Dry soil determines the pseudoviviparous reproduction in Comanthera nivea (Eriocaulaceae) in the Campos Rupestres in south-eastern Brazil

Pseudovivipary is an asexual reproduction strategy correlated with extreme environments. Comanthera nivea occurs in habitats with low water retention. This study investigated the effect of soil moisture availability on C. nivea pseudoviviparous reproduction and flowering. We established four permanent plots (1 × 1 m), two in a shaded area, in which we marked 15 rosettes in each plot, and two in a full-sun area, in which we marked 10 rosettes in each plot. We made monthly observations from August 2016 to January 2017, to quantify the number of flower heads and of pseudoviviparous ramets per rosette, and measured soil moisture. Our results showed a high correlation between soil moisture and flowering. Flowering in C. nivea occurs in periods of increased soil moisture, whereas pseudoviviparous reproduction occurs in the driest period. The advantages of a pseudoviviparous canopy-forming strategy in habitats with scarcity of water in the soil are discussed.     

Reproductive allocation in rhizomatous,seminiferous, and pseudoviviparous Leiothrix (Eriocaulaceae) species

Pseudoviviparous species are considered to rely almost entirely on vegetative propagation, because flowers are replaced by sprouts, and seedling recruitment is rare. We compared reproductive allocation (inflorescence and seed production) in three propagation modes presented by sympatric species of Leiothrix (Eriocaulaceae): rhizomatous and seminiferous (RS—L. crassifolia); rhizomatous, seminiferous, and pseudoviviparous (RSP—L. spiralis); and seminiferous and pseudoviviparous, in which seed production is considered rare due to reduced inflorescence size and small number of pistillate flowers (SP—L. arrecta and L. propinqua). We hypothesize that such propagation modes constitute a continuum of reproductive investment, that is: RS > RSP > SP. We harvested 154 Leiothrix spp. individuals at the Serra do Cipó, SE Brazil, from which we recorded the number of capitula and seeds, mean seed weight, and dry biomass allocated to plant structures. We then compared distinct propagation modes in relation to reproductive allocation, inflorescence-based and seed-based reproductive effort, and biomass partitioning. Contrary to expectations, the reproductive investment hierarchy found was SP ≥ RS > RSP. Our results do not fully concur with the current view that pseudoviviparous plants allocate few resources to reproduction. We suggest that the larger reproductive investment observed in SP helps to wait for better recruitment conditions in crowded and highly competitive mature populations (temporal escape), and to cope with destructive disturbances such as fire, since SP species lacks rhizomes.     

Seasonal timing of pseudoviviparous reproduction of Leiothrix (Eriocaulaceae) rupestrian species in South-eastern Brazil

BACKGROUND AND AIMS: Pseudovivipary is an asexual reproductive strategy. Leiothrix spiralis and L. vivipara (Eriocaulaceae) are pseudoviviparous and occur in rupestrian grasslands, a habitat that has a predominance of sandy and shallow soil, with low water retention. This study aims to investigate the seasonal variation effect of moisture availability on L. spiralis and L. vivipara pseudoviviparous reproduction, and to compare their life history attributes, on rupestrian grasslands in Southeastern Brazil. METHODS: A field study was conducted, including observations concerning pseudoviviparous reproduction and measurement of demographic variables in both L. spiralis and L. vivipara. Soil moisture measurements were also performed to study its effect on the pseudoviviparous reproduction of L. spiralis and L. vivipara. KEY RESULTS: Flower head and plantlet production in L. spiralis were highly correlated with soil moisture. All scapes split off in the drier period, indicating that this is a splitter ramet species. Plantlet mortality was positively correlated with scapes splitting off. The L. vivipara phenophases were not synchronized to the variation in soil moisture, since flower heads and plantlets were produced throughout the year. Moreover, the splitting off of scapes was not observed. In addition, plantlets were formed early, as soon as the flower heads appeared, and remained suspended. Therefore, this species was called 'canopy forming'. CONCLUSIONS: Seasonal timing of pseudoviviparous reproduction can be a vital component of the successful establishment of plantlets in L. spiralis, considering that in this species the plantlets are formed only after the flower head touches the ground. In contrast, in L. vivipara, the plantlets are formed early, without touching the ground. Moreover, L. spiralis is a splitter ramet species, while L. vivipara is a canopy-forming species. The pseudoviviparous canopy-forming strategy appears to be more advantageous than the splitter ramet strategy, because even under similar soil moisture conditions, the survival of L. vivipara plantlets was greater than that of L. spiralis.     

