Cactus Species Research Articles

Winners and losers in the predicted impact of climate change on cacti species in Baja California

The Cactaceae is considered one of the most threatened taxa in the world. However, the extent to which climate change could compromise the conservation status of this group has rarely been investigated. The present study advances this issue under three specific aims: (1) to assess the impact of climate change on the distribution of endemic cacti species in the Baja California Peninsula (n = 40), (2) to study how the impact of climate change is distributed in this group according to the species’ conservation status, and (3) to analyze how these impacts are organized from a biogeographical and functional perspective. We addressed these objectives under three socioeconomic emission pathways (RCP 2.6, 4.5, and 8.5), and using two extreme migration scenarios: full climate change tracking and no migration. Altogether, all socioeconomic emission pathways under the two extreme migration scenarios show consistency regarding the identity of the species most vulnerable to climate change, and depict a discrepant future scenario that has, on one hand, species with large potential habitat gains/stability (winners); and on the other, species with large habitat reductions (losers). Our work indicates that winner species have a tropical affinity, globose growth, and includes most of the currently threatened species, whereas loser ones are in arid and Mediterranean systems and are mostly non-threatened. Thus, current and future threat factors do not overlap in the biogeographic and taxonomic space. That reveals a worrisome horizon at supraspecific levels in the study area, since the total number of threatened species in the future might largely increase.

Vivipary in cuban cacti and an assessment of establishment success in Leptocereus scopulophilus

Vivipary is the germination of a seed inside of a fruit before it is separated from the mother plant. In the present study, the populations of several Cuban cactus species are explored in search of vivipary and Leptocereus scopulophilus is used as a model species to evaluate the effectiveness of vivipary in the establishment of offspring. Vivipary is a relatively common phenomenon in Cuban cacti from different ecosystems with variable temperature, rainfall and salinity, whose frequencies of population vivipary and average of viviparous seedlings per fruit are usually low. In L. scopulophilus, vivipary does not constitute a more efficient reproductive strategy that favors establishment, which is typically the limiting factor for the perpetuation of viviparous species. On the other hand, viviparous seedlings will be favored in environments with high levels of humidity and availability of safe sites, which are sporadic in semiarid environments.

Periderm coverages on five species of long-lived columnar cactus species of central Mexico

Sunlight exposures have resulted in periderm coverages on more than 40 species of tall, long-lived columnar cactus species in the Americas. Periderm coverages start on equatorial surfaces and eventually cover all surfaces. Periderm coverages lead to tissue morbidity and eventual cactus death. After more than 80% of periderm coverage on saguaro (Carnegiea gigantea) cacti, the probability of cactus death was greater than 95% within eight years. Periderm coverage characteristics were not similar for five species of tall, long-lived columnar cactus species endemic to the Tehuacán-Cuicatlán Valley (18° N), Puebla, Mexico. For four species, trough coverages were higher for south-facing surfaces than north-facing surfaces. For these four species periderm ratios were near 2:1, S:N. This 2:1 ratio is coincident with the ratio of direct sunlight exposures on S: N surfaces. For one species, the amounts of periderm were low so no differences in periderm coverages occur of south to north were present. Unlike cacti at other locations, crests of species of this study did not show a directional effect. The results indicate that periderm formation occurred first on south-facing surface and eventually occurred on other surfaces. Results with Random Forest, an algorithm, reinforce results of periderm percentages. Random forest was used to determine surfaces coverages that predict periderm coverages on other surfaces. As expected, neighboring surfaces were the best predictors of periderm coverages. Other surfaces were not good predictors of periderm coverages indicating that other surfaces had periderm coverage before or after the predicted surfaces. Random Forest data were the same for all five species. Although, the patterns of the five species showed some variability, they all support that hypothesis that periderm coverages start on south-facing surfaces and eventually occur on north-facing surfaces and they are caused by sunlight.

