In Memoriam
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In Memoriam
Kenneth A. Christiansen (1924–2017)
expand article infoDavid C. Culver
‡ American University, Washington, United States of America
Open Access

One of the great speleobiologists and Collembola systematists, Ken Christiansen, died on November 26, 2017, at the age of 93. Ken was truly unique; no one who ever came in contact with him ever forgot him. A scholar and intellect of the first order, he always had time and enthusiasm for the work of his students and colleagues. His level of energy and enthusiasm was such that even into his 80’s, his colleague and fellow collembologist Louis Deharveng called him “Hurricane Ken” after a visit to Louis at the Paris Museum of Natural History. He touched the lives of generations of students at Grinnell College and the lives of generations of Collembola taxonomists and speleobiologists throughout the world.

One of the most formative influences on Ken’s life, surpassed only by his wife Phyllis and their four children, was his service in World War II in the U.S. Army Second Armored Infantry Division as a forward observer in the campaigns in Europe and North Africa. A genuine war hero and fierce anti-fascist, he was awarded a bronze star and an oak leaf cluster for bravery in combat. I once asked Ken what rank he achieved and he told me he was promoted to corporal three times! Anyone who believes the phrase that there are no atheists in a foxhole never met Ken and for many years he was famous at Grinnell for his atheism lecture.

Taking advantage of the GI Bill, Ken went to Boston University and Harvard University, and graduated with a Ph.D. from Harvard in 1951. His thesis (Christiansen 1958d) was on a rather large group of Collembola (the genus Entomobrya), large both in the sense of numbers of species and in terms of body size, reaching more than 1 mm in the Lilliputian Collembola world. His first job was at American University in Beirut, where he took advantage of his location to study the Collembola of Lebanon and Syria (Christiansen 1956c, 1957, 1958b). Sometime during his stay, probably in the summer of 1954, when he spent time in Switzerland with European collembologists Gisin and Delamare Deboutteville among others, he became interested in cave Collembola, of which there are many. Shortly after that he embarked on the study of adaptation in cave Collembola, especially the convergent evolution of antennal and appendage lengthening, as well as changes in claw structure. In 1955, he accepted a faculty position at Grinnell College in Iowa, where he stayed for the rest of his career.

While the winds of neo-Darwinism were blowing strongly in North America (especially at Harvard, the home institution of the great evolutionist Ernst Mayr), they were at best a faint breeze in continental Europe, the center of research on subterranean biology at the time. In a series of papers that continued for the next six decades (Christiansen 1960a, 1960b, 1965, 1982b, 1992a, 1995, 2003a, 2004, 2012; Christiansen and Culver 1968, 1969, Peck and Christiansen 1990), he offered what was really the first neo-Darwinian explanation for the morphological convergence of not only eye and pigment loss, but also appendage elongation and claw modification, of many lineages of cave Collembola. In 1962, he wrote his only paper in French (of course that is one more than any other cave biologist from the U.S.), coining a new term for the suite of evolutionarily convergent features found in cave organisms—troglomorphy (Christiansen 1962). This short paper, in an obscure journal, is a highly cited papers in cave biology, with over 100 citations. Together with Thomas Barr and Thomas Poulson, he established a North American school of subterranean biology, one with neo-Darwinism at its core. This was the first time since the 19th century that North Americans became a presence in the field. In the 19th century, neo-Lamarckians, especially A.S. Packard, brought North America to prominence in the field.

It was also in the 1960’s that he initiated the study of the ecology of Hunters Cave in Iowa (Christiansen 1961b, Christiansen et al. 1961), one of the first ecological studies of a whole cave. Later on, he wrote another paper on cave ecosystems, this time with Michel Bouillon (Christiansen and Bouillon 1978) on caves in the Pyrenees. He spent two sabbatical leaves in 1962, 1967 and 1968 at the Laboratoire Souterrain in Moulis, France, then the leading research institution for subterranean biology. Until at least the mid 1970’s, he was the only North American with extensive contacts and collaborations in continental Europe.

