Daniel Negreiros

Toward an old‐growth concept for grasslands, savannas, and woodlands

We expand the concept of “old growth” to encompass the distinct ecologies and conservation values of the worlds ancient grass-dominated biomes. Biologically rich grasslands, savannas, and open-canopy woodlands suffer from an image problem among scientists, policy makers, land managers, and the general public, that fosters alarming rates of ecosystem destruction and degradation. These biomes have for too long been misrepresented as the result of deforestation followed by arrested succession. We now know that grassy biomes originated millions of years ago, long before humans began deforesting. We present a consensus view from diverse geographic regions on the ecological characteristics needed to identify old-growth grasslands and to distinguish them from recently formed anthropogenic vegetation. If widely adopted, the old-growth grassland concept has the potential to improve scientific understanding, conservation policies, and ecosystem management.

The occurrence and effectiveness of hypersensitive reaction against galling herbivores across host taxa

1. Hypersensitive reaction is an important type of induced defence by which the plant elicits a defence response to pathogens and insects. Hypersensitive reaction has been argued to be the most common plant resistance mechanism against insect herbivores that have intimate associations with their host plants.

Tyranny of trees in grassy biomes.

![Figure][1] Highland grassland in Brazil is considered a forest landscape restoration opportunity PHOTO: G. W. FERNANDES Tree planting, fire suppression, and exclusion of megafaunal herbivores (native or domestic) are ecologically reasonable restoration strategies in deforested landscapes

CSR analysis of plant functional types in highly diverse tropical grasslands of harsh environments

The classification of plant species according to the CSR ecological strategy scheme has been proposed as a common language that allows comparison among species, communities, and floras. Although several studies on European continent have demonstrated a consistent association between CSR strategies and key ecosystem processes, studies of this type are still lacking in other ecoregions worldwide. For the first time, the CSR strategy scheme is applied in a tropical plant community. In a Brazilian mountain grassland ecosystem characterized by both high biodiversity and environmental stress, we sampled various functional traits of 48 herbaceous species in stony and sandy grasslands, and evaluated the relationship between CSR strategies and functional traits with several environmental parameters. The extremely infertile soils in the two studied habitats may have acted as a major environmental filter leading to a clear predominance of the stress-tolerant strategy in both communities. However, fine-scale environmental differences between the two communities resulted in the filtering of distinct functional trait values. The sites with coarser soil texture, lower percentage of plant cover and (paradoxically) higher mineral nutrient concentrations favored plants with narrower leaves, higher stress tolerance, lower competitiveness, and higher sclerophylly (i.e., lower specific leaf area and higher leaf dry matter content). The comparison between the functional character of stony and sandy communities evidenced the influence of soil texture and water availability in the environmental filtering. This study highlighted the validity of the CSR classification outside the temperate region where it was originally developed and corroborated.

Phylogeny strongly drives seed dormancy and quality in a climatically buffered hotspot for plant endemism.

Background and Aims Models of costs and benefits of dormancy (D) predict that the evolutionarily stable strategy in long-term stable environments is for non-dormancy (ND), but this prediction remains to be tested empirically. We reviewed seed traits of species in the climatically buffered, geologically stable and nutrient-impoverished campo rupestre grasslands in Brazil to test the hypothesis that ND is favoured over D. We examined the relative importance of life-history traits and phylogeny in driving the evolution of D and assessed seed viability at the community level. Methods Germination and viability data were retrieved from 67 publications and ND/D was determined for 168 species in 25 angiosperm families. We also obtained the percentage of embryoless, viable and dormant seeds for 74 species. Frequencies of species with dormant and non-dormant seeds were compared with global databases of dormancy distribution. Key Results The majority of campo rupestre taxa (62·5 %) had non-dormant seeds, and the ND/D ratio was the highest for any vegetation type on Earth. Dormancy was unrelated to other species life-history traits, suggesting that contemporary factors are poor predictors of D. We found a significant phylogenetic structure in the dormancy categorical trait. Dormancy diversity was highly skewed towards the root of the phylogenetic tree and there was a strong phylogenetic signal in the data, suggesting a major role of phylogeny in determining the evolution of D versus ND and seed viability. Quantitative analysis of the data revealed that at least half of the seeds produced by 46 % of the surveyed populations were embryoless and/or otherwise non-viable. Conclusions Our results support the view that long-term climatic and geological stability favour ND. Seed viability data show that campo rupestre species have a markedly low investment in regeneration from seeds, highlighting the need for specific in situ and ex situ conservation strategies to avoid loss of biodiversity.

Insetos galhadores associados a duas espécies de plantas invasoras de áreas urbanas e peri-urbanas

Insects have been considered as important bioindicators of environmental changes and habitat quality. In spite of its sessile habit, easy localization, abundance and host specificity, insects that induce galls have not been utilized in studies of this nature. It was investigated the suitability of gall-inducing insects associated to two ruderal host plant species (Baccharis dracunculifolia and Vernonia polyanthes: Asteraceae) as bioindicators of habitat quality. The following questions were addressed: (i) is gall-inducing insect diversity influenced by different types of land use?; (ii) are the responses of galling insect communities different between host plants?; (iii) how does the biotic and physical features of the biotope influence the gall-inducing insect diversity? It was found 6,226 galls, belonging to six galling insect species on V. polyanthes and 11 galling species on B. dracunculifolia. No difference was found in galling species richness among land use types. Nevertheless, gall-forming insect abundance was statistically different among the biotopes studied. Insect galls were more numerous in biotopes with lower urbanization levels. Gall abundance showed a strong and positive relationship with the percentage of vegetal cover. Gall-forming insect communities on both host species showed differential responses to the different land use types. The results suggest that three factors may be involved with galling insect diversity in urban areas: (i) habitat structure in the biotope; (ii) resource abundance (host plant abundance and distribution); and (iii) frequency and intensity of management in reserves, parks, city squares, wastelands found at a given urban area.

