Ecology https://doi.org/10.1002/ecy.2913 (2019)

Climate warming and the invasion of foreign species are two major factors driving ecosystem change. For plants, the timing (phenology) of flowering can shift under warming conditions, with the ability to change generally greater for invasive species than natives. Interaction between climate change and invasive species may thus heighten the pressure on threatened natives, but this remains poorly studied.

Credit: Julian Elliott Photography / Photolibrary / Getty Images Plus / Getty

Justyna Giejsztowt, at the Victoria University of Wellington, NZ, and US and NZ colleagues, investigated the impact of warming on flower phenology and reproductive success for invasive heather (Calluna vulgaris) and endemic monoao (Dracophyllum subulatum). Under experimental warming (+1.7 °C), heather had earlier first flowering and peak flower production. Monoao flowers were then more likely to appear concurrent with particularly high heather flower density. The negative impact of heather on monoao seed weight observed in areas of high floral density suggests that warming-induced increases in phenological overlap between invasive and native species may increase competition for pollination — of particular pertinence in the context of global pollinator declines.