Abstract: . Mixed mating, where a single tree progeny results from a mixture of selfing and outcrossing, is widespread in conifers and could be an evolutionary advantage at ecological margins when mating partners become scarce. This study analyzes how the mating system responds to bioclimate and density variations. We surveyed published data on the mating system of Abies, Picea and Pinus species when information on bioclimate and stand density was available. Our survey revealed that Mediterranean species demonstrate a lower selfing rate than other species and that the proportion of selfed versus outcrossed progeny is not fixed within species. The highest variability in mating types within populations was found when stand density was the most variable. To show how density affects the proportion of selfed versus outcrossed progeny, we used isozymes to genotype single tree seeds from a marginal Abies alba forest in Mediterranean France (Mont Ventoux) where low-to high-density stands are found. We then tested the adaptive potential of the different high and low density progenies by sowing them under controlled nursery conditions and measuring germination rate and seedling survival after 4 yr under 3 different water regimes. Although the mean value of outcrossing rate was typical for mixed mating conifers (tm = 0.85), individual outcrossing rates varied from 0.05 to 0.99 and were strongly correlated with stand type and density (tm from 0.87 in high-density to 0.43 in low-density marginal stands). Significantly fewer seeds from the low density marginal stand germinated (32% vs. 53% in the high density mature stand), although seedlings from the marginal stand had a better 4-yr survival (81%) than seedlings from the high-density mature stand (63%) when the three water regimes (from least to most stressful) were averaged. Trees from low density stands may be at a selective disadvantage because they produce more selfed progeny than trees from high-density stands. However, selfed seeds may be purged early on (at the embryo stage) and the remaining seeds tend to produce seedlings with better fitness. Variability of the selfing rate might thus be an adaptive strategy for species in highly contrasted environments where selection of both reproductive assurance and avoidance of inbreeding depression may be density dependent.

Abstract: . Ecologists, when analyzing the output of simple experiments, often have to compare statistical samples that simultaneously are of uneven size, unequal variance and distribute non-normally. Although there are special tests designed to address each of these unsuitable characteristics, it is unclear how their combination affects the tests. Here we compare the performance of recommended tests using generated data sets that simulate statistical samples typical in ecological research. We measured rates of type I and II errors, and found that common parametric tests such as ANOVA are quite robust to non-normality, uneven sample size, unequal variance, and their effect combined. ANOVA and randomization tests produced very similar results. At the same time, the t-test for unequal variance unexpectedly lost power with samples of uneven size. Also, non-parametric tests were strongly affected by unequal variance in large samples, yet non-parametric tests could complement parametric tests when testing samples of uneven size. Thus, we demonstrate that the robustness of each kind of test strongly depends on the combination of parameters (distribution, sample size, equality of variances). We conclude that manuals should be revised to offer more elaborate instructions for applying specific statistical tests.

Abstract: . We examine the patterns of germination response to fire in the fire-prone flora of the Sydney basin, south-eastern Australia, using examples from several decades of research. The flora shows a strong response to fire-related germination cues. Most species show an interaction between heat and smoke, a number respond only to heat, whilst a few are likely to respond only to smoke. Many recruit in the first 12 months after fire and show no obvious seasonal patterns of recruitment, whilst several species have a strong seasonal germination requirement, even in this essentially aseasonal rainfall region. Key challenges remaining include designing future seed germination studies within the context of informing the germination response surface to smoke and heat interactions, and incorporation of the impact of varying soil moisture on seed germination post-fire, including its affect on resetting of seed dormancy. An understanding of the resilience of species to frequent fire also requires further work, to identify species and functional types most at risk. This work must ideally be integrated within the framework of the management of fire regimes that will change under a changing climate. We suggest that the functional classification of plant types in relation to fire could be enhanced by a consideration of both the type of germination response to fire (type of cues required) and the timing of the response (seasonally driven in response to seed dormancy characteristics, or independent of season). We provide a simplified version of such an addition to functional trait classification in relation to fire.

