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Besnard G.,CNRS Biological Evolution and Diversity Laboratory | Dupuy J.,CNRS Biological Evolution and Diversity Laboratory | Larter M.,French National Institute for Agricultural Research | Cuneo P.,The Australian Botanic Garden | And 3 more authors.
Evolutionary Applications | Year: 2014

Humans have introduced plants and animals into new continents and islands with negative effects on local species. This has been the case of the olive that was introduced in Australia, New Zealand and Pacific islands where it became invasive. Two subspecies were introduced in Australia, and each successfully invaded a specific area: the African olive in New South Wales (NSW) and the Mediterranean olive in South Australia. Here, we examine their origins and spread and analyse a large sample of native and invasive accessions with chloroplast and nuclear microsatellites. African olive populations from the invaded range exhibit two South African chlorotypes hence supporting an introduction from South Africa, while populations from South Australia exhibit chlorotypes of Mediterranean cultivars. Congruently, nuclear markers support the occurrence of two lineages in Australia but demonstrate that admixture took place, attesting that they hybridized early after introduction. Furthermore, using an approximate Bayesian computation framework, we found strong support for the serial introduction of the African olive from South Africa to NSW and then from NSW to Hawaii. The taxon experienced successive bottlenecks that did not preclude invasion, meaning that rapid decisions need to be taken to avoid naturalization where it has not established a large population yet. © 2013 The Authors. Evolutionary Applications published by John Wiley & Sons Ltd.


PubMed | Australian Department of Primary Industries and Fisheries, CNRS Biological Evolution and Diversity Laboratory, French National Institute for Agricultural Research and The Australian Botanic Garden
Type: Journal Article | Journal: Evolutionary applications | Year: 2014

Humans have introduced plants and animals into new continents and islands with negative effects on local species. This has been the case of the olive that was introduced in Australia, New Zealand and Pacific islands where it became invasive. Two subspecies were introduced in Australia, and each successfully invaded a specific area: the African olive in New South Wales (NSW) and the Mediterranean olive in South Australia. Here, we examine their origins and spread and analyse a large sample of native and invasive accessions with chloroplast and nuclear microsatellites. African olive populations from the invaded range exhibit two South African chlorotypes hence supporting an introduction from South Africa, while populations from South Australia exhibit chlorotypes of Mediterranean cultivars. Congruently, nuclear markers support the occurrence of two lineages in Australia but demonstrate that admixture took place, attesting that they hybridized early after introduction. Furthermore, using an approximate Bayesian computation framework, we found strong support for the serial introduction of the African olive from South Africa to NSW and then from NSW to Hawaii. The taxon experienced successive bottlenecks that did not preclude invasion, meaning that rapid decisions need to be taken to avoid naturalization where it has not established a large population yet.


Nguyen K.Q.,University of Technology, Sydney | Cuneo P.,The Australian Botanic Garden | Cunningham S.A.,CSIRO | Krix D.W.,University of Technology, Sydney | And 2 more authors.
Biological Invasions | Year: 2016

Invasive African olive, Olea europaea ssp. cuspidata (Wall. ex G.Don) Cif., forms increasingly dense stands between initial and mature stages of invasion, leading to a progressive decline in native plant diversity. Here, we examined the response of leaf-litter invertebrates to increasing time since olive invasion. We compared invertebrate assemblages among early-stage olive (0–7 years since invasion, scattered olive shrubs and seedlings in native woodland), mature olive (>15 years, uniform olive stands dominated by multi-trunked trees) and uninvaded native grassy woodland habitats (both mature stands and edges) in a critically endangered ecological community of south-eastern Australia. Invertebrate species richness was significantly reduced in mature olive compared with early-stage olive and mature native woodland habitats. Species richness did not differ significantly between early-stage olive habitat and mature native woodland, demonstrating resistance in species richness to initial invasion. Invertebrate species composition of native woodlands differed significantly from both mature olive and early-stage olive habitats, demonstrating a lack of resistance in species composition to initial olive invasion. Compositional differences were principally driven by reduced abundances within Coleoptera, Hymenoptera and Polyxenida in mature olive habitat compared with mature native woodland. These changes were significantly correlated with an increase in bare ground, plant canopy cover and litter depth, and higher moisture and lower temperature within leaf litter, in mature olive habitat. Our findings show that negative ecological impacts of invasive African olive extend beyond plants to leaf-litter invertebrate assemblages and that significant impacts on invertebrate species assemblage composition occur early in the invasion process. © 2016 Springer International Publishing Switzerland


