In this paper we describe two aspects of the reproductive ecology of an invasive pine (Pinus nigra) in New Zealand – the distribution of fecundity within a population and the timing of seed release.
By distribution of fecundity we mean how many cones each tree produced each year. Typically, plant populations have right skewed distributions of fecundity. This means that a few individuals produce a lot of cones, while the majority produce very few. We found that P. nigra was no exception, with a right skewed, negative binomial distribution being a good fit to each year’s observed fecundity. The negative binomial distribution is the distribution of cones you would expect to see if every tree had a different ability to produce cones (perhaps due to genetic differences or fine scale environmental heterogeneity). We also found that even though trees varied a lot in their cone production from year to year, it was always the same trees that produced the most cones. This means that a few individuals have far higher lifetime reproduction than the rest of the population.
We also found that P. nigra tended to release more seeds when conditions were windy and dry, a result that has implications for the spread of this particular invasive population. Due to the mountains surrounding our study site, the warm dry winds tend to be far stronger than cool damp ones, and as such the pine trees preferentially release seeds when conditions favour long distance dispersal.
More info: Shaun Coutts s.coutts@
Coutts S, P Caplat, K Cousins, N Ledgard & YM Buckley (2012). Reproductive ecology of Pinus nigra in an invasive population: individual and population level variation in seed production and timing of seed release. Annals of Forest Science DOI 10.1007/s13595-012-0184-5