Cactus Species Research Articles

Influence of microhabitat on functional attributes of two columnar cacti with different distribution ranges

Microhabitat variations condition the ability of plant populations to colonize and recruit. Normally cacti species need nurse conditions for establishment of seedlings, resulting in patches under forest cover and increasing the contrasting conditions between slopes with different solar exposure and humidity percentage. We hypothesize that Cephalocereus senilis, a species with restricted range, will have constant functional attributes at each slope and therefore greater sensitivity to environmental variation than Stenocereus dumortieri, a species of wide distribution. This study contrasts microhabitat response of two cacti with different distribution ranges using several functional traits: spatial association pattern, variation in morphological attributes, habitat disturbance conditions and community association. The main contributions of this work are: i) use of a multivariate approach that allows observation of variation patterns between different conditions of exposure and ii) contrast of wide and restricted distribution species in response to dry environmental requirements. The functional attributes of C. senilis are constant (density, morphology, disturbance conditions and associated vegetation), with the exception of the spatial arrangement of individuals, clumped towards an eastern orientation and regularly spaced on the western orientation. In contrast, S. dumortieri has different functional attributes, performing better on unexposed hillsides (aggregation radii smaller, highest density, larger plants, more preserved environment and greater diversity of associated vegetation). Our results are an example of the general response to micro-environmental variation of wide (tolerance) and restricted (avoidance) species in dry environments at both the population and community levels, representing an evolutionary evidence of adaption divergence.

Phytotoxicity of carbon nanotubes and nanodiamond in long-term assays with Cactaceae plant seedlings

We present the results of long-term phytotoxicity assays of single-walled and multi-walled carbon nanotubes (SWNTs and MWNTs, respectively) and nanodiamond (ND) employing cactus species Ferocactus latispinus, Melocactus matanzanus and Parodia ayopayana. They are small and slow growing plants, which is convenient for long-term assays using the substrate volumes as small as a few milliliters, contrary to the commonly reported experiments with crop species. The soil-based experiments described allow for a better match of the real environmental situation. After a few months (up to 40 weeks) observations of seedling growth, we concluded that pristine arc-discharge SWNTs exhibit the strongest phytotoxic effect as compared to pristine MWNTs, purified SWNTs and ND, which can be attributed to a high amount of impurities (including remainders of the catalyst used for their synthesis) in as-prepared SWNTs. We found that after first three months of exposure, nanomaterials might produce seemingly favorable effect on seedling growth, which can invert after a more prolonged exposure. Therefore, careful evaluation of the possible phytotoxic effects must include observations for several months, whereas shorter assays might produce misleading results.

The dispersal and spread of invasive alien Myrtillocactus geometrizans in the southern Karoo, South Africa

The invasion of Cactaceae into semi-arid and arid ecosystems in South Africa is of conservation concern, particularly those species that produce juicy fruit that attract avian frugivores.Bird-dispersed Bilberry Cactus (Myrtillocactus geometrizans) is invading natural areas around the village of Prince Albert and appears to have originated from a cactus collection that was established about 40 years ago, and from there has spread locally over an area of about 1 km2. We surveyed the invaded area, recording a GPS point and size data for each of 156 Bilberry Cactus plants.The height-class distributions of Bilberry Cactus plants recorded in our survey suggest that recruitment is episodic rather than continuous or annual, with clearly defined invasion, or survival events.As this cactus species matures slowly and recruits episodically, the rate of the invasion has been slow. However, the presence of suitable pollination and dispersal mutualists and indigenous shrubs that serve as protective host plants suggest that the populations will continue to grow and spread unless controlled. Moreover the large size of mature Bilberry Cactus plants is likely to have a negative effect on the small endemic succulents that share the same host plants.

