No abstract

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 ex situ conservation. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 172, 187–204.

The potential for indigenous species to establish outside their natural range and become weeds is less well recognised than the potential for exotic species to become weeds. In this study, the weed potential of a native Australian legume, Swainsona sejuncta Joy Thomps., was assessed using weed risk assessment protocols (the 'Pheloung system') and germination experiments. The Pheloung system uncovered several traits indicating that S.�sejuncta has significant weed potential. These traits include production of the toxin swainsonine, a short generative time, production of large numbers of viable seeds, and formation of a dense canopy. The species appears to benefit from cultivation, and seedlings emerged along paths surrounding garden beds. The Pheloung system did not give a definitive outcome for rejection or acceptance (high or low weed potential, respectively) but indicated that further evaluation is required. However, if S. sejuncta naturalises outside its limited native range in the future, then the species would be considered to have a high weed potential. Experiments in addition to the Pheloung system showed that S. sejuncta germinated rapidly over a wide range of temperatures once the seed coat was broken, reflecting a high competitive ability. Consequently, cultivation and commercialisation of S. sejuncta as an ornamental plant is not recommended without further research.

No abstract