SummaryThis review reports on the processes associated with costs of reproduction, including some theoretical considerations, definitions and methodological aspects, followed by a list of the situations where costs are difficult to find. Despite some exceptions, case studies, examined by trade-offs between reproduction and other life-history traits, generally support the predictions of the cost of reproduction hypothesis. The cost of reproduction as an evolutionary determinant of sexual dimorphism in life history traits in dioecious species was specifically tested, considering that the higher cost of reproduction in females has driven the life history traits related to sexual dimorphism. Females of woody dioecious species were consistently smaller than males supporting the costs of reproduction hypothesis. By contrast, females of herbaceous perennials were generally the larger sex, which did not fit the expectations of the hypothesis. Finally, the mechanisms that enable the compensation of the reproductive costs are detailed, including the plastic responses of photosynthesis and growth, the effects of the timing of investment, plant architecture and plant physiological integration. I. IntroductionLife history traits, such as growth, survival and reproduction, are linked through constraining relationships, implying that to be the best in all ecological situations is not biologically possible and to be well fitted to even one situation requires a compromise. We refer to these compromises as tradeoffs or costs between life history variables (Reznick, 1985). The concept of costs has taken on an important role in the development of many fields in evolutionary biology since the introduction of cost-benefit analyses into biology and it has been closely linked to the notion of evolutionary trade-offs and constraints (Williams, 1966a,b; Levins, 1968;Roff, 1992). Specifically, the costs of reproduction are defined in terms of losses in the potential future reproductive success caused by current investments in reproduction ( Jönsson, 2000). In a historical perspective, the idea that reproduction competes with other functions is as old as the study of natural history itself ( Jönsson & Tuomi, 1994). The historical development of this idea was mainly due to animal ecologists but a number of works by plant ecologists were compiled by Harper (1977) who concluded that perennial polycarpic plants often show an inverse correlation between vegetative growth and the production of fruit and seed which suggests that fecundity and vegetative activity are not wholly compatible. If reproduction carries no costs either in terms of future survival or fecundity an organism should begin reproducing at the earliest possible age (Roff, 1992). The fact that this does not seem to happen (most plants need to achieve a minimum size for reproduction) suggests that reproduction costs exist. The question of whether this threshold minimum size for reproduction mainly reflects the cost of reproduction or, alternatively, is a reflection of some allom...

Summary1. The effects of the present biodiversity crisis have been largely focused on the loss of species. However, a missed component of biodiversity loss that often accompanies or even precedes species disappearance is the extinction of ecological interactions. 2. Here, we propose a novel model that (i) relates the diversity of both species and interactions along a gradient of environmental deterioration and (ii) explores how the rate of loss of ecological functions, and consequently of ecosystem services, can be accelerated or restrained depending on how the rate of species loss covaries with the rate of interactions loss. 3. We find that the loss of species and interactions are decoupled, such that ecological interactions are often lost at a higher rate. This implies that the loss of ecological interactions may occur well before species disappearance, affecting species functionality and ecosystems services at a faster rate than species extinctions. We provide a number of empirical case studies illustrating these points. 4. Our approach emphasizes the importance of focusing on species interactions as the major biodiversity component from which the 'health' of ecosystems depends.

Summary 1We explored whether seedling recruitment was spatially predicted by seed rain (spatial concordance) at different scales (microsite, microhabitat and site) in the birddispersed trees Crataegus monogyna , Ilex aquifolium and Taxus baccata , in temperate secondary forests in north-west Spain. 2 We propose that both spatial concordance within each scale and consistency of concordance patterns across scales are dependent on differences between seed rain and post-dispersal processes in the partitioning of spatial variance at each scale. 3 We measured the density of dispersed seeds, the percentage of post-dispersal seed predation by rodents and the density of emerged first-year seedlings at sampling stations distributed throughout five microhabitats (under canopies of parental trees and in open gaps) and four localities over two seasons. 4 Seed rain density of all tree species varied most at the microhabitat scale, but microsite and site differences accounted for most of the spatial variance in post-dispersal seed predation and, especially, in seedling establishment. 5 All three species showed concordance between seed rain and seedling establishment at the microhabitat scale, because strong patchiness in avian-generated seed rain overrode the slight uncoupling effects exerted by the more homogeneous post-dispersal processes. Seed rain was also a good predictor of recruitment of Ilex and Crataegus at the microsite scale, but, for Taxus , the rather homogeneous dispersal across microsites contrasted with the heterogeneous post-dispersal losses. At the site scale, only Taxus showed a positive trend of concordance. 6 Concordance patterns were maintained from microsite to microhabitat in Crataegus and Ilex , and from microhabitat to site in Taxus . Low-variance allocation to the site scale at the seed rain stage precluded complete consistency in Crataegus and Ilex . 7 Positive responses of recruitment to seed dispersal depended on both species and scale, resulting in a complex template for dispersal-limitation effects on metapopulations and communities.

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2003. Facilitation by herbivore-mediated nurse plants in a threatened tree, Taxus baccata: local effects and landscape level consistency. -Ecography 26: 739-750.We investigated the regeneration of a threatened tree, the yew Taxus baccata, in relation to the presence of fleshy-fruited woody plants acting as seed dispersal foci as well as protecting yew recruits against ungulate herbivores. We seek to determine if local facilitative effects are consistent across landscape in the Cantabrian range (NW Spain). Yew seed rain by birds mostly concentrated under yew trees and beneath hollies Ilex aquifolium. Seedling emergence distributed similarly to seed rain, but first-year seedling survival was higher beneath hollies. In one site where woody vegetation was structured as nucleation centres (multispecific patches of fleshy-fruited plants acting as foci for seed rain) yew recruits mostly occurred in yew-dominated centres, suggesting dispersers-mediated facilitation. However, holly was the main nurse plant for most of these recruits, considering the nurse as the species whose canopy covered directly the yew recruit. Living beneath nurse plants reduced herbivore damage on saplings and enhanced seedling survival. A planting experiment with yew rooted-cuttings beneath different spiny shrubs corroborated this effect. Additional evidence on yew recruitment limitation by herbivory emerged from one population where ungulates were fence-excluded. Our results suggest that nurse plants mitigate the negative effect of herbivores on yew regeneration, by providing defence against browsing and trampling. Shelter ability related to nurse structure, cone-shaped shrubs with branches at their bases acting better as a barrier. Paradoxically, this structure resulted from heavy browsing on nurse plants. The study of yew regeneration and habitat structure in seven sites provided evidence for the consistency of facilitation by holly at the landscape level, since local values of yew recruitment positively related to nurse ground cover. Range-scale yew management must consider the local functioning of the interaction among avian seed-dispersers, nurse fleshyfruited plants and ungulate herbivores, in combination with regional measures, targeting the habitats where facilitation emerges.