Addressing the red flags in cochineal identification: The use of molecular techniques to identify cochineal insects that are used as biological control agents for invasive alien cacti

Invasive Cactaceae cause considerable damage to ecosystem function and agricultural practices around the world. The most successful biological control agents used to combat this group of weeds belong to the genus Dactylopius (Hemiptera: Dactylopiidae), commonly known as ‘cochineal’. Effective control relies on selecting the correct species, or in some cases, the most effective intraspecific lineage, of cochineal for the target cactus species. Many of the Dactylopius species are so morphologically similar, and in the case of intraspecific lineages, identical, that numerous misidentifications have been made in the past. These errors have resulted in failed attempts at the biological control of some cactus species. This study aimed to generate a multi-locus genetic database to enable the accurate identification of dactylopiids. Genetic characterization was achieved through the nucleotide sequencing of three gene regions (12S rRNA, 18S rRNA, and COI) and two inter-simple sequence repeats (ISSR). Nucleotide sequences were very effective for species-level and D. tomentosus lineage-level identification, but could not distinguish between the two lineages within D. opuntiae commonly used for biological control of various Opuntia spp. Fragment analysis through the use of ISSRs successfully addressed this issue. This is the first time that a method has been developed that can distinguish between these two D. opuntiae lineages. Using the methods developed in this study, biological control practitioners can ensure that the most effective agent species and lineages are used for each cactus target weed, thus maximizing the level of control.

First report of a subgroup 16SrII-D phytoplasma associated with Opuntia cylindrica fasciated disease in Oman.

Cacti are evergreen perennial succulent plants that are used as ornamental and hedge plants. The fruits and leaves are also used as forage in some areas (Dewir, 2016). Cactus species are susceptible to several pathogens, including phytoplasma. In March 2020, three cactus plants (Opuntia cylindrica) out of ten (30% incidence) exhibited phytoplasma symptoms, including stunted growth, fasciation in stems and cladodes, color changes of the tips of cladodes to purple, and having clusters of highly proliferating cladodes. The plants were located in the Botanic Garden at Sultan Qaboos University, Muscat, Oman (N:23º59'14"; E:58º16'34"). PCR assays were carried out on the DNA samples extracted from young cladodes of three each of symptomatic and asymptomatic plants using phytoplasma-universal 16S rRNA primers, P1/P7 in direct PCR followed by R16F2n/R16R2, P4/P7 in the nested PCR. Distilled water (DW) and Alfalfa witches' broom phytoplasma (AlfWB) were used as negative and positive controls in each assay, respectively. In addition, amplification of the partial translocase protein A (secA) gene in the symptomatic cactus samples was done using SecA-II-F1/SecA-II-R1 (targeting 2140 bp) followed by SecA-II-F1/SecAR4 (targeting 1510 bp) (Al-Subhi et al., 2018). All the symptomatic plants and the positive control were positive for both genes (16S and secA), but no amplification was observed from the asymptomatic samples and DW. Sequence analysis and similarity searches against BLASTn revealed that the phytoplasma 16S rRNA (MT327813) shared 100% sequence identity with that of 'Candidatus Phytoplasma aurantifolia' isolate CB04 (MT555412) from India. The secA gene sequence (MT331815) analysis showed 100% identity with Cicer arietinum phyllody (KX358585). The associated phytoplasma was designated as cactus fasciated phytoplasma (CFP). Phylogenetic trees based on CFP 16Sr rRNA,secA genes, and a combined phylogenetic tree showed clustering of the CFP with the 16SrII-D subgroup phytoplasmas. The association of the aster yellows and peanut witches'-broom phytoplasma groups with other cactus species has already been reported from Lebanon, Mexico, China, Italy and Egypt (Dewir, 2016). The 16SrII phytoplasma in association with O. cylindrica showing fasciated stem has been reported from Egypt (Omar et al., 2014). A series of diverse plant species in association with 16SrII-D phytoplasma has been reported from Oman (Al-Subhi et al., 2018). However, this is the first report of a cactus phytoplasma disease in Oman belonging to the 16SrII-D subgroup phytoplasmas. Some fasciated cactus species are attractive and therefore cultivated as new ornamental plants and transported around the world, which may pose a new threat to other economically important crops.

