Evolution and speciation in other molluscs

I have conducted a number of allozyme-based studies of other groups of molluscs in collaboration with accomplished malacologists. I have used patterns of genetic variability and genetic distance to re-define biological species in groups where conchology is misleading, and to address issues of phylogeny. Noteworthy contributions among the seven papers listed here include:

  • Publication 89 on genetic variation and species differentiation in Nautilus. I discovered that Nautilus is not really a living fossil but rather a post-Miocene radiation of six sibling species. This paper was reprinted in 2010.
  • Publication 109 shows that allozymes can be used to resolve the phylogeny of a remarkable radiation of 27 species of Australian camaenid land snails with very small geographic ranges discovered by the late Alan Solem in the isolated Ningbing Range in northwestern Australia.
  • Publication 112 showing that a much-studied Pacific coast dogwhelk, Nucella (=Thais) emarginata, is actually two species.
  • Publication 116 showing that 27 species of Asian clams, Corbicula, are actually conchologically defined populations or varieties of a single genetic species.

Publications

65. Woodruff, D.S., M. Mulvey, W.B. Saunders and M.P. Carpenter. Genetic variation in the cephalopod Nautilus belauensis. Proceedings of the Academy of Natural Science (Philadelphia) 135:147–153. (1983c).
Note: A methods paper demonstrating that multilocus allozyme surveys can be based on tentacle tip snips from live animals and that Nautilus were genetically variable enough to permit a phylogenetic reconstruction. Bruce Saunders (Bryn Mawr) and I were co-PI's on this NSF-funded research project. My postdoctoral fellow, Peg Mulvey, and laboratory assistant, Pat Carpenter, ran the first gels. [No. of ISI citations: 6]

79. Woodruff, D.S., L.L. McMeekin, M. Mulvey and M.P. Carpenter. Population genetics of Crepidula onyx: Variation in Californian slipper snail recently established in China. The Veliger 29(1):53–63. (1986g).
Note: We describe our study of a subtidal snail, resembling one found in San Diego, that has recently invaded Hong Kong harbour. Our allozymic genetic markers confirm its identity as the Californian snail and implicate Los Angeles harbor as the source. I collected the snails and graduate student Lori McMeekin ran the gels with assistance from Mulvey and Carpenter. See also publication 217. [No. of citations: 23]

89. Woodruff, D.S., M.P. Carpenter, W.B. Saunders and P.D. Ward. Genetic variation and species differentiation. In: Nautilus: The Biology and Paleobiology of a Living Fossil. Saunders, W.B. and N.H. Landman, eds. Plenum Press, New York, pp. 65–83. (1987h).
Note: Allozymes reveal Nautilus to be a cluster of six species that evolved by peripatric speciation in the last 10 million years. See also Publication 77: “Is Nautilus a living fossil? The genes say No!” This report is based on the application of the methods developed in Publication 65 to the whole genus. Saunders (Bryn Mawr) collected most of the Nautilus and Peter Ward (Washington) contributed a sample from New Caledonia. [No. of citations: 14]

109. Woodruff, D.S. and A. Solem. Allozyme variation in the Australian camaenid land snail, Cristilabrum primum: a prolegomenon for a molecular phylogeny of an extraordinary radiation in an isolated habitat. The Veliger 33(2):129–139. (1990d).
Note: This methods paper, the first of a planned series with the late Alan Solem, shows that allozyme variation can be used to resolve speciation and phylogeographic patterns in Australian camaenid land snails from the Ningbing Range in northwestern Australia. Solem discovered a remarkable radiation of three genera and 27 species in this isolated, 52 km long limestone mountain range. The species have very restricted, typically allopatric geographic ranges and replace one another every kilometer, on average, along the range. In a series of monographs Solem described the different species of snails and found their anatomy to be so variable (interspecifically) as to preclude the establishment of phylogenetic relationships. Allozymes, in contrast, provide a good indication of the group’s history and speciation appears to have occurred serially, as the snails dispersed along the range from two points of colonization. Two other manuscripts await completion. [No. of citations: 13]

112. Palmer, A.R., S. Gayron and D.S. Woodruff. Reproductive, morphological and genetic evidence for two cryptic species of Northeastern Pacific Nucella. The Veliger 33(4):331–344. (1990g).
Note: Rich Palmer (Alberta) discovered the situation and my graduate student, Scott Gayron, and I resolved it using allozymes. Nucella were formerly referred to the genus Thais and the two cryptic species known as “T. emarginata” were widely used and confused as a model experimental animal for half a century. [No. of citations: 48]

116. Kijviriya, V., E.S. Upatham, V. Viyanant and D.S. Woodruff. Genetic studies of Asian clams, Corbicula, in Thailand: allozymes of 21 nominal species are identical. American Malacological Bulletin 8(2):97–106. (1991c).
Note: Varaporn Kijviriya, as Upatham's graduate student, used morphometrics and allozymes to reaffirm the traditional taxonomy of the 21 species of Thai clams. She re-analyzed her genetic results in my laboratory and we found that, although conchologically very variable, the clams were all referable to a single species. [No. of citations: 11]

135. Woodruff, D.S., V. Kijviriya and E.S. Upatham. Genetic relationships among Asian Corbicula: Thai clams are referable to topotypic Chinese Corbicula fluminea. American Malacological Bulletin 10(1):51–53. (1993a).
Note: I collected clams in China and showed they were genetically indistinguishable from the Thai samples described in Publication 116. [No. of citations: 10]

217. Plutchak, L.L., R.E. Simmons and D.S. Woodruff. Multilocus allozyme heterozygote deficiencies in Crepidula onyx: geographic and temporal patterns among adult snails in Mission Bay, California. Journal of Molluscan Studies 72:337–348. (2006c) Note: With Master’s students Lori McMeekin Plutchak and Rachel Simmons we establish that the heterozygotes were lost from the population in the larval or early settlement stages of life. This curious phenomenon has been observed in other sub-tidal molluscs in Europe and has, thus far, eluded explanation. Our report has led to further investigations in Europe and South America. [No. of citations: 5]

224. Woodruff, D.S., M.P. Carpenter, W.B. Saunders and P.D. Ward. Genetic variation and phylogeny in Nautilus. In: Nautilus 2: The Biology and Paleobiology of a Living Fossil. Saunders, W.B. and N.H. Landman, eds. Second edition with additions Springer, Netherlands, pp. 65–83. (2010). Note: Reprint of publication 89 [No. of citations: 7]

Nautilus belauensis Palau, Micronesia. Photographed in shallow water by Bruce Saunders. Tentacle tips collected non-destructively from live animals were used as a source of allozymes employed in the genetic studies reported in Publications 65, 89, 204, 224.