Seashore uplift and the distribution of the bull kelp Durvillaea willana Lindauer in New Zealand

The endemic bull kelp Durvillaea willana Lindauer grows on South and Stewart/Rakiura Islands, with a small North Island population on the northern Wairarapa coast. Drawing on field observations, the distribution of this species is mapped. Within its biogeographic range, there are three lengthy tracts of rocky shore where the kelp is conspicuously absent. These distributional gaps are: Wellington's south coast (despite proximity to populations on the South Island side of Cook Strait), the southern and central Wairarapa Coast, and in South Westland. Theorising that these gaps have been caused by earthquake‐driven coastal uplift, this paper examines the effects on Durvillaea species of a 7.8 Mw earthquake in 2016, which raised around 100 km of seashore along the Kaikōura coast, plus the historical evidence of uplift along the Akatore Fault, south of Dunedin. This evidence suggests that the requirements for such local extinctions are that the uplift is consistently higher than the kelp's vertical range, and that it occurs along an entire rocky coastal tract flanked by barriers to recolonisation such as long beaches or deep ocean–major obstacles to a non‐buoyant kelp with poor dispersive ability.