Lack of fire rather than pollinator absence may drive population decline in the critically endangered

Abstract

Context and aim Stands of the critically endangered Banksia conferta in north-eastern New South Wales show low recruitment and were examined to elucidate whether pollinator absence or fire history best explained this. Methods Motion-detection cameras were deployed at three sites to identify potential pollinators, and age structure within stands and past follicle production were assessed through tree measurements and follicle counts. Key results In total, 691 fauna-triggered image sequences were recorded between June and December 2019. Six mammal and 10 bird species were detected, but only 10 of these were observed probing inflorescences. White-cheeked Honeyeater and Sugar Glider combined comprised 66% of all fauna interactions, and of all 400 Banksia probes, 45% were from White-cheeked Honeyeaters and 18% were by Sugar Gliders. Different size structures of B. conferta were evident at each site, consistent with older and younger populations post-fire. Significantly more Banksia individuals (5×) were present at the younger site, likely governing pollinator composition through interspecific competition within pollinator guilds, and past follicle production was also greater here. Conclusions Pollinator absence is not the cause of low recruitment in this population, and current stand structure and follicle production reflect past fire history. The three sites differed in their dominant fauna foragers, suggesting that B. conferta is a pollinator-generalist. Birds appear to operate as the key pollinating species during the day but are replaced by small mammals at night. Follicle production is higher in younger post-fire plants. Implications The absence of fire from older populations for over 55 years is of concern, and population decline seems likely without fire intervention.