Mammillaria Pectinifera Research Articles

Tectono-stratigraphic basin evolution in the Tehuacán-Mixteca highlands, south western México.

The morphological evolution of the basins in the Sierra Madre del Sur (SMS), southern México is poorly understood. This work explains for the first time the geomorphological development of the tectonic, fluvially-interconnected SMS basins named San Juan Raya (SJRb) and Zapotitlán (ZAPb). The evolution of the SJRb and ZAPb are analysed within the context of the transformations of the well-studied Tehuacán basin (TEHb). A new interpretation of a series of tectonic features of the TEHb valley area is also presented. Published geological data and extensive field work provided the basis for our geomorphological and evolutionary interpretation of basin evolution of this part of Mesoamerica during the late Cenozoic. Stratigraphic and sedimentary records suggest that after the late Cretaceous-early Cenozoic orogeny the TEHb and ZAPb were closed basins, and that the TEHb graben system was activated during the Paleogene as a response to the dominant regional NW-SE trending faults. We propose that the ZAPb and SJRb formed sequentially during the Neogene as a result of new E-W, N-S and NE-SW faults. The continuation of the TEHb extension during the Oligocene widened its lowland area and allowed the formation of an extensive lake. No alluvial or fluvial records of this interval are found in the ZAPb and SJRb. No sedimentation rather than formation and subsequent erosion of such sediments is supported by the basin morphology and by the absence of re-worked alluvial deposits at the outlet area where both connect to the TEHb. By middle to late Miocene the TEHb lost its endorheic configuration, ending the lake-type deposition while new faults initiated the opening of the ZAPb. Intensive tectonics, alluvial deposition and the confinement of the Tehuacán lake to the north sector of this basin characterised the Pliocene. During the late Pliocene to the early Pleistocene the formation of the SJRb was initiated. Quaternary faulting related to basin extension along the north watershed of the SJRb and ZAPb is supported by independent data on the biogeography of the cactus Mammillaria pectinifera. We introduce the idea that the departure from the regional NW-SE fault alignment that formed the major Miocene basins to a more local E-W trend that formed Neogene-Quaternary basins was probably a response to the latest post-orogenic relaxation of the crust in the Mixteca terrane.

Landscape genetics reveals inbreeding and genetic bottlenecks in the extremely rare short-globose cacti Mammillaria pectinifera (Cactaceae) as a result of habitat fragmentation

Mammillaria pectinifera is an endemic, short-globose cactus species, included in the IUCN list as a threatened species with only 18 remaining populations in the Tehuacán-Cuicatlán Valley in central Mexico. We evaluated the population genetic diversity and structure, connectivity, recent bottlenecks and population size, using nuclear microsatellites. M. pectinifera showed high genetic diversity but some evidence of heterozygote deficiency (FIS), recent bottlenecks in some populations and reductions in population size. Also, we found low population genetic differentiation and high values of connectivity for M. pectinifera, as the result of historical events of gene flow through pollen and seed dispersal. M. pectinifera occurs in sites with some degree of disturbance leading to the isolation of its populations and decreasing the levels of gene flow among them. Excessive deforestation also changes the original vegetation damaging the natural habitats. This species will become extinct if it is not properly preserved. Furthermore, this species has some ecological features that make them more vulnerable to disturbance such as a very low growth rates and long life cycles. We suggest in situ conservation to prevent the decrease of population sizes and loss of genetic diversity in the natural protected areas such as the Tehuacán-Cuicatlán Biosphere Reserve. In addition, a long-term ex situ conservation program is need to construct seed banks, and optimize seed germination and plant establishment protocols that restore disturbed habitats. Furthermore, creating a supply of living plants for trade is critical to avoid further extraction of plants from nature.

