Desert Cacti Research Articles

Morpho-palynological and anatomical studies in desert cacti (Opuntia dillenii and Opuntia monacantha) using light and scanning electron microscopy.

Opuntia is the most diverse and widely distributed drought resistant promising genus of family Cactaceae. The cladodes were utilized to quantify the chemical composition of these plants helpful in lignocellulose conversion and their application towards biofuel production. The present study was aimed to evaluate and compare the taxonomic relationship based on morphology, stem anatomy and palynology of important desert cacti including Opuntia dillenii and Opuntia monacantha. This study also evaluates the potential usefulness of morphological, anatomical and pollen traits using light and scanning electron microscopy. The obtained microcharacters of stem and flowers are considered diagnostic at the generic and specific levels. Some distinguishing morphological features observed were elliptical to obovate cladodes, 1-7 spines per areole and presence of glochidia in O.dillenii. Pollen and stem anatomical characters of the studied taxa are considered highly diagnostic at the generic and species levels. The epidermis has irregular and wavy cells, with straight to sinuate wall pattern and paracytic stomata. Pollen grains appear as pantoporate and prolate spheroidal having reticulate to perforate-reticulate sculpturing while exine semi-tectate to tectate. The taxonomic features studied could be valuable to elaborate and helpful in correctly identification of Opuntia species. The methods of diverse microscopic examination also providing sufficient evidence about the taxonomy of the Opuntia species. RESEARCH HIGHLIGHTS: Description and illustration of desert cacti Opuntia. Morpho-anatomy and palynology were studied with LM and SEM. Highly variation in taxonomic qualitative and quantitative features. Systematic significance based on taxonomic characters was presented.

Bioinspired Azimuthally Varying Nanoscale Cu Columns on Acupuncture Needles for Fog Collection

Inspired by the natural fog collection of the Namib beetles and desert cacti, a bioinspired design (BID) needle with a remarkable wettability gradient is introduced. Previous studies about directio...

The Evolution of Functional Traits in Plants: Is the Giant Still Sleeping?

The Evolution of Functional Traits in Plants: Is the Giant Still Sleeping?

Application of distance sampling for assessing abundance and habitat relationships of a rare Sonoran Desert cactus

Accurate abundance estimates of plant populations are fundamental to numerous ecological questions and for conservation. Estimating population parameters for rare or cryptic plant species, however, can be challenging and thus developing and testing new methods is useful. We assessed the efficacy of distance sampling for estimating abundance and habitat associations of the endangered Pima pineapple cactus (Coryphantha scheeri var. robustispina), a rare plant in the Sonoran Desert of southwestern North America that has traditionally been surveyed with census-based methods. Distance sampling (DS) involves measuring distances between focal objects and samples of lines or points, and modeling detection functions that adjust estimates for variation in detection probability (P). Although often used in animal systems, DS remains largely untested for plants. We encountered 105 live individuals along 36.9 km of transects in 11 study plots placed across much of the geographic range of the species, and estimated an average density of 1.47 individuals/ha (CV = 0.139). Compared to values from intensive censuses, density estimates from DS were underestimated by only 2.3% on average and highly correlated on the untransformed (r = 0.84) and logarithmic (r = 0.93) scales. Estimates of P averaged 0.49 and declined as soils became increasingly dominated by larger soil substrates, and somewhat with increasing vegetation volume and decreasing cactus height. Local densities increased with increasing slope and soil substrate size and decreased with increasing vegetation volume (P ≤ 0.024). Combined with careful survey design, DS offers an efficient method for estimating population parameters for uncommon and cryptic plants.