His work on evolution of cave animals was more than matched by his work on the taxonomy of cave animals. There are approximately 60 species of cave Collembola known from U.S. caves and he described nearly 50 of them! During the course of his career, he described species from all the major genera of Collembola occupying North American caves—Onychiurus (Pomorski et al. 2009), Pseudosinella [Christiansen 1960b, 1983; Christiansen and Luther 1986; Christiansen and Moberg 1988; Christiansen and Bellinger 1996b), Pygmarrhopalites (Christiansen 1966; Christiansen and Bellinger 1996a; Zeppelini and Christiansen 2003), Sinella (Christiansen 1960c), and Tomocerus (Christiansen 1964a).

Ken did not limit himself to the taxonomy of cave Collembola. He also described a number of non-cave dwelling species from the U.S. (Christiansen 1956b, 1958d; Christiansen and Bellinger 1973; Christiansen and Tucker 1977), Hungary (Wang et al. 2002c), Ascension Island (Christiansen 1998b), Lebanon and Syria (Christiansen 1956c, 1957, 1958b), Chile (Christiansen 1963), Mexico (Christiansen et al. 1985), and even fossil Collembola (Christiansen 1971d; Christiansen and Pike 2002). Among his international works, that in China stands out. Following at stint as a Visiting Professor at Nanjing University in 1990, he wrote more than 20 papers with Chinese colleagues on the Collembola of China [Chen and Christiansen 1993, 1996, 1997, 1998, 2004; Wu and Christiansen 1997; Ma and Christiansen 1998; Li and Christiansen 1997; Wang and Christiansen 2000; Wang et al. 2002a, 2002b, 2002d, 2003a, 2003b, 2003c, 2003d, 2003e; Chen et al. 2002; Jia et al. 2003; Ma et al. 2003, 2004; Madele et al. 2004). With Peter Bellinger, he wrote two editions of the “The Collembola of North America north of the Rio Grande”, a four volume work which is more than 1500 pages in length (Christiansen and Bellinger 1980–1981, 1998).

During his six decades at Grinnell, he introduced countless students to caves and cave biology, often in Hunter Cave. He introduced a number of students to research, and was an enthusiastic mentor to even the most unprepared student. Several of his students went on to get Ph.D’s and pursue research careers in ecology and evolutionary biology, including David Culver, Richard Seifert, and Mary Willson, He was also collaborator, mentor, and friend to generations of collembologists, and co-wrote papers with a number of colleagues, including Bellinger, Chen, Culver, de Gama, Li, Palacios-Vargas, Wang, and Zeppelini.

For anyone who has met Ken, a recitation of his academic achievements does not do justice to his influence or his character. Ken was enthusiastic in his support both of intellectual areas of interest, like cave biology and Collembola, and in those of us who shared these interests. Ken never claimed priority or seniority; he was the ideal colleague and mentor. He had an overall joie de vivre which infected those who came in contact with him. He had numerous interests outside of science, including acting in community theater, listening to opera, making wine, and studying history, especially military history. His enthusiasms and overall attitude are all the more remarkable for the many traumatic experiences in his wartime years, in a unit with high mortality. Without complaint or self pity, he kept these stresses and strains under control, with the support and understanding of his loving wife, Phyllis. I had the great fortune to be his student, colleague, and friend for more than 50 years. No one had a greater influence on me as a scientist or a person, and I am grateful to have known him. I am certainly not alone in this, and a little bit of Ken lives on in the best of each of us who knew him.