Drivers of fire occurrence in a mountainous Brazilian cerrado savanna: Tracking long-term fire regimes using remote sensing

Fire is a natural disturbance in savannas, and defines vegetation physiognomy and structure, often influencing species diversity. Fire activity is determined by a wide range of factors, including long and short term climatic conditions, climate seasonality, wind speed and direction, topography, and fuel biomass. In Brazil, fire shapes the structure and composition of cerrado savannas, and the impact of fire on vegetation dynamics is well explored, but the drivers of variation in fire disturbance across landscapes and over time are still poorly understood. We reconstructed 31 years of fire occurrence history in the Serra do Cipó region, a highly-diverse cerrado landscape, located in the southern portion of the Espinhaço mountain range, state of Minas Gerais, Southeastern Brazil. We mapped burn scars using a time series of Landsat satellite images from 1984 to 2014. Our questions were 1) How does fire occurrence vary in time and space across the Serra do Cipó cerrado landscape? 2) Which climatic drivers may explain the spatial and inter-annual variation in fire occurrence on this landscape? 3) Is fire occurrence in this cerrado landscape moisture-limited or fuel-limited? We evaluated the inter-annual variation and distribution of burned areas, and used linear models to explain this variation in terms of rainfall amount (determinant of fuel load production), seasonal rainfall distribution (determinant of dry fuel availability), abnormality of precipitation (Standardized Precipitation Index – SPI), and vegetation type (Enhanced Vegetation Index – EVI). Contrary to our expectations, annual rainfall volume was weakly and negatively correlated with burned area, and the strongest predictor of burned area was drought during the ignition season. The length of the dry season and the distribution of rain along the season determined ignition probability, increasing fire occurrence during the driest periods. We conclude that the mountain cerrado vegetation at Serra do Cipó has a moisture-dependent fire regime, in contrast to the fuel-dependent fire regimes described for African savannas. These findings imply that savannas at different continents may have different recovery and resilience capabilities when subjected to changes in the fire regime, caused by direct anthropogenic activities or indirectly through climatic changes. The possible effects of these changes on cerrado landscapes are still unknown, and future studies should investigate if currently observed fire regimes have positive or negative impacts on vegetation diversity, recovery, resilience and phenology, thus helping managers to include fire management as conservation measure.     

Relationship between seed and clonal growth in the reproduction of Carex rugulosa Kük. in riverside meadows

Carex rugulosa Kük. develops riverside vegetation in brackish marshes along the lower parts of rivers. Because the rhizomatous ramets grow densely (590–950/m²) in its developed population, it is expected that seedlings cannot get enough light to grow if seeds germinate in crowded ramets. We studied the reproductive contribution of seed in a marshy meadow of the Ohashi River, Japan. The number of seeds produced was 6900–14 200/m² in 2002. The number of buried seeds in the following germination season differed among sites from 1190 to 2690/m². No seedlings were observed at plots where the ramets from rhizomes grew densely. In contrast, seedlings appeared in plots where all rhizomatous ramets were artificially cut. The number of seedlings corresponded to 17.5–39.5% of that of buried seeds. All these seedlings were submerged and died when it rained heavily. In the genotype analysis using allozyme detection, one of the phosphoglucoisomerase loci ( Pgi-2 ) indicated a pair of alleles. Among eight plots (each plot was 50 or 60-cm square), four showed an excess of heterozygotes and two showed homozygote domination in the Pgi-2 genotype. These results suggest that: (i) seed germination is suppressed in crowded ramets; (ii) seedling survival is severely reduced by inundation; and (iii) the population is usually maintained by clonal growth. As germination is induced in open areas, it is hypothesized that the main role of seed is recovery after vegetation decline caused by environmental stresses or colonization to other areas without dense vegetation.     

