Melocactus Species Research Articles

Double mutualism involving Melocactus (Cactaceae) and lizards in the Brazilian Caatinga: Another isolated case or is it an established interaction?

AbstractThis work discusses a fascinating ecological relationship, in which the lizard Tropidurus cocorobensis and the cactus Melocactus violaceus engage in a double mutualism. In this interaction, observed in a Caatinga, a dry tropical forest in Northeastern Brazil, T. cocorobensis feed on the nectar and pollen of M. violaceus, transferring the grains to the stigmas of another flower, acting as a potential pollinator. Additionally, the lizards consume fruits of M. violaceus, helping to disperse the seeds. The concentrated nectar of M. violaceus attracts lizards, and the morphological compatibility between the small pink flowers and the size of T. cocorobensis is important to this double mutualism. The findings mentioned here highlight the importance of Tropidurus lizards in the reproductive success of Melocactus species and provide insights into the coevolution of these species in a seasonal and resource‐scarce environment, like the Caatinga.

Comparative nectar dynamics in four ornithophilous Melocactus (Cactaceae) species in a seasonally dry tropical forest

AbstractNectar is an important floral resource, often representing the only source of water for pollinators in arid environments. We investigated whether successive nectar removal would affect the nectar production dynamics of four Melocactus species growing in the Caatinga domain. Nectar was serially extracted from flowers four times per day at regular 60‐min intervals after anthesis. The cactus species showed a consistent pattern of secretion linked to ornithophily, with no significant responses to successive nectar removal and no reabsorption. Nectar secretion covered the entire period of anthesis, starting at 2:30 p.m. and continuing to 5:30 p.m., with the production of 11–38 μl per flower, with sugar concentrations of 10%–32% (3–16 mg of sugar). Individual flowers produced average amounts of 16.9–3.43 mg of sugar per day, corresponding to energy values of 0.06–0.28 kJ. Sympatric populations produced an average of 150–200 flowers per day. The nectar produced by Melocactus can therefore meet the daily energy needs of hummingbirds, which is of special importance during the dry season, when resources are scarce in the Caatinga.

A New Miniature Melocactus (Cactaceae) from Puerto Rico

A new species of Melocactus is described from Puerto Rico. This miniature species, with a stem no more than 70 mm in diameter, is of uncertain affiliation but is unlikely to be a close relative of M. intortus, the only other Melocactus known from Puerto Rico, due to the lack of a pink-coloured stigma, smaller stem dimensions and distinct seed structure. There are morphological similarities with some other Caribbean species: M. lemairei and M. praerupticola of Hispaniola, and M. guitartii (= M. curvispinus) from Cuba.

Integrative approaches to ex situ conservation of endangered Melocactus from Brazilian ecosystems

Melocactus Link & Otto is one of the most representative and endangered genera of Cactaceae in Sergipe. This study evaluates ex situ conservation under two integrative approaches: the rescue of adult plants to set a germplasm bank and the analysis of different substrates to establish a seedling bank of rescued species. We collected thirty individuals of each species and cultivated them in a greenhouse for twelve months. We evaluated the number of flowers, fruits, and seeds daily, as well as the mortality rate of adult plants. We evaluated five substrates to establish the seedling bank 1 – sand, 2 – sand + commercial soil (1:1), 3 – sand + goat manure (1:1), 4 – soil (100% volume) and 5 – soil + goat manure (1:1). We found mortality rates of 0%, 10% and 50% for M. zehntneri, M. violaceus subsp. margaritaceus and M. sergipensis, respectively. We found two phenological patterns for the species in the germplasm bank: a continuous production of flowers, fruits and seeds throughout the year and another pattern, with periods of greater production of flowers, fruits, and seeds. We also found positive correlations between the environmental factors and the phenological stages of the species. We conclude that substrates ‘sand’ and ‘sand + soil’ are the most suitable to produce seedlings of the three species of Melocactus.

