Geographic Distribution and Conservation of Cactaceae from Tamaulipas Mexico

An inventory of the species of Cactaceae from Tamaulipas, Mexico was carried out. The study area was divided into 48 squares of 30 min of latitude and 30 min of longitude. Collections were made at 60 sampling sites distributed over an area extending in to the bordering states of San Luis Potosí, Nuevo León, Veracruz and Texas (USA). Species diversity per squares and their geographic distribution range were obtained. Results showed a diversity of 120 species and 53 subspecies, of total 49 are considered as endangered by the CITES, IUCN, and SEMARNAT. The genera most represented were Mammillaria, Coryphantha, Echinocereus and Opuntia. Index of Geographical Expansion (IGE) was calculated for each species. Highest diversity per squares as well as the IGE for each species was found at square 66 (Jaumave) IGE = 52%, 72 (Tanque Blanco) IGE = 22% and 59 (Cd. Victoria) IGE = 7%. It was for these sites that had the highest number of endemic taxa and thus are recommended as priority sites for conservation. This information may help establish natural protected areas by the government of the State of Tamaulipas.     

Chemical Composition of Cacti Wood and Comparison with the Wood of Other Taxonomic Groups

The aims of this study were to determine the wood chemical composition of 25 species of Cactaceae and to relate the composition to their anatomical diversity. The hypothesis was that wood chemical components differ in relationship to their wood features. The results showed significant differences in wood chemical compounds across species and genera (P < 0.05). Pereskia had the highest percentage of lignin, whereas species of Coryphantha had the lowest; extractive compounds in water were highest for Echinocereus, Mammillaria, and Opuntia. Principal component analysis showed that lignin proportion separated the fibrous, dimorphic, and non‐fibrous groups; additionally, the differences within each type of wood occurred because of the lignification of the vascular tissue and the type of wall thickening. Compared with other groups of species, the Cactaceae species with fibrous and dimorphic wood had a higher lignin percentage than did gymnosperms and Acer species. Lignin may confer special rigidity to tracheary elements to withstand desiccation without damage during adverse climatic conditions.     

Comparative pollination biology of Venezuelan columnar cacti and the role of nectar-feeding bats in their sexual reproduction

The floral biology, reproductive system, and visitation behavior of pollinators of four species of columnar cacti, Stenocereus griseus, Pilosocereus moritzianus, Subpilocereus repandus, and Subpilocereus horrispinus, were studied in two arid zones in the north of Venezuela. Our results support the hypothesis that Venezuelan species of columnar cacti have evolved toward specialization on bat pollination. Additional information on the floral biology of a fifth species, Pilosocereus lanuginosus, was also included. All species showed the typical traits that characterize the pollination syndrome of chiropterophily. All species but Pilosocereus moritzianus were obligate outcrossers. Nectar and pollen were restricted to nocturnal floral visitors. Two species of nectar-feeding bats, Leptonycteris curasoae Miller and Glossophaga longirostris Miller, were responsible for practically all the fruit set in these cacti. Frequency of bat visitation per flower per night was highly variable within and between species of cactus, with average frequencies varying between 27 and 78 visits/flower/night. In general terms, the pattern of floral visitation through the night was significantly correlated with the pattern of nectar production and nectar sugar concentration for all species of cactus. Under natural pollination, fruit:flower ratios varied from 0.46 in Subpilocereus repandus to 0.76 in Stenocereus griseus. The efficiency of bat pollination in terms of seed:ovule ratio was high in all species, varying between 0.70 and 0.94.     

Presence of paratracheal water storage tissue does not alter vessel characters in cactus wood

This research tested hypotheses that the presence of water storage tissues immediately adjacent to vessels would protect vessels from cavitation and would result in evolution of broader vessels that occur in fewer, smaller clusters relative to vessels surrounded by a matrix of fibers. We examined 21 species that have dimorphic wood, that is, at one stage in their life they produce a wood with a fibrous matrix surrounding the vessels and at another stage they produce wood with abundant paratracheal parenchyma or wide-band tracheids. In only one species were vessels in the water storage matrix broader than those in the fibrous matrix of the same plant. In most specimens, fibrous wood had smaller clusters of vessels than water storage wood, and a greater percentage of vessels in fibrous wood were solitary. Presence of abundant paratracheal water storage tissue was not correlated with a reduced number or size of rays. Axial masses in fibrous wood were not consistently narrower than those of water storage wood, consequently their vessels were not consistently closer to water stored in rays. Wood strength may be more important than conduction safety in determining vessel cluster size and widths of rays and axial masses.     

