Parasites and Dung Beetles as Ecosystem Engineers in a Forest Ecosystem

Dung beetles serve as the intermediate host for Streptopharagus pigmentatus, a nematode parasite that infects an old world primate, the Japanese Macaque (Macaca fuscata). This study compares the behaviors of infected and uninfected beetles in both transmission dynamics and the ecological role of the parasite. The results suggest that parasitism does not alter the beetle’s use of shelter or choice of substrate on Yakushima Island, Japan. However, infected beetles consume significantly less feces. Dung beetles remove the majority of fecal material in this forest ecosystem, eliminating breeding grounds for many insect pests and burying nutrients that are essential for plant health. Thus, the nematode parasite S. pigmentatus, by altering its host’s behavior, changes the availability of fecal resources to both plant and animal communities and should therefore be classified as an ecosystem engineer.     

Competition between Exotic and Native Insects for Seed Resources in Trees of a Mediterranean Forest Ecosystem

The seeds of both cedar-of-Lebanon (Cedrus libani) and Cyprus cedar (Cedrus brevifolia) are attacked in their natural range by a specialised chalcid, Megastigmus schimitscheki. From 1995 to 1999, seeds were screened for insect damage in the main cedar plantations of southern France, as well as in the stands where cedar is mixed with firs (Abies spp.). X-rays were used to identify chalcid-infested seeds from which the insects were then reared. The surveys revealed the presence of M. schimitscheki in all the stands of Atlas cedar, Cedrus atlantica, planted at Mt Ventoux, southeastern France. The chalcid also infested seeds of an exotic fir, Abies pinsapo, planted in the same area. However, it has not yet reached the cedar plantations in southwestern France, where the seeds are colonised by a related exotic insect, Megastigmus pinsapinis, originating from North Africa. The latter species was common in cedar seeds at Mt Ventoux in the early 1990s but seems to have been supplanted by M. schimitscheki in the invasion zone. A native chalcid species, Megastigmus suspectus, was also shown to have shifted to a slight extent from a native fir, A. alba, onto cedar. The presence of three chalcid species competing for cedar seed resources may result in a substantial decline of the regeneration potential of that tree species. At Mt Ventoux, up to 92.6% of the cedar seeds were attacked, with 86.8% due to M. schimitscheki. The survey also revealed the widespread presence of another North American chalcid, Megastigmus rafni, in the fir stands of southern France. This revised version was published online in July 2006 with corrections to the Cover Date.     

Successional Change and Resilience of a Very Dry Tropical Deciduous Forest Following Shifting Agriculture

We analyzed successional patterns in a very dry tropical deciduous forest by using 15 plots differing in age after abandonment and contrasted them to secondary successions elsewhere in the tropics. We used multivariate ordination and nonlinear models to examine changes in composition and structure and to estimate forest recovery rates and resilience. A shrub phase characterized early succession (0–3 yr); afterwards, the tree Mimosa acantholoba became dominant. Below its canopy, sprouts and seed-regenerated individuals of mature forest species slowly accumulated. Canopy height, plant density, and crown cover stabilized in less than 15 yr, whereas species richness, diversity, and basal area continued to increase. The pioneer species group has very low diversity and the long-lived pioneer phase typical of humid forests is absent; species composition may therefore recover soon as suggested by convergence toward mature forest species composition. The time trend of plant density also differed from humid forests for it lacked its characteristic density decline, presumably because of differences in regeneration mechanisms between very dry and other less water-stressed forest types. As opposed to the prevailing hypothesis, resilience was not higher than in moister forests, and thus factors other than structure relative simplicity must be accounted for when assessing resilience.     

The Seed and Fern Spore Bank of a Recovering African Tropical Forest

Seed banks contribute to forest regeneration after disturbance, but less is known about fern spore banks, particularly in a paleotropical context. We sampled the buried seed and fern spore bank in Mabira Forest, a 300 km² forest in central Uganda, to explore the effect of time since disturbance. Soil cores (5 cm depth) were taken from 39 plots across three different classes of ‘recovery’: (1) not disturbed since 1950; (2) logged between 1950 and 1980; and (3) cleared for agriculture between 1970 and 1990 but reforested since. Plant emergence was monitored in a glasshouse. We predicted that the seed bank would reflect time since disturbance, with more pioneer species in recently disturbed stands, and that the fern spore bank would reflect stand age less closely due to greater dispersal capacity. We recorded a median 752 seeds per square meter, most of which were trees; the most abundant species was the invasive tree Broussonetia papyrifera. The fern spore bank was twice as dense, but 95 percent of fern spores were of one species, Christella parasitica. Tree seed density was significantly affected by time since disturbance with fewer seeds in the older stands. Herb seed density, fern spore density, and species richness for all groups were not significantly affected by time since disturbance. Neither seed bank nor fern spore bank closely resembled the aboveground vegetation. We compared our results to existing literature on seed banks in tropical forests, finding that our densities are relatively high for African forests, but low compared to the Neotropics and Australia.     