Abstract: . Species distributional data based on lattice data often display spatial autocorrelation. In such cases, the assumption of independently and identically distributed errors can be violated in standard regression models. Based on a recently published review on methods to account for spatial autocorrelation, we describe here a new statistical approach which relies on the theory of wavelets. It provides a powerful tool for removing spatial autocorrelation without any prior knowledge of the underlying correlation structure. Our wavelet-revised model (WRM) is applied to artificial datasets of species’ distributions, for both presence/absence (binary response) and species abundance data (Poisson or normally distributed response). Making use of these published data enables us to compare WRM to other recently tested models and to recommend it as an attractive option for effective and computationally efficient autocorrelation removal.

Abstract: . The drier parts of the Mediterranean biome of southwest Australia contain the largest remaining Mediterranean woodlands and shrublands on Earth. Despite this, there has been no formal, comprehensive assessment of their biodiversity. The region abuts the southwest Australian floristic region which has received much scientific attention. The aim of this paper is to provide the first general overview of the biodiversity of part of this intact, yet relatively unknown, Mediterranean ecosystem. We do this by synthesizing data from State Government agencies and published research. We found that, like other parts of southwest Australia, the region has globally significant levels of plant species diversity. More than 2400 plant species, including 291 species considered threatened, have been recorded, representing one-sixth of all Australia’s vascular plant species. Eleven of Australia’s 23 major vegetation groups are represented even though the region covers less than 1% of continental Australia. We documented 170 vertebrate species, including 31 threatened species, with a particularly high richness of reptile species (n = 46). We highlight how little is known about this region. For example, 116 vertebrate species not recorded in the region probably occur there based on their habitat requirements and known distributions. An examination of plant and vertebrate diversity in the region, using a half degree latitude and longitude grid cells, showed a highly heterogeneous pattern of species richness and vulnerability, with a general decline in species richness from southwest to northeast. Conservation strategies that rely on capturing the highest levels of biodiversity in a series of protected areas are unlikely to guarantee protection for all species given these high levels of heterogeneity. Instead, a region-wide conservation plan should involve targeted ecological research, consideration of ecological processes and stakeholder consultation.

Abstract: . Disturbance in Mediterranean shrub lands creates gaps that break up the shrub cover and potentially restrict productivity and other ecosystem processes. Gaps make up to about 20% of the low Macchia area at the Castel Volturno nature reserve (southern Italy). The plant community consists mainly of small annual species (legumes, grasses and forbs) that germinate in November and die out before the onset of summer drought. The inter-annual variability in productivity and the relative abundance of legumes, grasses and forbs were assessed over 4 yr (2004–2007) to evaluate main potential modifications of ecosystem processes determined by the occurrence of gaps in the shrub cover. In the study years, at the peak production, plant mass varied from about 250 to 700 g m−2; biomass belowground allocation varied from 23% in the wettest to 44% in the driest year. Belowground/aboveground biomass ratios were negatively related to rainfall and positively related to the length of the dry period, showing that water availability controls biomass allocation patterns. Legumes were the most abundant fraction (about 60%) of the aboveground mass in the wettest year. In the drier years legumes exhibited a shorter life cycle and senesced by mid-spring. Among the three functional groups monitored, legumes were the most sensitive to water shortage and their biomass was positively related to the amount of rainfall and negatively related to the length of the dry period. The higher fraction of legume mass was associated with higher nitrogen content in plant tissues and in the soil. Senesced annual species decomposed more than senescent Phillyrea sp. leaves. The stability of organic carbon pool, evaluated through the endogenous mineralization coefficient (CEM), was lower in gaps than in understorey soils.

