Delayed fertilization facilitates flowering time diversity in Fagaceae

Fagaceae includes typical masting species that exhibit highly synchronized and fluctuating acorn production. Fagaceae shows an interesting feature in that fertilization is delayed by several weeks to more than 1 year after pollination. Although delayed fertilization was recorded over a century ago, the evolutionary advantage of delayed fertilization is still poorly understood. Here, we present a new hypothesis that delayed fertilization facilitates temporal niche differentiation via non-overlapping flowering times among species. Comparing flowering and fruiting times in 228 species from five genera in Fagaceae, we first show that there is a close association between a wider spread of flowering times and the likelihood of a 2-year fruiting habit in which there is a long delay from pollination to fertilization. To study the coevolution of flowering time and delayed fertilization, we developed a mathematical model that incorporates the effects of competition for pollinators, seed predator satiation and unfavourable season for reproduction on fitness. The model shows that delayed fertilization facilitates the diversification of flowering time in a population, which is advantageous for animal-pollinated trees that compete over pollinators. Our new hypothesis about the coevolution of delayed fertilization and flowering time will provide new insight into the evolution of masting. This article is part of the theme issue ‘The ecology and evolution of synchronized seed production in plants’.

Evidence for iceberg fertilization of the NW Atlantic

Icebergs are known to have a significant fertilizing impact on primary productivity in the Southern Ocean, but this link is yet to be investigated in the Northern Hemisphere. This study combines sightings of icebergs with satellite-derived ocean colour data from 1998 to 2015, to seek such a relationship in the NW Atlantic. Despite the obscuring coincidence of the seasonal iceberg flux with the spring bloom of chlorophyll, it is shown that there is a large-scale, one-month-lagged regional correlation between iceberg flux and chlorophyll levels. In addition, a spatial time-lag analysis is consistent with the main cause for the iceberg-chlorophyll relationship being through advection of the nutrients entrained in iceberg meltwater. This leads to a delayed fertilization response of 2–4 weeks. There are a range of possible sources for the nutrients likely leading to this delayed response. The Northern Hemisphere impact of iceberg meltwater on primary production is much less pronounced than in the Southern Ocean, but it is discernible.

Reproduction

In this chapter the diverse mating systems exhibited by birds are described and explained. The chapter begins with a discussion of anisogamy and resulting behavioural differences exhibited by male and female birds. Sperm competition, sperm storage, and delayed fertilization are discussed and their consequences in terms of reproductive behaviours and systems are explained. Courtship systems and behaviours are discussed. Social monogamy, polygamy, and lekking behaviour are examined and examples of field research are given to support offered hypotheses. Bird song is considered in some detail through discussion of the function of song and of the genetic, neurological, and physiological control of singing. Particular attention is given to the impact of noise pollution on singing behaviour. The chapter concludes with a discussion of chick rearing including brood size management.