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Abstract. Both means and year-to-year variances of climate variables such as temperature and precipitation are predicted to change. However, the potential impact of changing climatic variability on the fate of populations has been largely unexamined. We analyzed multiyear demographic data for 36 plant and animal species with a broad range of life histories and types of environment to ask how sensitive their long-term stochastic population growth rates are likely to be to changes in the means and standard deviations of vital rates (survival, reproduction, growth) in response to changing climate. We quantified responsiveness using elasticities of the long-term population growth rate predicted by stochastic projection matrix models. Short-lived species (insects and annual plants and algae) are predicted to be more strongly (and negatively) affected by increasing vital rate variability relative to longer-lived species (perennial plants, birds, ungulates). Taxonomic affiliation has little power to explain sensitivity to increasing variability once longevity has been taken into account. Our results highlight the potential vulnerability of short-lived species to an increasingly variable climate, but also suggest that problems associated with short-lived undesirable species (agricultural pests, disease vectors, invasive weedy plants) may be exacerbated in regions where climate variability decreases.

Harrison. S. and Bruna, E. 1999. Habitat fragmentation and large-scale conservation: what do we know for sure? -Ecography 22: 225-232.We review the ecological effects of habitat fragmentation, comparing the theoretical approaches that have been taken to understanding it with the existing evidence from empirical studies. Theory h;is emphasized the spatial aspects of fragmentation and the role of dispersal among patches, and has generated interesting predictions such as a nonlinear relationship between ihe amount of remaining habitat and the probability of species persistence. However, while the few available large-scale empirical studies of fragmentation all tend to show that it has major effects, these documented effects tend to be relatively simple ones such as the degradation of habitat quality vs'ithin fragments. There is good reason to be cautious of any claim that corridors or the spatial configuration of remaining habitat can compensate for the overall loss of habitat. 5.

Increased temporal variance in life-history traits is generally predicted to decrease individual fitness and population growth. We show that a widely used result of stochastic sensitivity analysis that bolsters this generality is flawed because it ignores the effects of correlations between vital rates. Considering the effects of these correlations (although ignoring autocorrelations), we show that the apparently simple relationship between vital rate variance and fitness can be considerably more complex than previously thought. In particular, the previously estimated negative sensitivities of fitness or population growth to variance in a vital rate can be either enhanced by positive correlations between rates or reversed by negative correlations, even to the point that variability in a rate can increase fitness or population growth. We apply this new sensitivity calculation to data from the desert tortoise and discuss its interpretation in light of the factors generating vital rate correlations.Keywords: stochasticity, matrix models, sensitivity, elasticity. The constellation of effects that variable environments have on individual fitness and population growth is a major focus of both life-history analysis and demography (Cole 1954;Cohen 1966Cohen , 1968Lewontin and Cohen 1969;Schaffer 1974;Tuljapurkar and Orzack 1980;Ellner 1985a Ellner , 1985b Ellner , 1987Lande and Orzack 1988;Orzack 1993). For instance, many general theories of life-history evolution rely on some consideration of the effects of temporal variability (Gillespie 1977; Seger and Brockman 1987;Stearns 1992;Hairston and Bohonak 1998). Similarly, it is increasingly recognized that the failure to consider environmental stochasticity in demographic analyses can result in less precise and frequently biased results (Tuljapurkar 1990;Caswell 2001;Fieberg and Ellner 2001;Doak et al., forthcoming).A long tradition of theoretical work has predicted that temporal variation in the components of individual performance is important in shaping population dynamics and life-history patterns. However, careful empirical analysis of the effects of stochasticity has been far less common, in part because of difficulties in using the types of data most commonly and readily collected to test these predictions. The exception to this mismatch is the use of demographic data and models to link empirical estimates of variance and correlation among life-history traits with the effects of stochasticity on population performance and fitness (Boyce and Perrins 1987;Kalisz and McPeek 1993;Liou et al. 1993;Philippi 1993aPhilippi , 1993bPfister 1998;Menu et al. 2000;Menu and Desouhant 2002). A key generality to emerge from stochastic demography is that temporal variation in growth, survival, and other vital rates will negatively influence population growth and fitness. In particular, variation in the vital rates to which population growth is most sensitive will disproportionately decrease stochastic growth, and thus there should be strong selection against variation ...

Functional diversity has been postulated to be critical for the maintenance of ecosystem functioning, but the way it can be disrupted by human-related disturbances remains poorly investigated. Here we test the hypothesis that habitat fragmentation changes the relative contribution of tree species within categories of reproductive traits (frequency of traits) and reduces the functional diversity of tree assemblages. The study was carried out in an old and severely fragmented landscape of the Brazilian Atlantic forest. We used published information and field observations to obtain the frequency of tree species and individuals within 50 categories of reproductive traits (distributed in four major classes: pollination systems, floral biology, sexual systems, and reproductive systems) in 10 fragments and 10 tracts of forest interior (control plots). As hypothesized, populations in fragments and control plots differed substantially in the representation of the four major classes of reproductive traits (more than 50% of the categories investigated). The most conspicuous differences were the lack of three pollination systems in fragments-pollination by birds, flies and non-flying mammals-and that fragments had a higher frequency of both species and individuals pollinated by generalist vectors. Hermaphroditic species predominate in both habitats, although their relative abundances were higher in fragments. On the contrary, self-incompatible species were underrepresented in fragments. Moreover, fragments showed lower functional diversity (H' scores) for pollination systems (−30.3%), floral types (−23.6%), and floral sizes (−20.8%) in comparison to control plots. In contrast to the overwhelming effect of fragmentation, patch and landscape metrics such as patch size and forest cover played a minor role on the frequency of traits. Our results suggest that habitat fragmentation promotes a marked shift in the relative abundance of tree reproductive traits and greatly reduces the functional diversity of tree assemblages in fragmented landscapes.