Comparative germination ecology of species endemic of Banded Ironstone Formation
by Subhashi Rajapakshe
The Banded Ironstone Formation ranges and granite outcrops of the South Western Australian floristic region host a high number of rare and range-restricted plant species. A significant proportion of these taxa are endangered or likely to be threatened in near future by anthropogenic activities such as mining. MSc student Subhashi Rajapakshe is investigating the comparative germination ecology of several plant species endemic to these habitats with the aim of generating research data that is essential for planning cost-efficient conservation and management strategies.
The Banded Ironstone Formation (BIF) ranges and granite outcrops of the South Western Australian Floristic Region host unique plant communities that are floristically distinct from the deep-soil vegetation of the broader surrounding matrix. Although these geographically isolated, island-like shallow-soil ecosystems habour many range-restricted species, the ecological drivers behind these patterns of plant diversity are unclear. A significant proportion of the flora from BIF and granite outcrop habitats are threatened or likely to become threatened in the near future by anthropogenic activities such as mining. As a guide to understanding the ecological filters that regulate in situ species persistence, the use of a life stage transition framework is useful. One of the most critical steps of a life stage transition framework is the progression from seed to seedling, which is regulated by a host of different factors. Temperature and water stress have been identified as two primary factors affecting the germination response of all species which vary significantly across ecosystems and environments including those occupied by short-range endemics. Therefore, research data on the germination response of short-range taxa to temperature and drought stress is essential to plan cost-efficient conservation and management strategies. However, information on how BIF endemics and granite outcrop specialists respond to changes in these factors, particularly compared to more widely occurring taxa, are scarce. This project aims to investigate how seeds of selected range-restricted flora of BIF ranges and granite outcrops respond to fluctuations in temperature and moisture content in comparison to common co-occurring species, which in terms of taxonomy and functional group, are quite similar. This project will generate research data that is critical for managing in-situ populations of rare species and for planning cost-efficient relocation and re-introduction programmes.
The major objective of this research program is to investigate the comparative seed ecology of species endemic to BIF ranges and granite outcrop ecosystems with widely occurring sympatric taxa from across south-western Australia. The proposed research will seek to address the following research questions:
1. Do seeds of non-dormant range-restricted species exhibit any measurable differences in sensitivity to incubation temperature compared to common co-occurring species?
2. Do seeds of physically-dormant range-restricted species exhibit any measurable differences in sensitivity to incubation temperature compared to common co-occurring species?
3. Do different populations of non-dormant range-restricted species show any measurable differences in optimal temperature requirements for germination?
4. Are seeds of non-dormant range-restricted species more sensitive to moisture stress than widely distributed co-occurring taxa when incubated under water-limited conditions?
5. Are seeds of physically dormant range-restricted species more sensitive to moisture stress than widely distributed co-occurring taxa when incubated under water-limited conditions?
Temperature fluctuations and water stress have been identified as two of the major factors affecting the seedling recruitment success of range-restricted taxa. However, there is a shortage of information on how BIF specialists and granite outcrop endemics of South Western Australia respond to changes in these factors. This will be one of the first studies to generate research data on comparative germination ecology of shallow-soil short-range endemics and common co-occurring deep-soil taxa of South Western Australia. The proposed project will generate research data that is essential to manage existing in situ populations of the BIF ranges and granite outcrops, optimise the use of seeds in propagation and restoration programs, and to identify suitable in situ environments for future translocations or reintroductions of range-restricted species.