Absence of mammals and the evolution of New Zealand grasses

Anthropogenic alteration of biotic distributions and disturbance regimes has dramatically changed the evolutionary context for the differentiation of species traits. Some of the most striking examples in recent centuries have been on islands where flightless birds, which evolved in the absence of mammalian carnivores, have been decimated following the widespread introduction of exotic predators. Until now, no equivalent case has been reported for plants. Here, we make use of robust analytical tools and an exceptionally well-sampled molecular phylogeny to show that a majority of New Zealand danthonioid grasses (Poaceae) may have adapted to the relaxed vertebrate herbivore pressure during the late Cenozoic through the development of a distinctive and unusual habit: abscission of old leaves. This feature occurs in only about 3 per cent of the world's roughly 11,000 grass species and has been empirically shown to increase plant productivity but to reduce protection against mammal grazing. This result suggests that release from a selective pressure can lead to species radiations. This seemingly anachronistic adaptation may represent an overlooked factor contributing to the severe decline in the geographical extent and species diversity of New Zealand's indigenous grasslands following the introduction of herbivorous terrestrial mammals in the 19th century.

Management of Himalayan thar (Hemitragus jemlahicus) in New Zealand: the influence of Graeme Caughley

Graeme Caughley developed many of his ideas on wildlife management, and how it should be underpinned by evidence rather than by dogma, during the mid-1960s when he was working for the New Zealand Forest Service and doing the fieldwork for his Ph.D. on the population dynamics of Himalayan thar in the Southern Alps of New Zealand. However, there was a 30-year lag between the advice on the management of wild animals Caughley was providing to the New Zealand Government in the 1960s and its uptake in a national plan to manage thar in the 1990s. Eventually his ideas of setting measurable goals that were based on science, in this case on his ideas on interactive systems between herbivores and their food supply, and on management systems that led to stable outcomes were at least partially taken up. This paper reviews how some of Caughley’s ideas were, or were not, included in a plan developed in 1993 and its subsequent application to manage Himalayan thar in New Zealand.