Tri-trophic interactions among congeneric sympatric host plants of Chamaecrista, seed predators and parasitoids

The defensive role against seed predation of a set of plant traits in 13 congeneric sympatric taxa (Chamaecrista: Leguminosae), and the influence of the third trophic level on seed predators’ performance and host range were investigated. Taxa co-occur in rupestrian grasslands in Serra do Cipó, Brazil, and belong to three taxonomic sections. Fruit production, fruit pubescence, and seed size were analyzed. Measures of these traits in the 13 taxa were regressed separately against seed predation rates by endophagous and ectophagous insects. Time of seed production and fruit pubescence showed no influence on seed predation rates by either predator type. Seed size was positively correlated to bruchid seed predation, but negatively related to ectophagous seed predation. There was a negative correlation between glandular fruit trichome length and parasitism rates of bruchids, suggesting that seed predation pressure may have produced evolutionary responses from plants (fruit trichome reduction), which should facilitate parasitoid action.     

Symplocos saxatilis (Symplocaceae), a new dioecious species from Serra do Cipó, Minas Gerais, Brazil

Symplocos saxatilis from Serra do Cipó, Minas Gerais State, Brazil, is newly described and illustrated on the basis of field and herbarium studies. It appears to be restricted to “campo rupestre” (rocky field) habitats. This new species is characterized by its 1- to 3-flowered pedunculate inflorescence, 11 to 14 staminodes of the pistillate flowers, and 0.7–1.5 mm thick endocarp.     

Five new taxa in Eriocaulaceae from the Chapada Diamantina of Bahia,Brazil

Five new taxa in Eriocaulaceae from the Chapada Diamantina of Bahia, Brazil are described and illustrated and their diagnostic characters discussed and compared with other similar taxa. Eriocaulon ligulatum var. dimerum occurs only between Len?óis and Palmeiras; Paepalanthus carvalhoi occurs in Palmeiras, Mucugê and Barra da Estiva; P. umbrosus, P. multicapitatus and P. oblongifolius are known only from the Serra da Chapadinha near Len?óis.     

Responses of Hedysarum Laeve, a guerrilla clonal semi-shrub in the Mu Us sandland, to local sand burial

In arid and semi-arid inland deserts,one of the environmental stresses for plants is recurrent sand burial,which can influence the physical and biotic microenvironments of the plants and soil.Previous studies have shown that different levels of sand burial have different effects on plants.Slight sand burial could increase the height increment,leaf biomass and the number of new ramets of the plants while heavy sand burial could impair the growth of the plants and even decrease their chances of survival.In other words,below a certain threshold level of burial,the growth of plants is stimulated probably because of multiple factors.However,as the level of burial increases,the positive response starts to decline until it becomes a negative value.Arid and semi-arid inland deserts are frequently colonized and stabilized by many rhizomatous clonal plants.Clonal physiological integration often helps clonal plants buffer local environmental stress encountered by ramets.A rhizomatous clonal semishrub,Hedysarum laeve (H.laeve),is the dominant plant species and important for vegetation restoration in the Mu Us sandland.To investigate whether clonal integration can increase the threshold of sand burial and help rhizomatous H.laeve tolerate heavy sand burial,we conducted a field experiment.The results showed that slight sand burial could accelerate ramet growth and enhance leaf biomass,stem biomass and shoot biomass,while heavy sand burial reducesed the biomass of the plant and impairs survival and growth of the ramets.Clonal integration increased the threshold of sand burial.Under heavy sand burial,ramets connected to other ramets not buried in sand were more in terms of height increment,stem biomass,leaf biomass and shoot biomass compared to the ramets encountering sand burial but disconnected from other ramets.It suggested that clonal physiological integration could help H.laeve ramets tolerate relatively heavy sand burial.We also discussed that clonal integration plays a role in H.laeve presence in the Mu Us sandland.     

Four new species of Trembleya (Melastomataceae: Microlicieae) from Serra do Cabral, Minas Gerais, Brazil

Nine species of the Brazilian endemic genus, Trembleya, were collected during a floristic survey of the tribe Microlicieae on Serra do Cabral, an isolated mountain range in north-central Minas Gerais State, Brazil. Four of these are newly described and illustrated here: Trembleya inversa, T. purpurascens, T. rubra, and T. serrulata, represent new taxa for the genus. These new species appear to be endemic to Serra do Cabral where they occur in campo rupestre and cerrado vegetation. Serra do Cabral has the distinction of harboring more species of Trembleya than any other mountain range in Brazil.     