Extrafloral nectaries of Cylindropuntia imbricata (Cactaceae) in the southern Chihuahuan Desert: anatomy and interaction with ants

Cylindropuntia imbricata is a common cactus species from North American deserts that has extrafloral nectaries (EFNs). We assessed: (i) the anatomical structure of the EFNs of C. imbricata to determine whether they are vascularized or not, and (ii) whether water availability in the soil and soil temperature are related to the abundance of ants visiting C. imbricata. The study site was in San Luis Potosi, Mexico, in the southern Chihuahuan Desert. EFNs of C. imbricata are vascularized, so they have a constant flow of resources and can produce nectar even when the plant experiences periods of drought, although perhaps less nectar. The availability of water was the most vital factor as a regulator of the interaction between the EFNs of C. imbricata and the ants. Irrigation increased the abundance of visitor ants, with the main species being Liometopum apiculatum, Crematogaster opuntiae and Pseudomyrmex pallidus, with L. apiculatum the most abundant species of them. The present work is the first to investigate the anatomy of the EFNs of C. imbricata and the first to demonstrate their functional relevance in cacti.

Global gap analysis of cactus species and priority sites for their conservation.

Knowing how much biodiversity is captured by protected areas (PAs) is important to meeting country commitments to international conservation agreements, such as the Convention on Biological Diversity, and analyzing gaps in species coverage by PAs contributes greatly to improved locating of new PAs and conservation of species. Regardless of their importance, global gap analyses have been conducted only for a few taxonomic groups (e.g., mangroves, corals, amphibians, birds, mammals). We conducted the first global gap analysis for a complete specious plant group, the highly threatened Cactaceae. Using geographic distribution data of 1438 cactus species, we assessed how well the current PA network represents them. We also systematically identified priority areas for conservation of cactus species that met and failed to meet conservation targets accounting for their conservation status. There were 261 species with no coverage by PAs (gap species). A greater percentage of cacti species (18%) lacked protection than mammals (9.7%) and birds (5.6%), and also a greater percentage of threatened cacti species (32%) were outside protected areas than amphibians (26.5%), birds (19.9%), or mammals (16%). The top 17% of the landscape that best captured covered species represented on average 52.9% of species ranges. The priority areas for gap species and the unprotected portion of the ranges of species that only partially met their conservation target (i.e., partial gap) captured on average 75.2% of their ranges, of which 100 were threatened gap species. These findings and knowledge of the threats affecting species provide information that can be used to improve planning for cacti conservation and highlight the importance of assessing the representation of major groups, such as plants, in PAs to determining the performance of the current PA network.

The influence of cactus spine surface structure on puncture performance and anchoring ability is tuned for ecology.

Spines are common morphological features found in almost all major biological groups offering an opportunity to explore large-scale evolutionary convergence across disparate clades. As an example, opuntioid cacti have spines with barbed ornamentation that is remarkably similar in form and scale to that found on porcupine quills, suggesting specific biomechanical convergence across the animal and plant kingdoms. While the mechanics of porcupine quills as defensive mechanisms has been previously tested, the mechanics of cactus spines (which have evolved to fill a number of functions including defence, climbing and dispersal) has not been characterized. Here we study the puncturing and anchoring ability of six species of cactus, including both barbed and non-barbed spines. We found that barbed spines require less work to puncture a variety of targets than non-barbed spines. Barbed spines also require more work than non-barbed spines to withdraw from biological materials, owing to their barbs engaging with tissue fibres. These results closely match those found previously for barbed versus non-barbed porcupine quills, implying biomechanical convergence. The variation in performance of barbed versus non-barbed spines, as well as between barbed spines from different species, is probably tied to the diversity of ecological functions of cactus spines.

Physical characteristics of fruits and seeds of Opuntia sp. as evidence of changes through domestication in the Southern Mexican Plateau