Melocactus and the Suringars of Leiden

Willem Frederik Reinier Suringar and Jan Valckenier Suringar between them named a large number of Melocactus species in the middle of the nineteenth and start of the twentieth century. All of them subsequently have been considered to be synonyms of M. macracanthos, M. stramineus, M. curvispinus subsp. koolwijkianus or M. ×bozsingianus. W. Suringar visited the West Indies, Suriname, Guyana and Trinidad, collecting plants. In Curaçao he took special note of melocacti. Through a study of their descriptions, herbarium material and published images, several new synonyms of their taxa are designated in this paper. One Suringar Melocactus, M. stramineus, recently demoted to a subspecies of macracanthos, is reinstated as a good species. An assessment of the work of the Suringars is made. It is noted that, in spite of reservations about their species concept, the Suringar taxa are valid and have to be considered in any taxonomic study of melocacti from the West Indies.

Taxonomic implications of seed morphology in Melocactus (Cactaceae) from Cuba

Although Melocactus is the second-most diverse cactus genus in Cuba, there is still no consensus regarding species circumscription. Seed morphology has not been used for classifying species in this group in Cuba, despite the taxonomically useful data obtained in some other genera of Cactaceae. In this study, seeds were evaluated for all Melocactus taxa known from Cuba, and seed morphological variability was analysed. Seed descriptions for each studied taxon (or localities) are presented here. We analysed 10 quantitative, and 19 qualitative characters in 50 seeds of 14 accessions. Seeds of the native species of Melocactus of Cuba are small to medium-sized, which place them among the smaller in the Cactoideae, and their shape is circular to broadly oval. Our results show that seven quantitative and six qualitative characters evaluated were suitable to distinguish among taxa. Such characters allowed establishing a general seed pattern for the M. matanzanus and M. curvispinus group, however, seeds in the M. harlowii group were less distinguishable using these characters. Colliculate relief characterized seeds of the M. matanzanus group with the testa border not expanded, while the M. curvispinus group seeds were identified by their ventro-apical keel. The most useful characters for species delimitation in the M. curvispinus group were seed length, and hilum-micropylar region characters. Significant characters that reveal differences within the M. harlowii group are lustre, seed relief and testa border expansion. Citation: Lemus-Barrios H., Barrios D., Garcia-Beltran J. A., Arias S. & Majure L. C. 2021: Taxonomic implications of seed morphology in Melocactus (Cactaceae) from Cuba. – Willdenowia 51: 91–113. Version of record first published online on 5 April 2021 ahead of inclusion in April 2021 issue.

Reintroduction of illegally extracted Melocactus violaceus (Cactaceae) in Brazil

AbstractCactaceae is one of the most threatened plant families, in part as a result of the illegal extraction of plants for ornamental use. However, reports of the seizure and reintroduction of cacti are scarce and do not include species of Melocactus, the genus of Cactaceae in Brazil that has the highest number of threatened species. The coroa-de-frade Melocactus violaceus is endemic to Brazil and categorized as Vulnerable on the IUCN Red List. We report the seizure of 37 individuals of coroa-de-frade extracted illegally from their natural habitat, the results of their reintroduction to Paulo César Vinha State Park, in Espírito Santo state, Brazil, and provide information for environmental monitoring agencies regarding how to proceed in seizure cases, with the goal of minimizing the impacts of this illegal practice on the species. After seizure, 25 individuals were cultivated in a greenhouse and 12 were reintroduced in restinga, the natural area of occurrence of the species. After 6 months, survival was 76% for those individuals cultivated in the greenhouse and 84% for those planted in restinga, showing that rapid reintroduction of species with ornamental appeal, preferentially in their natural habitat, can reduce the impacts of illegal extraction. This reintroduction protocol can be used by managers of conservation units, contributing to the maintenance of threatened cactus species in their natural habitat.