Partial Bibliography

  • Baquero E, Jordana R, Christiansen KA (2004) Redescription of Nothobrya scubarti Arlé 1961 (Collembola Entomobryomorpha) Entomological News 115: 31–34.
  • Baquero E, Martinez M, Christiansen K, Jordana R (2004) A new genus and species of Entomobryidae (Collembola Entomobryomorpha) from the Iberian Peninsula. Entomological News 115: 229–235.
  • Chen J-X, Christiansen KA (1996) A new species of Ptenothrix from China (Collembola: Dicyrtomidae). Florida Entomologist 79: 587–91. https://doi.org/10.2307/3496072
  • Chen J-X, Christiansen KA (1997) The subgenus Cceobrya of the genus Sinella (Collembola Entomobryidae) with special reference to the species of China. Annals Entomological Societyof America 90: 1–19. https://doi.org/10.1093/aesa/90.1.1
  • Chen J-X, Christiansen KA (1998) Tomocerus (s.s.) spinulus, a new species of Chinese springtail. Entomological News 109: 51–55.
  • Chen J-X, Wang F, Christiansen KA (2002) A new species of Pseudosinella from Guilin China (Collembola: Entomobryidae). Journal of Kansas Entomological Society 75: 80–85
  • Christiansen KA (1954) Ratios as a means of specific differentiation in Collembola. Entomological News 65: 176–177.
  • Christiansen KA (1956a) A recently introduced species of collembolan. Entomological News 67: 129–130.
  • Christiansen KA (1956c) The Collembola of Lebanon and western Syria. Part I. General considerations and the Family Onychiuridae. Psyche 64: 119–133. https://doi.org/10.1155/1956/62859
  • Christiansen KA (1957) The Collembola of Lebanon and western Syria. Part II. Families Cyphoderidae and Oncopoduridae. Psyche 64: 77–89. https://doi.org/10.1155/1957/32941
  • Christiansen KA (1958a) Geographic variation and the subspecies concept in the collembolan Entomobrya guthriei. Systematic Zoology 7: 10–15. https://doi.org/10.2307/2411473
  • Christiansen KA (1958c) The entomobryiform male genital plate. Proceedings of the Iowa Academy of Science 65: 474–476
  • Christiansen KA (1958d) The Nearctic members of the genus Entomobrya (Collembola). Bulletin of the Museum of Comparative Zoology 118: 440–545.
  • Christiansen KA (1959) The mystery of Entomobrya duolineata solved (Collembola). Entomological News 70.
  • Christiansen KA (1960a) A preliminary survey of the knowledge of North American cave Collembola. American Midland Naturalist 64: 39–44. https://doi.org/10.2307/2422892
  • Christiansen KA (1960c) The genus Sinella Brook (Collembola: Entomobryidae) in Nearctic caves. Annals of the Entomological Society of America 53: 481–491. https://doi.org/10.1093/aesa/53.4.481
  • Christiansen KA (1961b) The Collembola of Hunters Cave. Bulletin of the National Speleological Society 24: 59–62.
  • Christiansen KA (1962) Proposition pour la classification des animaux cavernicoles. Spelunca Memoires 2: 76–78.
  • Christiansen KA (1963) Preliminary notes on the genus Entomobrya in South America with special reference to Patagonia. Bio de l’Amerique Australe 2: 149–168.
  • Christiansen KA (1964a) A Revision of the Nearctic members of the genus Tomocerus (Collembola: Entomobryidae). Revue d’Ecologie et de Biologie du Sol 1: 639–678.
  • Christiansen KA (1966) The genus Arrhopalites (Collembola : Sminthuridae) in the United States and Canada. International Journal of Speleology 2: 43–73. https://doi.org/10.5038/1827-806X.2.1.5
  • Christiansen KA (1967) Competition between collembolan species in culture jars. Revue d’Ecologie et de Biologie du Sol 4: 438–462.
  • Christiansen K (1970a) Scope and direction of contemporary soil arthropod research. Pesticides in the Soil: Ecology, Degradation and Movement.
  • Christiansen KA (1970b) Experimental studies on the aggregation and dispersion of Collembola. Pedobiologica 10: 180–198.
