Genecology ofAgrostis capillarisL. (Poaceae) — an invader into New Zealand: 2. Responses to light, soil fertility, and water availability

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Abstract
Fifteen populations of the naturalised grass, Agrostis capillaris, sampled from southern New Zealand, were examined for responses to a range of levels of light, fertility, and water availability. Populations from open, dry areas had genetically low, but plastic, allocation to shoots. Populations from shady areas were more upright than average, and had greater leaf areas, whereas a lawn population was prostrate, but had high allocation to shoots. There was evidence of genecological variation in response to the marked site differences in soil-water availability. Population-based variation in specific leaf area was correlated with rainfall and soil nitrogen and phosphate levels. Differences between populations in other characters did not correlate with environmental trends. Responses indicate some adaptation of populations to their local environments in New Zealand, but also high within-population variation and some instances of nonadaptation. Plasticity is high — as much as 80% of the total variation between treatments — as is typical for a weedy, invasive species. Plasticity, coupled with some genecological differentiation, seems the most likely explanation for the widespread distribution, both spatially and ecologically, of Agrostis capillaris in New Zealand.