Quantifying demographic uncertainty: Bayesian methods for integral projection models

Abstract Integral projection models (IPMs) are a powerful and popular approach to modeling population dynamics. Generalized linear models form the statistical backbone of an IPM. These models are typically fit using a frequentist approach. We suggest that hierarchical Bayesian statistical approaches offer important advantages over frequentist methods for building and interpreting IPMs, especially given the hierarchical nature of most demographic studies. Using a stochastic IPM for a desert cactus based on a 10‐year study as a worked example, we highlight the application of a Bayesian approach for translating uncertainty in the vital rates (e.g., growth, survival, fertility) to uncertainty in population‐level quantities derived from them (e.g., population growth rate). The best fit demographic model, which would have been difficult to fit under a frequentist framework, allowed for spatial and temporal variation in vital rates and correlated responses to temporal variation across vital rates. The corresponding posterior probability distribution for the stochastic population growth rate (λS) indicated that, if current vital rates continue, the study population will decline with nearly 100% probability. Interestingly, less supported candidate models that did not include spatial variance and vital rate correlations gave similar estimates of λS. This occurred because the best fitting model did a much better job of fitting vital rates to which the population growth rate was weakly sensitive. The cactus case study highlights several advantages of Bayesian approaches to IPM modeling, including that they: (1) provide a natural fit to demographic data, which are often collected in a hierarchical fashion (e.g., with random variance corresponding to temporal and spatial heterogeneity); (2) seamlessly combine multiple data sets or experiments; (3) readily incorporate covariance between vital rates; and, (4) easily integrate prior information, which may be particularly important for species of conservation concern where data availability may be limited. However, constructing a Bayesian IPM will often require the custom development of a statistical model tailored to the peculiarities of the sampling design and species considered; there may be circumstances under which simpler methods are adequate. Overall, Bayesian approaches provide a statistically sound way to get more information out of hard‐won data, the goal of most demographic research endeavors.

Not all the infected develop the disease — A “Lotus and Cactus” model

The immunogenetic dictum “not all the infected develop the disease” can best be explained by a “Lotus and Cactus” model. Lotuses grow in ponds and cacti in deserts: analogously, we can say that tubercle patient's lung (genetic makeup) functions as an ideal ‘broth’ for Mycobacterium tuberculosis (M.tb) germs to grow, but not the lungs of an endemic control. HLA association studies from Europe to Asia since 1983 till date, have shown a persistent HLA DR2 (15) association. Further, HLA DR2 and non-DR2 endemic controls showed disparate patterns of immune responses and gene expressions. The host and pathogen MHC diversities, Th1–Th2 paradigm and cytokine circuits all may play a crucial role in TB susceptibility. It is possible to decipher the protective immunity by controlling the known confounders — epidemiological, demographic, socio-biological and also host and pathogen diversities. This has become significant with our understanding on the ‘out of Africa’ migration and neolithic co-dispersal of M.tb with modern human. Divergence and expansion of various MHCs (eg HLA-DRB1*15, HLA-B*57) and non-MHC alleles in various continents might be responsible for the skewed transmission and distribution of the infectious diseases around the globe. The ‘Lotus and Cactus’ model proposed here exemplifies this. A holistic genetic epidemiology approach employing modern tools is the need of the hour to better understand infectious disease susceptibility.

Theoretical Exploration of Barrel-Shaped Drops on Cactus Spines

To survive an arid environment, desert cacti are capable of harvesting water from fog by transporting condensed water drops using their spines. Cactus spines have a conical shape. In this work, on the basis of the difference of liquid pressure, a new theoretical model has been developed for a barrel-shaped liquid drop on a conical wire. This model is further simplified to interpret the effects of contact angles, conical angle, surface microgrooves, and gravity on the drop movement along a cactus spine.

How to Duet with a Saguaro

Abstract How to Duet with a Saguaro was a contemplative performance project exploring relationships with the iconic Sonoran Desert cactus, Carnegiea gigantea. Through a series of ‘somatic’ experiments, including one that involved standing with the cactus for an hour, the artist uncovers new meanings of both ‘duet’ and ‘performance’.

Bioinspired one-dimensional materials for directional liquid transport.

