Seed size and the regeneration niches of one rare (Melaleuca deanei) and three common (Melaleuca styphelioides,Melaleuca thymifolia and Melaleuca nodosa) Melaleuca (Myrtaceae) species of the Sydney region |
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| Authors: | Alison Hewitt Paul Holford Adrian Renshaw Glenn Stone E Charles Morris |
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| Institution: | 1. School of Science and Health, University of Western Sydney, Penrith, New South Wales, Australia;2. School of Computing, Engineering and Mathematics, University of Western Sydney, Penrith, New South Wales, Australia |
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| Abstract: | Melaleuca species occupy varied habitats across Australia with 16 members of the genus occurring in the Sydney district including the rare species Melaleuca deanei F. Muell. Little is known of their germination and recruitment requirements. This paper reports on experiments assessing the effects of temperature, water potential, fire cues, light and shade levels on germination in four species of Melaleuca native to the Sydney region. For the shade experiment, seedling survival at 12 months is also reported. The experiments tested the hypothesis that M. deanei, which exhibits few seedlings in the field, has limited seedling recruitment because of its particular requirements for germination and establishment. Further, that it differs in these requirements from three common congenerics: M. nodosa (Sol ex Gaertn.) Sm., M. thymifolia Sm. and M. styphelioides Sm. Results indicate that M. deanei has a substantially similar temperature and water potential range for germination to the common congeners from 15 to 35°C, and 0 to ?0.65 ψ. Melaleuca nodosa displayed the broadest regeneration niche on all factors assessed. Germination of M. styphelioides was significantly reduced in the dark and M. styphelioides and M. deanei were most sensitive to shade in the seedling establishment/post‐germination phase. Melaleuca deanei had significantly larger seed that was slower to germinate in all experiments. Germination of the four species was unaffected by the application of heat and smoke. The substantially similar germination parameters exhibited by the four species, despite differences in habitat, may reflect their close phylogenetic affinities. The effects of fire on stimulating seed release from the canopy, the high‐light environment post‐fire together with adequate follow‐up rainfall may all be critical in seedling establishment for M. deanei. |
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| Keywords: | fire cue germination light phylogenetic niche shade temperature water potential |
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