Cycling Dynamics of NH4 + and Amino Acid Nitrogen in Soils of a Deciduous Boreal Forest Ecosystem

Conventional studies of nitrogen (N) cycling in forest ecosystems have focused on inorganic N uptake as the primary source of N for plant metabolism. More recently, however, alternative sources of N for plant nutrition, such as free amino acids, have gained attention, particularly in nutrient-limited systems. Using a multiple stable isotope (¹³C and ¹⁵N) design, that allowed us to simultaneously assess root uptake of ammonium (NH₄ ⁺) and glycine, we compared the cycling dynamics of NH₄ ⁺ and amino acid N within the soils of several interior Alaskan floodplain balsam poplar stands. Our design included multiple sampling periods extending from 45 min to 14 days, which permitted us to study interpool transfers of our carbon (C) and N isotopes over time. Microbial biomass N was the largest sink of both ¹⁵N-ammonium and glycine. Percent recovery of ¹⁵N for this pool was an order of magnitude larger than fine-root ¹⁵N uptake for most sampling periods. Although recovery of ¹⁵N in fine-root biomass was small, amino acid N and NH₄ ⁺ were assimilated at approximately the same rate irrespective of sampling period, and total recovery was still increasing 2 weeks after application. Recovery of ¹⁵N in bulk soil samples did not vary significantly over time for either treatment. However, bulk soil ¹³C declined steadily during the experiment, measuring less than 30% recovery of added label after 14 days. We suspect that the majority of ¹³C lost from our soils was respired. Soil microorganisms strongly outcompeted plants in the short term for both NH₄ ⁺ and amino acid N. However, amino acid N appears to cycle through soil N pools at approximately the same rate as inorganic N forms. The similarity in uptake patterns for inorganic and organic N suggests that these stands are meeting part of their N requirements directly from amino acids.     

Repercussions of Simulated Climate Change on the Diversity of Woody-Recruit Bank in a Mediterranean-type Ecosystem

Extreme climatic events have the potential to affect plant communities around the world, and especially in the Mediterranean basin, where the frequency of milder and drier summers is expected to be altered under a global-change scenario. We experimentally investigated the effect of three contrasting climatic scenarios on the diversity and abundance of the natural woody-recruit bank among three characteristic habitats in a Mediterranean-type ecosystem: forest, shrubland, and bare soil. The climatic scenarios were dry summers (30% summer rainfall reduction), wet summers (simulating summer storms), and current climatic conditions (control). Seedling emergence and survival after the first summer was recorded during 4 consecutive years. The wet summer boosted abundance and diversity at emergence and summer survival, rendering the highest Shannon H??index. By contrast, the dry summer had no effect on emergence, although survival tended to decline. Nonetheless, the habitat had a key role, bare soil showing almost null recruitment whatever the climatic scenario, and forest keeping the highest diversity in all of them. Our results show that recruit-bank density and diversity depends heavily on extreme climatic events. Community dynamics will depend not only on increased drought but also on the balance between dry and wet years.     

Seed germination ecology of Polymnia canadensis (Asteraceae), a monocarpic species of the North American Temperate Deciduous Forest