Bioethanol production from cactus cladode biomass: considerations of harvesting time, dry matter concentrations, and enzymatic hydrolysis

Cactus pear biomass has the potential for bioethanol production in dry regions. However, its low solids concentration and pH variations may hinder the process of alcoholic fermentation. The objectives of this study were as follows: (1) to evaluate the effects of harvest time and season on biomass pH and dry matter concentration of cladodes of two cactus pear species commonly used as forage (Nopalea cochenillifera and Opuntia stricta); (2) to compare the hydrolysis of fresh and dried biomass (10% w v−1 solids); (3) to compare increasing periods of two temperatures (65 °C or 105 °C) to concentrate the biomass to 10% and 30% solids; and (4) to perform enzymatic hydrolysis and fermentation of biomass dried to 30% solids. Biomass pH ranged from 3.0 to 5.6, from early morning to late afternoon, with higher diurnal variation during the dry season, when their solids concentrations were higher than in the rainy season (12–16% × 7–10%). Hydrolyzed fresh and dried biomass had similar glucose, xylose, and galacturonic acid concentrations. Drying at 105 °C for 12 h was the best temperature and period to reach 30% of solids. The enzymatic hydrolysis of the biomass dried to 30% solids yielded 65.3 and 80.0 g of glucose L−1. After fermentations (33 °C; 8 h; Saccharomyces cerevisiae), ethanol was produced to 29.4 and 37.5 g L-1 from N. cochenillifera and O. stricta biomasses, respectively. Therefore, early morning during the dry season is the best moment to harvest the cladodes, whose biomass can be partially dried at 105 °C for 12 h to 30% solids load before being hydrolyzed and fermented for bioethanol production. This procedure reduces the time, energy, and inputs needed in the process.

Relationship between weather conditions and the physicochemical characteristics of cladodes and mucilage from two cactus pear species.

Climate change, limited water resources and expected population increases would require crops which contribute toward more resilient, more productive, more sustainable and climate-smart food systems. The cactus pear is a drought-resistant and sustainable food source to humans and livestock alike. Cactus mucilage has multiple applications in the food and packaging industry. It is eco-friendly, economical, functional and has multiple health benefits. However, the researchers observed umpteen variations in extracted mucilage yield and viscosity every time the cladodes were harvested, making the standardisation of formulations troublesome. We aimed to examine the effect of weather conditions on the physicochemical characteristics of cactus pear cladodes and mucilage extracted over two seasons to understand these observed variations in mucilage characteristics. Forty cladodes, ten from each of Opuntia ficus-indica Algerian, Morado and Gymno-Carpo and Opuntia robusta Robusta were harvested every month from February to August in Bloemfontein, South Africa. Daily weather data were obtained, weight and moisture contents determined on cladodes and yield, viscosity, pH, conductivity and malic acid content determined on extracted mucilage. Pearson correlation coefficients were calculated between the weather conditions, cladode properties, and mucilage properties. Contrary to common belief, neither increasing cladode weight as they grow, nor rainfall were the leading causes of mucilage inconsistencies. However, the correlations showed a relationship between environmental temperatures, cladode pH and conductivity, and mucilage viscosity and yields. In hot summer weather, the pH was lower, which led to an abundance of positive ions in cladodes. The H+ ions neutralise the negative charges along the outstretched mucilage molecule, causing it to coil up, reducing the viscosity of the mucilage. Thus, environmental temperatures rather than rainfall or cladode maturity influenced the physicochemical characteristics of mucilage. The findings should make an essential contribution in predicting the physicochemical characteristics of mucilage for specific food-related functions by observing the weather conditions.

Reduced ecosystem services of desert plants from ground-mounted solar energy development

Deserts are prioritized as recipient environments for solar energy development; however, the impacts of this development on desert plant communities are unknown. Desert plants represent long-standing ecological, economic and cultural resources for humans, especially indigenous peoples, but their role in supplying ecosystem services (ESs) remains understudied. We measured the effect of solar energy development decisions on desert plants at one of the world’s largest concentrating solar power plants (Ivanpah, California; capacity of 392 MW). We documented the negative effects of solar energy development on the desert scrub plant community. Perennial plant cover and structure are lower in bladed treatments than mowed treatments, which are, in turn, lower than the perennial plant cover and structure recorded in undeveloped controls. We determined that cacti species and Mojave yucca (Yucca schidigera) are particularly vulnerable to solar development (that is, blading, mowing), whereas Schismus spp.—invasive annual grasses—are facilitated by blading. The desert scrub community confers 188 instances of ESs, including cultural services to 18 Native American ethnic groups. Cultural, provisioning and regulating ESs of desert plants are lower in bladed and mowed treatments than in undeveloped controls. Our study demonstrates the potential for solar energy development in deserts to reduce biodiversity and socioecological resources, as well as the role that ESs play in informing energy transitions that are sustainable and just. Although deserts have been the focus of large-scale solar power development, this study finds that ecosystem services are degraded during such development, with impacts not only on plants and animals, but indigenous peoples as well.

