Tatiana Cornelissen

Ecology and evolution of plant diversity in the endangered campo rupestre: a neglected conservation priority

BackgroundBotanists, ecologists and evolutionary biologists are familiar with the astonishing species richness and endemism of the fynbos of the Cape Floristic Region and the ancient and unique flora of the kwongkan of south-western Australia. These regions represent old climatically-buffered infertile landscapes (OCBILs) that are the basis of a general hypothesis to explain their richness and endemism. However, few ecologists are familiar with the campo rupestre of central and eastern Brazil, an extremely old mountaintop ecosystem that is both a museum of ancient lineages and a cradle of continuing diversification of endemic lineages.ScopeDiversification of some lineages of campo rupestre pre-dates diversification of lowland cerrado, suggesting it may be the most ancient open vegetation in eastern South America. This vegetation comprises more than 5000 plant species, nearly 15xa0% of Brazil’s plant diversity, in an area corresponding to 0.78xa0% of its surface. Reviewing empirical data, we scrutinise five predictions of the OCBIL theory, and show that campo rupestre is fully comparable to and remarkably convergent with both fynbos and kwongkan, and fulfills the criteria for a classic OCBIL.ConclusionsThe increasing threats to campo rupestre are compromising ecosystem services and we argue for the implementation of more effective conservation and restoration strategies.

Similar responses of insect herbivores to leaf fluctuating asymmetry

Fluctuating asymmetry (FA) represents small, random variation from symmetry and it has been used as an indicator of plant quality and susceptibility to herbivory. In this study, the effects of FA on the responses of distinct herbivore species belonging to several guilds were examined along an environmental gradient in south Florida. This approach was chosen because it relies on a multi-species approach to the study of fluctuating asymmetry and patterns of herbivory between and within plants along an environmental gradient of salinity and plant stress. To examine differences in FA between and within plant communities, seven plant species were investigated. Four of these plants were coastal species and three species occurred in upland communities. Levels of FA were assessed before herbivory and plants were followed for the whole herbivory season in 2006. Coastal plants exhibited significantly higher salt concentration, higher percentage of asymmetric leaves and higher asymmetry levels than upland plants. Herbivore abundance varied widely amongst the seven species studied, but quantitative syntheses of our results indicated significant and positive responses of insect herbivores to leaf asymmetry: insects were 25.11% more abundant on more asymmetric plants and stronger effects of asymmetry were observed for leaf miners compared to gall-formers. As demonstrated by other recent studies, FA might be used as a reliable stress indicator, leading to similar responses of insect herbivores to variation in leaf symmetry.

A Meta-Analysis of the Effects of Fragmentation on Herbivorous Insects

ABSTRACT We reviewed the evidence for the effects of fragmentation on insects and plants by conducting a meta-analysis for the effects of artificial forest edge formation on insect herbivore abundance, herbivore richness, and plant herbivory, with data pooled from 31 studies and 159 independent comparisons. Hedges d was used as the metric to combine all studies. Edge formation exhibited strong effects on plant herbivory rates, as edge plants exhibited 70% more damage than interior plants. Edges also increased herbivore abundance by 14% and herbivore richness by almost 65%, and effects of edge formation were stronger for Lepidoptera (mainly caterpillars) and Orthoptera. Edge effects were also stronger for forested ecosystems compared with open habitats and for temperate regions. Because the studies here evaluated did not simultaneously evaluate bottom-up and top-down factors, the mechanisms responsible for the patterns found cannot be properly addressed, although variation in host plant chemistry, relaxation of pressure exerted by natural enemies, or both, can be suggested as potential factors explaining variation in herbivory between edge and interior habitats. Higher herbivory rates on edge habitats, as shown by our meta-analytical review, have the potential to alter community composition and should be studied in detail to unravel their effects on ecosystem functioning.