  • Christiansen KA (1970c) Invertebrate populations in the Moulis Cave. Annales de Speleologie 25: 244–273.
  • Christiansen KA (1970d) Survival of Collembola on clay substrates with and without food added. Annales de Speleologie 25: 849–852.
  • Christiansen KA (1971a) Factors affecting predation on Collembola by various arthropods. Annales de Speleologie 26: 98–106.
  • Christiansen KA (1971d) Notes on Miocene Amber Collembola from Chiapas. University of California Publications in Entomology 63: 45–48.
  • Christiansen KA (1973) The genus Pseudosinella in Mesoamerican caves. Bulletin of the Association of Mexican Cave Studies. 5: 129–134.
  • Christiansen KA (1982a) Notes on Mexican cave Pseudosinella with the description of six new species. Folia Entomologica Mexicana 55: 3–25.
  • Christiansen KA (1982b) The zoogeography of cave Collembola east of the Great Plains. Bulletin of the National Speleological Society 44: 32–41.
  • Christiansen KA (1985) Regressive evolution in cave Collembola. Bulletin of the National Speleological Society 47: 89–100.
  • Christiansen KA (1990) Collembola. In: Dindal DL (Ed.) Soil biology guide. Wiley Interscience, New York, 965–995.
  • Christiansen KA (1992a) Cave life in light of modern evolutionary theory. In: Camacho AI (Ed.) The natural History of Biospeleology. Museo Nactional de Ciencias Naturales, Madrid, 453–472.
  • Christiansen KA (1992b) Springtails. The Kansas School Naturalist 39: 1–16.
  • Christiansen KA (1995) La evolucion de la vida cavernícola. Mundos Subterráneos 6: 25–33.
  • Christiansen KA (1998a) Las Colas de Resorte. (Spanish translation by Palacios Vargas). Mundos Subterraneos 9: 1–18.
  • Christiansen KA (2003a) Adaptation: morphological (external). In: Gunn J (Ed.) Encyclopedia of caves and karst science. Fitzroy-Dearborn, New York, 7–9.
  • Christiansen KA (2003b) Speciation. In: Gunn J (Ed.) Encyclopedia of caves and karst science. Fitzroy-Dearborn, New York, 665–666.
  • Christiansen KA (2004) Morphological adaptations. In: Culver DC, White WB (Eds) Encyclopedia of caves. Academic/Elsevier Press, Amsterdam, 386–397.
  • Christiansen KA (2009) The Collembola of Fennoscandia and Denmark (Fauna Entomologica Scandinavica volumes 35 and 42), volume 42 part II: Entomobryomorpha and Symphypleona). Systematic Entomology 34: 401–402. https://doi.org/10.1111/j.1365-3113.2008.00459.x
  • Christiansen KA, Barra JA (1975) Experimental study of aggregation during the development of Pseudosinella impediens (Collembola, Entomobryidae). Pedobiologia 15: 343–347.
  • Christiansen KA, Bellinger PF (1973) Six new Nearctic species of the genus Friesea. Pan Pacific Entomologist 49: 390–395.
  • Christiansen KA, Bellinger PF (1974) Collembola from Hawaiian caves. Pan Pacific Entomologist 16: 31–40.
  • Christiansen KA, Bellinger PF (1980–1981) The Collembola of North America North of the Rio Grande, four volumes. Grinnell College.
  • Christiansen KA, Bellinger PF (1988) Marine littoral Collembola of North and Central America. Bulletin of Marine Science 42: 215–245.
  • Christiansen KA, Bellinger PF (1992a) The Collembola of Hawaii. University of Hawaii Press, Honolulu, HI.
  • Christiansen KA, Bellinger PF (1992b) Update Collembola of North America. Part I families Hypogastruridae. Grinnell College.
  • Christiansen KA, Bellinger PF (1994a) Biogeography of Hawaiian Collembola: the simple principles and complex reality. Oriental Insects 28: 307–351.
  • Christiansen KA, Bellinger PF (1995) The biogeography of Collembola. Polskie Pismo Entomologiczne 64: 279–294.
  • Christiansen KA, Bellinger PF (1996a) Cave Arrhopalites new to science. Journal of Karst and Cave Studies 58: 168–1890
