Yucca Elata Research Articles

Impact of soil residual auxin herbicide on seedling emergence and biomass differs between soil types, water pulse event, and seedling species

Synthetic‐auxin herbicides are often used to control woody plants and aid in grassland restoration. Seed‐based restoration is common alongside herbicide applications and there may be unintended effects of these herbicides on dryland plants at the seed and seedling stages. Additionally, abiotic conditions at the time of herbicide application may influence herbicide–soil–plant interactions. We conducted a greenhouse study to examine the effects of a common shrub‐control herbicide mix and its interaction with soil type and a post‐herbicide water pulse on common desert plant seeds and seedlings. In this greenhouse study, we found that a subset of species responded negatively to soil residual herbicide activity of a mixture of aminopyralid, clopyralid, and triclopyr at the seed and seedling stages. Species sensitive to soil herbicide residues were primarily shrub and forb species that are often the target species of herbicide applications for woody plant control, such as honey mesquite (Prosopis glandulosa) and creosote bush (Larrea tridentata). However, two shrub species (four‐wing saltbush [Atriplex canescens], soaptree yucca [Yucca elata]) and one perennial grass species (Arizona cottontop [Digitaria californica]), which are used in dryland restoration projects, were found to be particularly sensitive to soil residual herbicide activity. Thus, if using these herbicides to control woody plants and restore herbaceous vegetation via active seeding or relying on the in situ seed bank, considerations should be given to what species are used in the seed mix, what species are already present in the soil seed bank, and other details of the circumstances of herbicide application.

The importance of the soap tree plant (Kelreiteria Paniculata) in environmental protection and landscaping in the climatic conditions of the Namangan region

Soapwood grows in countries with a warm climate, but northern India is the main area of its location. Sapindus is a tree with 5-10 pairs of leaves, somewhat reminiscent of our mountain flower. The tree can grow up to 25 meters in height and has beautiful green-white flowers. After that, beautiful fruits appear, similar to nuts in the shell. Then they are used instead of soap and shampoo, because they contain 40 percent of saponin. It is this substance that actively removes dirt from any fabric and surface.

Rescue and dissemination of ancestral knowledge of the Montuvio people to produce traditional soap

The work deals with the recovery of ancestral knowledge in the Montuvio Manabita people as an extension proposal to the community, for which the main objective was to disseminate ancestral knowledge through the planting of the traditional soap tree to produce natural liquid soap that can be used to wash clothes by hand, in a washing machine and even as a shampoo. The project was located in the El Limón commune of the Picoazá rural parish of the Portoviejo canton, in the Manabí province of the zone4. We worked with an intentional sample of 20 families, the technique of focus groups; The method to be used contemplates two phases, the first of planting the soap on the edges of the farms, preferably on the banks of the irrigation canals or the river, and the second phase of training on the production of soap using soap seeds. The result was that the dissemination of ancestral knowledge in the communities constitutes a practical application that can contribute as a way of reactivating the local post-covid-19 economy, applying ancestral techniques for the elaboration of various products from the Manabí field.

Effects of Different Irradiation Treatments on Total Saponins Content of Sapindus mukorossi.

Sapindus mukorossi Gaertn is also known as Mu Huanzi, You Huanzi, soap tree, etc. The pericarp of Sapindus mukorossi contains many saponins, which is a type of natural non-ionic surfactant. Its extract has vigorous surface activity and biological activities such as bacteriostasis, oxidation resistance, and free radical scavenging. The Sapindus mukorossi extract is an environmentally friendly washing product that microorganisms can be rapidly decompose in nature without any environmental pollution.This study aims to investigate the effects of E-beam and Co60-γ irradiation on the total saponins content in the crude extract of the S mukorossi. The S mukorossi powder is irradiated with E-beam and Co60-γ ray at doses of 0, 4, 6, 8, 10, and 12 kGy for E-beam and 0, 50, 100, 150, and 200 Gy, respectively, for Co60-γ ray. The changes in the content of total saponins in the crude extract, total detergency, and the bacteriostatic abilities before and after the irradiation were analyzed. The results showed that the content of total saponins in samples irradiated by E-beam was significantly higher than that in non-irradiated samples. The saponins yield was the highest at a radiation dose of 6 kGy, and the detergency and bacteriostatic ability were also the strongest. After low-dose Co6-γ irradiation, the total saponins in the S mukorossi crude extract, and detergency and bacteriostatic ability had no apparent change. Conclusion: E-beam irradiation at a dose of 6 kGy can effectively improve the content of total saponins in the crude extract of S mukorossi powder. In addition, its effects on detergency and bacteriostatic abilities are relatively significant. The findings provide sufficient reference data for the further development of S mukorossi commodities.

