Abstract:
The late-Pleistocene Last Glacial Maximum (LGM; 34,000-18,000 years ago)
had a major influence on the geographic distributions and genetic diversity of modem
species. Continuous temperate forests in New Zealand were believed restricted to the
northern North and South Islands, but growing evidence suggests persistence of
additional LGM forest refugia throughout the glaciated South Island.
The objectives of this project were to identify LGM refugia for five endemic,
widely distributed forest-dwelling Coleoptera, Agyrtodes labralis (Leiodidae),
Brachynopus scutellaris (Staphylinidae), Epistranus lawsoni (Zopheridae), Hisparonia
hystrix (Nitidulidae) and Pristoderus bakewelli (Zopheridae), and to evaluate how the
detected patterns reflected that of the temperate forest community. Mitochondrial DNA
(COI) was amplified from approximately 1000 beetles from the length of mainland New
Zealand to generate a phylogeographic history, or spatially and temporally explicit
genealogy, for each species. These were compared against ecological niche models
(ENMs), which relate collection localities to environmental data on moisture,
temperature, wind and solar radiation to map the geographic distribution of each species
under modem and LGM climate conditions.
Results yielded a complex picture of temperate forest community evolution.
Forest refugia shared by at least two species were detected near Karamea, between
Nelson and Marlborough, at Kaikoura and near the Haast River mouth. Forest was
largely absent elsewhere in the South Island, particularly in the southeast. The three
flighted species had intra-specific divergence dates consistent with Pliocene-Pleistocene
climate change, with A. labralis and B. scutellaris showing signs of persistence in multiple South Island refugia while H. hystrix was largely restricted northward. The two flightless species (£. lawsoni, P. bakewelli) had much older divergence dates,
consistent with the topographic evolution of New Zealand over the last 10 million years.
Only A. labralis, B. scutellaris, and E. lawsoni yielded statistically supported ENMs,
with projected current and LGM distributions largely congruent among these three.
Each species shared some features of its results, like individual migration routes or
projected refugia, but no general patterns were detected among all five, indicating that
forest species retreated into and expanded out from the same refugia by a variety of
routes, rather than travelling together as an intact community.