Local dispersal pathways during the invasion of the cactus moth, Cactoblastis cactorum, within North America and the Caribbean

Cactoblastis cactorum, a species of moth native to Argentina, feeds on several prickly pear cactus species (Opuntia) and has been successfully used as a biological control of invading Opuntia species in Australia, South Africa and native ruderal Opuntia species in some Caribbean islands. Since its introduction to the Caribbean its spread was uncontrolled, invading successfully Florida, Texas and Louisiana. Despite this long history of invasion, we are still far from understanding the factors determining the patterns of invasion of Cactoblastis in North America. Here, we explored three non-mutually exclusive explanations: a) a stepping stone model of colonization, b) long distance colonization due to hurricanes, and/or c) hitchhiking through previously reported commercial routes. Genetic diversity, genetic structure and the patterns of migration among populations were obtained by analyzing 10 nuclear microsatellite loci. Results revealed the presence of genetic structure among populations of C. cactorum in the invaded region and suggest that both marine commercial trade between the Caribbean islands and continental USA, as well as recurrent transport by hurricanes, explain the observed patterns of colonization. Provided that sanitary regulations avoiding human-mediated dispersal are enforced, hurricanes probably represent the most important agent of dispersal and future invasion to continental areas.

Traditional management of Cactaceae by local populations in the semi­arid region of Brazil

Cactaceae species are important resources in the semi-arid region of Brazil and have been used and managed in a specific way by farmers to optimize and ensure the availability of cacti to rural communities. Thus, this study aimed to investigate management techniques used by residents of four rural communities in the municipality of Cabaceiras, Paraiba, Northeast Brazil. For this, semi-structured interviews were conducted with 44 informants. Seventeen of them reported performing some type of management using the following cacti species: Pilosocereus gounellei (F.A.C. Weber) Byles & G.D. Rowley subsp. gounellei, Cereus jamacaru DC. subsp. Jamacaru, Pilosocereus pachycladus F. Ritter subsp. pernambucoensis (F. Ritter) Zappi, Tacinga palmadora (Britton & Rose) N.P. Taylor & Stuppy, and Melocactus zehntneri (Britton & Rose) Luetzelb. Ex situ and in situ management techniques were recorded. The first one performed by transplantation of propagules and the second one by tolerance. The species propagation is carried out using shoots and vegetative parts. Of the species identified, only Cereus jamacaru has more than one form of management. In addition to management, informants use rudimentary techniques such as burning the vegetative parts for fodder purposes.

Antioxidant Activity Analysis of <i>Opuntia</i> Species as Influenced by Season and Plant Parts

The prickly pear cactus (Opuntia), native to Mexico, has grown in popularity and is locally grown and adapted on Jeju Island. The fruits of this cactus species are in particular widely employed as raw materials, which are then processed into various food and medicinal items, including chocolates and vitamins, for purposes of human consumption. Because this crop has been dubbed one of Jeju’s iconic agricultural crops, research studies elucidating the prickly pear cactus’ medicinal properties, including antioxidant activity, of this particular plant and related cultivated species have demonstrated high value to the scientific community. Currently, consumers do not purchase products f or c onsumption a lone, but in a ddition f or t heir added health benef its. The present study in particular honed in on two species of prickly pear cactus that are cultivated on Jeju Island which include: ‘Baeknyeoncho’ (Opuntia ficus-indica) and ‘Cheonnyeoncho’ (Opuntia humifusa). From these species, s pecif ci p lant p arts i ncluding t he f lower, mature and y oung stems, roots, a nd f ruit w ere subjected to further antioxidant analysis, which included the determination of polyphenol, flavonoid, DPPH radical, ABTS radical, and anthocyanin levels. These particular antioxidants were determined during two seasons, over the course of the summer and winter. Results revealed that the antioxidant activity for both species was more active during the summer season. Antioxidant levels occurred at the highest rates within t he flowers o f the c actus plants. However, of significant note was that the cactus stem, in both mature and young plants, possessed higher antioxidant activity compared to those of the fruit that is currently employed for commercial purposes.