Floral morphometry, anthesis, and pollination success of Mammillaria pectinifera (Cactaceae), a rare and threatened endemic species of Central Mexico

Reproductive biology in the highly diverse Cactaceae family is described in only few species. Given that a large number of species are rare, threatened, or endangered, and the entire family is included in Appendix II of CITES, the limited knowledge about their reproductive biology is of major concern. Mammillaria pectinifera is an endangered, small, globose cactus endemic to the Tehuacán-Cuicatlán region in Central Mexico. We aimed to characterize some basic aspects of its reproductive biology in three populations. We described flower morphology and anthesis, identified floral visitors, and evaluated the occurrence of spontaneous self-fertilization and the success of open pollination. Diurnal anthesis in flowers lasted about 4 h/day and almost all flowers lasted only one day after opening. The analyses of variance revealed differences in flower morphology among populations. Herkogamy was positive and significantly different among populations. Field experiments revealed that open-pollinated flowers were highly successful in setting fruits and seeds. These results corroborate those reported in other Mammillaria species. Autonomous self-pollination was negligible and ineffective. Bees of the genus Ceratina were dominant among the captured flower visitors, and estimations of their maximum foraging distance indicated successful outcrossing in plants. This study indicates almost complete dependency of M. pectinifera on pollinators for fruits and seeds production. Our results serve as a basis for future research on reproductive biology of M. pectinifera and other rare and endangered cacti.

Distribución geográfica y estado de conservación de las poblaciones de Mammillaria pectinifera

Mammillaria pectinifera is an endangered cactus endemic to the Tehuacán Valley. In the mid-1990s, 6 localities with few individuals were known. This information was crucial for protecting the species through national and international legal instruments. To enhance the knowledge on its geographic distribution and conservation status, exploratory expeditions were made: first throughout ecological areas similar to those known with existing populations, and later based on a predictive model of geographic distribution. Results show that the species is composed by at least 31 localities and a much larger number of individuals, and suggest the need of stronger emphasis on exploration with the best available methods and tools in order to assess the distribution, abundance and pressure on a slightly conspicuous species. In spite of the substantial increase in localities, and considering the fact that 55% of them are within the Tehuacán-Cuicatlán Biosphere Reserve, the cactus is under high anthropogenic pressure, suggesting that the species is vulnerable to disappearing in some localities if deterioration rates of its habitat are not reduced in the short term.

Research Article Quaternary origin and genetic divergence of the endemic cactus Mammillaria pectinifera in a changing landscape in the Tehuacán Valley, Mexico

The endemic Mexican cactus, Mammillaria pectinifera, shows low dispersal capabilities and isolated populations within the highly dissected landscape of Tehuacán Valley. These characteristics can restrict gene flow and act upon the genetic divergence and speciation in arid plants. We conducted a phylogeographic study to determine if the origin, current distribution, and genetic structure of M. pectinifera were driven by Quaternary geomorphic processes. Sequences of the plastids psbA-trnH and trnT-trnL obtained from 66 individuals from seven populations were used to estimate genetic diversity. Population differentiation was assessed by an analysis of molecular variance. We applied a stepwise phylogenetic calibration test to determine whether species origin and genetic divergence among haplotypes were temporally concordant with recognizable episodes of geomorphic evolution. The combination of plastid markers yielded six haplotypes, with high levels of haplotype diversity (h = 0.622) and low nucleotide diversity (π = 0.00085). The populations were found to be genetically structured (F(ST) = 0.682; P < 0.00001), indicating that geographic isolation and limited dispersal were the primary causes of genetic population differentiation. The estimated origin and divergence time among haplotypes were 0.017-2.39 and 0.019-1.237 mya, respectively, which correlates with Pleistocene tectonics and erosion events, supporting a hypothesis of geomorphically-driven geographical isolation. Based on a Bayesian skyline plot, these populations showed long term demographic stability, indicating that persistence in confined habitats has been the main response of this species to landscape changes. We conclude that the origin and haplotype divergence of M. pectinifera were a response to local Quaternary geomorphic evolution.

The effects of serotiny and rainfall‐cued dispersal on fitness: bet‐hedging in the threatened cactus Mammillaria pectinifera

AbstractSerotiny—the retention of seeds in the mother plant for over a year—in unpredictable environments may increase the probability that at least some seeds are dispersed during favorable periods. Propagules may be expelled when environmental cues announcing favorable conditions occur, or be gradually released into the environment. This could be a bet‐hedging strategy increasing the long‐term fitness by reducing interannual variability in reproduction. However, the impact of seed retention on the population dynamics of serotinous species and its contribution to fitness has been barely explored under field conditions. We assessed these issues in the threatened Mammillaria pectinifera, a small globose cactus that gets established only in exceptionally rainy years. This species expels some seeds actively during unusually rainy periods, while dispersing others passively over several years. Dynamics of the seeds in the mother plant over two very contrasting years in terms of precipitation was incorporated into a stochastic matrix model. Seed retention was found to increase significantly the probability that some of the seeds retained in any given year are dispersed within a subsequent rainy period. Active seed‐expulsion raises this probability even further. As expected in bet hedgers, seed retention increased fitness in the presence of temporal variability. Active fruit expulsion did not affect fitness, but reduced demographic stochasticity. The incomplete serotiny and fruit expulsion observed is the evolutionary outcome expected for the environment and life‐history attributes of the species.

