Conservation of Wilsonia backhousei (Convolvulaceae) and Lampranthus tegens (Aizoaceae)

Publication Type:
Thesis
Issue Date:
2007
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NO FULL TEXT AVAILABLE. Access is restricted indefinitely. ----- Successful conservation and restoration of saltmarsh requires an understanding of the biology and ecology of the constituent species, particularly when those species are themselves threatened. The aim of this project was to investigate the biology, ecology and genetics of two threatened species found in the endangered saltmarsh communities of NSW - Wilsonia backhousei Hook. f. (Convolvulaceae) and Lampranthus tegens (F.Muell.) N.E.Br (Aizoaceae) - in order to provide the knowledge necessary for effective conservation of the species, and successful restoration of their degraded habitats. A series of field, glasshouse and laboratory studies were undertaken to determine the environmental conditions that favour the presence and growth of both species, to describe their reproductive biology and investigate the effects of environmental conditions on reproductive success, and to investigate genetic variation within and among populations of W. backhousei. The distributions of both species were found to be significantly influenced by a number of environmental factors; a negative response to increasing salinity (though at different levels) was the only factor in common. The findings of the glasshouse study supported field observations of the relative positions of the two species in the marsh, with W. backhousei proving to be the more tolerant of the two in terms of salinity alone, and the combined effects of salinity and waterlogging. The abundance of W. backhousei in mono-specific stands was strongly influenced by sediment water content, while that of L tegens was weakly related to low sediment pH. The reproductive and genetic studies of W. backhousei indicated that the species is self-incompatible and principally wind-pollinated, with fruit dispersed by tides within an estuary. Seed yield in the species was significantly related to both sediment water content and the diversity of genotypes within a I 0 m radius, while germination was inhibited by an impermeable seed coat and highly saline substrates. The genetic study also revealed that single clones may spread over an area of more than 200m2 , that vegetative dispersal among sites does not appear to occur, and that the level of genetic diversity within a population is not related to site size. The reproductive study on L. tegens revealed that the species is facultatively outbreeding and insect-pollinated. Flower production and fruit yield were not related to any of the sediment parameters tested, however, fruit maturation was inhibited by tidal inundation during late spring and summer. The above results have practical implications in terms of both conservation and restoration for W. backhousei and L. tegens, and saltmarsh in general. These issues are discussed and recommendations for future studies are outlined.
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