Fluctuating asymmetry in leaves and flowers of sympatric species in a tropical montane environment

Fluctuating asymmetry (FA) represents small, random variations in traits, presumably with bilateral symmetry, and is widely used as a tool to measure developmental instability in plants and animals. Because FA is a quick, simple and reliable measure, it has been frequently used for monitoring levels of environmental stress. This study investigated whether FA can be used as a predictor of individual developmental instability for four sympatric Melastomataceae species. To achieve that aim, 20 individuals of Trembleya laniflora, T. parviflora, Lavoisiera campos-portoana and Tibouchina heteromalla were marked in southeastern Brazil and monitored before and during the flowering season. The FA index was calculated as the mean of the difference in the width or length between the left and right sides measured for each leaf or flower. All studied species exhibited asymmetry in the leaves and flowers, but the leaves of L. campos-portoana and the petal width of T. heteromalla exhibited directional asymmetry, also an indicator of developmental instability. The highest level of leaf asymmetry was found in T. heteromalla and on flowers of L. campos-portoana. None of the studied species exhibited a significant relationship between the FA level of the leaves and flowers on an individual basis, indicating that environmental and/or genetic sources of stress might act differently on different plant traits. For the studied species, measurements of FA can be suggested as useful tools to biomonitor levels of stress experienced by both leaves and flowers within the Melastomataceae family.

Cerrado to Rupestrian Grasslands: Patterns of Species Distribution and the Forces Shaping Them Along an Altitudinal Gradient

Due to clear variations in a relatively small area, mountains represent natural laboratories for evolutionary and ecological studies. In a large degree, these variations are driven by changes in climate and soil that occur along altitudinal gradients and influence the ecology, evolution and geography of species. In spite of being old and eroded, the southern Brazilian mountains provide enough variation and heterogeneity to influence species distribution and diversity. The best-known Brazilian mountain range is the Espinhaco (the Backbone mountains). The Espinhaco is a large natural watershed divider of major ecological importance in eastern Brazil. The altitudinal gradient in the Espinhaco Mountains is low when compared to other tall mountains in the world as it only varies from ca. 650 to 2.072 m a.s.l. at the Sun Peak (Pico do Sol). This chapter synthesizes the results of 10 studies that have collectively examined the soil, climate to better understand patterns and processes associated with biodiversity of key groups of organism, including of plants, termites, dung beetles, ants, butterflies, arbuscular mycorrhizal fungi, insect herbivores and birds in an altitudinal gradient (from 800 to 1400 m a.s.l.) at Espinhaco mountain range. In this mountain range, the soils are primarily poor and the vegetation is dominated by rupestrian grasslands, and both are known to vary along the altitudinal gradient hence providing opportunities for variation in the associated organisms.

Effects of fire disturbance on ant abundance and diversity: a global meta-analysis

We conducted a meta-analysis of the effects of fire on the abundance and alpha diversity of ants based upon data published over the past 70xa0years. Overall, fire reduced ant diversity by 18xa0%, but had no effect on ant abundance. However, there was significant variation in the effect of fire on ant diversity amongst different vegetation types. Fire significantly decreased ant diversity in forests—especially in tropical forests—whereas in deserts, grasslands, and savannas it did not. Similarly, fire had a strong negative mean effect on ant diversity in sites where it is uncommon, but did not significantly affect diversity where it is a recurrent phenomenon. There is evidence that, in forests, wildfires have a stronger negative effect on ant diversity than does prescribed burning. In addition, we found marginally significant differences in the effect of fire on the abundance and diversity of forest ants among studies that sampled ants at different times post-fire, or that sampled ants from different soil strata. In contrast, fire did not significantly affect the abundance or diversity of savanna ants, and this was true even after we took into account the geographic location of the study, the ant community sampled, the time since fire, and the fire regime. Overall, the results of our study indicate that habitat type is an important predictor of ant community responses to fire. However, even within a given habitat, reported effects were quite variable among the studies reviewed, evidencing the idiosyncratic nature of fire effects on ants.

The effects of landscape patterns on ecosystem services: meta-analyses of landscape services