Identification and Determination of Betacyanins in Fruit Extracts of Melocactus Species

Betacyanin pigments were studied in edible fruits of four Melocactus species, M. violaceus Pfeiff., M. bahiensis (Britton & Rose) Luetzelb, M. amoenus (Hoffm.) Pfeiff., and M. curvispinus Pfeiff., by means of chromatographic and mass spectrometric techniques. The main pigment constituent, melocactin, endogenously present in the Melocactus species, was identified as betanidin 5-O-β-sophoroside betacyanin, previously known as “bougainvillein-r-I”. The highest total concentration of betacyanins was found in fruits of M. amoenus (∼0.08 mg/g). Except for melocactin being the most abundant betacyanin (34.8–38.8%) in the analyzed species, a presence of its malonylated derivative, mammillarinin (15.2–19.9%), as well as more hydrophobic feruloyled and sinapoyled melocactins was confirmed by additional co-chromatographic experiments with authentic reference betacyanins. The acyl migration isomers of the malonylated betacyanins as well as a presence of 5′′-O-E-sinapoyl-2′-O-apiosyl-betanin (2.3–3.0%) found frequently in light-stressed cacti was also acknowledged.

Anatomy, Flow Cytometry, and X-Ray Tomography Reveal Tissue Organization and Ploidy Distribution in Long-Term In Vitro Cultures of Melocactus Species

Cacti have a highly specialized stem that enables survival during extended dry periods. Despite the ornamental value of cacti and the fact that stems represent the main source of explants in tissue culture, there are no studies on their morpho-anatomical and cytological characteristics in Melocactus. The present study seeks to address the occurrence of cells with mixed ploidy level in cacti tissues. Specifically, we aim to understand how Melocactus stem tissue is organized, how mixoploidy is distributed when present, and whether detected patterns of ploidy change after long periods of in vitro culture. To analyze tissue organization, Melocactus glaucescens and Melocactus paucispinus plants that had been germinated and cultivated in vitro were analyzed for stem structure using toluidine blue, Xylidine Ponceau, Periodic Acid Schiff, ruthenium red, and acid floroglucin. To investigate patterns of ploidy, apical, medial, and basal zones of the stem, as well as, periphery, cortex, and stele (vascular tissue and pith) regions of the stem and root apexes from four- and ten-year old cultured in vitro were analyzed by flow cytometry. X-ray micro-computed tomography (XRµCT) was performed with fragments of stems from both species. The scarcity of support elements (i.e., sclereids and fibers) indicates that epidermis, hypodermis, and wide-band tracheids present in cortical vascular bundles and stele, as well as water stored in aquifer parenchyma cells along the cortex, provide mechanical support to the stem. Parenchyma cells increase in volume with a four-fold increase in ploidy. M. glaucescens and M. paucispinus exhibit the same pattern of cell ploidy irrespective of topophysical region or age, but there is a marked difference in ploidy between the stem periphery (epidermis and hypodermis), cortex, stele, and roots. Mixoploidy in Melocactus is not related to the age of the culture, but is a developmental trait, whereby endocycles promote cell differentiation to accumulate valuable water.

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.

Maintaining genetic integrity with high promiscuity: Frequent hybridization with low introgression in multiple hybrid zones of Melocactus (Cactaceae)

Hybridization and introgression between species in contact/hybrid zones provide important insight into the genetic and ecological mechanisms of speciation. Cactaceae represents the most important radiation of true succulent angiosperms in the New World. This diversification continues to date, with species experiencing few intrinsic barriers to gene flow and the frequent occurrence of natural hybridization. Here, we used RAD-Seq single-nucleotide polymorphism (SNP) data to investigate the genetic architecture of hybridization in four hybrid zones hosting Melocactus concinnus and four congeneric species (M. ernestii, M. glaucescens, M. paucispinus, and M. zehntneri). Our results revealed that M. concinnus is highly promiscuous in sympatric areas and hybridizes with various species distributed in Morro do Chapéu (Diamantina Plateau, Bahia), eastern Brazil. However, the contemporary genomic introgression among the investigated species is very low (c. 2–5%), confirming that even in the face of hybridization, Melocactus species maintain their genetic integrity. The genomic cline approach showed a large fraction of loci deviating from a model of neutral introgression, where most of the loci are consistent with selection favoring parental genotypes. Our results suggest the occurrence of weak premating but strong postmating reproductive isolation in the analyzed cactus species. Furthermore, as most of the Melocactus species are restricted in distribution, hybridization might negatively affect their integrity if hybrids replace the parental species.