Lethal Doses of Saponins from Quillaja saponaria for Invasive Slug Arion vulgaris and Non-Target Organism Enchytraeus albidus (Olygochaeta: Enchytraeidae).

Simple SummaryThe Spanish slug, known by its scientific name Arion vulgaris, causes significant damage to agriculture and private gardens around the world. To control this pest, the use of saponin-rich plant extracts is gaining importance as they exhibit strong molluscicidal activity against gastropods and are safe (as saponin residues) in agriculture products. However, despite their proven safety in food, they still do not have a widespread application due to their liquid form and the absence of more accurate knowledge of their effects on other organisms. In this study we evaluated an extract from the bark of the soap tree Quillaja saponaria on slugs and on the white worms Enchytraeus albidus. It was found that slugs were significantly more sensitive to saponin extract at 2 and −1 °C compared to 15 °C. The lethal effect of saponins was stronger on adult slugs than on juveniles. However, lethal effect on worms was much stronger than on slugs. Overall, our results show that Q. saponaria saponins may be a successful slug control tool, especially during colder periods, but its concentration should be selected according to the age of slugs. However, high toxicity to white worms limits its use as an environmentally benign alternative means of slug control.The slug, Arion vulgaris Moquin-Tandon, 1855, is a serious pest in agriculture and private gardens. White worm, Enchytraeus albidus Henle, 1837, is an important model of decomposer organism in the terrestrial ecosystem. Saponins, which are secondary metabolites of plants, have previously been shown to have some molluscicidal effect. We investigated which doses of saponins are lethal to the slug, A. vulgaris, and to the non-target organism, E. albidus. An aqueous solution with different concentrations of saponin extract from the bark of the soap tree, Quillaja saponaria Mol., was used in repeat treatments. Slugs were tested in filter paper contact tests as they are naturally exposed to soil contact while crawling. Worms were tested in soil contact tests as they live below ground. It was found that lethality of saponins depends on the slug age group and the environmental temperature. The median lethal concentration (LC50, at 15 °C) on adults was 68.5 g/L, and on juveniles, 96.9 g/L. The slugs were significantly more sensitive at 2 and −1 °C compared to 15 °C. The LC50 (at 6 ℃) on E. albidus was 2.7 g/L (or 0.5 g/kg dry weight of soil), far below those in A. vulgaris (at 15 ℃ and lower). The LC50 for worms at -1℃ was also significantly lower than at 6 ℃. Therefore, we can conclude: (1) that Q. saponaria saponins may be a successful slug control tool used during colder times of the year, but its concentration should be selected according to the age group of A. vulgaris; (2) this measure is more toxic than expected to white worms, which limits its use.

Comparative assessment of purified saponins as permeabilization agents during respirometry

Saponins are a diverse group of secondary plant metabolites, some of which display hemolytic toxicity due to plasma membrane permeabilization. This feature is employed in biological applications for transferring hydrophilic molecules through cell membranes. Widely used commercial saponins include digitonin and saponins from soap tree bark, both of which constitute complex mixtures of little definition. We assessed the permeabilization power of pure saponins towards cellular membranes in an effort to detect novel properties and to improve existing applications.In a respirometric assay, we characterized half-maximal permeabilization of the plasma membrane for different metabolites, of the mitochondrial outer membrane for cytochrome C and the full solubilization of mitochondrial inner membrane protein complexes.Beyond the complete list as repository for the field, we highlight several findings with direct applicability. First, we identified and validated α-chaconine as alternative permeabilization agent in respirometric assays of cultured cells and isolated synaptosomes, superior to digitonin in its tolerability for mitochondria. Second, we identified glycyrrhizic acid to form exceptionally small pores impermeable for adenosine diphosphate. Third, in a concentration dependent manner, tomatine proved to be able to selectively permeabilize the mitochondrial outer, but not inner membrane, allowing for novel states in which to determine cytochrome C oxidase activity.In summary, we provide a list of the permeabilization properties of 18 pure saponins. The identification of two saponins, namely tomatine and chaconine, with direct usability in improved or novel cell biological applications within this small subgroup demonstrates the tremendous potential for further functional screening of pure saponins.