Abstract: . Alpine snowbeds are characterised by a very short growing season. However, the length of the snow-free period is increasingly prolonged due to climate change, so that snowbeds become susceptible to invasions from neighbouring alpine meadow communities. We hypothesised that spatial distribution of species generated by plant interactions may indicate whether snowbed species will coexist with or will be out-competed by invading alpine species – spatial aggregation or segregation will point to coexistence or competitive exclusion, respectively. We tested this hypothesis in snowbeds of the Swiss Alps using the variance ratio statistics. We focused on the relationships between dominant snowbed species, subordinate snowbed species, and potentially invading alpine grassland species. Subordinate snowbed species were generally spatially aggregated with each other, but were segregated from alpine grassland species. Competition between alpine grassland and subordinate snowbed species may have caused this segregation. Segregation between these species groups increased with earlier snowmelt, suggesting an increasing importance of competition with climate change. Further, a dominant snowbed species (Alchemilla pentaphyllea) was spatially aggregated with subordinate snowbed species, while two other dominants (Gnaphalium supinum and Salix herbacea) showed aggregated patterns with alpine grassland species. These dominant species are known to show distinct microhabitat preferences suggesting the existence of hidden microhabitats with different susceptibility to invaders. These results allow us to suggest that alpine snowbed areas are likely to be reduced as a consequence of climate change and that invading species from nearby alpine grasslands could outcompete subordinate snowbed species. On the other hand, microhabitats dominated by Gnaphalium or Salix seem to be particularly prone to invasions by non-snowbed species.

Abstract: . Community structure was studied across six different habitat types in an amphibian assemblage constituted by 24 species belonging to five families, from Lake Nabugabo, Uganda. We employed a suite of different statistical methods, including univariate, multivariate, and Monte Carlo procedures to investigate the randomness/nonrandomness and the seasonal effects (wet versus dry season) of the community assembly. We calculated for each species in each habitat type an index of relative abundance by using a time constrained counting technique, with 48 1-h counts for each habitat type. Co-occurrence was analysed by C score with 30 000 simulations; resource partitioning patterns by RA2 and RA3 algorithms with 30 000 simulations; and apparent dissimilarity among species in terms of habitat use by UPGMA dendrograms. After pooling data from wet and dry seasons, it resulted that the amphibian community was non-randomly assembled according to C-score analyses, but both RA2 and RA3 were unable to uncover any competitive structure for the dataset. Seasonal effects were evident, and although C score analyses confirmed a nonrandom structure for the community under study (particularly in wet season), RA3 showed that species with high relative abundance tended to significantly concentrate in one habitat type (swamp forest) rather than to partition the habitat resource. UPGMA dendrograms grouped the species differently in dry versus wet seasons. Overall, the comparative evidence of 1) non-random community structure according to C-score analysis, and 2) absence of resource partitioning according to niche overlap null models analysis, suggests that community organization in Lake Nabugabo amphibians is generated by habitat affinities rather than by interspecific competition.

Abstract: . We estimated differences, five years after a wildfire, in soil and vegetation between Pinus halepensis stands that were once burnt (1998) and stands that were burnt twice in a short time interval (1995 and 1998), in the area of Penteli, central Greece. The parameters monitored were the physical and chemical attributes of upper soil layer and the vegetation composition, density and height. The results showed that five years after the wildfire, soil pH did not differ between areas burnt once and twice, while the organic matter was higher in the once-burnt areas. The vegetation composition was similar in the two areas and the dominant species were those pre-existing the fire. On the contrary, vegetation density was considerably lower in the twice-burnt areas. The height of woody species oscillated in the same levels in the two areas. The plant community was composed mainly by resprouting species, like Quercus coccifera, Pistacia lentiscus, or Phillyrea latifolia, and less individuals from seed-regenerated species, like Pinus halepensis, Cistus monspeliensis, and C. creticus. It is suggested that the recurrence of wildfire affected negatively the ecosystem attributes, and contributed to the increased risk of degradation.