The Opuntia genus has high diversity and wide distribution in Mexico; it has fruit (1) with thin skin and seeds surrounded by sweet and abundant pulp, (2) with thin skin and seeds surrounded by scarce or null pulp, known as dry fruits, (3) with thick, succulent, acid and edible peel, with seeds surrounded by sparse pulp, known as acid prickly pear or “xoconostle”, and (4) with intermedial characteristics between 1 and 2 types, and named “xocotuna”. The aim of this study was to characterize the fruits and seeds of 114 variants from 17 cactus species (Opuntia, Cactaceae) collected in the Mexican Plateau. The biomass of the skin, pulp and the normal and aborted (dehydrated) seeds from fruits of those variants and species obtained from 347 collects, from the Southern High Plateau of Mexico, were determined; as well as total soluble solids content (°Brix) in the pulp and quantified the length, width, and thickness of the seeds, the total number of normal and aborted and the hardness of the normal ones. The sampling units were 347 collects, with six repetitions per variant and one fruit as an experimental unit. The statistical treatment of the data included Pearson correlation analysis, principal component analysis (PCA) and conglomerates. The fruit biomass and number of aborted seeds were the most important variables according to the PCA and separated the species and variants according to a gradient. In the classification, the tendency to higher content of aborted seeds was observed in Opuntia albicarpa and Opuntia ficus-indica, species from much humanized environments and with the highest degree of domestication. The home gardens or backyard environment concentrated the greater Opuntia variant diversity. The pulp biomass is closely related to the proportion of normal and aborted seeds.

Reproductive phenology of cacti species in the Brazilian Chaco

In this study, we made monthly assessments of the reproductive phenology of ten cacti species that are widely distributed in the Brazilian Chaco over a 2-year period. We tested whether different climatic regimes in this region promoted the evolution of different reproductive strategies among cacti species. We applied circular statistics and the Rayleigh test to determine whether flowering and fruiting were seasonal and to detect significant periodic patterns. Multiple linear regressions were used to determine the influence climatic variables had on the number of flowers and fruits produced by each species. The flowering and fruiting periods began during the rainy season and peaked in November and January, respectively. Annual and continuous patterns were observed, which presented extended durations. The timing of flowering and fruiting was positively associated with day length and temperature. Rainfall was not significant in any of the models. In the Brazilian Chaco, the cacti reproductive phenophases were triggered by changes in day length and temperature. The similarity in flowering and fruiting patterns among the cacti species with extended durations generated a significant amount of overlap in flowering and fruiting, which may be a strategy to maintain pollinator and seed disperser populations in this environment.

Pre-germination treatments in four prickly pear cactus (Opuntia sp.) species from Northeastern Mexico

Pre-germination treatments in four prickly pear cactus (Opuntia sp.) species from Northeastern Mexico

Gas exchange characteristics of giant cacti species varying in stem morphology and life history strategy.

Giant cacti species possess long cylindrical stems that store massive amounts of water and other resources to draw on for photosynthesis, growth, and reproduction during hot and dry conditions. Across all giant cacti taxa, stem photosynthetic surface area to volume ratio (S:V) varies by several fold. This broad morphological diversity leads to the hypothesis that giant cacti function along a predictable resource use continuum from a "safe" strategy reflected in low S:V, low relative growth rates (RGR), and low net assimilation rates (Anet ) to a high-risk strategy that is reflected in high S:V, RGR, and Anet . To test this hypothesis, whole-plant gas exchange, chlorophyll fluorescence, and whole-spine-tissue carbon isotope ratios (δ13 C) were measured in four giant cacti species varying in stem morphology and RGR. Measurements were conducted on five well-watered, potted plants per species. Under conditions of mild diel temperatures and low atmospheric vapor pressure deficit, Anet , transpiration (E), and stomatal conductance (Gs ) were significantly higher, and water-use efficiency (Anet : Gs ) was lower in fast-growing, multi-stemmed species compared to the slower growing, single-stemmed species. However, under warmer, less optimal conditions, gas exchange converged between stem types, and neither δ13 C nor chlorophyll fluorescence varied among species. The results add to a growing body of evidence that succulent-stemmed plants function along a similar economic spectrum as leaf-bearing plants such that functional traits including stem RGR, longevity, morphology, and gas exchange are correlated across species with varying life-history strategies.

