarelli, J.W. Sites, Jr. 2006. Estimating population structure under non-equilibrium conditions in a conservation context: Continent-wide population genetics of the giant Amazon river turtle Podocnemis expansa (Chelonia; Podocnemidae). Molecular Ecology 15: 985-1006  PDF

23. Valenzuela, N. 2006. (Book Review). Incubation of Reptile Eggs: Basics, Guidelines, Experiences, by Gunther Kohler. Quarterly Review of Biology 81:290-291. PDF



 22. BOOK: Valenzuela, N. and V. Lance, Eds. 2004. Temperature Dependent Sex Determination in Vertebrates. Smithsonian Books. Washington D.C PDF

21. Valenzuela, N., D.C. Adams, R.M. Bowden, and A.C. Gauger 2004. Geometric morphometric sex estimation for hatchling turtles: a powerful alternative for detecting subtle sexual shape dimorphism. Copeia. 2004(4): 735–742 PDF

20. Valenzuela, N. 2004. Evolution and maintenance of temperature-dependent sex determination. Pp. 131-147. In Valenzuela, N. and V. Lance, Eds. Temperature Dependent Sex Determination in Vertebrates. Smithsonian Books. Washington D.C PDF

19. Valenzuela, N. 2004. Temperature-dependent sex determination. Pp. 211-227. In Deeming D.C. Ed. Reptilian Incubation: Environment & Behaviour. Nottingham University Press. PDF



 18. Valenzuela, N., D.C. Adams, and F.J. Janzen. 2003. Pattern does not equal process: Exactly when is sex environmentally determined? American Naturalist 161 (4): 676-683  PDF

17. Kagima, B. W., N. Valenzuela, T. Engstrom, B. Bock. 2003. Preliminary population genetic study of the yellow spotted Amazon river turtle (Podocnemis unifilis) using microsatellite DNA data. Integrative and Comparative Biology 43: 1025-1025.



 16. Milne-Morjan, C. and N. Valenzuela. 2001. Is ground-nuzzling by female turtles associated with soil surface temperatures? Journal of Herpetology 35(4): 668-672  PDF

15. Valenzuela, N. and F. J. Janzen. 2001. Nest-site philopatry and the evolution of temperature-dependent sex determination. Evolutionary Ecology Research 3: 779-794  PDF

14. Valenzuela, N. 2001. Constant, shift and natural temperature effects on sex determination in Podocnemis expansa turtles. Ecology 82(11): 3010–3024  PDF

13. Valenzuela, N. 2001. Maternal effects on life history traits in the Amazonian giant river turtle Podocnemis expansa. Journal of Herpetology 35(3): 368-378 PDF

12. Valenzuela, N. 2001. Genetic differentiation among nesting beaches in the highly migratory giant river turtle (Podocnemis expansa) from Colombia. Herpetologica 57(1): 48-57   PDF



 11. Valenzuela, N. 2000. Multiple paternity in side-neck turtles Podocnemis expansa: evidence from microsatellite DNA data. Molecular Ecology 9: 99-106 PDF



 10. Adams, D. C., M. S. Di Bitetti, C. H. Janson, L. B. Slobodkin, and N. Valenzuela. 1997.  An “audience effect” for ecological terminology: use and misuse of jargon. Oikos 80:632-636 PDF

9. Valenzuela, N, E. Martínez, and R. Botero.  1997. Field study of sex determination in Podocnemis expansa from Colombian Amazonia. Herpetologica 53(3):390-398   PDF


 8. Valenzuela, N, E. Martínez, and R. Botero. 1995. Preliminary model of sex determination of Podocnemis expansa from Colombian Amazonia. Proceedings of the International Congress of Chelonian Conservation and Biology. Pp. 276-278.


 7. Lance,V.A., N. Valenzuela and P. von Hildebrand. 1992. A hormonal method to determine the sex of hatchling giant river turtles, Podocnemis expansa. Application to endangered species research. American Zoologist 32:16A PDF


Undergraduate work (1990-1994)


6. Valenzuela, N. 1994. Early behavioral development of three wild infant Cebus apella in Colombia.  Selected Proceedings of the XIVth Congress of the International Primatological Society, Strasbourg, France, 1992. Current Primatology, Volume II. Social Development, Learning and Behaviour. (Roeder, J.J., Thierry, B., Anderson, J.R. and N. Herrenschmidt, eds.). Pp. 297-302. PDF

5. Valenzuela, N. 1993. Social contacts between infants and other group members in the wild Cebus apella. Field Studies of New World Monkeys at La Macarena, Colombia 8: 1-9 PDF

4. Valenzuela, N. 1992. Early development of three wild infant Cebus apella at La Macarena, Colombia. Field Studies of New World Monkeys at La Macarena, Colombia 6: 15-23  PDF

3. Espinel A. and N. Valenzuela. 1991. Adaptaciones genéticas a la malaria en poblaciones afroaborígenes del Pacífico Colombiano. Revista de Antropología y Arqueología. 7:117-130 PDF

2. Groot de Restrepo, H., A. Espinel, N. Valenzuela, D. Sicard, P. Angulo, and D. Nieto. 1991. Variabilidad Genética en el Género Cebus en Colombia. Proceedings of the II Congreso de Primatología, Barranquilla, Colombia.

1. Espinel A., N. Valenzuela, A. Fajardo, J. Umaña, and G. Quintero. 1990. Breve reseña de las actividades primatológicas en Colombia. Boletín Primatología Latinoamericana 2(1):62-68.


COPYRIGHT NOTICE: Reprints of published articles are provided as a service to enhance accessibility and the exchange of information. In downloading, you agree to comply with United States copyright law (Title 17, United States Code), such that the reprints are not to be "used for any purpose other than private study, scholarship, or research." All copyrights remain with the original publishers of the articles. Please make only a single copy of any article, for personal use only.