Abstract: . We studied the effects of small-scale vegetation disturbances on biodiversity in an abandoned coppice forest in central Japan during 2004–2006. We assessed biodiversity by examining vegetation regeneration and by changes in the diversity and abundance of ground beetles after experimental manipulations including tree felling, vegetation clearing, and litter removal. Our experimental design was dictated by the need of producing only small disturbances; therefore we could not replicate plots. Instead, we used a repeated measures approach during three years to document the consistency of experimental effects. We found that the diversity of regenerating vegetation increased dramatically due to recruitment of many new species after clearing ground vegetation. Tree cutting caused strong environmental changes and affected vegetation regeneration rate but not diversity. Tree cutting also significantly increased the diversity of ground beetle species, while litter removal affected the abundance of ground beetles. Our results suggest that a sound conservation practice shall combine tree cutting with ground vegetation clearing and litter removal. Besides, conservation of abandoned forests may be based on low-intensity labor, including tree cutting on restricted areas. Finally, ground beetles appeared to be surprisingly sensitive to vegetation disturbance on a restricted area and thus can be suggested for monitoring such small-scale-disturbance-based conservation practices.

Abstract: . In multi-species communities the stability of a system is difficult to assess from field observations. This is the case for example for competitive interactions in plant communities. If a mathematical model can be formulated that underlies the processes in the community, a community matrix can be constructed whose elements represent the effects of each species onto every other (and itself) at equilibrium. The most common competition model is the Lotka-Volterra equation set. It contains interspecific competition coefficients to represent the interactions between species. In plant community ecology several attempts have been made to quantify competitive interactions and to assemble a community matrix, so far with limited success. In this paper we discuss a method to use pairwise interaction coefficients from experimental plant communities to analyse feasibility and stability of multi-species sets. The approach is contrasted with that of Wilson and Roxburgh (1992) and is illustrated using data from Roxburgh and Wilson (2000a). Results from Wilson and from this study differ (some times substantially), with our approach being more pessimistic about stability and coexistence in plant communities.

Abstract: . Small rodents were captured in two regions in western Sweden. One represents an agricultural landscape were captures were made in 19 small habitat islands and in two small forests. The other represents a forest region were captures were made in four sites in a continuous forest. The captures were made for seven years. There were no clear indications of cyclicity. Within both regions, wood mice captures were in synchrony among sites. For bank voles, this was only true in the forest region and for field voles in the agricultural region. Captures of field voles were too few for analysis in the forest region. Among species, captures were not synchronous in the agricultural region but captures of wood mice and bank voles were synchronous in the forest region. These results suggest a role of landscape structure for the population dynamics of these species, rather than differences in predator function.

Abstract: . Living organisms respond both to current and previous environments, which can have important consequences on population dynamics. However, there is little experimental evidence based on long-term field studies of the effects of previous environments on the performance of individuals. We tested the hypothesis that trees that establish under different environmental conditions perform differently under similar post-establishment conditions. We used the slow-growing, evergreen Mediterranean oak Quercus ilex subsp. rotundifolia as target species. We analyzed the effects of previous environments, competition effects and tradeoffs among life-history traits (survival, growth, and reproduction). We enhanced seedling establishment for three years by reducing abiotic environmental harshness by means of summer irrigation and artificial shading in 12 experimental plots, while four plots remained as controls. Then these treatments were interrupted for ten years. Seedlings under ameliorated environmental conditions survived and grew faster during early establishment. During the post-management period, previous treatments 1) did not have any effect on survival, 2) experienced a slower above-ground growth, 3) decreased root biomass as indicated from reflectivity of Ground Penetration Radar, 4) increased acorn production mostly through a greater canopy volume and 5) increased acorn production effort. The trees exhibited a combination of effects related to acclimation for coping with abiotic stress and effects of intra-specific competition. In accordance with our hypothesis, tree performance overall depended on previous environmental conditions, and the response was different for different life-history traits. We recommend early management because it increased plot cover, shortened the time to attain sexual maturity and increased the amount of acorn production. Plots such as those assessed in this study may act as sources of propagules in deforested agricultural landscapes thus aiding natural establishment of new plants.