One-dimensional materials (1D) capable of transporting liquid droplets directionally, such as spider silks and cactus spines, have recently been gathering scientists' attention due to their potential applications in microfluidics, textile dyeing, filtration, and smog removal. This remarkable property comes from the arrangement of the micro- and nanostructures on these organisms' surfaces, which have inspired chemists to develop methods to prepare surfaces with similar directional liquid transport ability. In this Account, we report our recent progress in understanding how this directional transport works, as well our advances in the design and fabrication of bioinspired 1D materials capable of transporting liquid droplets directionally. To begin, we first discuss some basic theories on droplet directional movement. Then, we discuss the mechanism of directional transport of water droplets on natural spider silks. Upon contact with water droplets, the spider silk undergoes what is known as a wet-rebuilt, which forms periodic spindle-knots and joints. We found that the resulting gradient of Laplace pressure and surface free energy between the spindle-knots and joints account for the cooperative driving forces to transport water droplets directionally. Next, we discuss the directional transport of water droplets on desert cactus. The integration of multilevel structures of the cactus and the resulting integration of multiple functions together allow the cactus spine to transport water droplets continuously from tip to base. Based on our studies of natural spider silks and cactus spines, we have prepared a series of artificial spider silks (A-SSs) and artificial cactus spines (A-CSs) with various methods. By changing the surface roughness and chemical compositions of the artificial spider silks' spindle-knots, or by introducing stimulus-responsive molecules, such as thermal-responsive and photoresponsive molecules, onto the spindle-knots, we can reversibly manipulate the direction of water droplet's movement on the prepared A-SSs. In addition, the A-SSs with nonuniform spindle-knots, such as multilevel sized spindle-knots and gradient spindle-knots, further demonstrate integrated directional transport ability for water droplets. Through mimicking the main principle of cactus spines in transporting water droplets, we were able to fabricate both single and array A-CSs, which are able to transport liquid droplets directionally both in air and under water. Lastly, we demonstrated some applications of this directional liquid transport, from aspects of efficient fog collection to oil/water separation. In addition, we showed some potential applications in smart catalysis, tracer substance enrichment, smog removal, and drug delivery.

“A Desert Cactus”: The Literary Friendship of Katherine Anne Porter and Kay Boyle

Conservées à l’Université du Maryland, les archives Katherine Anne Porter sont riches de soixante-seize lettres échangées par Porter et Boyle entre 1931 et 1976. Un examen de cette correspondance, jusqu’ici inédite, révèle l’admiration mutuelle, l’affection et le respect que se portaient les deux écrivaines.

Multimodal Literacies, Pedagogy, and the Construction of Identity-Based Social Movements: The Case of Espina y Jugo in Mexico

This article looks closely at how the process of artmaking linked to social critique unfolds in one community-based educational setting in Latin America. Drawing on nine months of ethnographic fieldwork with a community-based popular education organization in the northern desert of Mexico, the article examines the pedagogical uses of poetry, music, and other modalities to disrupt dominant discourses about what it means, in this case, to be “Mexican.” At the center of the paper is an analysis of the “espina y jugo” (thorn and juice) metaphor, which refers to the outside and inside of the desert cactus. I argue that the processes of meaning-making and signification underlying the enactment of this metaphor represent a pedagogy that is oriented toward collective identity-building and social action. The enactment of such collective identities, forged in and through acts of multiliterate and multimodal engagement, can be interpreted as a pedagogy of the “new social movements of grassroots orientation” (Escobar, 1992b, p. 421).

Influences of the genetic neighborhood on ramet reproductive success in a clonal desert cactus

AbstractClonal structure in clonal plants can affect sexual reproduction. Individual ramets can decrease reproduction if their neighbors are ramets of the same genet due to inbreeding depression or self‐incompatibility. We assessed ramet reproductive success in the partial self‐incompatible Ferocactus robustus (Cactaceae) as a function of floral display size in focal ramets and floral display size and clonal structure of their reproductive neighborhoods. Ramets were labeled, sized in number of stems, mapped and genetically identified through RAPD markers in one population. A pollen dispersal area of 15‐m radius was established for each ramet to determine the clonal diversity in the neighborhoods. Flower production and fruit set were counted on a monthly basis during one reproductive season as a surrogate of ramet fitness. We expected a decrease in individual ramet reproductive success as a function of the number of reproductive ramets of the same genet in the neighborhood. A total of 272 sampled ramets revealed 116 multilocus genotypes, showing high clonal diversity in the population (G/N = 0.43, D = 0.98). Clonal diversity of neighborhoods ranged from 0.06 to 1 and fruit set varied from 0 to 76.9%. Individual ramet reproductive success was influenced by (1) mate availability, (2) floral display size of a genet within the reproductive neighborhood, and (3) the proportion of distinguishable genotypes. Floral display size of genets and ramets coupled with the genetic diversity within the reproductive neighborhood determines the low sexual reproduction in F. robustus.