Sommerville K.D.,The Australian Botanic Garden | Martyn A.J.,The Australian Botanic Garden | Offord C.A.,The Australian Botanic Garden
Botanical Journal of the Linnean Society | Year: 2013

The germination requirements of 19 herbs in the Australian Alps were investigated to determine which species may be sensitive to predicted climate changes. Seeds were subjected to factorial treatments of cold stratification for 0, 4, 8 and 12 weeks, followed by incubation at constant temperatures of 10, 15, 20 and 25°C and alternating temperatures of 20/5 and 20/10°C. Germination responses were used to identify stratification-dependent species, to classify dormancy and to determine optimum conditions for laboratory germination. Ordinal logistic regression was used to determine whether the duration of stratification required for ≥50% germination could be predicted by seed weight, seed length, embryo:seed ratio or species distribution (latitudinal range, altitudinal range and maximum altitude). The Kruskal-Wallis test was used to determine any significant differences in stratification requirement between endospermic and non-endospermic seeds. Species varied considerably in their response to the treatment combinations, and therefore their dormancy class. No significant predictors of stratification requirement were identified by ordinal logistic regression (P>0.9); however, there was a significant difference in stratification requirement between endospermic and non-endospermic seeds (P=0.003). Species with non-endospermic seeds did not require any stratification to germinate well over a range of temperatures, and appear most likely to remain stable or expand in range in response to climate warming. Conversely, the need for ≥8 weeks of cold stratification was associated with the presence of endosperm and either a restricted distribution or upland ecotypes of widely distributed species. Alpine species with endospermic seed and a restricted distribution are most likely to contract in range under climate change and would be appropriate to prioritize for exsitu conservation. © 2013 The Linnean Society of London.


PubMed | The Australian Botanic Garden
Type: Journal Article | Journal: Annals of botany | Year: 2011

Under predicted climate change scenarios, increased temperatures are likely to predispose trees to leaf and other tissue damage, resulting in plant death and contraction of already narrow distribution ranges in many relictual species. The effects of predicted upward temperatures may be further exacerbated by changes in rainfall patterns and damage caused by frosts on trees that have been insufficiently cold-hardened. The Araucariaceae is a relictual family and the seven species found in Australia have limited natural distributions characterized by low frost intensity and frequency, and warm summer temperatures. The temperature limits for these species were determined in order to help understand how such species will fare in a changing climate.Experiments were conducted using samples from representative trees of the Araucariaceae species occurring in Australia, Agathis (A. atropurpurea, A. microstachya and A. robusta), Arauacaria (A. bidwilli, A. cunninghamii and A. heterophylla) and Wollemia nobilis. Samples were collected from plants grown in a common garden environment. Lower and higher temperature limits were determined by subjecting detached winter-hardened leaves to temperatures from 0 to -17 C and summer-exposed leaves to 25 to 63 C, then measuring the efficiency of photosystem II (F(v)/F(m)) and visually rating leaf damage. The exotherm, a sharp rise in temperature indicating the point of ice nucleation within the cells of the leaf, was measured on detached leaves of winter-hardened and summer temperature-exposed leaves.Lower temperature limits (indicated by FT(50), the temperature at which PSII efficiency is 50 %, and LT(50) the temperature at which 50 % visual leaf damage occurred) were approx. -55 to -75 C for A. atropurpurea, A. microstachya and A. heterophylla, approx. -7 to -9 C for A. robusta, A. bidwillii and A. cunninghamii, and -105 to -11 C for W. nobilis. High temperature damage began at 475 C for W. nobilis, and occurred in the range 485-52 C for A. bidwillii and A. cunninghamii, and in the range 505-535 C for A. robusta, A. microstachya and A. heterophylla. Winter-hardened leaves had ice nucleation temperatures of -55 C or lower, with W. nobilis the lowest at -68 C. All species had significantly higher ice nucleation temperatures in summer, with A. atropurpurea and A. heterophylla forming ice in the leaf at temperatures >3 C higher in summer than in winter. Wollemia nobilis had lower FT(50) and LT(50) values than its ice nucleation temperature, indicating that the species has a degree of ice tolerance.While lower temperature limits in the Australian Araucariaceae are generally unlikely to affect their survival in wild populations during normal winters, unseasonal frosts may have devastating effects on tree survival. Extreme high temperatures are not common in the areas of natural occurrence, but upward temperature shifts, in combination with localized radiant heating, may increase the heat experienced within a canopy by at least 10 C and impact on tree survival, and may contribute to range contraction. Heat stress may explain why many landscape plantings of W. nobilis have failed in hotter areas of Australia.

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