Knowledge of the reproductive ecology of the invasive Salix cinerea, in its invaded range, assists in more targeted management strategies

Abstract

Management for invasive species is expensive, costing millions of dollars every year and is sometimes unsuccessful. Current control efforts for the highly invasive willow species, Salix cinerea, are extensive, costly, and not always effective because of rapid post-removal reinfestation. An improved knowledge of the reproductive ecology of this species will help design control strategies that minimise future expansion and make current control efforts more effective. To explicitly examine the reproductive ecology of this species in its invaded range in south-eastern Australia, field observations of population structure and sex ratios, pollination experiments and germination trials were undertaken across the Ovens catchment in Victoria. Pollination-exclusion experiments strongly suggest that Salix cinerea in Australia employs two pollen-dispersal mechanisms, with insects being the dominant vector and wind playing a small but significant role (ambophilous). Seed had high initial germination rates, above 95%, but seed is very short-lived with rapid linear decline in germinability until 8 weeks, after which there was no germination at all. An improved understanding of the limited seed bank of this species and the potential it has for long distance pollination has highlighted that preventing reinfestation after control efforts should be focussed on limiting seed production and dispersal. A greater understanding of a species reproductive ecology, particularly of weed species, in their new environment can assist land managers to more effectively target their efforts for long-term eradication strategies.