CARACTERIZAÇÃO DA FERTILIDADE DOS SOLOS DE QUATRO LEGUMINOSAS DE CAMPOS RUPESTRES, SERRA DO CIPÓ, MG, BRASIL

The goal of the present study was to characterize the nutritional quality of the soils colonized by four endemic leguminous shrubs of Serra do Cipo, southeastern Brazil: Calliandra fasciculata Benth., Chamaecrista ramosa (Vog.), Collaea cipoensis Fortunato and Mimosa foliolosa Benth. A mixed soil sample collected between 0 and 15cm depth was obtained in four subpopulations of each species. Each mixed sample resulted from the combination of 20 simple samples (four samples of five adult individuals) in each subpopulation. Routine, organic matter, micronutrients, and granulometric analysis were performed for each sample. The soils colonized by the four species were sandy, acidic, deficient in all macronutrients, and with high aluminum saturation. However, the levels of organic matter, zinc, iron, and bore ranged from medium to high. There was no significant difference in organic matter, phosphorus, iron, bore, sulphur, potential acidity, and granulometric parameters among the soils of the four species. The results of the present study corroborate previous studies in rupestrian field soils of Serra do Cipo. Management plans and land rehabilitation programs should keep the conditions of low soil fertility because the endemic flora adapt well on these soils and may have increased competitive ability under these nutritional ranges.

Germinação de sementes de Lavoisiera cordata Cogn. e Lavoisiera francavillana Cogn. (Melastomataceae), espécies simpátricas da Serra do Cipó, Brasil

ABSTRACT – (Seed germination of Lavoisiera cordata Cogn. and Lavoisiera francavillana Cogn.(Melastomataceae), sympatric plant species from Serra do Cipo, Brazil). In this study, the seed germinationbehavior of two sympatric plant species that occur in habitats under diferent nutritional and moisture conditionsat Serra do Cipo, Southeastern Brazil, was evaluated. Seeds collected in the year of 2000 were placed to germinatein four replicates of 25 seeds under the temperatures at 15, 20, 25 and 30°C, and at 12 hour photoperiod. L. cordata showed higher germination percentage than L. francavillana (t=11.803, gl=30, p 0.05, N.S.). The germination percentages were correlated with the the radicleemergency rate for this species (r

Plant Resistance Against Gall-forming Insects: The Role of Hypersensitivity

The understanding of how plants defend themselves against attack by herbivores has been the focus of many studies since the beginning of the last century. Plants are not passive agents under attack by natural enemies or damage caused by environmental phenomena (Fernandes et al. 2000). Plant defense against herbivory can be categorized into three mechanisms: either flee, fight, or weather the attack. Plants can flee by developing before herbivore numbers are high (Feeny 1976), fight and defend themselves by being unsuitable food for herbivores (Renwvick 1983), or cope with herbivory through tolerance (Rosenthal & Kotanem 1994, Strauss & Agrawal 1999). Because herbivores are not always predictable, and plant defences may be costly (Schoonhoven et al. 1998), it is believed that some plant species can use damage suffered as a cue to induce resistance against subsequent herbivores. Karban & Baldwin (1997) refer to changes in plants after damage or stress as induced responses. These changes may or may not affect herbivores and/or plants that express these responses. On the other hand, the induced responses that reduce herbivore survival, growth rate, fecundity or preference for a plant are determined induced resistance. Finally, those induced responses that decrease the negative effects of attacks on plants are named induced defences. Induced resistance is an arthropocentric perspective, while induced defence is a phytocentric perspective of the changes in the plant in response to insect activity.

Influência da luz e da temperatura na germinação de sementes de Marcetia taxifolia (A. St.-Hil.) DC. (Melastomataceae)

Marcetia taxifolia (A. St.-Hil.) DC. (Melastomataceae) is a shrub widely distributed in the rupestrian fields of Serra do Cipo, Brazil. In spite of M. taxifolia being a potential species to be used in land rehabilitation, no complete study has been conducted regarding its seed germination. The goal of this work was to evaluate the effect of light and temperature on seed germination of M. taxifolia. Seeds were collected in May/2001 and were submitted to germination tests at constant temperatures of 15, 20, 25, 30 and 35oC under a photoperiod of 12 hours, and in the absence of light for 30 days. There were statistically significant differences between seed germination and mean time of germination for seeds submitted to the light and dark treatments at 15, 20, 25 and 30oC (p < 0,05; all). Seed germination under 35oC was totally inhibited. The higher germination percentages were obtained at 15 and 20oC, which differed significantly from the temperatures of 25 and 30oC (ANOVA = 13,65; p < 0,001). The data contribute to further studies focusing the propagation of M. taxifolia for land rehabilitation purposes.