DEVELOPMENT OF A METHOD FOR HYDROLYTIC CLEAVAGE OF MOLECULES SAPONINS – DERIVATIVES OF QUILLAJA ACID

The possibility of hydrolytic decomposition of glycosides soap tree Qullaja. The conditions for the complete hydrolysis of saponins: a mixture of hydrochloric acid, water, ethanol in a ratio of 4 :7.35 : 6.65, heating time – at least 6 hours. The composition of the carbohydrate part of saponins was established – xylose, glucuronic acid, galactose, arabinose were identified in all hydrolysates. The analysis of the obtained fraction of aglycone – willieboy acid physico-chemical methods. Based on the calculation results of chromatographic characteristics (mobility, number and height of theoretical plates), a system for elution of aglycone of the following composition is recommended: petroleum ether–chloroform–acetone (20 : 20 : 5). By the method of potentiometric titration in a non-aqueous solvent medium, the percentage of aglycone in the selected fractions was determined-88.23%. A comparative study of the aqueous solution of aglycone and saponins by UV spectrophotometry. A decrease in the intensity of absorption bands in the 230, 290 nm region responsible for the absorption of carbonyl structures is shown. Analyzed the IR spectra of saponins and willieboy acid identified bands assigned to the vibrations of functional groups of the aglycone and the carbohydrate residue.

Simulated rainfall sequences affect germination and biomass allocation of Chihuahuan desert native plants

Ecological restoration of many arid zones is a pressing issue because of recurrent loss of plant cover. Here, we conducted a germination and growth study of three framework plant species, native to the Chihuahuan Desert in Northern Mexico, to optimize the establishment for arid zone restoration. The plant species were Zinnia grandiflora Nutt., Menodora scabra A. Gray, and Yucca elata (Engelm.) Engelm, which were selected for their potential for restoration as drought tolerant species. We evaluated seed germination, survival, and biomass allocation of seedlings under four (high, medium, low, and very low) simulated rainfall sequences as irrigation treatments. Rainfall sequences were obtained from a previous study that considered 35 years of precipitation records. Each sequence is accounted for 20% of probability of a wet, normal, low, or very low year in terms of precipitation occurring in the study area. Germination was conducted in controlled greenhouse conditions and seeding was done in pots containing soil mix. Sequences produced soil moisture fluctuations in which germination percent was higher for M. scabra (88%) and Z. grandiflora (31%) on the high sequence compared to the other sequences. Survival at the end of the treatments was above 80% of all the three species, and seedlings allocated more aboveground biomass as the moisture increased and more belowground biomass as moisture decreased. Implications under our study conditions include that germination of Y. elata would not be negatively affected by low soil moisture, and the best germinative results for Z. grandiflora and M. scabra would be achieved under higher soil moisture.

Estrés osmótico y germinación de Yucca elata y Menodora scabra, dos especies de plantas nativas del desierto Chihuahuense

La propagación de plantas es esencial para la restauraciónde ecosistemas degradados. Las zonas áridas presentan especies vegetales altamente resistentes a la sequía como Yucca elata (Engelm.) Engelm. y Menodora scabra A. Gray. Generalmente se acepta que, como parte del cambio climático, la sequía puede intensificarse en duración y frecuencia en estas zonas. Por lo tanto, la germinación de las dos especies se evaluó en diferentes niveles de estrés osmótico para determinar su respuesta a diferentes niveles de humedad. La germinación en las dos especies se redujo a medida que se incrementó el estrés osmótico, pero en Y. elata no se presentó inhibición (13 % germinación), a -1.5 MPa, mientras que en M. scabra si se presentó inhibición (0 % germinación) a este nivel de potencial osmótico. Estas respuestas muestran que la germinación de Y. elata es menos afectada por la sequía que la germinación de M. scabra. Esto representa diferentes potencialidades de manejo en programas de restauración ecológica. Mientras que Y. elata pudiera tener éxito germinando directamente en el suelo en estrés por sequía, M. scabra pudiera establecerse trasplantándola en campo en etapa de plántula o con el uso de nodrizas.