POPULATION BIOLOGY OF THE MELON CACTUS Melocactus violaceus subsp. violaceus (CACTACEAE) ON A BRAZILIAN SANDY COASTAL PLAIN

There is a notable lack of ecological information about South American cacti species and the existing information isn't evenly distributed among life forms and geographic regions. Here, the population structure of a globose cactus species ( Melocactus violaceus ) on a Brazilian restinga was described and the patterns presented were compared with those reported to other Melocactus species. Cacti density observed on the study area was lower than that reported to other species of the genus. No association between population density and habitat selection or average diameter was found, implying that denso-dependent factors are not important on this population. The population was dominated by young individuals and fitted a log-normal size distribution, which suggests that it was under constant germination and the establishment of seedlings was not subject to unstable environmental conditions. Following a cohort of M. violaceus through time would provide critical information on the population status of this threatened species.

Fate of cohorts in Melocactus (Cactaceae) species is affected by rainfall uncertainty and microrelief structures

Associations between plants and substrate in drylands enhance the ability of nutrient pools buildup and seedling establishment. However, this relationship has not been extensively demonstrated in populations of lithophytic plants. We report the effects of microrelief and neighboring plants on the population structure of Melocactus species in the semi-arid region of northeastern Brazil. The size classes of five populations and the seedling fate in two populations were examined through point pattern analysis. Association patterns between size classes were positive between seedlings and adults in all the populations. Cohorts were positively related to rainfall (>60 %). Recruitment events were microhabitat-dependent and showed high mortality levels (>70 %). The spatio-temporal decoupling between seedling fate and adults may favor population dynamic changes under rainfall uncertainty. Based on our analyses, we suggest that the relationship among size classes, microhabitat, and rainfall in lithophytic populations of Melocactus is crucial to buffer negative effects of environmental severity in seedling recruitment and survival.

Dispersão de sementes de Melocactus glaucescens e M. paucispinus (Cactaceae), no Município de Morro do Chapéu, Chapada Diamantina - BA

Objetivou-se identificar os dispersores de duas espécies de Melocactus, verificar o padrão de liberação dos frutos, correlacionando-o com a remoção por frugívoros e variação térmica do cefálio, bem como caracterizar a distribuição espacial. Para tanto, foram realizadas observações focais, testes de germinação, registros da emergência, extrusão e remoção de frutos, da temperatura do cefálio, de interações formigas-diásporos e distribuição espacial. Lagartos (2 espécies) e formigas (3 espécies) foram os dispersores das espécies estudadas. A dormência das sementes não foi quebrada pela passagem pelo trato digestivo dos lagartos. As maiores taxas de remoção dos frutos pelos lagartos ocorreram nas horas centrais do dia, coincidindo ou sendo posterior aos picos de extrusão. As taxas de emergência e extrusão foram mais intensas pela manhã, o que aumentou as chances de remoção dos frutos no dia da liberação, evitando dissecação e predação. Não houve correlação entre a liberação dos frutos e a variação térmica do cefálio. O desenvolvimento do fruto gera tensão nas fibras do cefálio que promove sua emergência ou expulsão. A expulsão de frutos emergidos pode ser auxiliada pela dilatação das fibras em resposta ao aquecimento, tensão da união das fibras na base e saída de outros frutos. A distribuição espacial dos indivíduos parece ser influenciada pelo comportamento dos dispersores.

Preliminary study on genetic relationships of Melocactus Link &amp; Otto of the family Cactaceae revealed through karyotype, DNA content and RAPD analysis

The genetic relationships of 10 species of Melocactus was determined using karyotype, Interphase Nu- clear Volume (INV), 4C DNA content and RAPD markers. Somatic chromosome number varied from 2n=22 to 2n=44. Detailed karyotype analysis showed interspecific variation along with structural alteration of chromosomes. Significant variation in INV and nuclear DNA content were noted among the species. DNA content per chromo- some varied from 0.812pg in M. ernestii (2n=44) to 1.13pg. in M. bahiensis (2n=22). Interspecific RAPD polymor- phism varied from 42.85% in between M. bahiensis and M. ernestii to 75.60% in between M. zehntneri and M. ernestii ssp ernestii. Phylogenetic tree obtained from RAPD markers revealed M. curvispinus as an original species of the group with a wide assemblage of M. peruvianus, M. bahiensis ssp bahiensis f. acispinosus and M. zehntneri. M. bahiensis ssp bahiensis f. acispinosus claimed as separate species and separated out from M. oreas group as well as M. zehntneri from M. violaceus group. Close genetic homology among M. ernestii ssp ernestii, M. ernestii, and M. matanzanus confirmed the right placement of these species in M. oreas group where M. ernestii ssp ernestii could be considered as a species. Distant affinity of M. bahaensis with M. ernestii under a same group confirmed its right position in M. oreas group. M. concinnus with the M. ernestii and M. bahiensis forming a separate distinct branch of the tree confirm its origin from a same ancestor and disagree with its placement in M. violaceus.

