Evolution and Ecological Change During the New Zealand Quaternary

Abstract

The biotic- and ecological-changes of the New Zealand Quaternary unfolded against a background of mountain-building, marine transgression and volcanism—a legacy of the mid-Tertiary that continued unabated through the Plio-Pleistocene. In the stable, warm northern regions much of the old Tertiary biota survives; in the mountainous, glaciated south, species-rich clades have radiated into the mountains and dry, lee-side habitats of the Quaternary. During cold glacial periods, forest was sparse in the southern two-thirds of the archipelago, but nowhere was it eliminated. Forest blanketed all regions below treeline during interglacials. The repeated climate fluctuations of the Quaternary left a strong imprint on biotic distributions. In southern districts, we infer widespread glacial survival of nearly the entire biota with rapid local spread during interglacial warmings, and only limited invasion from more distant areas. However, not all species distributions can be attributed to recent Quaternary glacial cycles. Molecular studies of numerous invertebrate, vertebrate and plant groups have shown that biotic patterns may just as easily reflect mountain building, Pliocene island formation and reabsorption, and long-distance trans-oceanic dispersal. Human settlement in the 13th century destroyed more than one third of the lowland forests and eliminated a large proportion of the terrestrial bird fauna including the large herbivorous moa. The current biota is still adjusting to the consequences of increased fire in an archipelago where fire was not naturally common, loss of avian browsers and pollinators, and introduction of invasive species.