Australasian Plant Conservation
Originally published in Australasian Plant Conservation 19(3) December 2010 - February 2011, p 13-14
Reconstructing new populations of the endangered Rutidosis leptorrhynchoides (Button Wrinklewort) at two sites in south‑western Victoria
Greening Australia/University of Melbourne. Email email@example.com
Native grasslands of south-eastern Australia have been reduced to one per cent of their historical range. Severe fragmentation of this once widespread flora poses a serious threat to the viability of many species that exist as small and isolated populations (Morgan 1998). Rutidosis leptorrhynchoides (Button Wrinklewort), a multi-stemmed, herbaceous perennial is an Asteraceae species endemic within these broader temperate south-eastern grassland communities. The species is listed as threatened under Victoria’s Flora and Fauna Guarantee Act 1998 and as endangered under the Commonwealth’s Environment Protection and Biodiversity Conservation Act 1999. Only 20 natural populations of Rutidosis are thought to remain within two broad zones of south-eastern Australia—one across New South Wales and the Australia Capital Territory and the other across southern and south-western Victoria (Young et al. 1999).
Issues to consider
Rutidosis seed is transient in the seed bank and is typically dispersed less than 0.5 m from the parent plant. Rutidosis also exhibits a self-incompatible breeding system (characteristic of many Asteraceae) which functions to reduce the risk of inbreeding depression. Such systems work most effectively in large, genetically diverse populations. However, half of these populations consist of low numbers of individuals (<200) and studies have confirmed that these small populations are prone to inbreeding depression (Morgan 1998; Young and Murray 2000).
Of the 20 south-eastern populations, the northern 15 are primarily diploid in regard to chromosome number, while the southern communities are wholly diploid, wholly tetraploid or mixed (Brown and Young 2000). These authors argue that because of the high risk of sterility in triploid plants, establishing new founder populations should avoid introducing mixed ploidy populations which would be counter-productive and wasteful of expensive resources. Conservation of this species should thus look to increase the size and genetic characteristics of existing small populations. When attempting to reconstruct new populations, programs should also consider the implications of population size and the genetic make-up (where this information exists) of source populations.
Greening Australia’s Grassy Groundcover Research Project has for some time investigated the reconstruction of species-rich grassland by direct seeding (Gibson-Roy et al. 2010). Originally thirteen 1 ha trial sites were established across south-western Victoria to test methods of direct seeding and weed control. In recent years a number of other sites have been established, consolidating learnings from the initial study. One such site was initiated in 2008 in partnership with VicRoads (Western Region). It aimed to reconnect high quality roadside remnants separated by historically planted non-endemic native tree plantations on the Glenelg Highway near Wickliffe in the state’s south-west (Carland and Kennedy 2010).
During the late 1980s and early 1990s attempts were made to re-establish populations of Rutidosis at five sites in south-western Victoria (four using tube stock and one seeded) (Young and Murray 2000). Assessments of survival in 1996 showed that while there had been some reductions and some increases in numbers across the sites (from 25 to 300 individuals remaining across the five sites) the species remained at each. Aware of these encouraging outcomes and buoyed by the Grassy Groundcover Research Project’s experience in reconstructing grassland by direct seeding, a further goal of this project was to re-establish two new founder populations of Rutidosis within both newly reconstructed grasslands.
Cognisant of the preceding discussions concerning population size, breeding systems and ploidy levels, seed from a nearby small (n=26) remnant tetraploid population located 3 km from the sowing site was combined with seed from a larger (n>5000) population (also tetraploid) located approximately 100 km from the seeding site. Small amounts of seed were taken from as many reproductive individuals as possible (i.e. 500+ in the large population) over the whole period of seed ripening and bulked and sub-sampled to obtain propagation material. From these small but diverse samples of seed from both source populations, plants were propagated to establish a production population (n=500). Rutidosis was grown as part of a larger seed production program, along with many other local species (Figure 1). The aim of the seed production system was to produce the quantities of seed required to undertake a field-scale seeding program.
Figure 1. A range of species (including Rutidosis leptorrhynchoides) growing in a containerised production system used to produce the desired quantities of seed for sowing at field scale
Figure 2. A diverse range of grassland species establishing at one of the two sites. Across both sites >1000 Rutidosis leptorrhynchoides are present.
Seed from the production program and a limited number of plants (approximately 150) were introduced onto bare/cleared sites in spring of 2009 using the Grassy Groundcover Research Project’s purpose-built seeder (Carland and Kennedy 2010). Since that time emergence and establishment from a whole suite of sown species has been extremely encouraging (Figure 2). In regard to Rutidosis, surveys undertaken 12 months following seeding show that up to 90% of the planted individuals have survived at both sites. More importantly, seedling emergence from sown seed is widespread and consistent, indicating that new populations of >1000 individuals have been established. Earlier sowings of the Research Project have confirmed that, in most cases, survival from individuals present at this point (post-seeding) is largely maintained, given appropriate management regimes.
This Grassy Groundcover Research Project trial aimed to reconstruct species-rich grassland and to recreate two new populations of the nationally threatened Rutidosis leptorrhynchoides. While it is still early in the establishment phase, it seems likely that both goals will be achieved. The Rutidosis component of the program also highlights how conservation and restoration projects can utilise and benefit from a breadth of important information generated in aligned disciplines (such as the genetic studies used to informed decisions at our sites). In doing so they may increase the likelihood of success in restoring viable and persistent native systems.
Thanks go to Frank Carland and Natasha Kennedy of VicRoads (Western Region), David Franklin and Ron Woff of Franklin Plant Native, Rod White of Greening Australia and Simeon Buckley for their assistance and support in undertaking this project.
Brown, A.H.D. and Young, A.G. (2000). Genetic diversity in tetraploid populations of the endangered daisy Rutidosis leptorrhynchoides and implications for its conservation. Heredity 85: 122–9.
Carland, F. and Kennedy, N. (2010). Restoring critically endangered grassland on roadsides in the Victorian Volcanic Plain. Australasian Plant Conservation 19: 22–3.
Gibson-Roy, P., Moore, G.M., Delpratt, C.J. and Gardner, J. (2010). Expanding horizons for herbaceous ecosystem restoration: the Grassy Groundcover Restoration Project. Ecological Management & Restoration 11: 175–85.
Morgan, J.W. (1998). Effects of population size on seed production and germinability in an endangered, fragmented grassland plant. Conservation Biology 13: 266–73.
Young, A.G., Brown, A.H.D. and Zich, F.A. (1999). Genetic structure of fragmented populations of the endangered daisy Rutidosis leptorrhynchoides. Conservation Biology 13: 256–65.
Young, A.G. and Murray, B.G. (2000). Genetic bottlenecks and dysgenic gene flow into re-established populations of the grassland daisy, Rutidosis leptorrhynchoides Australian Journal of Botany 48: 409–16.