Foliar ontogeny in Gymnostoma deplancheanum and its evolutionary and ecological significance for scleromorphy and xeromorphy in Casuarinaceae (Fagales)
| Autor: | Veit Martin Dörken, R. F. Parsons, Phil G. Ladd |
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| Rok vydání: | 2019 |
| Předmět: |
Gymnostoma deplancheanum
Leaf reduction Morphology Anatomy Scleromorphy Xeromorphy 0106 biological sciences Casuarina Allocasuarina Casuarinaceae Ecology biology Physiology Forestry Plant Science biology.organism_classification Deserts and xeric shrublands Fagales 010603 evolutionary biology 01 natural sciences Taxon Gymnostoma Genus ddc:570 Botany 010606 plant biology & botany |
| Zdroj: | Trees. 33:653-668 |
| ISSN: | 1432-2285 0931-1890 |
| DOI: | 10.1007/s00468-018-1806-9 |
| Popis: | Key messageThe phylogenetically basal genus of the Casuarinaceae, Gymnostoma, from relatively mesic environments, shows morphological and anatomical structures that are precursors to xeromorphic modifications in the derived genera Casuarina and Allocasuarina.Gymnostoma is the basal genus of the Casuarinaceae with a long evolutionary history and a morphology that has changed little over many millions of years. From a wide distribution in the Tertiary of the southern hemisphere, it is now restricted to islands in the Pacific Ocean, the Malesian region and one small area of northeastern Queensland where it occurs in mesic climates, often on poor soils. The unique vegetative morphology it shares with other more derived genera in the family appears to be xeromorphic. Its distribution combined with the fossil evidence that early Tertiary Gymnostoma occurred with other taxa whose morphology indicated they grew in mesic environments implies that the reduction in the photosynthetic organs was not specifically related to growing in xeric environments. It may be related to evolutionary adaptation to growing on nutrient poor substrates that may also suffer from seasonal water deficit. The foliage reduction then served as a pre-adaptation for derived species to help them cope with the aridity that developed on the Australian continent through the later part of the Tertiary. The fusion of the leaves to the stem to form phyllichnia was a precursor which enabled the development of specific adaptations in the derived genera Casuarina and Allocasuarina to improve water conservation, such as stomata restricted to furrows between the phyllichnia and proliferation of structural sclerenchyma that helps prevent cell collapse under drought conditions. published |
| Databáze: | OpenAIRE |
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