A rabies vaccine adjuvanted with saponins from leaves of the soap tree (Quillaja brasiliensis) induces specific immune responses and protects against lethal challenge

Quillaja brasiliensis (Quillajaceae) is a saponin producing species native from southern Brazil and Uruguay. Its saponins are remarkably similar to those of Q. saponaria, which provides most of the saponins used as immunoadjuvants in vaccines. The immunostimulating capacities of aqueous extract (AE) and purified saponin fraction (QB-90) obtained from leaves of Q. brasiliensis were favorably comparable to those of a commercial saponin-based adjuvant preparation (Quil-A®) in experimental vaccines against bovine herpesvirus type 1 and 5, poliovirus and bovine viral diarrhea virus in mice model. Herein, the immunogenicity and protection efficacy of rabies vaccines adjuvanted with Q. brasiliensis AE and its saponin fractions were compared with vaccines adjuvanted with either commercial Quil-A or Alum. Mice were vaccinated with one or two doses (on days 0 and 14) of one of the different vaccines and serum levels of total IgG, IgG1 and IgG2a were quantified over time. A challenge experiment with a lethal dose of rabies virus was carried out with the formulations. Viral RNA detection in the brain of mice was performed by qPCR, and RNA copy-numbers were quantified using a standard curve of in vitro transcribed RNA. All Q. brasiliensis saponin-adjuvanted vaccines significantly enhanced levels of specific IgG isotypes when compared with the no adjuvant group (P≤0.05). Overall, one or two doses of saponin-based vaccine were efficient to protect against the lethal rabies exposure. Both AE and saponin fractions from Q. brasiliensis leaves proved potent immunological adjuvants in vaccines against a lethal challenge with a major livestock pathogen, hence confirming their value as competitive or complementary sustainable alternatives to saponins of Q. saponaria.

Irradiance-based treatments of Quillaja brasiliensis leaves (A. St.-Hil. & Tul.) Mart. as means to improve immunoadjuvant saponin yield

Quillaja brasiliensis (soap tree) is native of southern Brazil. A purified fraction of saponins from leaves of Q. brasiliensis, QB-90, had significant immunoadjuvant activity in several experimental vaccines. The accumulation of QB-90 in cultured leaf disks and seedlings was previously shown to be responsive to different stresses, including UV-C and higher white light irradiance. An investigation on the regulation of QB-90 accumulation by irradiance treatments in young plants and in harvested leaves of trees of different ages was carried out. Young plants exposed to acute UV-C for 2–4d or to red light enrichment for 30d accumulated significantly more QB-90 in leaves than control plants. Red light treatment of plants did not increase carbohydrate content, indicating that its effects on saponin yield were not due to photosynthesis changes. The influences of irradiance treatments on QB-90 content of leaves from juvenile and adult trees, as well as the impact of temperature on saponin content of adult leaves, were investigated during post-harvest periods. QB-90 yield of adult leaves was not affected by various temperature treatments. A significant increase in the concentration of QB-90 both in juvenile and adult leaves was observed after exposure to UV-C radiation for 15min. Exposing leaves to visible irradiance enriched in red color was effective in increasing QB-90 yield after 48h of treatment in adult leaves and after 12h in juvenile leaves. QB-90 content in detached leaves was relatively stable over a 10d dark period, indicating that results of exposure to UV-C and red irradiance were a direct consequence of metabolic elicitation of bioactive saponins in leaves. Out of the best results of each light treatment on detached juvenile leaves, UV-C proved to be the most efficient to increase QB-90 content. Irradiance-based treatments can be a valuable tool to improve yields of immunoadjuvant saponins in soap tree.

