Mast Seeding Research Papers - Academia.edu (original) (raw)

M ast seeding-often called masting-has long intrigued biologists as one of the most bizarre reproductive behaviours found in nature 1,2. This behaviour consists of the synchronous production of highly variable seed crops over time 3. Masting has often been considered an evolutionary paradox because organisms that skip reproductive attempts should have lower fitness than those that reproduce at every opportunity 4. Nonetheless, the fact that this reproductive behaviour is found in different lineages suggests that masting behaviour should be beneficial, at least under certain scenarios. The most widely accepted hypotheses explaining the selective advantages of masting are all related to economies of scale 5,6. Briefly, these hypotheses state that, in terms of fitness, it is more efficient for plants to produce a large number of seeds every few to several years than to produce a constant number every year. This general mechanism includes the predator satiation hypothesis 2,7-9 , where predators are starved during years of null or low reproduction and satiated during high reproduction mast years, leaving large numbers of seeds intact. Another example is the pollination efficiency hypothesis 5,10,11 , which states that, particularly for wind-pollinated plants, saturating the atmosphere with pollen in a given year is more efficient than producing regular amounts of pollen each year to ensure pollination. Given that masting is present in only a modest percentage of plant species 12 , such economies of scale are apparently advantageous only under certain circumstances. What those circumstances are remains, so far, under debate. The environmental stress hypothesis 13 suggests that masting behaviour should be stronger under unfavourable growing conditions or limitation of resources-conditions under which economies of scale should be more beneficial 3,11,14. This is because plants growing in unfavourable environments presumably experience more difficulties in acquiring the required resources to reproduce, as suggested by the resource accumulation hypothesis 15,16. According to this hypothesis, plants growing under favourable conditions will be able to accumulate the required amount of resources every year and, therefore, present a regular pattern in seed production, without exhibiting any underlying negative temporal autocorrelation that could indicate resource depletion after reproduction 15. The opposite is true for plants growing in unfavourable conditions, which will exhibit high interannual variability and negative temporal autocor-relation in seed production due to potential resource depletion after seeding. However, there is no current empirical evidence suggesting that species with higher interannual variability in fruit production are more likely to exhibit negative temporal autocorrelation than species that produce seeds more regularly. In contrast, weather variability has been found to be a key factor driving interan-nual variability in fruit production in many plant species 11,17-20. Therefore, temporal patterns in weather events (that is, temporal variability and autocorrelation) could potentially shape the temporal patterns of fruit production 21. Foliar nutrient concentrations play a key role in plant ecophysi-ology and ecosystem functioning: photosynthetic rates are linked to foliar nitrogen (N) and phosphorus (P) concentrations 22-24. Together with carbon, they are the basis of ecological stoichiom-etry 25,26 and are fundamental parts of the elementome or the bio-geochemical niche 27 , useful for inferring ecological traits from the elemental composition of organisms 28. N and P, as well as carbon (C), have been suggested to be potential resources determining seed production and masting behaviour 14,29-31 , because seeds and fruits are enriched with N and P compared with vegetative tissues 32. Mast seeding is one of the most intriguing reproductive traits in nature. Despite its potential drawbacks in terms of fitness, the widespread existence of this phenomenon suggests that it should have evolutionary advantages under certain circumstances. Using a global dataset of seed production time series for 219 plant species from all of the continents, we tested whether mast-ing behaviour appears predominantly in species with low foliar nitrogen and phosphorus concentrations when controlling for local climate and productivity. Here, we show that masting intensity is higher in species with low foliar N and P concentrations, and especially in those with imbalanced N/P ratios, and that the evolutionary history of masting behaviour has been linked to that of nutrient economy. Our results support the hypothesis that masting is stronger in species growing under limiting conditions and suggest that this reproductive behaviour might have evolved as an adaptation to nutrient limitations and imbalances. NAturE PLANtS | www.nature.com/natureplants