Ecology evolution and speciation in the Australian frogs, Pseudophryne.

My doctoral research on the small Australian toadlets of the genus Pseudophryne culminated in a paper in the journal Science showing that their interspecific hybrid zones could be relatively stable and ancient phenomenon in which limited mismating did not threaten the integrity of otherwise independently evolving semispecies (Publication 51). At the time, hybrid zones were widely believed to be unstable transient phenomena that led to fusion or to full reproductive isolation and speciation. I have published 9 papers on Pseudophryne (and 3 on related topics) but the bulk of my observations on Pseudophryne morphological variation, larval development, in vitro hybridization experiments and on the hybrid zones themselves remain unpublished in my 1972 thesis, and will be the focus of future papers.

Interspecific hybridization between male Pseudophryne dendyi (yellow arm patch) and female P. semimarmorata (red arm patch). Pair discovered under leaf litter during light rain, 20.5 km N. of Tyers, Victoria, at 2300 hrs., April 4 1969. Eggs are visible beneath female’s right foot. Hybrid embryonic mortality can exceed 30% versus 5% for homogamous clutches.

Publications

10. Woodruff, D.S. and M.J. Tyler. Additions to the frog fauna of South Australia. Records of the South Australian Museum 15:705–709. (1968a).
Note: Our fieldwork in southeastern South Australia led to discovery of geographic range extensions for two species. [No. of citations: 5]

17. Woodruff, D.S. Amphibians and reptiles from Simbai, Bismark-Schrader Range, New Guinea. Memoirs of the National Museum Victoria 33:57–63. (1972a).
Note: First report of the fauna of previously remote district and description of a case of sexual dichromatism in a skink. [No. of ISI citations: 7]

18. Woodruff, D.S. Australian anuran chromosome numbers. Herpetological Review 4(69):208. (1972b).
Note: I reported the chromosome numbers for six leptodactylids and one hylid. [No. of citations: 3]

23. Woodruff, D.S. Natural hybridization and hybrid zones. Systematic Zoology 22:213–218. (1973e).
Note: I provided an improved nomenclature for describing hybrid zones without reference to ambiguous taxonomic or evolutionary criteria. [No. of citations: 78]

24. Woodruff, D.S. Bassiana. Australian Journal of Science 4(10):409. (1973f).
Note: I suggested a name for the region including Tasmania, the Bass Strait Islands and adjacent Australian mainland, which was exposed as a single land area and evolutionary theater during times of lower sea levels. [No. of citations: 2]

31. Woodruff, D.S. Morphological and geographical variation of Pseudophryne corroboree (Anura: Leptodactylidae). Records of the Australian Museum 30:99–113. (1975e).
Note: I provided the first detailed report on variability of this colorful black and yellow striped toadlet isolated on two mountain ranges in southeastern Australia. Some of my discussion has been rendered moot by the subsequent discovery that the two populations are chromosomally distinct and recognition as separate species. [No. of ISI citations: 7]

33. Woodruff, D.S. Embryonic mortality in Pseudophryne (Anura: Leptodactylidae). Copeia 1976:445–449. (1976a).
Note: Toadlet’s lay small batches of large eggs in rudimentary nests on land in areas which subsequently become flooded. I provided the first quantitative data of natural embryonic mortality patterns. These observations enabled me to demonstrate the relative inviability of natural hybrids and explain the genodynamics of hybrid zones. [No. of citations: 16]

34. Woodruff, D.S. North Queensland toadlets of the genus Pseudophryne. Queensland Naturalist 21:142–143. (1976b).
Note: I confirmed an 800 km range extension and closed an 80-year gap in the record of sightings of toadlets in north Queensland. [No. of ISI citations: 1]

35. Woodruff, D.S. Courtship, reproductive rates, and mating system in Australian Pseudophryne (Anura: Leptodactylidae). Journal of Herpetology 10:313–318. (1976c).
Note: I provided the first quantitative observations on clutch size and of nests containing embryos at two or more stages of development, indicating a temporal bet-hedging, iteroparous breeding strategy. This report led to a more focused PhD study (Thumm 2005, Sydney). [No. of citations: 18]

38. Woodruff, D.S. Male postmating brooding behavior in three Australian Pseudophryne (Anura: Leptodactylidae). Herpetologica 33:296–303. (1977b).
Note: I discussed the reasons why male toadlets remain with their eggs in their nests and continue to call. [No. of citations: 21]

43. Woodruff, D.S. Hybridization between two species of Pseudophryne (Anura: Leptodactylidae) in the Sydney Basin, Australia. Proceedings of the Linnean Society of New South Wales 148(3):131–147. (1978a).
Note: I provided the first detailed distributional mapping and analysis of the interactions between two species of toadlets around Sydney. This paper provided a framework for a subsequent PhD thesis for which I served as the external examiner (Stauber 2006, Sydney). [No. of citations: 7]

51. Woodruff, D.S. Postmating reproductive isolation in Pseudophryne and the evolutionary significance of hybrid zones. Science 203:561–563. (1979a).
Note: I reported the major result of my doctoral thesis: the narrow hybrid zones separating parapatrically distributed species of toadlets are hybrid sinks and relatively ancient. At the time, hybrid zones were thought to be more transient. In Pseudophyne, the postmating isolating mechanisms are strong enough to preclude the selection for premating mechanisms, and the result is an evolutionary stalemate. [No. of citations: 31]

58. Woodruff, D.S. Towards a genodynamics of hybrid zones: Studies of Australian frogs and West Indian land snails. In: Essays on Evolution and Speciation in Honor of M. J. D. White. Atchley, W.R. and D.S. Woodruff, eds. Cambridge University Press, Cambridge, Mass., pp. 171–197. (1981a).
Note: I edited this Festschrift for my former mentor at the University of Melbourne and presented a detailed description of several hybrid zones showing that asymmetries in the hybrid zones may be artifacts of sampling. This book and paper were reprinted by CUP in 2010. [No. of citations: 48]

C16. Woodruff, D.S. Pseudophryne hybrid zones. In preparation
Note: The text for a monograph (morphological variation, distribution, reproductive and developmental biology, and characterization of the hybrid zones in the 1960s) has been prepared but the figures have not yet been re-drawn to UC Series in Zoology standards.