Effects of habitat fragmentation on the reproductive ecology of four plant species in mallee woodland

Habitat fragmentation has the potential to affect plant reproduction by changing the community of pollinators and natural enemies, the neighborhood of potential mates, the availability of resources, and microclimate. I examined the effect of habitat fragmentation on reproduction of four species found in mallee woodlands of central New South Wales, Australia: Acacia brachybotrya, Senna artemisioides, Eremophila glabra, and Dianella revoluta. At six sites I surveyed plants in a reserve and in a nearby linear strip of vegetation. Two additional sites were established in a large reserve. Many effects were apparent at the extreme end of fragmentation, revealed by two-way analysis of covariance comparing reserves and linear strips at each site. The nature of the response differed among species. Flower production was greater in most linear strip fragments for S. artemisioides and E. glabra. Fruit set efficiency was significantly greater in linear strips for S. artemisioides and significantly lower for A. brachybotrya, E. glabra, and D. revoluta. Fruit predation was lower in most linear strips for E. glabra. For A. brachybotrya, fruit predation was significantly lower in linear strips. The net effect of these changes was a significant increase in whole-plant seed production for S. artemisioides, a significant decrease in whole-plant seed production for A. brachybotrya and in whole-plant fruit production for D. revoluta, and no consistent effect on whole-plant fruit production for E. glabra. In contrast, the only pattern apparent when the effect of fragment size was considered over a range from linear strips <40 m wide to a reserve >140,000 ha was a positive correlation between the fragment size and fruit-set efficiency of A. brachybotrya. These results suggest that habitat fragmentation can significantly alter important reproductive functions of species, by changing both the plant's physical environment and its interactions with animals.