Extinctions can dramatically reshape biological communities. As a case in point, ancient mass extinction events apparently facilitated dramatic new evolutionary radiations of surviving lineages. However, scientists have yet to fully understand the consequences of more recent biological upheaval, such as the megafaunal extinctions that occurred globally over the past 50 kyr. New Zealand was the world's last large landmass to be colonized by humans, and its exceptional archaeological record documents a vast number of vertebrate extinctions in the immediate aftermath of Polynesian arrival approximately AD 1280. This recently colonized archipelago thus presents an outstanding opportunity to test for rapid biological responses to extinction. Here, we use ancient DNA (aDNA) analysis to show that extinction of an endemic sea lion lineage (Phocarctos spp.) apparently facilitated a subsequent northward range expansion of a previously subantarctic-limited lineage. This finding parallels a similar extinction-replacement event in penguins (Megadyptes spp.). In both cases, an endemic mainland clade was completely eliminated soon after human arrival, and then replaced by a genetically divergent clade from the remote subantarctic region, all within the space of a few centuries. These data suggest that ecological and demographic processes can play a role in constraining lineage distributions, even for highly dispersive species, and highlight the potential for dynamic biological responses to extinction.

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Archaeozoological data from two New Zealand regions, Greater Hauraki in northern North Island and Otago-Catlins in southern South Island, are examined to document exploitation of the marine environment by Maori prior to European settlement. Data from 107 reliably dated archaeological assemblages are summarized to show the range of shellfish, finfish, marine bird and marine mammal taxa that were harvested and the relative importance of species within each of these classes. Regional differences in faunal spectra are detected and shown to be attributable chiefly to geographic variations in availability of taxa. Changes over time are apparent in the northern region, but are much less marked in the south. Marine mammals and birds disappear or decline in abundance, with human predation the most likely cause. Changes in the composition of shellfish and finfish harvests reflect changes in the location and organization of human settlements, driven largely by expanding demand for land suitable for horticulture.Keywords: archaeozoology; Maori prehistory; marine resources; human impacts; shellfish; finfish; coastal birds; marine mammals Introduction This paper summarizes archaeological data on human use of marine resources in two New Zealand study areas. The purpose is to assist in understanding the nature and causes of changes in coastal and marine shelf ecosystems over the timescale of human occupation. It is part of a broader collaborative project that is attempting to use knowledge of the past to improve future fisheries management. Led by Alison MacDiarmid of NIWA, the scope of this project is summarized by its title*Taking Stock: Longterm effects of climate variation and human impacts on the structure and functioning of New Zealand marine shelf ecosystems. This sets out to build a mass balance model of current coastal and marine shelf ecosystems in two study areas, and then estimate how it might have operated during five earlier time slices:

Southern New Zealand is a cool-temperate insular region, first colonized about 800 BP by hunter-gatherers. Archaeological data, particularly from the site at Shag River Mouth, show that small villages, established early in the settlement sequence, were occupied only briefly and that by about 400 BP village habitation had ceased. Ethnographic observations and some archaeological evidence show that villages were re-established late in the sequence, by about 200 BP. It is argued that these phases of sedentary settlement largely reflect different responses to relative scarcity of resources. In the early phase, transient villages were established close to rich resource clumps, notably of seals and moas, and these were depleted serially until that settlement mode was no longer practical. In the later phase, villages were sustained by long-distance movement of dispersed resources, in a system facilitated by new socio-political conditions.