Genetic pollution of native eucalypt gene pools—identifying the risks

Abstract

The contamination of native-eucalypt gene pools via exotic pollen is of concern as (i) pollen dispersal is believed to be much more widespread than seed dispersal, (ii) reproductive barriers are often weak between closely related species, (iii) European settlement has already had a major impact on Australia's eucalypt woodlands and mallee, (iv) there has been a rapid expansion of eucalypt plantations and restoration plantings in Australia and (v) Australia is the custodian of an internationally important genetic resource. Pollen flow between plantation and native eucalypt species has already been reported and implementation of strategies to minimise the risk and consequences of genetic pollution is important if Australian forestry is to be considered sustainable. The risks associated with the introduction of non-native species, provenances and hybrids include direct effects on the gene pool through genetic pollution as well as indirect effects on dependent biodiversity. In many cases, the risk of genetic pollution will be small due to strong barriers to hybridisation between distantly related species, differences in flowering time or poor fitness of hybrids. There is no risk of hybridisation between species from the different major eucalypt genera and/or subgenera (e.g. symphyomyrts, monocalypts, eudesmids, bloodwoods and angophora). The main plantation species are symphyomyrts and within this subgenus, the probability of successful hybridisation generally decreases with increasing taxonomic distance between species. The planting of non-local provenances or improved material within the range of native populations has the potential to have an impact on local gene pools to varying degrees, indicating the requirement for the adoption of management strategies to reduce this risk. Naturally small or remnant populations are at particular risk. A framework for assessment of the risk of genetic pollution is developed herein.

Entomofauna polinizadora de Eucalyptus nitens en huertos semilleros del centro sur de Chile

“…Los trabajos publicados incluyen ejemplos de búsqueda de patrones relacionados con variaciones de altitud (Malo y Baonza 2002), latitud (Ollerton y Cranmer 2002), insularidad (Ollerton y Cranmer 2002, Jordano et al 2003, fragmentación y complejidad del paisaje (Tscharntke y Brandl 2004) y estadío sucesional luego de un disturbio (Potts et al 2003). Al mismo tiempo, estos estudios reflejan la dificultad inherente a la obtención de este tipo de información, lo cual plantea un compromiso constante entre resolución espacial (de local a global), resolución taxonómica (de especies individuales a la comunidad entera) y esfuerzo de muestreo (de unos pocos días a años).…”

Use of functional traits to identify Australian forage grasses, legumes and shrubs for domestication and use in pastoral areas under a changing climate

“…This process would be a form of grassland restoration introducing forage species or varieties not native to the new areas. Many restoration guidelines strongly recommend the use of local sources of seed in native plant revegetation projects because of an assumed local adaptational advantage and lower risk of unwanted genetic effects (Jones et al 2001;Volis et al 2002;Potts et al 2003;Lenssen et al 2004;Capelle and Neema 2005;McKay et al 2005;O'Brien et al 2007;Byrne et al 2011). Whalley et al (2013) have argued that these assumptions do not apply to Australian native grasses because of their evolutionary history, flexible breeding systems and relatively short population turnover times.…”

Is Australia ready for assisted colonization? Policy changes required to facilitate translocations under climate change.

“…Risk of genetic invasion at the recipient site is not often considered in movement of plants and animals in Australia, although genetic risk is considered in eucalypt plantations (Potts et al 2003;Barbour et al 2008a, b) and a genetic risk assessment has recently been developed for implementation in revegetation programmes (Byrne et al in press). In addition, a decision tree for prediction of outbreeding depression in rare species translocations of both plants and animals has recently been developed (Frankham et al 2011).…”

“…Therefore, genetic risk assessment evaluates factors influencing the likelihood of genetic exchange between populations that are sufficiently divergent that some negative impact is possible, rather than the consequences of the exchange (Potts et al 2003).…”