Book Review: Desert Wisdom Agaves and Cacti

Book Review: Desert Wisdom Agaves and Cacti

Stochastic development in biologically structured population models

Variation in organismal development is ubiquitous in nature but omitted from most age- and stage-structured population models. I give a general approach for formulating and analyzing its role in density-independent population models using the framework of integral projection models. The approach allows flexible assumptions, including correlated development times among multiple life stages. I give a new Monte Carlo numerical integration approach to calculate long-term growth rate, its sensitivities, stable age-stage distributions and reproductive value. This method requires only simulations of individual life schedules, rather than iteration of full population dynamics, and has practical and theoretical appeal because it ties easily implemented simulations to numerical solution of demographic equations. I show that stochastic development is demographically important using two examples. For a desert cactus, many stochastic development models, with independent or correlated stage durations, can generate the same stable stage distribution (SSD) as the real data, but stable age-within-stage distributions and sensitivities of growth rate to demographic rates differ greatly among stochastic development scenarios. For Mediterranean fruit flies, empirical variation in maturation time has a large impact on population growth. The systematic model formulation and analysis approach given here should make consideration of variable development models widely accessible and readily extendible.

Effect of reproductive modes and environmental heterogeneity in the population dynamics of a geographically widespread clonal desert cactus

AbstractThe dynamics of plant populations in arid environments are largely affected by the unpredictable environmental conditions and are fine‐tuned by biotic factors, such as modes of recruitment. A single species must cope with both spatial and temporal heterogeneity that trigger pulses of sexual and clonal establishment throughout its distributional range. We studied two populations of the clonal, purple prickly pear cactus, Opuntia macrocentra, in order to contrast the factors responsible for the population dynamics of a common, widely distributed species. The study sites were located in protected areas that correspond to extreme latitudinal locations for this species within the Chihuahuan Desert. We studied both populations for four consecutive years and determined the demographic consequences of environmental variability and the mode of reproduction using matrix population models, life table response experiments (LTREs), and loop and perturbation analyses. Although both populations seemed fairly stable (population growth rate, λ∼1), different demographic parameters and different life cycle routes were responsible for this stability in each population. In the southernmost population (MBR) LTRE and loop and elasticity analyses showed that stasis is the demographic process with the highest contributions to λ, followed by sexual reproduction, and clonal propagation contributed the least. The northern population (CR) had both higher elasticities and larger contributions of stasis, followed by clonal propagation and sexual recruitment. Loop analysis also showed that individuals in CR have more paths to complete a life cycle than those in MBR. As a consequence, each population differed in life history traits (e.g., size class structure, size at sexual maturity, and reproductive value). Numerical perturbation analyses showed a small effect of the seed bank on the λ of both populations, while the transition from seeds to seedlings had an important effect mainly in the northern population. Clonal propagation (higher survival and higher contributions to vital rates) seems to be more important for maintaining populations over long time periods than sexual reproduction.

