Rhabdothamnus solandri (Gesneriaceae) is a North Island native forest shrub. Its main endemic pollinators are bellbird, stitchbirds and tui. Bellbirds and stitchbirds have been locally extinct on mainland Northland for the last 100 years, and tui numbers are low. This study aimed to find out what effect the loss of endemic pollinators was having on pollination and fruit set of Rhabdothamnus, and whether or not this was likely to impact on the long term density of this species at mainland sites. Four mainland sites near Whangarei were used; Bream Head, Mt Tiger, AH Reed and Barge Park. An island reserve site, Lady Alice Island was used for comparison as it is predator free, has high numbers of bellbirds and tui, and good populations of Rhabdothamnus.

Flowers of Rhabdothamnus are relatively long-lived (mean 8 days), self-compatible, show a large degree of herkogamy (spatial separation of male and female function) and a small degree of dichogamy (time separation). Mean percent fruit set was in most cases significantly higher for hand-cross pollinated flowers than for natural flowers at mainland sites (67% and 25% respectively) but not for Lady Alice (59% and 52% respectively) indicating flowers were pollen limited and seed production reduced on mainland sites. This was associated with a shortage of native birds visiting the flowers. Bellbirds were the only avian pollinators visiting flowers on Lady Alice but were absent on the mainland site. Mean germination was 60.7% in petri dishes and 1.7 % (2002 sowings) and 4.8% (2003 sowings)in the field. Some seed sown in 2002 germinated in the field in 2003 indicating seeds of Rhabdothamnus may remain dormant, for at least one year. The mean number of seedlings still alive after one year was significantly higher in sown plots in 2003 (7.5 per 200 cm²) compared with unsown plots (0.4) indicating populations of Rhabdothamnus are partly seed limited. In field surveys more seedlings (plants < 0.5 cm tall) were present in Rhabdothamnus populations on Lady Alice than on mainland sites (11.8 and 2.8 per 144 m² plot respectively). Overall these results indicate Rhabdothamnus is seed limited at mainland sites and that this is in part caused by a lack of native pollinators. Predispersal seed predation was high on Lady Alice compared with mainland sites (50% and 9% of total fruit set respectively) partly negating the expected advantage of the increased seed production on Lady Alice Island.

As Rhabdothamnus adult plants have the ability to resprout from their bases, to be long- lived, and to develop seed dormancy, the threat to the survival of these plants may not be immediate. However, many of these adults may be approaching the ends of their lives and as pollinators have been reduced on the mainland for over a century, the reliance on seed for replacement of these individuals may be more important than indicated. Both populations of Rhabdothamnus and their seed herbivores may be reliant on populations of native pollinators for their long-term survival. There are suggestions other native plants are also suffering from a loss of native pollinators. Restoring populations of the three endemic pollinators at mainland sites is therefore important if we want to maintain effective interactions among species and ensure the persistence of all native plants.