Drosera spatulata from the South Island, New Zealand have interesting morphologies that differ to those more commonly known in cultivation. Notably, these plants have straight, glandless petioles that are clearly distinct from the glandular laminae. Several forms exist that correlate with their ecological niche and geographic location.
Perhaps the most striking form is found in lowland swamps in the Fiordland region in the mountainous southwest of the nation. The plants here have very long and thin petioles that keep the laminae held above the dense sphagnum moss that constantly threatens to smother the sundews. Interestingly, plants growing in drier locations directly adjacent to these swamps, such as roadside seepages and tracks adopt a more compact morphology.



This phenomenon whereby wet-growing plants have a thin, elongated petiole while those in nearby dry niches have fleshier, shorter petioles is observed in locations all up the West Coast of New Zealand. These morphological traits make sense in context of their niches – plants in wet sites require longer petioles to keep their traps held above water and may be slightly etiolated due to the shade of surrounding foliage. Those in drier niches generally grow more exposed to the elements and are more compact as a result.




Other factors also influence the morphology of the plants. A large, hairy form of D. spatulata grows in the coastal heathlands near Westport. This is the warmest region along the West Coast, which may favour larger varieties of the species. The plants attain a size comparable to those in Australia while maintaining a robust morphology due to the moist but not waterlogged habitat.

Around Westport, there are habitats called ‘terraces’ – plateaus about 100-200 m elevation that were formed through the uplift of the ancient coastline. Although not particularly different climactically from the coast, these terraces are much more exposed to the sun, rain and wind. The sandy substrate is so leached and eroded that it only supports sparse vegetation up to knee height. In this extremely deprived habitat, D. spatulata is correspondingly stunted with wiry petioles, crimson colouration and often growing only a few leaves.



The range of D. spatulata also extends to subalpine to alpine areas in the mountains where it grows around tarns, swampy clearings and seepage areas. These areas are generally covered by snow in winter (even in summer it can dip below freezing) and must be cold-adapted. To deal with the temperature, these plants adopt a compact morphology, often growing smaller with shorter leaves. Plants in very exposed spots like in cushion grasses often have fewer flower buds per stem, although adjacent specimens sheltered by bushes can grow to larger proportions.





It is unknown whether these morphological differences result from genetically distinct ‘forms’, or if they manifest from the phenotypic plasticity of the same genotypes. The most likely scenario is a combination of both scenarios. Studies of specimens growing in the same swamp having elongated leaves in waterlogged pools or compact leaves in raised mounds suggest that the immediate niche can affect the morphology of individual specimens. Notwithstanding, geographically isolated populations such as those from lowland versus montane habitats could provide a barrier to gene flow and lead to the evolution of distinct genotypes. Comparing clonally propagated plants grown in wet, dry, warm and cold conditions could shed light on the extent to which conditions affect their morphologies.

