RESEARCH ARTICLE Limited pollen-mediated dispersal and partial self-incompatibility in the rare ironstone endemic Tetratheca paynterae subsp. paynterae increase the risks associated with habitat loss P. A. Butcher • D. Bradbury • S. L. Krauss Received: 4 April 2011 / Accepted: 1 August 2011 / Published online: 17 August 2011 Ó Springer Science+Business Media B.V. 2011 Abstract Patterns of mating and dispersal are key factors affecting the dynamics, viability and evolution of plant populations. Changes in mating system parameters can provide evidence of anthropogenic impacts on populations of rare plants. Tetratheca paynterae subsp. paynterae is a critically endangered perennial shrub confined to a single ironstone range in Western Australia. Mining of the range removed 25% of plants in 2004 and further plants may be removed if the viability of the remaining populations is not compromised. To provide baseline genetic data for moni- toring mining impacts, we characterised the mating system and pollen dispersal over two seasons in T. paynterae subsp. paynterae and compared mating system parameters with two other ironstone endemics, T. paynterae subsp. cremnobata and T. aphylla subsp. aphylla that were not impacted by mining. T. paynterae subsp. paynterae was the only taxon showing evidence of inbreeding (t m = 0.89), although hand pollination revealed pre-zygotic self-incompatibility limits the production of seed from self-pollen. In a year of lower fruit set (2005), the estimate of correlated paternity increased from 20 to 35%. Direct estimates of realised pollen dispersal, made by paternity assignment in two small populations where all adult plants were genotyped, revealed a leptokurtic distribution with 30% of pollen dispersed less than 3 m and 90% less than 15 m. Restricted pollen dispersal maintains the strong genetic structuring of the adult populations in succeeding generations. As a consequence of preferential outcrossing, any reduction in effective population size, flowering plant density and/or the abundance and activity of pollinators may impact negatively on population viability through reduced seed set, increased inbreeding and increased correlated paternity. Keywords Tetratheca Á Breeding system Á Paternity analysis Á Pollen flow Á Microsatellite Á Mining impacts Introduction Threats to the viability of a species or population can be assessed by considering the probability of dispersal or pollinator failure, reproductive dependence on the pollina- tor (mutualism) and demographic dependence on seeds (Bond 1994). Plants often compensate for high risk in one with low risk in another. For example, self-incompatible plants that are more at risk of pollinator failure than self- compatible plants may compensate by vegetative propaga- tion. Species with more specialised pollination systems are more at risk of pollinator failure than generalist pollinators. In an analysis of which traits indicate vulnerability to extinction Bond (1994) noted that if interactions between plants, their pollinators and dispersers are interrupted by human activity then the risk of extinction accelerates. The genetic consequences of a disruption in the delivery of pollinator services can be most efficiently assessed through an analysis of the mating system and patterns of P. A. Butcher Á D. Bradbury Á S. L. Krauss Kings Park and Botanic Garden, Botanic Gardens and Parks Authority, Fraser Avenue, West Perth, WA 6005, Australia e-mail: donna.bradbury@bgpa.wa.gov.au S. L. Krauss e-mail: skrauss@bgpa.wa.gov.au P. A. Butcher (&) 14 Bombi Road South, Macmasters Beach, NSW 2251, Australia e-mail: penny.butcher@bigpond.com D. Bradbury Á S. L. Krauss School of Plant Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia 123 Conserv Genet (2011) 12:1603–1618 DOI 10.1007/s10592-011-0258-1