Tree ferns are large and charismatic plants but poorly known ecologically. Furthermore the sporophyte part of the fern life-cycle is only present as a result of the success of a most inconspicuous life stage: the gametophyte. We argue that the location of the gametophyte in large part determines the location of the sporophyte. While it is possible to correlate the presence of tree ferns in the landscape in relation to soil moisture (crucial for sexual reproduction in ferns), and to observe the light and nutrient conditions in which they are growing, identifying the environmental parameters that affect the distribution of tree ferns requires an understanding of gametophyte ecology. Globally, almost nothing is known about the ecology of tree fern gametophytes. The aim of our research was to identify whether the gametophytes of three New Zealand Cyathea species have light and nutrient niches that differ among themselves and might help explain niche partitioning of sporophytes. To achieve this we used a multi-factorial multi-level (3 × 4) approach to establish the relative importance of a range of naturally available forest soil phosphorus concentrations and photosynthetic active radiation levels on the success of spore germination and gametophyte development in three indigenous Cyathea (C. dealbata, C. medullaris, C. smithii).
Results/Conclusions
Results showed that germination of the spores of the three species of Cyathea was significantly influenced by light levels, with C. medullaris (a pioneer spp.) favouring higher light levels than the two understory species C. dealbata and C. smithii. Nutrient availability did not have a significant effect on germination, but subsequent development of the gametophytes was more sensitive to relative nutrient availability. This experiment provided evidence that the gametophytes of the NZ Cyathea have different niches partitioned on gradients of nutrients and light, and this provides an initial filter for differences in sporophyte distribution.