毛乌素沙地游击型克隆半灌木羊柴对局部沙埋的反应

不同程度的沙埋是生长在干旱和半干旱区内陆沙丘的植物经常遭遇的事件,沙埋可以改变植物所处的生物和非生物环境条件。已有研究表明不同程度的沙埋对于植物的影响不同。轻微程度的沙埋可以增加植物高度、促进生物量的积累和新生分株的产生。如果沙埋强度不断增加,对植物的影响由正效应逐渐转变为负效应。即超过一定沙埋阈值后,沙埋会削弱植物的生长,甚至影响植物的存活。干旱和半干旱区内陆沙丘中常常生长着许多克隆植物,克隆整合常常可以缓解克隆植物分株所遭受的局部环境胁迫。根茎型克隆植物羊柴(Hedysarum laeve)是毛乌素沙地的优势半灌木之一,也是当地重要的固沙植物。为了探讨克隆整合的作用是否可以提高沙埋阈值,并有助于羊柴忍受高强度的沙埋,以其为研究对象开展了野外实验。结果表明:轻微程度的沙埋(例如沙埋深度是原始羊柴分株高的10%~20%)可以加速羊柴分株的高生长,提高叶片生物量、茎生物量以及整个地上部分的生物量。高强度的沙埋(例如沙埋深度是原始羊柴分株高的80%~100%)会削弱羊柴分株的存活和生长。在与不遭受沙埋分株相连的情况下,羊柴分株遭受沙埋的阈值高于没有分株相连的,而且在高强度的沙埋下,前者(有分株相连的遭受沙埋的分株)比后者(没有分株相连的遭受沙埋的分株)在株高增量、茎生物量、叶片生物量以及地上分株生物量上都要显著高。这暗示着克隆整合提高了羊柴遭受沙埋的阈值并有助于羊柴分株忍受高强度的沙埋。     

Low genetic diversity but local genetic differentiation in endemic Minasia (Asteraceae) species from Brazil

Espinhaço Range is a Brazilian chain of mountains, extremely rich in endemic species. Minasia has six species, all perennial herbs endemic to this range. Twenty-two populations were sampled from all Minasia species and assayed for allozyme variation. The species showed low genetic variation, compatible with the expectation for endemics. Genetic identities in Serra do Cipó and Diamantina were high, even between populations of different species. On the other hand M. cabralensis, from Serra do Cabral, was more differentiated from the other species. We also observed a marked genetic differentiation within M. cabralensis. Most strikingly, two close populations of this species showed very different allele frequencies. Our findings highlight the importance of local differentiation in campos rupestres. The observed genetic structure indicates that substantial portions of genetic diversity could be lost with the extinction of only one population, which is especially threatening considering the already low genetic diversity.     

WATER SHARING AMONG RAMETS IN A DESERT POPULATION OF DISTICHLIS SPICATA (POACEAE)

Clonal growth enables plants to transport resources among separately rooted but connected ramets, a potential advantage in patchy or unpredictable habitats. Nevertheless, clonal plants are relatively scarce in deserts. To test whether clonal integration of water relations can increase plant performance under natural conditions in a desert species, water movement was traced and connection among ramets was manipulated in the rhizomatous grass Distichlis spicata in Death Valley, California. To examine potential costs of clonal growth form, connections were mapped and analyzed for dry mass and nitrogen content. Movement of dye showed potential transport of water among five ramets up to 1.4 m apart. Severance of connecting rhizomes increased mortality and decreased water potential of individual ramets within 36 hr, indicating that water sharing among ramets could be of significant benefit. However, plants had a high investment of mass and nitrogen in underground organs, which might be a cost of clonal growth associated with desert environments.     

Spatial analyses of the phylogenetic diversity of Minaria (Apocynaceae): assessing priority areas for conservation in the Espinhaço Range,Brazil