  • Christiansen KA, Bellinger PF (1996b) Cave Pseudosinella and Oncopodura new to science. Journal of Karst and Cave Studies 58: 37–52
  • Christiansen KA, Bellinger PF (1998) The Collembola of North America North of The Rio Grande, Revised Edition, Grinnell College.
  • Christiansen KA, Bellinger PF (2000a) A survey of the genus Seira (Hexapoda: Collembola: Entomobryidae) in the Americas. Caribbean Journal of science 36: 1–75.
  • Christiansen KA, Bellinger PF (2000b) Redescriptions of some of Salmon’s isotomid types. Contributions of the Biological Laboratory of Kyoto University 29: 103–115.
  • Christiansen KA, Bellinger PF (2003) Collembola. In Encylopedia of Insects. Academic Press/Elsevier. Amsterdam, 235–239.
  • Christiansen KA, Bernard EC (2008) Critique of the article “Collembola (springs) (Arthropoda: Hexapoda: Entognatha) found in scrapings from individuals diagnosed with dulosry pareasitosis. Entomological News 119: 537–540. https://doi.org/10.3157/0013-872X-119.5.537
  • Christiansen KA, Bouillon M (1978) An evolutionary and ecological analysis of the terrestrial arthropods of caves in the central Pyrenees with special reference to Collembola. Bulletin of the National Speleological Society 40: 103–117.
  • Christiansen KA, Culver DC (1969) Geographical variation and evolution in Pseudosinella violenta. Evolution 23: 602–621. https://doi.org/10.2307/2406856
  • Christiansen KA, Culver DC (1987) Biogeography and the distribution of cave Collembola. Journal of Biogeography 14: 459–477. https://doi.org/10.2307/2844976
  • Christiansen KA, Grow AB (1974) Cheatotaxy in the Nearctic member of the genus Friesea. Revue d’Ecologie et de Biologie du Sol 11: 37–99.
  • Christiansen KA, Grow AB (1976) Chaetotaxy in Folsomia. Revue d’Ecologie et de Biologie du Sol 13: 611–627.
  • Christiansen KA, Luther G (1986) Two new species of Hawaiian Pseudosinella (Collembola: Entomobryomorpha: Entomobryidae). Proceedings of the Hawaiian Entomological Society 26: 45–51.
  • Christiansen KA, Pike E (2002) Cretaceous Collembola (Arthropoda, Hexapoda) from the Late Cretaceous of Canada. Cretaceous Research 23: 165–188
  • Christiansen KA, Reddell JR (1986) The cave Collembola of Mexico, Speleological Monographs 1: 127–164.
  • Christiansen KA, Snider RT (1996) Aquatic Collembola. In: Merritt W, Cummins K (Eds) Aquatic insects of North America (3rd edn). Kendall Hunt, 84–96.
  • Christiansen KA, Tucker BE (1977) Five new species of Orchesella. Proceedings of the Iowa Academy of Science 84: 1–13.
  • Christiansen KA, Tucker BE (1977) Four new nearctic species of Folsomia (Collembola: Isotommidae). Revue d’Ecologie et de Biologie du Sol 14: 371–382.
  • Christiansen KA, Wang H (2006) A revision of the genus Typhlogastrura in North American caves with description of five new species. Journal of Cave and Karst Studies 68: 85–98.
  • Christiansen KA, Bellinger FP, daGama MM (1983) A catalogue of the species of the genus Pseudosinella. Ciencia Biologica 5: 1–31.
  • Christiansen KA, Bellinger PF, da Gama MM (1991) Computer asssisted identification of specimens of Pseudosinella. Revue d’Ecologie et de Biologie du Sol 27: 231–246.
  • Christiansen KA, Doyle M, Kahlert M, Gobaleza D (1992) Interspecific interactions between collembolan populations in culture. Pedobiologia 36: 274–286.
  • Christiansen KA, Lyman Johnson (1972) Contact behaviour in Collembola. Pedobiologia 12: 222–228.
  • Christiansen KA, Palacios-Vargas JG, Ojeda M (1985) , Taxonomia y biogeografia de Troglopedetes (Collembola: Paronellidae). Folia Entomologica Mexicana 65: 3–35.
  • Christiansen KA, Tecklin J, Willson M (1961) Preliminary study of the microarthropod ecology of Hunters Cave. Bulletin of the National Speleological Society 24: 62–70.