Frugivory and seed dispersal in the endemic cactus Eulychnia acida: extending the anachronism hypothesis to the Chilean Mediterranean ecosystem

BackgroundEulychnia acida is an endemic Chilean cactus species whose fruits show several traits that, taken as a whole, are compatible with a seed dispersal syndrome by large herbivore vertebrates. Since only a few large native mammals exist in Chile at present, cactus fruit consumption and seed dispersal may be coopted by introduced mammals as predicted by Janzen and Martin’s (1982) hypothesis for tropical ecosystems.FindingsWe describe the current frugivore species of E. acida in a protected semiarid-Mediterranean ecosystem using field measurements and feeding experiments. In addition, to examine a potential role as seed dispersers of the cactus species, we offered fruits and performed germination tests on seeds defecated by Lama guanicoe and the introduced goat Capra a. hircus under captivity conditions. Our data indicate that while fruits of E. acida are pecked by the Chilean tinamou, Nothoprocta perdicaria, and the Chilean mockingbird, Mimus thenca, and eaten by the brush-tailed rodent, Octodon degus, none of these species could be considered a legitimate seed disperser. Unlike L. guanicoe, the goat C. a. hircus did not reduce seed germination, having a neutral effect.ConclusionsResults from this study indicate that introduced C. a. hircus was the only species showing a potential role in the seed dispersal process of E. acida. In the absence of native frugivore species, goats might play an important role in population recruitment of the endemic cactus. These results extend Janzen and Martin’s (1982) anachronism hypothesis to the Chilean Mediterranean ecosystem.

Comparison of total polyphenol content, antioxidant activity, and antimicrobial potential among nine cactus pear (Opuntia spp.) cultivars and their by-products

Nopal cacti (Opuntia spp.) are important natural resources in semi-arid zones throughout theworld, where their fruits and stems are used as forage or human food depending on the varietyand ripeness of the cladode. Members of the genus Opuntia show variable phytochemicalcomposition as well as a high capacity for adaptation to extreme environmental conditions. Onepart of the process to prepare and use of “nopalitos” for human consumption includes removalof modified leaves or thorns, which is approximately 20% of the fresh weight of cladodes isconsidered as a by-product (production residue). The objective of this study was to evaluatethe phytochemical composition, antioxidant capacity, and antibacterial potential of cladodesand cladode by-products from nine nopal cultivars. Young cladodes (<1 month, nopalitos) andtheir corresponding by-products were washed, dried, and macerated in ethanol. Ethanolextracts were isolated by evaporation and resuspended in water. Total phenols and flavonoidswere quantified, and antioxidant capacity was assessed by spectroscopic assays [troloxequivalent antioxidant capacity (TEAC) and percent inhibition of diphenylpicrylhydrazyl (DPPH)radicals]. Antimicrobial activities of the extracts against Vibrio cholerae and Clostridiumperfringens were determined by the well diffusion method and calculation of minimalbactericidal concentration (MBC) by agar plate assay. All extracts tested showed antioxidantand antibacterial activities. Extracts of cladodes and their corresponding by-products showedsimilar MBCs for C. perfringens (around 15 mg ml-1) and V. cholerae (4.0 mg ml-1). However,extracts of cladode by-products showed higher antioxidant capacity than those of cladodesaccording to both DPPH and TEAC assays. Higher concentrations of phenols and flavonoidswere also found in the extracts of by-products (ranging from 91.23 to 853.78 mg gallic acidequivalents per gram dry weight and from 17.10 to 39.42 mg quercetin equivalents per gramdry weight, respectively). This study demonstrates that nopal cactus species exhibit higherantioxidant activity and contents of both phenols and flavonoids in cladode by-products thanthat in their corresponding cladodes. Our data indicate that discarded cladode by-products maybe are a potentially valuable resource for nutraceutical and drug development.