The protection of areas that shelter high evolutionary diversity represented by geographically and phylogenetically isolated lineages is becoming an important conservation strategy. Nevertheless, the spatial distribution of this component of biodiversity is still unknown for most groups, which limits its application for selecting priority areas to conserve. In the present study, we reconstructed the phylogeny of Minaria (Apocynaceae) based on plastid (trnH-psbA, rps16, trnS-trnG and trnD-trnT) and nuclear (ITS and ETS) DNA markers and 34 morphological characters, and analysed the geographic distribution of the phylogenetic diversity (PD) and endemism (PE) in this genus. Minaria includes 21 species that are highly concentrated in the Espinhaço Range, in eastern Brazil, most of which (～75%) are narrowly distributed. The spatial analyses of PD and PE of Minaria indicate four evolutionary relevant areas in this region. The Serra do Cipó and the Diamantina Plateau contain 10 endemic species and present the highest levels of PD. However, the two other areas also deserve special attention. Rio de Contas has high levels of PE, because of two endemic sister species that represent a phylogenetically isolated lineage and the Southern Espinhaço Range houses the most critically endangered species of the genus. Most endemic species of Minaria occur in vegetation islands on rocky outcrops (campos rupestres). These low-fuel areas are less susceptible to fire, suggesting that the Espinhaço Range has served as a historical refuge for fire-sensitive lineages. Our results suggest that conservation units in the Espinhaço Range cover a great proportion of the evolutionary diversity of Minaria and that fire management is probably an important strategy to preserve this endemic biodiversity.     

Two types of division of labour in clonal plants: benefits, costs and constraints

Clonal plants spread vegetatively within their habitats by forming rooted ramets on stolons or rhizomes. Each of these ramets is capable of an independent existence after establishment. Nevertheless, ramets remain physically connected by stolon or rhizome internodes for variable periods of time, thereby allowing for resource movement and signal transduction within clones.Interconnected ramets of clonal plants, though potentially independent and totipotent, can specialize functionally in the performance of limited numbers of tasks such as the uptake of resources from above- vs below-ground sources, carbohydrate storage, vegetative spread and sexual reproduction. Such specialization and cooperation is comparable to a division of labour in economic systems or in colonies of social animals. The ecological significance of division of labour in clonal plants may be found in the increased efficiency of entire clones in exploiting their environments.Two different types of division of labour in clonal plants will be discussed in this review. The first type is an environmentally-induced specialization of ramets in the uptake of locally abundant resources (plastic division of labour), which can be found in several stoloniferous species. Evidence exists that this response increases resource uptake in spatially heterogeneous environments. The second type of division of labour, which occurs mainly in rhizomatous species, relates to a developmentally-programmed specialization and cooperation between interconnected ramets. This response pattern is thought to enhance plant performance by restricting the number of tasks for individual ramets and thereby significantly increasing the efficiency of task performance. In some plants, such an inherent division of labour is likely to contribute to nutrient extraction from poor and unpredictably variable sources.In this article not only benefits but also potential costs and constraints on division of labour in clonal plants are shown. The aim is to provide a review of existing knowledge and to develop concepts and hypotheses for future research.     

Serologic evidence of Leishmania infection in free-ranging wild and domestic canids around a Brazilian National Park

Transmission of disease between wildlife, domestic animals, and humans is of great concern to conservation issues and public health. Here we report on the prevalence of anti-Leishmania sp. antibodies in 21 wild canids (7 Chrysocyon brachyurus, 12 Cerdocyon thous, and 2 Lycalopex vetulus) and 74 free domestic dogs (Canis familiaris) sampled around the Serra do Cipó National Park. In dogs, the apparent prevalence was 8.1% and in wild canids it was 19% (2 crab-eating foxes, C. thous, and 2 maned wolves, C. brachyurus). Management of the domestic dog population with evaluation of incidence changes in humans and wildlife, and enlightenment on the role of wild reservoirs are essential issues for future action and research.     

Fruits of Mimosa foliolosa (Fabales: Fabaceae) as Sleeping Shelter for Megachile (Pseudocentron) botucatuna (Hymenoptera: Megachilidae)

Several plant parts or organs are often used by insects for aggregation and even as resting areas. We first report the use of fruits of the legume Mimosa foliolosa pachycarpa as a night shelter for Megachile (Pseudocentron) botucana Schrottky (Hymenoptera: Megachilidae) in Serra do Cipó, southeastern Brazil. Only a single bee was found per fruit, in 86 fruits out of 1,003 fruits opened. The present findings augmented the occurrence of the phenomenon among bees, which is new to the harsh mountaintop environments in the Brazilian rupestrian fields.     