Evaluación del riesgo de extinción de Mammillaria pectinifera, cactácea endémica de la región de Tehuacán-Cuicatlán

Mammillaria pectinifera (Cactaceae) is an endemic species from the Tehuacan-Cuicatlan region at the Mexican States of Puebla and Oaxaca. Although it is considered as a threatened species under Mexican law NOM-059-ECOL-2001, and it is already included in the CITES Appendix I, ecological studies reveal serious vulnerability to extinction of its populations. In this study, we conducted an extinction risk assessment for M. pectinifera based on the protocol of the Method for Evaluation of Risk of Extinction for Mexican Wild Species (MER) from Appendix I of NOM-059-ECOL-2001, which is based on a qualitative assessment of 4 criteria for evaluating extinction risk of any wild species in the Mexican territory. The present assessment relies on data from field studies on 7 populations as well as information from several sources. The MER assessment resulted in a risk score of 12 points and, accordingly, we propose to consider M. pectinifera as a species under extinction risk (P) in NOM-059-ECOL-2001. Also, it should be included again in the Red List of IUCN. Finally, we suggest ways for improving the assessment of Criterion D of the MER.

The adaptive value of cued seed dispersal in desert plants: Seed retention and release in Mammillaria pectinifera (Cactaceae), a small globose cactus

Serotiny, or delayed seed dispersal, is common in fluctuating environments because it hedges the risks of establishment. Mammillaria pectinifera (Cactaceae) facultatively expels fruits in the year they are produced or retains them to disperse the seed over several years. We tested whether M. pectinifera increased fruit expulsion as a response to increased rainfall. While no fruit expulsion was observed in 1997, a dry year, in the wetter 1998 around 20% of all fruits formed were expelled from the maternal plant. A greenhouse experiment showed that high moisture results in the plants expelling all their fruits. Because in 1998 establishment was five times higher than in 1997, this response seems to be highly adaptive: Active fruit expulsion and consequent seed release increases the probability of establishment during pulses of high precipitation.

Growth response of three globose cacti to radiation and soil moisture: An experimental test of the mechanism behind the nurse effect

Abstract Cactus seedlings often establish under nurse plants which modify environmental conditions by increasing moisture and decreasing solar radiation, which may cause beneficial and detrimental effects, respectively, on seedling growth. Three soil moisture treatments (5%, 25% and 60%) and two solar radiation levels (100% exposure=243 μmol m −2 s −1 , and 40%=102 μmol m −2 s −1 ) were used in a factorial design to analyze seedling growth response of three rare cactus species ( Mammillaria pectinifera , Obregonia denegrii and Coryphantha werdermannii ). The variables evaluated were relative growth rate (RGR), root/shoot ratio ( R / S ), and K (RGR roots /RGR shoot ), obtained from an initial seedling harvest (6-month-old seedlings) and a final harvest 6 months after treatment application. All three species had slow RGRs (0.002–0.012 g g −1 day −1 ). O. denegrii had the lowest RGR values, but was the only species for which R / S and K varied with soil moisture. While all seedlings responded markedly to soil moisture, no response was observed to radiation treatments. The latter might have been related to the relatively low solar radiation levels present in the greenhouse. Yet, our results suggest that the main benefit nurse plants offer to seedlings is the increase in soil moisture.