The cacti of Franz Meyen from his around the world voyage 1830–1832

Dr. Franz Meyen (1804–1840), a physician and naturalist undertook a voyage around the world in the years 1830–1832 on board the Prussian vessel “Prinzess Louise”. Based on this journey he described numerous plants including four species of cacti. These species along with a fifth described later by Louis Pfeiffer based on Meyen's account are discussed and illustrated based on recent visits to the localities recorded by Meyen. Cereus fascicularis a name of uncertain application, although the type of the genus Weberbauerocereus and hence of significant nomenclatural importance, is dealt with and a theory as to its true identity proposed. A new combination in the genus Cumulopuntia is also proposed based on the long overlooked name Pereskia glomerata.

Composition, Structure, and PGPR Traits of the Rhizospheric Bacterial Communities Associated With Wild and Cultivated Echinocactus platyacanthus and Neobuxbaumia polylopha.

The Queretaro semi-desert in central Mexico is the most southern extension of the Chihuahua desert. This semi-arid zone shelters a vast cactus diversity with many endemic species. Currently, two cacti species from this semi-desert namely, Echinocactus platyacanthus and Neobuxbaumia polylopha are under a threat to their survival. So far, there are no reports on the bacterial communities associated with these plants. In this study, we assessed the structure and diversity of the rhizospheric bacterial communities associated with Echinocactus platyacanthus and Neobuxbaumia polylopha growing in wild and cultivated conditions. Samples of E. platyacanthus were also approached with culture-based methods in search of isolates with plant growth promoting abilities. Metagenomic DNA was extracted from rhizospheric samples and used for Illumina sequencing of the 16S rRNA gene. α-diversity and amplicon sequence variant (ASV) richness were higher in both groups of E. platyacanthus samples. All samples accounted for 14 phyla, and the major 6 were common to all treatments. The dominant phyla in all four sample groups were Actinobacteria and Proteobacteria. Analysis at family and genus levels showed association patterns with the cultivated samples from both species grouping together, while the wild samples of each cactus species were grouping apart. High abundance values of Rubrobacteraceae (15.9–18.4%) were a characteristic feature of wild E. platyacanthus samples. In total, 2,227 ASVs were scored in all 12 rhizospheric samples where E. platyacanthus samples showed higher richness with 1,536 ASVs. Regarding the growing conditions, both groups of cultivated samples were also richer accounting for 743 and 615 ASVs for E. platyacanthus and N. polylopha, respectively. The isolates from E. platyacanthus rhizosphere were mainly assigned to Bacilli and Gammaproteobacteria. In total 35 strains were assayed for PGPR traits (IAA and siderophore production, phosphate solubilization, and fungal growth inhibition). Strains obtained from plants growing in the wild displayed better PGPR characteristics, stressing that naturally occurring wild plants are a source of bacteria with diverse metabolic activities, which can be very important players in the adaptation of cacti to their natural environments.

Do different cultivation environments influence the germination and initial growth of three threatened Brazilian cacti species?

Melocactus sergipensis, Melocactus violaceus, and Melocactus zehntneri are under threat of extinction. Their wild populations are exploited by predatory extraction, because the potential as ornamental plants. Thus, alternatives for sustainable production and conservation are needed. The present study investigated the influence of artificial (growth room) and natural light (greenhouse) on the in vitro germination and growth of these three Melocactus species, and their effects during the acclimatization. Plants were established in vitro and cultivated for 56 days under two lighting conditions (absence/ presence of light) and two light intensity (artificial light: 40 µmol m-2 s-1/ natural light: 160 µmol m-2 s-1). The samples were acclimatized in a greenhouse. The data were analyzed using an Analysis of Variance and compared by Tukey's test (P<0.05). The seeds of all three species depend on light for their germination, with natural light being the most effective environment, resulting in higher germination and growth rates. The seedlings produced in vitro, under natural light, also presented higher survival and growth rates during acclimatization, in particular M. zehntneri. The natural light in the greenhouse is viable for the production of M. sergipensis, M. violaceus, and M. zehntneri seedlings, from in vitro germination to the acclimatization.

Natural colourants analysis and biological activities. Association to molecular markers to explore the biodiversity of Opuntia species.