The seed germination of Polymnia canadensis was studied in relation to its wide variation in life history and its ecology as a mostly facultative biennial, a life cycle type that is rare in stable forest habitats in eastern North America. The seed dormancy and germination characteristics of P. canadensis were like some other herbaceous woodland species of diverse life cycle types. That is, its seeds have physiological dormancy, and they (1) germinated to higher percentages after cold stratification, (2) germinated better in light than in darkness and (3) formed a persistent soil seed bank. Since its seed dormancy and germination characteristics are not uncommon and are not particularly associated with any one life cycle type in woodlands, those properties do not contribute to the rarity of its life cycle type in deciduous forests. These properties are also found in many facultative biennials of open, disturbed habitats and in other Asteraceae of various life cycle types. In addition, the germination phenology of P. canadensis differed between mesic and dry field sites in central Kentucky. At the dry sites, most of the yearly germination occurred in fall, while at the mesic sites most germination occurred in the spring due to being inhibited during fall. A reciprocal seed transplant experiment conducted in two different years demonstrated that the cause of this difference was environmental and that there was no source x site interaction; i.e., no difference between sources in phenotypic plasticity for germination phenology. Absence of genetic effects was also shown by no consistent pattern in the few differences between seed sources in seed incubation laboratory experiments and in a germination phenology experiment in glasshouse flats. Exposure of seeds to a high ratio of far-red/red light prior to or during incubation did not inhibit germination. Neither did changes in leaf litter thickness qualitatively alter germination phenology in field quadrats or in glasshouse flats. Thus, germination in fall at mesic sites was inhibited by other unknown factor(s), perhaps interacting with the effects of closed tree canopy and/or thick leaf litter.     

Incorporating Climate Change and Exotic Species into Forecasts of Riparian Forest Distribution

We examined the impact climate change (CC) will have on the availability of climatically suitable habitat for three native and one exotic riparian species. Due to its increasing prevalence in arid regions throughout the western US, we predicted that an exotic species, Tamarix, would have the greatest increase in suitable habitat relative to native counterparts under CC. We used an ecological niche model to predict range shifts of Populus fremontii, Salix gooddingii, Salix exigua and Tamarix, from present day to 2080s, under five general circulation models and one climate change scenario (A1B). Four major findings emerged. 1) Contrary to our original hypothesis, P. fremontii is projected to have the greatest increase in suitable habitat under CC, followed closely by Tamarix. 2) Of the native species, S. gooddingii and S. exigua showed the greatest loss in predicted suitable habitat due to CC. 3) Nearly 80 percent of future P. fremontii and Salix habitat is predicted to be affected by either CC or Tamarix by the 2080s. 4) By the 2080s, 20 percent of S. gooddingii habitat is projected to be affected by both Tamarix and CC concurrently, followed by S. exigua (19 percent) and P. fremontii (13 percent). In summary, while climate change alone will negatively impact both native willow species, Tamarix is likely to affect a larger portion of all three native species'' distributions. We discuss these and other results in the context of prioritizing restoration and conservation efforts to optimize future productivity and biodiversity. As we are accounting for only direct effects of CC and Tamarix on native habitat, we present a possible hierarchy of effects- from the direct to the indirect- and discuss the potential for the indirect to outweigh the direct effects. Our results highlight the need to account for simultaneous challenges in the face of CC.     

Disturbance Effects on the Seed Bank of Mexican Cloud Forest Fragments1

The density and floristic composition of the soil seed bank was assessed in six cloud forest fragments with different levels of human disturbance in central Veracruz, Mexico. A total of 8416 seeds germinated in 60 soil samples, at 5‐cm depth, corresponding to 107 species, 85 genera, and 48 families. Significant differences were found among study sites in seed densities with values ranging from 873 to 3632/m². Tree species contributed 20 percent of the total soil seed bank in four sites and herbs accounted for the majority of the species in each site. Among tree species, Trema micrantha displayed the highest seed density, accounting for 84 percent of the germinated seeds. In general, the tree species composition of the soil seed bank did not closely reflect the composition of the tree community. Results suggest that disturbance produced by human activities (trail use, selective cutting of trees, livestock) may influence the size and composition of the soil seed bank in forest fragments. Sites where human activity has been reduced showed the highest proportion of dormant seeds.     

福建闽清福建青冈天然林种子雨和种子库

对福建闽清黄楮林自然保护区的福建青冈(Cyclobalanopsis chungii)天然林的种子雨和土壤种子库进行了观测和分析.结果表明,福建青冈种子雨持续2个月,其高峰期在11月下旬～12月上旬,总量为12.44个m~(-2),在种子散布过程中完好种子、虫蛀种子、败育种子、霉烂种子和萌发种子的比例差异明显,其中虫蛀种子是萌发种子的19.44倍.土壤种子库中虫蛀种子占53.79%,与种子雨相比,完好种子和萌发种子数量分别减少2.15个m~(-2)和0.20个m~(-2).土壤种子库种子存活率仅13.51%,动物捕食率达45.90%,说明动物的捕食和搬运是福建青冈种子缺失的原因之一.福建青冈天然林土壤种子库有69种植物种子,但种子数量较少,且分布不均匀,种子库中78.42%种子分布在2～5 cm土层中.福建青冈天然林中实生幼苗少与福建青冈种子本身特性及其生长环境密切相关,福建青冈种子发育成熟后因动物侵扰、虫蛀、霉烂和败育等情况发生,难以在土壤中长期保存,以致福建青冈林分天然更新严重受阻.     