Influence of Range Condition on Pronghorn (Antilocapra americana) and Cattle Diets in Southern New Mexico

Clemente F., Holechek, J. L., Valdez, R., Mendoza, G.D. 2009. Influence of range condition on pronghorn (Antilocapra americana) and cattle diets in southern New Mexico. J. Appl. Anim. Res., 36: 13–16. A study was conducted to evaluate the influence of good (GC) and fair (FC) range condition classes on pronghorn and cattle diets. There was a higher preference for the GC (84%) than for the FC (16%) area (P<0.05). Pronghorn in GC consumed maximum shrubs (51.8%) followed by grasses (29.9%) and forbs (18.3%). In FC the sequence was the same but for the fact that shrubs constituted 83.5%. Whereas, cattle in both conditions consumed mostly grasses (98.5, 93.0%, respectively) and nominal forbs and shrubs. However, in FC the shrubs consumption was also substantial (6.9%). Major grass consumed was Sporobolus flexuosus and forb Croton pottsii by both pronghorn and cattle. On the other hand major shrubs consumed by cattle was Yucca elata. Pronghorn consumed Opuntia opuntia, Atriplex canescens and Prosopis glandulosa in GC and P. glandulosa, Ephedra truficata and O. opuntia in FC. The percentage of overlap between diets was higher in the GC (55.64%) than in the FC class (0.09%).

Fire in Chihuahuan Desert grassland: Short-term effects on vegetation, small mammal populations, and faunal pedoturbation

A prescribed burn resulted in significant decreases in canopy cover of the grasses: Bouteloua eriopoda, Sporobolus flexuosus, and Aristida purpurea. One year post-burn, basal cover of B. eriopoda remained significantly lower in burned patches than in unburned areas but there were no differences in basal cover of the other perennial grasses. Only one species of the 14 summer annual species occurred in both burned and unburned plots. There were six species of spring annuals in burned patches but no spring annuals in the unburned grassland ten months post-burn. Fire killed 100% of the snakeweed shrubs ( Gutierrezia sarothrae), 77% of the Ephedra torreyana shrubs, and 36% of the Yucca elata. All mesquite shrubs that were top-killed by fire, resprouted one month post-burn. Fire had no effect on abundance and species richness of rodents. There were fewer wolf spider, Geolycosa spp. burrows in burned areas than in unburned grassland. The area and volume of soil in termite galleries and sheeting were significantly larger in the unburned grassland than in the burned areas.

AIRSAR Studies of Woody Shrub Density in Semiarid Rangeland: Jornada del Muerto, New Mexico

This study evaluates the use of polarimetric Air borne S ynthetic A perture R adar (AIRSAR) data to assess woody shrub density in a semiarid site where the vegetation consists primarily of varied mixtures of herbaceous vegetation and shrubs. AIRSAR data and field observations of vegetation cover and growth form-composition were obtained for 59 sites in the Jornada del Muerto plain in southern New Mexico. Radar signature measures examined were C-, L- and P-band backscattering coefficients (σ 0) for HH, HV and VV polarizations, ratios of σ 0HH and σ 0HV to σ 0VV, and the HH–VV polarization phase difference and correlation coefficient. The most effective measure for estimation of shrub density was L-band σ 0HV, which distinguished among shrub density classes with no misclassification. Sensitivity of this measure to small amounts of shrub cover was indicated by successful separation of sites with <1% shrub cover from sites with 1–5% cover. Separability of shrub density classes was generally least for C-band signature measures. A distinctive radar signature was exhibited by dense stands of Yucca elata, a semitreelike plant with uniformly thick (≈10 cm diameter) fibrous stems. Yucca sites were distinguished from others by their high P-band σ 0HV relative to L-band σ 0HV. The results are largely explained by the greater sensitivity of longer wavelengths to larger canopy structural elements. L-band σ 0HV and other measures responsive to canopy volume scattering were more strongly related to shrub than to herbaceous plant cover because woody shrub canopies have numerous stems of the intermediate size to which L-band is most sensitive, whereas stems of this size are mostly lacking in herbaceous canopies. The uniform-diameter stems of yucca have larger dimensions to which P-band is more sensitive than L-band.