Synthetic colourants are subject to various allergies. As a result, the use of plant-based additives has proved promising. It is in this perspective that our objective was undertaken to investigate natural colourants from edible cactus. Opuntia species populations were single-sequence repeat (SSR) fingerprinted, the analysis of betalains and phenolic compounds and the evaluation of their biological potentials were also characterised. Photometric quantification of betalains and phenols showed an interspecific variation across Opuntia species. Opuntia ficus indica fruits showed the highest betalain [betaxanthins; 843.67 and betacyanins; 1400 mg/100 g dry weight (DW)] and polyphenol contents. Reversed-phase high-performance liquid chromatography (RP-HPLC) analysis showed that the variation of individual phenols profile was influenced by interspecific and genetic factors. Isorhamnetin-O-(di-deoxyhexosyl-hexoside) was the major compound and its content varied according to Opuntia species, while catechol was the predominant phenolic compound in O. humifusa with 1.88 μg/g DW. Concerning cactus species, Opuntia colourants exhibited a potent antiradical activity [half maximal inhibitory concentration (IC50 ) up to 1 μg/mL]. Opuntia species were effective against Gram-positive and Gram-negative bacterial strains [inhibition zone (IZ) up to 27 mm]. A high genetic diversity within Opuntia genotypes based on SSR markers was revealed. UPGMA (unweighted pair group method with arithmetic mean) dendrogram and PCoA (principal coordinate analysis) based on natural pigments and antimicrobial profiles indicated significant variation. The correlation approach proved the presence of a probably metabolic relationship between genetic markers, pigments and their biological activities. A possible association between molecular approach and metabolic profile analysis of Opuntia allows tracing the relationship among species for its genetic conservation.

Metabolite profiling of three Opuntia ficus-indica fruit cultivars using UPLC-QTOF-MS in relation to their antioxidant potential

Opuntia ficus-indica is the economically important cactus species belonging to the Cactaceae family. Its importance arises from its nutritional value and various biological activities such as antioxidant, anticancer and antimicrobial activities. This study attempts to characterize the metabolic profile of three O. ficus cultivars having different colors, i.e., red ‘Rose’, greenish white ‘Bianca’ and yellow-orange represented by peels and pulp tissues using ultra-performance liquid chromatography coupled to high resolution time of flight mass spectrometry (UPLC-QTOF-MS). A total of 45 metabolites were identified mainly flavonoids: isorhamnetin conjugates and phenolic acids, whereas betaxanthins and coumarins were present at lower levels. Principle component analysis and orthogonal projection discriminant analysis showed that dihydroxy psoralen-O-hexoside and glycosidic conjugates of ferulic acid were the most discriminatory metabolites among the peels and pulps within the different cultivars. On the other hand, the level of flavonoids was comparable among the cultivars. The antioxidant activity of peels and pulps extracts were further measured using 2,2-diphenyl-1-picrylhydrazyl and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) assays. ‘‘Rose’’ cultivar peel rich in dihydroxy psoralen-O-hexoside showed the highest antioxidant activity in both assays. This suggested that coumarins and flavonoids mediated high antioxidant activity of O. ficus-indica fruits although present at low levels.

Cryopreservation of seeds of Melocactus zehntneri Braun ex Ritter f. and Cereus gounellei Luetzelb ex Schum k. by the vitrification method

The Brazilian Caatinga houses a number of cacti species, which are considered endangered due to human influence. Two of them, Melocactus zehntneri Braun ex Ritter f. and Cereus gounellei Luetzelb ex Schum k., are endemic of the Brazilian Caatinga. Cryopreservation can provide a means for long-term preservation of endangered plant material. The aim of this study was to evaluate the efficiency of cryoprotectants for the cryopreservation of seeds from these two ­species. The treatments consisted of immersing seeds in different cryoprotectant solutions and vitrification solutions before storage in liquid nitrogen (NL) at -196 °C, as follows: T1- Control: no cryoprotectants; T2- PVS2 (10 min), T3- PVS2 + phloroglucinol 1% (10 min), T4- PVS2 (10 min) + Supercool 1%; T5- PVS2 + phloroglucinol 1% (10 min) + Supercool 1%. Seed germination was evaluated after cryopreservation. The experimental design was completely randomized with five treatments and five replicates per treatment. Seed moisture at the beginning of the experiment was 6.2% for M. zehntneri and 7.8% for C. gounellei. There were no statistically significant differences for the seed germination percentage among the different treatments. Therefore, we concluded that seed of these two cacti species can be cryopreserved directly without the need for cryoprotectant solutions.