落叶阔叶林内的光合作用和气孔传导率特征(英文)

本文根据Wang和BMdocchi(1989)最近提出的冠层辐射模型,进一步给出了一个模拟冠层光合作用速率和气孔传导率的模式.模式将冠层中每一层的叶面积分为向光叶、半影叶、和全遮荫叶三种,并分别计算其光合作用速率和气孔传导率。计算得到的光合速率廓线表明,在落叶阔叶林内,冠层下部的叶片常处于光照不足状态;半影效应使得透过林冠达于底部的辐射量增大,这对于林下植物的光合作用是有利的。 模式计算值与实测值之间的微弱差别应归因于纯辐射模型无法考虑湍流输送机制造成的CO_2传输和冠层底部耐荫性叶对于低光照的适应能力。     

Biometric Based Carbon Flux Measurements and Net Ecosystem Production (NEP) in a Temperate Deciduous Broad-Leaved Forest Beneath a Flux Tower

Biometric based carbon flux measurements were conducted over 5 years (1999–2003) in a temperate deciduous broad-leaved forest of the AsiaFlux network to estimate net ecosystem production (NEP). Biometric based NEP, as measured by the balance between net primary production (including NPP of canopy trees and of forest floor dwarf bamboo) and heterotrophic respiration (RH), clarified the contribution of various biological processes to the ecosystem carbon budget, and also showed where and how the forest is storing C. The mean NPP of the trees was 5.4 ± 1.07 t C ha⁻¹ y⁻¹, including biomass increment (0.3 ± 0.82 t C ha⁻¹ y⁻¹), tree mortality (1.0 ± 0.61 t C ha⁻¹ y⁻¹), aboveground detritus production (2.3 ± 0.39 t C ha⁻¹ y⁻¹) and belowground fine root production (1.8 ± 0.31 t C ha⁻¹ y⁻¹). Annual biomass increment was rather small because of high tree mortality during the 5 years. Total NPP at the site was 6.5 ± 1.07 t C ha⁻¹ y⁻¹, including the NPP of the forest floor community (1.1 ± 0.06 t C ha⁻¹ y⁻¹). The soil surface CO₂ efflux (RS) was averaged across the 5 years of record using open-flow chambers. The mean estimated annual RS amounted to 7.1 ± 0.44 t C ha⁻¹, and the decomposition of soil organic matter (SOM) was estimated at 3.9 ± 0.24 t C ha⁻¹. RH was estimated at 4.4 ± 0.32 t C ha⁻¹ y⁻¹, which included decomposition of coarse woody debris. Biometric NEP in the forest was estimated at 2.1 ± 1.15 t C ha⁻¹ y⁻¹, which agreed well with the eddy-covariance based net ecosystem exchange (NEE). The contribution of woody increment (Δbiomass + mortality) of the canopy trees to NEP was rather small, and thus the SOM pool played an important role in carbon storage in the temperate forest. These results suggested that the dense forest floor of dwarf bamboo might have a critical role in soil carbon sequestration in temperate East Asian deciduous forests.     

瓦屋山国家森林公园种子植物区系研究

瓦屋山国家森林公园位于青藏高原向四川盆地过渡的地区。区内有种子植物148科,686属,1743种。大科、大属在区系组成中起着非常重要的作用。区系成分的丰富性、温带成分的主体性、特有植物与珍稀濒危植物的集中性是该区种子植物区系的主要特征。     

Long-Term Effects of White-Tailed Deer Exclusion on the Invasion of Exotic Plants: A Case Study in a Mid-Atlantic Temperate Forest