Windows of Fruit Production in Yuccas: A Response to Pellmyr

James et al. (1994) studied patterns of flower and fruit production in 38 Yucca elata (Agavaceae) inflorescences, finding a clumped pattern of fruit production within the flowering period of each inflorescence. James et al. (1994) found no relationship between the timing of fruit production and the phonological sequence or vegetative characteristics of the plants. The timing of fruit production within the flowering period of an inflorescence was variable, and fruit production was not concurrent among inflorescences flowering at the same time. Also, neither environmental conditions, nor the relative abundance of the sole pollinator (the moth Tegeticula yuccasella, Prodoxidae) on the night that fruits were initiated explained variation in the timing of production. In short, James et al. (1994) were unable to identify any obvious mechanism for the window of fruit production. James et al. (1994) acknowledged that an alternative mechanism accounting for clumped fruit production was that moths only pollinated flowers on an inflorescence during a specific period, but this hypothesis could not be tested because of a lack of data. Pellmyr (1995) has identified the following areas of inadequacy in James et al's (1994) study: (1) failure to identify the causes of flower abortion and specifically not to test for a correlation between pollinator activity and fruit production; (2) failure to positively identify the species and sex of moths in flowers during censuses, making estimates of pollinator density invalid; (3) failure to account for species of invertebrate other than yucca moths or their close relatives, that damage flowers and cause fruit to abort; and (4) failure to ensure that the insertion of an ovipositor by a female yucca moth resulted in oviposition. In this paper we respond to these four areas of criticism, devoting most of the discussion to the first criticism, which was the primary theme of the paper by James et al. (1994). In summary, our responses are these: (1) Pellmyr incorrectly interprets the description of patterns of fruit production by James et al. (1994) as an attempt to attribute mysterious cause, failing to acknowledge that variation in pollinator activity was in fact considered as a possible mechanism. We assert that Pellmyr over-emphasises the effect of variation in pollinator activity as a cause of clumped and asynchronous fruit production by individual inflorescences and we provide two analyses not included in James et al. (1994) to lend weight to this assertion. (2) Pellmyr appears to have incorrectly interpreted the moth census as an attempt to est mate density, when it was intended to assess relative abundance (an index of abundance). However, Pellmyr correctly indicates that temporal change in the sex ratio of the moth population, if it occurred, may have been a weakness in the data. (3) The role of invertebrates other than T. yuccasella is irrelevant to the results because inflorescences were bagged during the study. And, (4) whether the insertion of the ovipositor does or does not result in oviposition is minor and does not bear greatly on the results the study.

Biological activity of saponins from two Dracaena species.

Many species of the west African "soap tree" Dracaena are used in traditional medicine for the treatment of a variety of diseases. In continuation of our search for anti-infective agents from plants implicated in traditional medicine, we evaluated the biological activities of saponins from extracts of Dracaena mannii and Dracaena arborea by using a battery of test systems such as radiorespirometry, Cytosensor bioautography, and agar dilution methods and molluscicidal tests. Bioassay-directed fractionation of the methanol extracts of seed pulp using a combination of chromatographic techniques, gel filtration, droplet countercurrent chromatography (DCCC), and low-pressure liquid chromatography (Lobar), led to the isolation and characterization of spiroconazole A, a pennogenin triglycoside [3 beta-O-[(alpha-L-rhamnopyranosyl(1-->2), alpha-L-rhamnopyranosyl(1-->3)-beta-D-glucopyranosyl]-17 alpha-hydroxyl-spirost-5-ene] (Fig. 1). As the active constituent, spiroconazole A exhibited pronounced antileishmanial, antimalarial, and molluscicidal activities. This paper also reports on the fungistatic, fungicidal and bacteriostatic activity of spiroconazole A against 17 species of fungi and 4 of bacteria.

Genetic Aspects of Diet Selection in the Chihuahuan Desert

Fecal microhistology and chemistry were used to evaluate botanical composition and quality of diets selected by Brangus cattle grazing Chihuahuan desert range in 3 seasons; fall: October, 1991; winter: January, 1992; and summer: July, 1992. Fecal samples were collected from 100 head in fall (58 2-8 year cows and 42 calves), 53 head (2-8 year-old cows) in winter, and 44 head (2-8 year-old cows) in summer. Paternal half sib analyses were used to estimate genetic and phenotypic variances and heritability estimates. Heritability is the proportion of total (phenotypic) variation which is due to additive genetic effects. The effect of sire within age was observed for percentage of Aristida spp. (P= 0.01), Sporobolus spp. (P= 0.09), total grasses (P = 0.02), Croton pottsii (Klotzsch) Muell.-Arg. (P= 0.03), and total forbs (P =0.02) in fall diets. The number of grass species in diets was also affected by sire (P=0.03). Heritability estimates were 0.87, 0.51, 0.78, 0.76, and 0.79 for percentages of Aristida spp., Sporobolus spp., total grasses, Croton pottsii, and total forbs, respectively. Heritability estimates for number of grass and forb species in fall diets were 0.68 and 0.26, respectively. Heritability estimates for winter samples were 0.40, 0.00, 0.37, and 0.27 for percentages of Sporobolus spp., total grasses, Yucca elata Engelm., and total shrubs, respectively. Heritability estimates for the number of grass and total species observed in winter diets were 1.11 and 0.47, respectively. Heritability estimates for percentages of Bouteloua spp., total grasses, Croton pottsii, Dalea spp., and total forbs in summer samples were 0.20, 0.55, 0.58, and 0.46, respectively. Heritability estimates for the number of grass and total species in summer diets were 0.49 and 0.79, respectively. These data suggest that genetic composition of beef cattle may affect diet selection under Chihuahuan desert conditions.

