Dr. Mark Harrington
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CSIRO/JCU Postdoctoral Research Fellow , Australian Tropical Herbarium |
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Office: |
E2.118G, Sir Robert Norman Building (E2), James Cook University, PO Box 6811, Cairns QLD 4870 |
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Phone: |
+61 (0)7 4042 1769 |
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Fax: |
+61 (0)7 4042 1842 |
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Email: |
Research
Origins of the Wet Tropics flora – a molecular perspective
Using molecular analyses to contribute to our understanding of the history of species diversification and historical biogeography of the Wet Tropics flora.
Main Aims
Generate general explanations about tempo and direction of evolution of the tropical rainforest flora.
What elements of the extant rainforest flora are potentially the results of old Gondwanan stock (relictual taxa) that have differentiated in situ, and what are the invasive elements, and where have they come from?
Background and Significance
The origins and evolution of the Australian tropical flora has fascinated botanists over the past 150 years. The original notion as postulated by eminent English botanist Joseph Hooker (1859) was that rainforests were ‘alien and invasive’, relatively recent introductions from New Guinea or south-east Asia. With the knowledge of continental drift, Webb and Tracey (1986) doubted that the composition of Australian rainforests arrived from external sources. Based on floristic comparisons they suggested that Australian rainforests rather than being depauperate samples of those of south-east Asia, are ‘remnants’ of the Ancient Gondwanan flora that once covered Australia. The concentration of ‘primitive’ families in Australia along with the presence of narrow endemics and ‘primitive’ angiosperms suggested that the tropical rainforests had acted as refugia for these components of the flora from Gondwanic times. While some aspects of the limited fossil record does demonstrate that many present-day rainforest taxa have a long history in Australia, the extent to which the extant flora is derived from Laurasian flora is still controversial. While maintaining that Australian tropical rainforests are a high centre of diversity and endemism, Thorne (1986) and Barlow and Hyland (1988), amongst others have argued that there has been a recent remixing with the Indo-Malesian flora after a long period of separation. The biological interaction between the Australian and New Guinea floras is also a topic of uncertainty and of differing interpretation, particularly within Iron Range-McIlwraith Range region of eastern Cape York Peninsular which is acknowledged as a major centre of diversity and endemism.
The organised campaign for tropical rainforest conservation in the late 1970-80s stressed the remnant nature of the Australian tropical rainforests, their aesthetic splendour, and their scientific values based especially on the new interpretations of their origins and their high concentration and distribution of flora and fauna. Rather than a recent immigrant flora from more exotic places, rainforest was acknowledged as an ancient component of the Australian landscape to be valued as part of the national heritage.
Many of the natural criterion examples for listing the Wet Tropics World Heritage Area are connected with the evolutionary history of the component flora and come from a time when there was no use of molecular data. Phylogenetic reconstructions using molecular phylogenies are becoming increasingly vital for gaining crucial insights into understanding evolutionary history. A recent example is the monogeneric Hydatellaceae (Trithuria - Australia 8 species, New Zealand 1 sp., India 1 sp.) which was thought to be a monocot, but molecular phylogenetic analyses of multiple plastid genes and associated non-coding regions identified this family as a new branch near the base of the angiosperm phylogenetic tree as sister group of Nymphaeales (with Amborella and Austrobaileyales sister to remaining Angiosperms). The surprising result was further corroborated by evidence from a nuclear gene and multiple morphological characters (Saarela et al. 2007).
Initial Scope
Angiosperm families and genera included in the “Australian Tropical Rain Forest Plants - Trees, Shrubs and Vines” (Hyland et al. 2003) and “Fruits of the Australian Tropical Rainforest” (Cooper and Cooper, 2004).
Relevance
This project adds to our core knowledge of the evolution of Wet Tropics flora and supports the heritage protection values of the World Heritage Area, and furthermore ensures that this knowledge is contemporary. While research outcomes will be published in peer reviewed journals they also will be able to be adapted to providing all stakeholders and the wider community with a fresh perspective on evolution and extinction in the Wet Tropics flora.
Selected Publications
Jones L.M., Gadek P.A., Harrington M.G. (2010) Population genetic structuring in a rare tropical plant: Idiospermum australiense (Diels) S.T.Blake. Plant Systematics and Evolution 286: 133-139.
Harrington M. G., Gadek P. A. (2010) Phylogenetics of hopbushes and pepperflowers (Dodonaea, Diplopeltis - Sapindaceae) based on nuclear ribosomal ITS and partial ETS sequences incorporating secondary-structure models. Australian Systematic Botany 23: 431-442.
Biffin E., Lucas E.J., Craven L.A., da Costa I.R., Harrington M.G., Crisp M.D. (2009) Evolution of exceptional species richness among lineages of fleshy-fruited Myrtaceae. Annals of Botany (London) 106: 79-93.
Harrington, M. G. and Gadek, P. A. (2009) A species well travelled – the Dodonaea viscosa (Sapindaceae) complex based on phylogenetic analyses of nuclear ribosomal ITS and ETSf sequences. Journal of Biogeography.
Buerki, S. Forest, F., Acevedo-Rodriguez, P., Callmander, M. W., Nylander, J. A., Harrington, M. G., Kupfer, P., Alvarez, N. (2009) Worldwide phylogeny of the soapberry family (Sapindaceae): plastid and nuclear markers reveal intricate relationships at subfamilial, tribal and generic levels. Molecular Phylogenetics and Evolution 51:238-258.
Biffin, E., Craven, L. A., Crisp, M. D., Gadek, P. A. and Harrington, M. G. (in press) Evolutionary relationships within Syzygium sens. lat. (Myrtaceae): molecular phylogeny and new insights on morphology. Proceedings of the Sixth International Flora Malesiana Symposium 2004 (Institute Penyelidikan: Kuala Lumpa).
Harrington, M. G., Biffin, E. and Gadek, P. A. (2009) Comparative study of the evolution of nuclear ribosomal spacers incorporating secondary structure analyses within Dodonaeoideae, Hippocastanoideae and Xanthoceroideae (Sapindaceae) Molecular Phylogenetics and Evolution 50:364-375.
Biffin, E and Harrington, M. G., Crisp, M. D., Craven, L. A. and Gadek, P. A. (2007) Structural partitioning, paired-sites models and evolution of the ITS rDNA in Syzygium and Myrtaceae. Molecular Phylogenetics and Evolution 42:124-139.
Harrington, M. G., Gadek, P. A. and Edwards, W. (2005) The potential for predation induced somatic embryogenesis in storage cotyledons. Oikos 111: 215-220.
Harrington, M. G., Edwards, K. J., Johnson, S. A., Chase, M. W. and Gadek P. A. (2005) Phylogenetic inference in Sapindaceae sensu lato using plastid matK and rbcL DNA sequences. Systematic Botany 30(2): 365-381.
Harrington, M. G. and Gadek, P. A. (2004) Molecular systematics of the Acmena alliance (Myrtaceae): phylogenetic analyses and evolutionary implications with reference to Australian taxa. Australian Systematic Botany 17: 63-72.