Exotic plant invasions and chronic high levels of herbivory are two of the major biotic stressors impacting temperate forest ecosystems in eastern North America, and the two problems are often linked. We used a 4-ha deer exclosure maintained since 1991 to examine the influence of a generalist herbivore, white-tailed deer (Odocoileus virginianus), on the abundance of four exotic invasive (Rosa multiflora, Berberis thunbergii, Rubus phoenicolasius and Microstegium vimineum) and one native (Cynoglossum virginianum) plant species, within a 25.6-ha mature temperate forest dynamics plot in Virginia, USA. We identified significant predictors of the abundance of each focal species using generalized linear models incorporating 10 environmental and landscape variables. After controlling for those predictors, we applied our models to a 4-ha deer exclusion site and a 4-ha reference site, both embedded within the larger plot, to test the role of deer on the abundance of the focal species. Slope, edge effects and soil pH were the most frequent predictors of the abundance of the focal species on the larger plot. The abundance of C. virginianum, known to be deer-dispersed, was significantly lower in the exclosure. Similar patterns were detected for B. thunbergii, R. phoenicolasius and M. vimineum, whereas R. multiflora was more abundant within the exclosure. Our results indicate that chronic high deer density facilitates increased abundances of several exotic invasive plant species, with the notable exception of R. multiflora. We infer that the invasion of many exotic plant species that are browse-tolerant to white-tailed deer could be limited by reducing deer populations.     

Effects of Seed Treatments on the Emergence of Oil Seed Rape Seedlings from Compacted Soil

Imbibition of seeds of oil seed rape (Brassica napus cv Jetneuf)in 10^–3 M aminoethoxyvinylglycine (AVG) or 10^–2silver thiosulphate (Ag⁺) had no effect on germination nor onthe emergence of seedlings from uncompacted or lightly compressedsoil, but significantly reduced emergence from moderately compressedsoil of 68.4 or 143.3 N cm^–2 impedance. Exertion of force by emerging control seedlings against a staticcantilever bar fitted with strain gauges reached a maximum (F_max)of 6 g over 10 h. Higher axial forces were achieved when theseedlings were emerging from compressed soil, without any changein the time required to reach F_max, so that the build-up offorce was considerably (1.8 fold) faster than in uncompressedsoil. This adaptive response to soil impedance was modified by theseed pretreatments employed. Seedlings from AVG or Ag⁺pretreatedseeds produced lower axial forces than controls, and neitherF_max nor the rate at which force developed showed any responseto soil compression. After pretreatment in 10^–3 ethephon or 10^–4 naphthaleneacetic acid (NAA) the seedlings achieved similar F_max to controlseedlings, but responded more rapidly to soil compression sothat the rate of build up of emergence force was 2.3 fold (NAA)or 2.8 fold (ethephon) faster in compressed than in uncompressedsoil. The results suggest that the exertion of force by a seedlingagainst a barrier involves a dynamic response to impedance onthe part of the seedling. This response can be either enhancedor suppressed by substances which affect ethylene productionor ethylene action. Such compounds may have promise for modifyingseedling emergence from impeding soils. Brassica napus, oil seed rape, seedling emergence, soil compaction, ethylene, Ethrel, silver, aminoethoxyvinylglycine, naphthalene acetic acid     

The Effects of Seed Dispersal on the Simulation of Long-Term Forest Landscape Change

The study of forest landscape change requires an understanding of the complex interactions of both spatial and temporal factors. Traditionally, forest gap models have been used to simulate change on small and independent plots. While gap models are useful in examining forest ecological dynamics across temporal scales, large, spatial processes, such as seed dispersal, cannot be realistically simulated across large landscapes. To simulate seed dispersal, spatially explicit landscape models that track individual species distribution are needed. We used such a model, LANDIS, to illustrate the implications of seed dispersal for simulating forest landscape change. On an artificial open landscape with a uniform environment, circular-shaped tree species establishment patterns resulted from the simulations, with areas near seed sources more densely covered than areas further from seed sources. Because LANDIS simulates at 10-y time steps, this pattern reflects an integration of various possible dispersal shapes and establishment that are caused by the annual variations in climate and other environmental variables. On real landscapes, these patterns driven only by species dispersal radii are obscured by other factors, such as species competition, disturbance, and landscape structure. To further demonstrate the effects of seed dispersal, we chose a fairly disturbed and fragmented forest landscape (approximately 500,000 ha) in northern Wisconsin. We compared the simulation results of a map with tree species (seed source locations) realistically parameterized (the real scenario) against a randomly parameterized species map (the random scenario). Differences in the initial seed source distribution lead to different simulation results of species abundance with species abundance starting at identical levels under the two scenarios. This is particularly true for the first half of the model run (0–250 y). Under the random scenario, infrequently occurring and shade tolerant species tend to be overestimated, while midabundant and midshade tolerant species tend to be underestimated. The over- and underestimation of species abundance diminish when examining long-term (500 y) landscape dynamics, because stochastic factors, such as fire, tend to make the landscapes under both scenarios converge. However, differences in spatial patterns, and especially species age-cohort distributions, can persist under the two scenarios for several hundred years. Received 24 November 1998; accepted 17 March 1999.     

