seed dispersal

The diets of moa (Aves: Dinornithiformes)

For tens of millions of years the ratite moa (Aves: Dinornithiformes) were the largest herbivores in New Zealand’s terrestrial ecosystems. In occupying this ecological niche for such a long time, moa undoubtedly had a strong influence on the evolution of New Zealand’s flora and played important functional roles within ecosystems. The extinction of moa in the 15th century ce therefore marked a significant event in New Zealand’s biological history, not only in terms of biodiversity loss, but in the loss of an evolutionarily and ecologically distinct order of birds.

Quantifying seed dispersal by birds and possums in a lowland New Zealand forest

Declines in native birds in New Zealand have raised questions about whether seed dispersal limits plant regeneration and whether introduced mammals such as brushtail possums (Trichosurus vulpecula) can replace absent native birds. We determined the relative contribution to seed dispersal by birds and possums in native secondary forest at Kowhai Bush, Kaikoura. The number of seeds dispersed per hectare per day by each animal species was determined based on the number of seeds per faecal pellet, the number of faecal pellets per animal per day, and the density of animals per hectare.

Introduced blackbirds and song thrushes: useful substitutes for lost mid-sized native frugivores, or weed vectors?

The New Zealand avifauna has declined from human impacts, which might leave some larger-seeded native plants vulnerable to dispersal failure. We studied fruit dispersal in a lowland secondary forest near Kaikoura, where the only remaining native frugivores are relatively small (silvereye Zosterops lateralis, and bellbird Anthornis melanura). We tested whether two larger exotic frugivores (blackbird Turdus merula and song thrush T. philomelos) dispersed native plants with seeds too large for the two smaller native frugivores.

Weta and the evolution of fleshy fruits in New Zealand

Fleshy fruits are typically coloured either red or black and are displayed in conspicuous locations where they can be easily located by birds. However, fleshy fruits in New Zealand are often white or translucently coloured and are displayed in the inner recesses of plant canopies. These characteristics have been attributed to coevolution with reptiles. I describe seed dispersal by a ground weta in Nelson lakes National Park, and hypothesise that the unusual characteristics of fleshy fruits in New Zealand may result from coevolution with weta.

The role of blackbirds (Turdus merula) in weed invasion in New Zealand

The naturalised European blackbird (Turdus merula) is the most widely distributed avian seed disperser in New Zealand. Together with the native silvereye (Zosterops lateralis) they are the major seed dispersers over large areas of New Zealand. I review the international literature on aspects of the ecology and behaviour of blackbirds relevant to their potential for dispersing weeds in New Zealand. Blackbirds eat a wide range of native and exotic fruit including many naturalised species.

Effects of forest edges, fruit display size, and fruit colour on bird seed dispersal in a New Zealand mistletoe, Alepis flavida

This study examined how forest edges, fruit display size, and fruit colour influenced rates of seed dispersal in an endemic, bird-dispersed, New Zealand mistletoe species, Alepis flavida. To examine rates of seed dispersal, fruit removal rates were compared between plants growing on forest edges and in forest interior, and also between two morphs of plants with different coloured fruits. Two aspects of fruit display size were examined: plant size and the neighbourhood of conspecific plants.

Possums as seed dispersers in New Zealand: A response to Williams (2003)

We agree with Williams’ (2003) response to our previous paper (Dungan et al., 2002) whereby data is presented in support of the contention that we overstated our argument that possums may be the only dispersal vector for large–seeded native New Zealand species. We contend that this does not alter our overall conclusions, but agree that additional work is needed to balance any potential positive effects of possums as seed dispersers against their significant negative impacts on forested ecosystems.

Are possums important dispersers of large-seeded fruit?

The claim by Dungan et al. (2002) that “in many areas possums may be the only potential dispersal vector for large-seeded native species” is unsubstantiated. There is little evidence possums excrete viable seed of large-seeded fruit greater than 10 mm diameter, and seeds up to this size are dispersed by a suite of bird species. Nowhere in New Zealand are there likely to be possums in the absence of this suite of bird species.

Vegetation change after artificial disturbance in an alpine Chionochloa pallens grassland in New Zealand

We describe the colonisation of artificially created gaps in an alpine grassland dominated by Chionochloa pallens. Twelve years after their creation, the 50 cm _ 50 cm gaps supported a distinctive vegetation composed of a mixture of perennial forbs, grasses and mosses. Three species (Bryum sp., Epilobium alsinoides and Plantago novae-zelandiae) were recorded only in the gaps.

Contribution by possums to seed rain and subsequent seed germination in successional vegetation, Canterbury, New Zealand

The contribution of seeds and fruit to the diet of the introduced brushtail possum (Trichosurus vulpecula) was examined in seral vegetation in lowland Canterbury, New Zealand. Fruit and seeds comprised c. 70% of total possum diet, and possums contributed 17% of the dispersed seed rain for the period of our study. The effect of gut passage on germination was measured for five seed species by germinating seeds recovered from faeces of captive and wild possums. At least one-quarter of seeds of four of the species germinated.