The regeneration of a protected Sonoran Desert cactus since 1800 A.D. over 50,000 km2 of its range

The tall, branched saguaro cactus (Carnegiea gigantea) is perhaps the best-recognized symbol of the desert. However, little is known about the regeneration and future of the species outside of a few well-studied populations. In 2000, data for 537 saguaros were collected in 30 populations throughout the northern Sonoran Desert. A recently developed technique now provides a mechanism by which to reconstruct individual age at multiple populations. This new technique is based on a general growth curve with a site-specific adjustment factor, which I calculate based on local growth data and a recognized relationship with summer rain. Thus, the year of establishment was estimated for all saguaros in each of the populations individually, followed by the merging of all individuals, to create a single regeneration and survivorship curve for the combined regional dataset. Unlike other studies that only look at regeneration at one site, this is the first study to look at the long-term regeneration of the species over an area of more than 50,000 km2, nearly the US portion of its range. The results suggest that over the long term, the population is quite stable, with a favorable period of regeneration in the late 1800s and early 1900s. It is also encouraging that the frequency of individuals that established in the most recent time period is relatively high. However, whether these youngest individuals will persist over the long-term in the face of future extreme freezing events (which can substantially thin populations) is not clear.

Population Graphs: the graph theoretic shape of genetic structure

Patterns of intraspecific genetic variation result from interactions among both historical and contemporary evolutionary processes. Traditionally, population geneticists have used methods such as F-statistics, pairwise isolation by distance models, spatial autocorrelation and coalescent models to analyse this variation and to gain insight about causal evolutionary processes. Here we introduce a novel approach (Population Graphs) that focuses on the analysis of marker-based population genetic data within a graph theoretic framework. This method can be used to estimate traditional population genetic summary statistics, but its primary focus is on characterizing the complex topology resulting from historical and contemporary genetic interactions among populations. We introduce the application of Population Graphs by examining the range-wide population genetic structure of a Sonoran Desert cactus (Lophocereus schottii). With this data set, we evaluate hypotheses regarding historical vicariance, isolation by distance, population-level assignment and the importance of specific populations to species-wide genetic connectivity. We close by discussing the applicability of Population Graphs for addressing a wide range of population genetic and phylogeographical problems.

Pollination biology of the columnar cactus Pachycereus pecten-aboriginum in north-western México

Columnar cacti in tropical deserts depend on nectar-feeding bats for their reproduction while species from extra-tropical deserts show a relatively generalized pollination system with both nocturnal and diurnal pollinators. Pachycereus pecten-aboriginum is a columnar cactus with a broad distribution along the Pacific coast of México, from Oaxaca to Sonora. Along its distribution, the nectar-feeding bat, Leptonycteris curasoae, changes from resident within the tropics to migratory in the Sonoran desert. If bat unpredictability has been an important force in the evolution of pollination systems in columnar cacti, P. pecten-aboriginum is expected to show a relatively generalized system in northern populations. We studied the pollination biology of P. pecten-aboriginum in two northern populations in the state of Sonora. Hand pollination experiments showed that this species has a self-incompatible, hermaphroditic breeding system. Although flowers open at night, they remain open and continue secreting nectar during the morning, allowing visitation by both nocturnal and diurnal pollinators. One population showed evidence of strong pollinator limitation while the results from both populations indicated that diurnal pollinators are more important than nocturnal pollinators. These results are discussed in terms of specialization vs. generalization in the pollination biology of columnar cacti in tropical and extra-tropical deserts.

Integration of Demographic Annual Variability in a Clonal Desert Cactus

Integration of Demographic Annual Variability in a Clonal Desert Cactus

Lack of UV radiation in Biosphere 2 — practical and theoretical effects on plants

UV radiation is an important physical stressor for many exposed organisms. It also has a diversity of positive roles in the biosphere, such as in UVA-dependent vision. In artificial ecosystems where the spectral quality is dramatically altered by the overlying structure these interelationships can be disturbed. Here practical and theoretical measurements are presented for the effects of UV exclusion on desert cacti in Biosphere 2. Cacti inside the biosphere lack flavonoids as a result of the attenuation of UVB and most of the UVA radiation caused by the glass structure. Although the theoretical inhibition to chloroplasts is less than outside, it is much greater than would be expected if the plants inside possessed flavonoids, since the small amount of UVA radiation (385–400 nm) that penetrates has a disproportionately greater theoretical effect. The importance of understanding the effects of UV exclusion in artificial ecosystems and the importance of exercising caution in interpreting the data from artificial enclosed ecosystems in the context of the natural world, is discussed.