Evaluation of the potential application of cactus (Opuntia ficus-indica) as a bio-coagulant for pre-treatment of oil sands process-affected water

Environmentally benign natural agents in the treatment of water are increasingly gaining interest due to their cost effectiveness, low toxicity and inherently renewable characteristics. In this context the aqueous mucilage of Opuntia ficus-indica (OFI), a species of cactus, was utilized as a bio-coagulant for pre-treatment of OSPW (Oil sands process-affected water) for the first time. Coagulation/ flocculation tests were performed both on model turbid water and OSPW to explore the performance of extracted bio-coagulant on different types of water with varying turbidity. Effect of different operating parameters such as initial turbidity, pH, different salts, storage time and dosages was studied. The bio-coagulant performed extremely well with 98% turbidity removal from OSPW at initial pH of 7 and 8 using 1500 mg/l within 60 min. The active coagulant compound in mucilage of OFI was found to be a combination of pectic polysaccharide, non-polysaccharide and the natural electrolytes especially divalent cations such as Ca+2 and Mg+2. Formation of exceptionally thread like large flocs reveals the possibility that mechanism of coagulation by OFI is adsorption facilitated by inter-particle bridging. A comparative study between bio-coagulant and alum was also conducted and it was found that bio-coagulant resulted a compact sludge with less volume compared to alum.

An Illustrated Field Guide as a Tool for Conservation of Cacti Species in the Brazilian Chaco

An Illustrated Field Guide as a Tool for Conservation of Cacti Species in the Brazilian Chaco

Chipping and Chemical Scarification Effects onSclerocactus glaucus(K.Schum.) L.D.Benson (Cactaceae) Seed Germination

Sclerocactus glaucus (K.Schum) L.D.Benson (Cactaceae) may have a very low germination rate (2–3%) in the wild. The seeds of this cactus species might need cold stratification and/or scarification to trigger germination. It has been suggested that chipping off a portion of the seed coat or soaking the seed in a bleach solution might increase germination rates for Sclerocactus spp. The purpose of our study was to determine if chipping off the pointed tip of the seed coat of Sclerocactus glaucus seeds and soaking them in a bleach solution would increase germination rates when compared to germination rates of untreated seeds.

Do cacti form soil seed banks? An evaluation using species from the Southern Central Andes.

There is controversy over whether cactus species form soil seed banks. Although it is commonly assumed that cacti do not form seed banks, very few studies have evaluated them. In this work, we analysed whether cactus species form soil seed banks, studying seed distribution, seed density and seed longevity in the Southern Central Andes. Soil samples were collected in two microhabitats (under nurse plants and in bare areas) at 12 selected sites. We determined seed presence-absence, density and distribution for 32 native cactus species. Seed longevity for six of these species was determined through a burial experiment. We recorded viable seeds for 62.5% of the 32 evaluated species, finding variation in seed density between microenvironments and among populations. In some species, the highest seed density was found under potential nurse plants. Seed germination and seed viability decreased with burial time, with seed longevity always being <24months after burial. Our results show strong evidence that cactus species do form seed banks. Seed density can vary between microenvironments and among populations, suggesting that cactus-nurse plant associations can also be explained by differential seed dispersal and not only by differential establishment. We found that Echinopsis and Gymnocalycium species form short-term seed banks. Our results will help to better understand the population dynamics of cactus species, a focal species group for conservation actions because many of them are threatened by human activities.

Will climate change cause spatial mismatch between plants and their pollinators? A test using Andean cactus species

Climate change can disrupt mutualisms by causing temporal or spatial mismatch between interacting species. However, the effects of climate change forecasts on biotic interactions remain poorly studied. In cactus species, pollination constitutes a fundamental process in the production of fruits and seeds. Thus, we aimed to analyse the impact of future climate change on the geographical distributions of 11 cactus species from the southern Central Andes and their spatial match with their pollinators. We used species distribution modelling to forecast the geographic range shifts of these cactus species and their pollinators under two future scenarios (RCP 4.5 and RCP 8.5) for the years 2050 and 2070. We predicted geographic range contractions under future scenarios that reached almost 80% for some cactus species. Our results indicate that the geographical distributions of cacti would be constrained by the presence of the pollinator species on which they depend in the present; however, climate change would not cause spatial mismatch between cacti and their animal pollinators in the future. For most cactus species, we predicted an increase in the spatial match with their mutualists under future scenarios. This is the first study that estimates the geographic range of cacti using both abiotic and biotic factors. Given the importance that positive interactions have on the life cycle of many plant species, our approach could be used to better understand the potential effects of climate change, particularly on species that are of special interest for conservation actions.