Fruit Abortion in Yucca elata and Its Implications for the Mutualistic Association with Yucca Moths

The yucca moth Tegelicula yuccasella is the sole pollinator of Yucca elata, on yucca fruits to complete its life cycle. A high percentage of pollinated flowers aborts, killing the T. yuccasella eggs and larvae in them. We examined patterns of fruit production and abortion in Y. elata, and related these patterns to vegetative characteristics, moth abundance, and environmental conditions. We studied 38 inflorescences throughout their flowering period, during one season in southern New Mexico, USA. Each night we recorded the number of flowers opening, the number of fruit formed, the relative abundance of yucca moths, and climatic conditions. We monitored 11786 flowers, resulting in 699 mature fruit. Large inflorescences produced more, but proportionately fewer fruit than small inflorescences

Pollination ecology of Yucca elata : An experimental study of a mutualistic association.

The pollination biology of a population of 250 Yucca elata (Liliaceae) plants was studied in southern New Mexico. Yucca elata and the prodoxid yucca moth Tegeticula yuccasella have a mutualistic association that is essential for the successful sexual reproduction of both species. However, a wide range of other invertebrate species visit flowers during the day and at night. Our aim was to quantify the role of yucca moths and other invertebrate visitors in pollination and fruit set, using manipulative field experiments. Inflorescences were bagged during the day or night (N=12 inflorescences) to restrict flower visitors to either nocturnal or diurnal groups. Yucca moths were active exclusively nocturnally during the flowering period and thus did not visit inflorescences that were unbagged during the day. None of the 4022 flowers exposed only to diurnal visitors set fruit, whereas 4.6% of the 4974 flowers exposed only to nocturnal visitors (including yucca moths) produced mature fruit. The proportion of flowers producing fruit in the latter treatment was not significantly different from unbagged control inflorescences. In a series of experimental manipulations we also determined that: (1) flowers opened at dusk and were open for two days on average, but were only receptive to pollen on the first night of opening; (2) pollen must be pushed down the stigmatic tube to affect pollination; and (3) most plants require out-cross pollination to produce fruit. The combination of these results strongly suggests that yucca moths are the only species affecting pollination in Y. elata, and that if another species was to affect pollination, it would be a rare event.

Herbivory of clonal populations: cattle browsing affects reproduction and population structure of Yucca elata.

The hypothesis that cattle browsing on inflorescences of the soaptree Yucca elata reduces reproductive success was investigated by comparing recruitment and population structure in six populations protected from grazing, six grazed during the flowering season and five grazed outside the flowering season. Cattle consumed 98% of inflorescences, which were found to be highly nutritious. Reduced recruitment in flower-grazed populations could not be attributed to reduced flower survival, as recruitment in non-flower grazed populations was also reduced. Changes in population structure were due to cattle browsing small caudices, including both genets and ramets. An alternate hypothesis of limited germination in soils compacted by cattle was not supported. Cattle browsing of inflorescences reduced reproductive effort, which may be due to the inability of the plants to resorb nutrients after flowering. Browsing also increased branching, probably through lack of apical dominance, whereas physical trampling increased procumbency. Cattle browsing implies a lack of genetic recruitment, possible local extinction of the yucca moth Tegeticula yuccasella, the exclusive pollinator of Y. elata, and local reduction in insect and bird biodiversity.