Fruit and seed studies in Australian Melicytus
The genus Melicytus (native Tree Violet) is suspected to include more than one species in Australia. A taxonomic revision is underway that focuses on traditional features for separating species. By studying fruit and seed structure, germination strategies and seedling morphology, it may be possible to provide a further means of distinguishing Australian taxa of Melicytus. It will also be useful to know if these taxa have different germination requirements depending on their biogeographical distribution.
The genus Melicytus (family Violaceae) is confined to the south-western Pacific region Australia, New Zealand, New Caledonia and some other smaller islands. It reaches its greatest diversity in New Zealand with over 20 species. They are woody shrubs or small trees that may be dioecious (i.e. plants are either male or female) or they may have bisexual flowers. Through most of Australia, we currently recognise only a single broadly circumscribed species, Melicytus dentatus. This species varies considerably across its range with some variants being quite distinct and confined to specific biogeographical regions. Two other species, M. latifolius and M. ramiflorus, occur on Norfolk and Lord Howe Islands respectively.
Plants grow over a wide area of south-eastern Australia from near sea level to the highest alpine areas. They usually grow in rocky areas, often in grasslands, grassy woodlands or herbfields. Plants may be low and sprawling sub-shrubs or erect shrubs to three metres tall. The branches are often rigid and spine-tipped and sometimes densely intermeshed.
Seed and fruit characters, along with germination data and seedling morphology, will be recorded from seeds collected from a range of habitats. By attempting to germinate seeds under a range of temperature and light regimes, and by examining the seedlings closely, we hope that we will discover variation not usually included in conventional taxonomic studies. We will compare variation in seed and fruit characters with variation in features traditionally used to distinguish Melicytus species, such as habit and flower structure. By understanding seed ecology we begin to better understand some of the evolutionary processes that have been responsible for speciation in the group.