Reproductive demography of ramets and genets in a rhizomatous clonal plant <Emphasis Type="Italic">Convallaria keiskei</Emphasis>

Clonal growth occurring below the ground makes it difficult to identify individuals and demonstrate the demographic features of a focal plant species. In this study, genotypically identified ramets of a rhizomatous clonal herb, Convallaria keiskei Miq., were monitored for their growth, survival, and reproduction from 2003 to 2006. After the monitoring period, their subterranean organs were excavated to explore the underground connections of established ramets and the direction of clonal growth. We then combined data on the fate of the monitored ramets with the information of rhizome connections, clarifying reproductive demography at both the ramet and genet levels. Although each ramet initiated both sexual reproduction (via flowering) and clonal growth, clonal growth tended to precede sexual reproduction. In a surveyed genet, 51.0% of ramets produced flowers and 29.6% generated clonal offspring during the study period. Consequently, we clarified the reproductive demography of C. keiskei: clonal growth tended to precede flowering in a ramet, and a genet can keep reproducing every season at the genet level, despite a ramet not having inflorescence every year.     

The role of sexual and vegetative reproduction in the population maintenance of a monocarpic perennial herb,Cardiocrinum cordatum var. glehnii

Because monocarpic perennial plants have only one reproductive opportunity in their entire life, they need to ensure offspring production. Some plants reproduce both sexually and vegetatively, and vegetative reproduction could possibly compensate for seed production. Therefore, the role and significance of these reproductive modes is likely to differ between monocarps and polycarps, which can reproduce many times. Cardiocrinum cordatum var. glehnii is a monocarpic perennial that reproduces both sexually and vegetatively (bulblet formation). Here, we investigated the characteristics and contribution to population maintenance of sexual and vegetative reproduction to reveal the significance of these two reproductive modes in this species. First, we found that bulblet formation occurred in plants after the three‐leaved rosette stage. Second, resource allocation experiments revealed that although resources were mainly invested in fruit maturation after the flowering season, resource allocation was switched from sexual reproduction to vegetative reproduction if seed production was insufficient. Third, the outcrossing rate in this species varied greatly according to the environment surrounding the population. However, reproductive assurance by selfing kept seed production stable even if flowers did not receive sufficient pollen for full seed set via outcross pollination, and moreover, there was no intensive inbreeding depression. Finally, genotypic identification of ramets suggested that daughter ramets derived from vegetative reproduction received the space that the mother flowering ramet had occupied until the previous year.     

Responses of Hedysarum Laeve , a guerrilla clonal semi-shrub in the Mu Us sandland, to local sand burial

In arid and semi-arid inland deserts, one of the environmental stresses for plants is recurrent sand burial, which can influence the physical and biotic microenvironments of the plants and soil. Previous studies have shown that different levels of sand burial have different effects on plants. Slight sand burial could increase the height increment, leaf biomass and the number of new ramets of the plants while heavy sand burial could impair the growth of the plants and even decrease their chances of survival. In other words, below a certain threshold level of burial, the growth of plants is stimulated probably because of multiple factors. However, as the level of burial increases, the positive response starts to decline until it becomes a negative value. Arid and semi-arid inland deserts are frequently colonized and stabilized by many rhizomatous clonal plants. Clonal physiological integration often helps clonal plants buffer local environmental stress encountered by ramets. A rhizomatous clonal semishrub, Hedysarum laeve (H. laeve), is the dominant plant species and important for vegetation restoration in the Mu Us sandland. To investigate whether clonal integration can increase the threshold of sand burial and help rhizomatous H. laeve tolerate heavy sand burial, we conducted a field experiment. The results showed that slight sand burial could accelerate ramet growth and enhance leaf biomass, stem biomass and shoot biomass, while heavy sand burial reducesed the biomass of the plant and impairs survival and growth of the ramets. Clonal integration increased the threshold of sand burial. Under heavy sand burial, ramets connected to other ramets not buried in sand were more in terms of height increment, stem biomass, leaf biomass and shoot biomass compared to the ramets encountering sand burial but disconnected from other ramets. It suggested that clonal physiological integration could help H. laeve ramets tolerate relatively heavy sand burial. We also discussed that clonal integration plays a role in H. laeve presence in the Mu Us sandland. __________ Translated from Journal of Plant Ecology (formerly Acta Phytoecologica Sinica), 2006, 30(2): 278–285 [译自: 植物生态学报]