Masting and Efficient Production of Seedlings: Balancing Costs of Variation Through Synchronised Fruiting.

The efficient conversion of tissues into reproductive success is a crucial aspect affecting the evolution of life histories. Masting, the interannually variable and synchronous seed production in perennial plants, is a strategy that can enhance reproductive efficiency by mitigating seed predation and pollen limitation. However, evaluating benefits is insufficient to establish whether efficiency has improved, as such assessments neglect the associated costs of masting, particularly during the critical seed-to-seedling stage. We conducted a parentage analysis of seedlings and adults in a population of 209 Sorbus aucuparia trees, monitored over 23 years, providing pioneering documentation of the effects of masting on the fitness of individual trees beyond the seed stage. Our results show high costs of interannual variation that can be mitigated by high synchrony and reveal the existence of phenotypes that appear to reap the benefits of masting while avoiding its costs through regular reproduction.

Relatives reproduce in synchrony: kinship and individual condition shape intraspecific variation in masting phenotype.

Masting (synchronous and interannually variable seed production) is frequently called a reproductive strategy; yet it is unclear whether the reproductive behaviour of individuals has a heritable component. To address this, we used 22 years of annual fruit production data from 110 Sorbus aucuparia L. trees to examine the contributions of genetic factors to the reproductive phenotype of individuals, while controlling for environmental variation. Trees sharing close genetic relationships and experiencing similar habitat conditions exhibited similar levels of reproductive synchrony. Trees of comparable sizes displayed similar levels of year-to-year variation in fruiting, with relatedness contributing to this variation. External factors, such as shading, influenced the time intervals between years with abundant fruit production. The effects of genetic relatedness on the synchrony of reproduction among trees and on interannual variation provide long-awaited evidence that the masting phenotype is heritable, and can respond to natural selection.

Badger Meles meles as Ecosystem Engineer and Its Legal Status in Europe.

The European badger plays an important role as a natural factor shaping species diversity in forests. Its extensive setts can be used by many other animals as shelters. Soil perturbations in their setts support plant communities that differ from the matrix landscape. The badger is also an effective seed disperser. We investigated its role as an ecosystem engineer in preserving species diversity and discussed its legal status across Europe. In most European countries (69.3% of the continent), the badger is hunted, sometimes year-round. The hunting season lasting through winter until early spring may have a negative effect on badger populations, especially when cubs are born in February. Although this species is Red Listed in 19 European countries (with categories ranging from LC to EN), the badger is strictly protected by law in 30.7% of its European range. A reduction in badger populations may limit its ecosystem services (seed dispersal, topsoil disturbances, microhabitat creation). Much new data on the importance of badgers in ecosystem engineering has allowed us to reconsider how we manage badger populations.

Costs and benefits of masting: economies of scale are not reduced by negative density-dependence in seedling survival in Sorbus aucuparia.

Masting is a widespread reproductive strategy in plants that helps to reduce seed predation and increase pollination. However, masting can involve costs, notably negative density-dependent (NDD) seedling survival caused by concentrating reproduction in intermittent events. Masting benefits have received widespread attention, but the costs are understudied, which precludes understanding why some plant species have evolved intense masting, while others reproduce regularly. We followed seed production, seed predation (both 13 yr), and seedling recruitment and survival (11 yr) in Sorbus aucuparia. We tested whether NDD in seedling survival after mast years can reduce the benefits of pulsed reproduction that come through predator satiation. Seed predation rates were extreme in our population (mean = 75%), but were reduced by masting. The commonly accepted, but untested, assertion that pulsed recruitment is associated with strong NDD was unsupported. Consequently, the proportion of seedlings that survived their first year increased with fruit production. This provides a rare test of economies of scale beyond the seed stage. Our results provide estimation of the costs of mast seeding, and indicate that these may be lower than expected. Low masting costs, if common, may help explain why masting is such a widespread reproductive strategy throughout the plant kingdom.

Is there tree senescence? The fecundity evidence.

Despite its importance for forest regeneration, food webs, and human economies, changes in tree fecundity with tree size and age remain largely unknown. The allometric increase with tree diameter assumed in ecological models would substantially overestimate seed contributions from large trees if fecundity eventually declines with size. Current estimates are dominated by overrepresentation of small trees in regression models. We combined global fecundity data, including a substantial representation of large trees. We compared size-fecundity relationships against traditional allometric scaling with diameter and two models based on crown architecture. All allometric models fail to describe the declining rate of increase in fecundity with diameter found for 80% of 597 species in our analysis. The strong evidence of declining fecundity, beyond what can be explained by crown architectural change, is consistent with physiological decline. A downward revision of projected fecundity of large trees can improve the next generation of forest dynamic models.

Seed predation selects for reproductive variability and synchrony in perennial plants.

Annually variable and synchronous seed production by plant populations, or masting, is a widespread reproductive strategy in long-lived plants. Masting is thought to be selectively beneficial because interannual variability and synchrony increase the fitness of plants through economies of scale that decrease the cost of reproduction per surviving offspring. Predator satiation is believed to be a key economy of scale, but whether it can drive phenotypic evolution for masting in plants has been rarely explored. We used data from seven plant species (Quercus humilis, Quercus ilex, Quercus rubra, Quercus alba, Quercus montana, Sorbus aucuparia and Pinus pinea) to determine whether predispersal seed predation selects for plant phenotypes that mast. Predation selected for interannual variability in Mediterranean oaks (Q. humilis and Q. ilex), for synchrony in Q. rubra, and for both interannual variability and reproductive synchrony in S. aucuparia and P. pinea. Predation never selected for negative temporal autocorrelation of seed production. Predation by invertebrates appears to select for only some aspects of masting, most importantly high coefficient of variation, supporting individual-level benefits of the population-level phenomenon of mast seeding. Determining the selective benefits of masting is complex because of interactions with other seed predators, which may impose contradictory selective pressures.