SPATIAL DISTRIBUTION AND ASSOCIATION WITH NURSE PLANTS OF THE BISHOP'S MITER CACTUS ASTROPHYTUM MYRIOSTIGMA IN THE CHIHUAHUAN DESERT

Nurse-protege interactions facilitate seedling establishment of many cacti species and might promote spatial aggregation of plants. In June 2014, we analyzed the spatial distribution pattern with Ripley's K-function and the possible association of Astrophytum myriostigma with nurse plants in two populations (Rioverde and Pozas, San Luis Potosi, Mexico). We estimated canopy cover of perennial plant species with a logarithmic scale method and determined the association, size, and orientation of A. myriostigma in relation to nurse plants. Astrophytum myriostigma had an aggregated distribution pattern; approximately 50% were associated with nurse plants at Rioverde and 63% at Pozas, with Hechtia glomerata (Bromeliaceae) being the main nurse plant species in both populations. Cacti associated with nurse plants at Pozas were larger than those not associated, and they did not have any significant orientation in relation to the nurse plant crown. In contrast, the size of associated and nonassociated cacti at Rioverde was similar, but they were established significantly more frequently under the north side of the nurse plant. The association of A. myriostigma with nurse plants is facultative, through either nurse plant protection or open spaces, likely related with abiotic nurses. Understanding nurse plant associations will help target key species for conservation and identify the most likely associations to increase the survival of reintroduced individuals.

Reductive Catalytic Fractionation of C-Lignin

Lignin composed solely of caffeyl alcohol units, or C-lignin, was recently discovered in the seed coats of a number of vanilla orchid and cactus species. The caffeyl alcohol monomer polymerizes into a highly uniform benzodioxane backbone, making C-lignin a promising substrate for lignin valorization, where heterogeneity is a key challenge. In this study, we used reductive catalytic fractionation (RCF) on vanilla seeds to investigate the depolymerization of naturally grown C-lignin. To overcome challenges associated with the high extractive content and poor sugar retention in vanilla seeds, the ratio of monomer yield to total lignin yield was used to isolate the depolymerization efficiency of C-lignin from the extraction efficiency of lignin from seeds. This approach allowed us to compare extents of depolymerization across lignin types and biomass feedstocks. C-Lignin RCF generated extents of depolymerization akin to those of hardwoods, despite observing incomplete benzodioxane cleavage due to catalyst deactivation caused by the seed extractives. In addition, depolymerization of C-lignin produced a favorable monomeric product distribution consisting of only propyl and propenyl catechol. These promising results suggest that genetic modification of other plant species to incorporate C-lignin has the potential to yield a single, valuable catechol product via RCF.

Evolution of coeloconic sensilla in the peripheral olfactory system of Drosophila mojavensis

Populations inhabiting habitats with different environmental conditions, such as climate, resource availability, predation, competition, can undergo selection for traits that are adaptive in one habitat and not the other, leading to divergence between populations. Changes in the olfactory systems of insects that rely on different host plants, for example, can occur in response to differences in sensory stimuli between habitats. In this study, we investigate the evolution of host preference by characterizing the coeloconic sensilla in Drosophila mojavensis, a species that breeds on different necrotic cacti across its geographic range. These cactus species differ in the volatile chemicals they emit, a primary sensory cue for host plant discrimination. Analysis of odor-evoked responses identified four coeloconic sensilla that were qualitatively similar to those of Drosophila melanogaster, but varied in the breadth and strength of their olfactory sensory neuron responses to some acids and amines. Variation in responses to certain odorants among D. mojavensis populations was also observed. Compared to D. melanogaster, there was a lack of sensitivity of antennal coeloconic type 3 (ac3) sensilla to primary ligands of OR35a across all populations. Consistent with this result was a lack of detectable Or35a gene expression. Using a comparative approach, we then examined odor specificity of ac3 sensilla for seven additional Drosophila species, and found that OR35a-like sensitivity may be limited to the melanogaster subgroup. The variation in specificity that was observed among species is not clearly attributable to the degree of ecological specialization, nor to the ecological niche.