Abstract: . This study presents a characterisation of the implementation of Adaptive Management (AM) from the analysis of 35 projects around the world. Our results reveal that AM projects are usually aimed at ecosystem management, conservation and restoration. Also, they mainly act upon forest or epicontinental water ecosystems and their goal is generally species exploitation and in most cases these projects act at a local scale. From a methodological point of view, most AM cases use an active approach and monitoring programs and were at the phase of problem identification. We found differences in the implementation of AM between developed and developing countries that were present in our samples in the following way: AM projects in developed countries were typically carried out by state agencies, and focused on solving problems concerning epicontinental waters and the public use of ecosystems. They had the support of national funds and used modelling techniques. In contrast, the AM projects from developing countries were mainly aimed at the conservation of natural protected areas and at the mitigation of environmental impacts derived from mining activities. The financial support of these projects was frequently provided by international organizations, and the use of modelling techniques was uncommon. For a better exploitation of all the possibilities of AM, we suggest the use of criteria to be customized to the specific needs of the socio-economic reality of every country and to monitor the results at a global scale to continuously improve this practice.

Abstract: . Erica andevalensis is an endemic vulnerable species that grows in metal-polluted soils from the Iberian Pyrite Belt. The genetic diversity of six E. andevalensis populations from Portugal and Spain was studied using PCR Inter-simple sequence repeat (ISSR). The obtained data showed that a) there is a very low genetic diversity within the populations from Portugal, and b) the populations sampled in Portugal are genetically different from the Spanish populations. The lack of genetic diversity in the Portuguese populations suggests the existence of founder effects and subsequent genetic isolation. Plant genetic diversity was also low in the Spanish populations, although the analysis showed that the studied populations were different among them. A Mantel test of the correlation between genetic and geographic distances was significant evidencing the genetic isolation by distance of the studied populations. The distinctiveness and low genetic diversity of the Portuguse populations emphasizes the importance of taking measures for their conservation.

Abstract: Accepted 2 July 2008 Copyright © EEF ISSN 1399-1183 AGORA is a lighter channel of communication between readers and contributors; it aims to stimulate discussion and debate, particularly by presenting new ideas and by suggesting alternative interpretations to the more formal research papers published in WEB ECOLOGY and elsewhere. A lighter prose is encouraged and no summary is required. Formal research papers, however short, will not be considered.

Abstract: and elsewhere. A lighter prose is encouraged and no summary is required. Formal research papers, however short, will not be considered.Like many ecologists we were intrigued by Tomas Grim’s original and thought-provoking evaluation of professional achievement amongst his Bohemian ecologist colleagues in your sister journal, Oikos (Grim 2008). In his paper, Grim argues and infers from a correlational analysis that publication success is negatively affected by beer drinking – an assumed correlate of ‘social activity’ – due to nega -tive effects of alcohol on cognitive performance. Here we question Grim’s conclusions. We criticize his focus on a single hypothesis, without consideration of reasonable al-ternatives, and note that his approach provides a valuable illustration of a more general flaw in ecological inference.Grim correlated publication success of Czech ecologists to their self-reported beer consumption. We note short-falls in this approach. We could, for example, quibble with Grim’s measures of publication success (Lortie et al. 2007), note the problems of using self-reported drinking as a measure of true alcohol consumption (Nevitt and Lundak 2005), question his neglect of gender differences (Bailly et al. 1991) and debate whether heavier drinkers really are involved in more social or anti-social behaviour (Ogle and Miller 2004). We might also note the paper focuses on just 10% of the variation in publication success – that part not explained by each ecologist’s age and duration of publica -tion career. However, this would be nit-picking. Our main concern is with Grim’s pessimism-by-default regarding the impending obscurity of drinking ecologists. As we justify below, there are good reasons to be more optimistic.