Biologia reprodutiva de Melocactus glaucescens Buining &amp; Brederoo e M. paucispinus G. Heimen &amp; R. Paul (Cactaceae), na Chapada Diamantina, Nordeste do Brasil

Foi estudada a biologia reprodutiva de Melocactus glaucescens e M. paucispinus (Cactaceae) no Municipio de Morro do Chapeu, Chapada Diamantina, Bahia, sendo abordados aspectos da fenologia, biologia floral, polinizacao e sistema reprodutivo. Foram registrados os periodos de floracao e frutificacao, visitantes florais, frequencia e tipo de visitas, alem de estrategia e comportamento dos visitantes as flores. Foram realizadas polinizacoes experimentais para verificar o sistema reprodutivo das especies. As duas especies de Melocactus estudadas apresentaram sobreposicao de floracao ao longo do periodo de estudo. Os atributos florais de ambas as especies sao tipicos da sindrome da ornitofilia: cores atrativas, estrutura tubulosa e producao de nectar com baixa concentracao de solutos, entre 20% e 30%. O beija-flor Chlorostilbon aureoventris Boucier & Mulsant (1948) foi o visitante mais frequente, com 82% e 89% do total de visitas para M. paucispinus e M. glaucescens, respectivamente. Outras especies de beija-flores e borboletas tambem visitaram as flores das especies. A sobreposicao no periodo de floracao e a similaridade na composicao da guilda de polinizadores destas e demais especies simpatricas de Melocactus favorece a hibridacao no genero, como foi observado na regiao. Melocactus glaucescens apresentou auto-incompatibilidade e alogamia, enquanto M. paucispinus e auto-compativel e autogâmica, porem com menor frutificacao em autopolinizacao do que em polinizacao cruzada, possivelmente devido a ocorrencia de depressao endogâmica. Polinizacoes interespecificas indicam a ocorrencia de inter-compatibilidade entre M. paucispinus e M. concinnus Buining & Brederoo, sustentando hipoteses correntes de hibridacao entre estas especies.

Variation in Karyotype and 4C DNA Content in Six Species of Melocactus of the Family Cactaceae.

Analysis of karyotype including somatic chromosome number determination, total chromosome length and volume, estimation of 4C DNA content and Interphase Nuclear Volume (INV) were carried out in 6 species of Melocactus of the family Cactaceae. Somatic chromosome number recorded 2n=22 in Melocactus bahiensis, M curvispinus, M robustispinus, M. townsendii and 2n=44 in M longispinus, M. matanzanus for the first time. Significant interspecific variation in nuclear DNA amount was recorded. The 4C DNA content varied from 20.55 pg in M. townsendii to 40.80 pg in M. longispinus. The correlation coefficient studies showed that the genomic chromosome length, chromosome volume and INV were possitively correlated. No interdependent was found between 4C DNA content and chromosome length or volume and INV. The structural alterations in the chromosomes as well as loss or addition of highly repetitive sequences in the genome showed variations in nuclear DNA at interspecific level indicating a macro- and micro-evolution of the species.

Melocactus inclinatus A new species from the Dutch Leeward Islands

A new species of Melocactus, M. inclinatus is described from 3 populations, 2 in Curaçao and 1 in Bonaire. It resembles M. macracanthos but differs in the dark green shiny epidermis, reddish brown spines and flat, snowwhite cephalium with red bristles around the base. It is considered rare and local.