Functional Group Identity Does not Predict Invader Impacts: Differential Effects of Nitrogen-fixing Exotic Plants on Ecosystem Function

The introduction of exotic plants can have large impacts on ecosystem functions such as soil nutrient cycling. Since these impacts result from differences in traits between the exotic and resident species, novel physiological traits such as N cycling may cause large alterations in ecosystem function. It is unclear, however, whether all members of a given functional group will have the same ecosystem effects. Here we look at a within functional group comparison to test whether an annual (Lupinus luteus) and a perennial (Acacia saligna) N-fixing exotic species cause the same effects on soil N cycling in the fynbos vegetation of South Africa. We measured litterfall quantity and quality, and soil total nitrogen and organic matter for each vegetation type as well. Available nitrogen was quantified using ion exchange resin bags monthly for 1 year. We used microcosms to evaluate litter decomposition. Although both exotic species increased the available nitrogen in the soil, only Acacia increased the total soil N and organic matter. This could be explained by the slow decomposition of Acacia litter in the microcosm study, despite the fact that Acacia and Lupinus litter contained equivalent N concentrations. Presumably, low carbon quality of Acacia litter slows its decomposition in soil, resulting in retention of organic nitrogen in Acacia stands after clearing for restoration purposes. The differences in long term impacts of these annual and perennial species highlight the fact that not all N-fixing exotic species exert equivalent impacts. Ecologists should consider multiple traits rather than broadly defined functional groups alone when predicting invader impacts.     

Developmental Patterns of Tree Dimensions in a Neotropical Deciduous Forest1

For 26 tree species in very dry tropical forest in Mexico, the developmental trends of relationships among trunk diameter, tree height, and crown diameter were inferred from a one‐time measurement of dispersed individuals across the size range from saplings to large, mature trees. On hillside sites in this high diversity forest, maximum dimensions were usually <10‐m height, 4‐m crown diameter, and 0.3‐m trunk diameter. The relationship of height to trunk diameter was characterized by an asymptotic, three‐parameter model. Crown diameter was a linear function of trunk diameter. The parameter values for both models varied widely among the species. In general, the dispersion among species of the height–crown diameter relationship increased linearly with trunk diameter (up to 0.2 m). Arborescent cacti were distant from other species at all sizes, although they were well modeled using the same equations. Empirical and theoretical features and limitations of the present and previous models, including mechanical buckling and water‐stress theories, are considered.     

Forest Fragmentation and Seed Germination of Native Species from the Chaco Serrano Forest

Habitat fragmentation is a widespread phenomenon that alters pollination and plant reproductive processes. These effects have demographic and genetic implications that determine offspring fitness and the long‐term viability of plant populations in fragmented systems. We evaluated fragmentation effects on early plant offspring fitness traits, individual seed mass, and percentage of seed germination in five native plant species (Acacia caven, Celtis ehrenbergiana, Croton lachnostachyus, Rivina humilis, Schinus fasciculatus) from the Chaco Serrano forest, a subtropical highly fragmented ecosystem. We found evidence of strong negative fragmentation effects on germination in the shrub C. lachnostachyus and the perennial herb R. humilis, after 30 d of controlled tests. No fragmentation effects were found in the studied traits on the remaining three tree species. We found significant maternal effects in offspring fitness traits in all five species. We discuss the relative magnitude of maternal vs. fragmentation effects taking into account both plant species' lifespan and the time elapsed in fragmentation conditions. We emphasize the need to increase the study of early and late plant offspring fitness produced in fragmented habitats coupled with analyses of genetic parameters and the pollination process in order to evaluate the conservation value of remnant forest fragments. Abstract in Spanish is available at http://www.blackwell‐synergy.com/loi/btp .