  • Jia S, Chen J-X, Christiansen KA (2003) A new collembolan species of the genus Homidia (Entomobryidae) from Hubei, China. Journal of the Kansas Entomological Society. 76: 610–615.
  • Li L-R, Christiansen KA (1997) A new species of Homidia from China (Collembola Entomobryidae). Florida Entomologist 80: 457–460. https://doi.org/10.2307/3495610
  • Ma Y, Christiansen KA (1998) A new species of Tomocerus (s.s.) from China. Entomological News 109: 47–51.
  • Ma Y, Chen J-X, Christiansen KA (2003) A new species of the genus Tomocerus (Tomocerina) from Xinjiang (Collembola Tomoceridae) with a discussion of Tomocerina. Journal of Entomological Science 38: 511–518. https://doi.org/10.18474/0749-8004-38.4.511
  • Ma Y, Chen J-X, Christiansen KA (2004) New species of the genus Tomocerus (Tomocerina) from China (Collembola: Tomoceridae) with a discussion of the subgenera of Tomocerus. Entomological News. 114: 41–46.
  • Madele Y-T, Chen J-X, Christiansen KA (2004) A new record of Tomocerus baicalensis from China with its redescription (Collembola: Tomoceridae). Entomological News 114: 47–50.
  • Peck SB, Christiansen KA (1990) Evolution and zoogeography of the invertebrate cave faunas of the Driftless Area of the Upper Mississippi Valley. Canadian Journal of Zoology 68: 73–88. https://doi.org/10.1139/z90-012
  • Pomorski R, Furgol J, Christiansen KA (2009) Review of North American species of the genus Onychiurus (Collembola: Onychiuridae), with a description of four new species From caves. Annals of the Entomological Society of America 102: 1037–1049. https://doi.org/10.1603/008.102.0612
  • Skarzynski D, Christiansen KA (2008) Ceratophysella richardi sp. n. (Collembola: Hypogastruridae) from USA, with synonymization of the genus Mitchellania with Ceratophysella. Annals of the Entomological Society of America 101: 989–992. https://doi.org/10.1603/0013-8746-101.6.989
  • Wang F, Christiansen KA (2000) A new species of Sinella (Collembola: Entomobryidae) from China. Entomological News 111: 332–336.
  • Wang F, Chen J-X, Christiansen KA (2002b) A new species of the subgenus Coecobrya from China (Collembola : Entomobryidae) . Journal of Entomological Science 37: 213–218. https://doi.org/10.18474/0749-8004-37.3.213
  • Wang F, Chen J-X, Christiansen KA (2002c) A new species of the subgenus Coecobrya from Hungary (Collembola: Entomobryidae). Journal of Kansas Entomological Society 75: 43–47.
  • Wang F, Christiansen KA, Chen J-X (2002d) A new speciesof Pseudosinella from China (Collembola Entomobryidae). Entomological News 113: 63–67.
  • Wang F, Chen J-X, Christiansen KA (2003a) A new species of Pseudosinella from Nanjing China (Collembola : Entomobryidae). Entomological News 113: 243–246.
  • Wang F, Chen J-X, Christiansen KA (2003c) Similarity of Pseudosinella hui sp. nov. (Collembola: Entomobryidae) to European and North American species. Journal of Entomological Research 38: 240–246. https://doi.org/10.18474/0749-8004-38.2.240
  • Wang F, Chen J-X, Christiansen KA (2003d) Taxonomy of the genus Lepidocyrtus s.l. (Collembola: Entomobryidae) in East Asia and Southeast Asiua and Malatsia with the description of a new species from the People’s Republic of China. The Canadian Entomologist 135: 823–837. https://doi.org/10.4039/n02-106
  • Wang F, Christiansen KA, Chen J-X (2003e) A new species of Pseudosinella from Xinjiang China (Collembola Entomobryidae). Journal Kansas Entomologhical Society 76: 603–609.
  • Wu M, Christiansen KA (1997) A new species of Arrhopalites from China (Collembola Sminthuridae). Florida Entomologist 80: 266–269. https://doi.org/10.2307/3495560
  • Zeppelini D, Christiansen KA (2003) Arrhopalites (Collembola: Arrhopalitidae) in U.S. caves with the description of seven new species. Journal of Cave and Karst Studies 65: 30–36.