PurposeThe recently introduced concept of ‘landscape services’—ecosystem services influenced by landscape patterns—may be particularly useful in landscape planning by potentially increasing stakeholder participation and financial funding. However, integrating this concept remains challenging. In order to bypass this barrier, we must gain a greater understanding of how landscape composition and configuration influence the services provided.MethodsWe conducted meta-analyses that considered published studies evaluating the effects of several landscape metrics on the following services: pollination, pest control, water quality, disease control, and aesthetic value. We report the cumulative mean effect size (E++), where the signal of the values is related to positive or negative influences.ResultsLandscape complexity differentially influenced the provision of services. Particularly, the percentage of natural areas had an effect on natural enemies (E++ =u20090.35), pollination (E++u2009=u20090.41), and disease control (E++u2009=u20090.20), while the percentage of no-crop areas had an effect on water quality (E++u2009=u20090.42) and pest response (E++u2009=u20090.33). Furthermore, heterogeneity had an effect on aesthetic value (E++u2009=u20090.5) and water quality (E++ =u2009−u20090.40). Moreover, landscape aggregation was important to explaining pollination (E++u2009=u20090.29) and water quality (E++u2009=u20090.35).ConclusionsThe meta-analyses reinforce the importance of considering landscape structure in assessing ecosystem services for management purposes and decision-making. The magnitude of landscape effect varies according to the service being studied. Therefore, land managers must account for landscape composition and configuration in order to ensure the maintenance of services and adapt their approach to suit the focal service.

Fluctuating Asymmetry as a Bioindicator of Environmental Stress Caused by Pollution in a Pioneer Plant Species

Abstract Fluctuating asymmetry (FA) is a widely used tool to detect developmental instability and plants under stressful conditions are expected to exhibit increased values of asymmetry, as well as higher levels of herbivory. This study evaluated whether dust from roads can cause major deviations in the axis of symmetry of leaves of the pioneer plant species Cecropia pachystachya Trécul (Urticaceae). It was also investigated whether plants exposed to dust have greater nitrogen content and higher levels of herbivory levels. Ten leaves of 20 individuals of C. pachystachya were collected on two roads with different levels of dust deposition and a control area. FA was calculated as the size-scaled difference between the right (RW) and left (LW) leaf widths and leaf area removed was determined by the ratio between leaf area removed and total leaf area. C. pachystachya plants in areas under strong influence of dust pollution exhibited the highest FA values (0.279 cm), whereas plants in the control area exhibited the lowest. A positive relationship between levels of leaf area removed by insects and a gradient of dust pollution was also observed. Differences in foliar nitrogen concentration among sampling areas indicated differences in leaf quality and influenced herbivory levels of Cecropia. This study indicated that FA can be used as an indicator of developmental instability of plants and those individuals under the impact of road dust and pollution might be more susceptible to insect attack.

Effects of plant quality and ant defence on herbivory rates in a neotropical ant-plant

1. Understanding the degree to which populations and communities are limited by both bottom‐up and top‐down effects is still a major challenge for ecologists, and manipulation of plant quality, for example, can alter herbivory rates in plants. In addition, biotic defence by ants can directly influence the populations of herbivores, as demonstrated by increased rates of herbivory or increased herbivore density after ant exclusion. The aim of this study was to evaluate bottom‐up and top‐down effects on herbivory rates in a mutualistic ant‐plant.

Antagonistic Interactions in the Rupestrian Grasslands: New Insights and Perspectives

Antagonistic interactions are main ecological forces in terrestrial communities and include several examples involving plants and animals. The studies performed in the rupestrian grasslands have mostly focused on patterns of herbivory and on the effects of plant quality and natural enemies on insect herbivore abundance and distribution. Herbivory rates recorded for plants in this ecosystem are within the range proposed for open areas (ca. 15 %), although a wider range of studies are still needed. Galling insect richness is highly variable amongst sites (between 18 and 241 species) and are mostly rich and abundant in xeric habitats compared to mesic habitats, corroborating the hypothesis of environmental harshness. Several new galling insect species have been discovered in this very diverse landscape, indicating its importance for insect radiation and evolution. Galling insect communities associated to host plants are influenced by host plant sex. Male plants generally host higher insect richness and herbivory levels than female plants. Gall insect richness sampled on 138 host plants in several rupestrian grassland sites indicates that larger plant families also host higher number of galling insects than smaller plant families or genera. Amongst the factors that influence host plant selection by herbivores in rupestrian grasslands aspects of plant quality such as leaf asymmetry, leaf sclerophylly and ant-interactions have been evaluated. However, mixed results for the effects of plant quality on insect abundance and performance have been found depending upon the insect-host system evaluated. Another antagonist interaction evaluated involves parasitism by two common species of mistletoes and results have shown that parasitism represents another important source of stress for host plants in the rupestrian grasslands. Finally, in this chapter we summarize several antagonistic, multitrophic and indirect interactions using plants in the genus Baccharis as a model, aiming to provide information and guidance for future studies.