Anatomical Characteristics of Sunlight-induced Bark (Periderm) Coverages on Columnar Cacti of Central Mexico

More than twenty-three species of tall, long-lived columnar cacti from a large variety of locations within the Americas show sunlight-induced periderm development on their stems. Periderm coverages lead to cactus morbidity and mortality. Our objective was to determine if periderm coverage patterns and anatomical characteristics of periderm formation differ among five cactus species located at a single site. Periderm coverages, patterns of periderm coverages and histological changes during the periderm formation process were determined for five native species of tall, long-lived columnar cacti in the Tehuac&amp;aacute;n Valley of Puebla, Mexico during May to June 2019. Periderm coverages and patterns of periderm on cactus surface varied among the species. On surfaces, some species had periderm form at crests initially, while one species had initial periderm form where troughs join. All species had the same internal tissues but the characteristics of these tissues varied among species. In response to periderm formation, one species retained its cuticle while one species retained its hypodermis intact and another produced cork cells inside the hypodermis. Overall, the histological changes that result from periderm formation were specific for each species and no pair of species showed the same responses to periderm formation. In conjunction with data from species from South America, eight distinct scenarios of histological manifestations were documented. Although, each of the five cactus species were in the same location and received the same amount of sunlight exposures, each species showed unique periderm coverages on surfaces, unique anatomical characteristics and unique anatomical responses. Thus, location was not the primary determinant of responses.

Are protected populations of two globular cactus species facing a demographic explosion or just a “bonanza” year?

Despite decades of research, controversy has emerged as to whether positive and negative interactions predictably shift with increasing environmental stress. We used projection matrices, to determine growth rate and elasticity and a LTR experiment to quantify the contribution of each matrix elements to the differences in λ observed between sympatric and syntopic sub-populations of globular cactus species in Brazil (Discocactus placentiformis and D. pseudoinsignis). We addressed the following questions: What is the growth rate of the two species when in sympatry and syntopy? What are the relative contributions of survival, growth, and fecundity to population growth? Which life cycle stages have the highest mortality? Do demographic differences between the two species account for observed differences in sub-population sizes? Both species exhibited higher densities when in syntopy than in sympatry. Seedling establishment and survival were high, and fecundity increased as plant diameter increased. Asymptotic population growth rates were significantly greater than one. The highest elasticity values were for stasis for the later ontogenetic stage and for the growths. It seems that the protection provided by the conservation area is efficient, and that the data were collected during a “bonanza” year, with high rainfall, when all or most reproduction and/or recruitment occur.

Establishing population boundaries and conservation proposals for Coleocephalocereus purpureus, a critically endangered cactus species microendemic from Caatinga biome

Coleocephalocereus purpureus (Buining & Brederoo) F. Ritter is a rare columnar cactus species endemic to four small habitat patches of a south-eastern caatinga inselberg elements located in Eastern Brazil. C. purpureus was listed as Critically Endangered by IUCN by habitat loss due to quarrying activities. Here, we used ten microsatellite markers to estimate genetic diversity and structure of C. purpureus populational groups to perform a remaining genetic diversity diagnosis and to define population boundaries. Our estimates of genetic diversity indicated that C. purpureus displayed moderated levels of genetic diversity, even though the species populational groups are small and fragmented. All genetic structuring approaches revealed that there is a clear differentiation in two populations isolated by the Jequitinhonha River, named here as South and North populations. The South population corresponds to a unique group placed in a disturbed non-protected area and the North population comprises three groups, including the admixtured and managed group placed in a Conservation Unit. As priority actions for the retention of genetic diversity of C. purpureus populations, we propose (i) that the isolated population should be considered as a prior for conservation efforts and managed as an independent unit; (ii) maintaining the integrity of the habitat within the four small patches that constitute the range of the species; (iii) continuous monitoring of genetic diversity of the populational groups; (iii) improve the quality of local pollinator habitats in order to avoid the inbreeding; and (iv) ex-situ conservation actions should be considered, especially the transfer of C. purpureus representatives to botanical gardens as well formation of a seed bank.