Assessing the ecological status of Mammillaria pectinifera Weber (Cactaceae), a rare and threatened species endemic of the Tehuacán-Cuicatlán Region in Central Mexico

Mammillaria pectinifera, is a rare cactus of central Mexico currently threatened by extinction due to its restricted geographical range, high habitat specificity, relatively low growth rate, and small population sizes. In this paper, we analyse its demographic performance over a 1-year period using survival, growth and reproduction data. We carried out a demographic analysis through a Lefkovitch size-based matrix model. As this cactus shows long-term fruit retention in the stem, we included the seed stage explicitly in our analyses. The matrix analysis revealed that the estimated population growth rate ( λ) is 0.743 suggesting a declining population with limited persistence ability. Juvenile and adult stages showed higher elasticity values than the other stages; however our matrix simulations resulted in a positive population growth rate only when fecundity entries and seedling establishment success were increased simultaneously. We suggest that any management plan aiming at the preservation of M. pectinifera should consider specific programs to enhance seedling establishment and adult survival.

The measurement of chronic disturbance and its effects on the threatened cactus Mammillaria pectinifera

Measuring how anthropogenic disturbance affects biological systems is crucial for conservation and management. However, it is often difficult to quantify disturbance when it occurs in a slow, long-lasting – or chronic – fashion. Because various human activities influence gradually an area, chronic disturbance must be measured on a continuous scale that accounts for different sources of disturbance. Here we propose a method to develop multimetric indices for chronic disturbance. The approach is exemplified by considering the effects of disturbance on the threatened cactus Mammillaria pectinifera. Fourteen indicators of three agents of disturbance (human activities, livestock raising and land degradation) were measured in 10 populations of M. pectinifera, and summarised through principal components analysis (PCA). An index for each agent was also developed. M. pectinifera achieved maximum density at intermediate values of the first PCA axis, which was related to disturbance intensity. Assessing only both extremes of the disturbance gradient, where density is low, would erroneously suggest that disturbance has no effect on this plant. The different disturbance agents act synergistically on M. pectinifera, and their combined effects are detrimental. Land degradation reduces plant density, while livestock enhances it. However, overgrazing promotes degradation, so maintaining appropriate livestock levels is critical for management. Our method allowed us to identify which agents have more impact on threatened species, and sets the basis to manage disturbance agents in a way compatible with conservation. The method proposed here can be easily modified for its use in other environments and to account for different forms of anthropogenic disturbance.

Habitat restriction in Mammillaria pectinifera, a threatened endemic Mexican cactus

This study deals with the habitat restriction of Mammillaria pectinifera, a threatened cactus species, con- fined to a few low density localities of the Tehuacan valley in tropical Mexico. We analysed the patterns of presence/ab- sence of M. pectinifera in relation to the presence/absence of 48 other plant species, and the variation of environmental factors in 120 sampling plots. A Principal Components Analy- sis revealed a clear segregation between plots with and with- out individuals of M. pectinifera. A classification analysis resulted in four groups: two with low prevalence and two with high prevalence of M. pectinifera. Paired comparisons be- tween plots with and without M. pectinifera allowed the characterization of its patterns of occurrence related to the variation of environmental factors. M. pectinifera was found on deep alkaline soils with relatively high surface stoniness and high water retention capacity, showing low species rich- ness compared with plots where it was absent. The limited distribution of M. pectinifera in the Tehuacan Valley seems to be related to particular requirements of this species, being restricted to certain suitable habitat patches. Nevertheless, it is likely that other aspects, such as poor dispersal and establish- ment abilities, or biotic interactions could be associated with the observed patterns.

In vitro propagation of three endangered cactus species

We tested the feasibility of in vitro culture techniques for the propagation of the three endangered cacti species Escobaria minima (Baird) D. Hunt, Mammillaria pectinifera (Ruempler) F.A.C. Weber and Pelecyphora aselliformis Ehrenberg. Twenty-five MS-based proliferation media were tested in preliminary experiments, with different combinations of the auxin NAA and either of the cytokinins BA, kinetin or TDZ. TDZ induced a good proliferation rate, albeit associated with abundant callus formation and hyperhydricity of axillary shoots. A high multiplication rate combined with good quality proliferated shoots and little or no callus induction was observed on media containing BA for E. minima and M. pectinifera and on a medium containing kinetin for P. aselliformis. These results were also confirmed in subsequent experiments in which different explants (shoot tips, bases and longitudinal sections) were used. Micropropagated plantlets were successfully restored to the field, where they reached the flowering stage. Plantlet regeneration of M. pectinifera and P. aselliformis from callus induced on media containing TDZ, but not 2,4-D, was also achieved.