Pollination biology of two columnar cacti (Neobuxbaumia mezcalaensis and Neobuxbaumia macrocephala) in the Tehuacan Valley,central Mexico

We document the pollination biology and mating systems of Neobuxbaumia mezcalaensis and Neobuxbaumia macrocephala, two Mexican giant columnar cacti. These two species form mixed forests in the western Tehuacan Valley, Mexico. The flowers of both N. mezcalaensis and N. macrocephala exhibit nocturnal anthesis, are self-incompatible, and are pollinated primarily by three species of nectar-feeding bats (Choeronycteris mexicana, Leptonycteris curasoae, and Leptonycteris nivalis). Neobuxbaumia mezcalaensis is androdioecious, a breeding system that appears to be uncommon among Cactaceae. Neobuxbaumia macrocephala is hermaphroditic. We hypothesize that columnar cacti show a geographical dichotomy in floral biology specialization that probably can be related to predictability in pollinator abundance.     

Seed germination of Melocactus sergipensis N.P. Taylor & M.V. Meiado,the newest Brazilian cactus destined for extinction

Recently, a new cactus was discovered in an area of the Caatinga, a tropical dry forest of north‐eastern Brazil. Although this discovery is excellent news, Melocactus sergipensis is critically endangered because it is affected by deforestation of native vegetation and chemicals used in the maize crop, next to the holotype locality. The aim of this study was to evaluate the seed germination and seedling survival of the newest Brazilian cactus. All germination treatments were performed at room temperature and white light or continuous darkness. For the evaluation of establishment, 50 seedlings were examined at 30‐day intervals for 5 months. I did not observe seed germination of M. sergipensis in continuous darkness, which shows that the newly discovered species is positive photoblastic. However, a high germinability was observed under white light (80.0 ± 10.8%), indicating that the seeds of the newly discovered species are able to germinate and the light is needed for seed germination. After 5 months, seedling mortality was less than 5%. These results show that the seedlings of the newly discovered cactus can be produced in a glasshouse, providing support for studies on ex situ conservation of a species that could become extinct in the near future.     

On the pigmented spherical bodies and crystals in tepals of cactaceous species in reference to the nature of betalains or flavonols

Red pigmented bodies were found in tepal cells of threeRebutia species, i.e.,R. grandiflora, R. hyalacantha andR. krainziana. The pigmented body within the vacuole was spherical and normally one per cell. It contained betalains which were validated from the visible spectra of tepal extracts and microspectrophotometric survey on vacuoles. Such a particular red pigmented body has already been found in some anthocyanin-producing plants, and called “anthocyanoplast”. Now, a similar structure has also been found for the first time in betalain-producing plants. Therefore, it may be called “betalainoplast”. InR. grandiflora, yellow pigmented bodies which were not well characterized due to their minimal size were also present as a betalainoplast. On the other hand, pigment-crystals were frequently present in the cells having flavonols such as those in pale yellow tepals of fourAstrophytum species, namely,A. asterias, A. capricorne, A. myriostigma andA. ornatum, with or without a trace of betalains. Yellowish crystals were determined as the crystal mass of quercetin by the UV spectral analysis and careful comparison of chromatographic properties with an authentic specimen. Contribution from the Research Institute of Evolutionary Biology, No. 86.     

The renowned cactus moth, Cactoblastis cactorum: its natural history and threat to native Opuntia floras in Mexico and the United States of America

Abstract. The cactus moth, Cactoblastis cactorum (Berg) (Phycitidae) is native to South America. It was released as a biological control agent against alien Opuntia- cacti in Australia in the 1920s, then in southern Africa, and latterly on several islands, including those in the Caribbean. In 1989, the cactus moth was discovered in Florida, in the United States of America, where it is now threatening the survival of indigenous Opuntia species. In this paper we identify some of the attributes that have contributed to the success of C. cactorum as a weed biological control agent. Many of these same qualities account for the problems that C. cactorum has caused in Florida and predispose it as a major threat to the speciose, native Opuntia- floras of Central and North America. An estimated 79 platyopuntia (prickly pear) species are at risk: 51 species endemic to Mexico; nine species endemic to the United States; and 19 species common to both countries. Many cultivated and wild Opuntia species, that are used in various ways, are also vulnerable to attack by C. cactorum , including at least 25 species in Mexico and three species in the United States, particularly the widely exploited and culturally important cultivars of O. ficus-indica . Some control strategies are suggested that may minimize the risk and consequences of invasion by the cactus moth. The wider implications of this threat to the practice of weed biological control and to conservation are discussed.     

A unique cactus with scented and possibly bat-dispersed fruits: Rhipsalis juengeri

Rhipsalis juengeri was described in 1995 as an unusual representative of epiphytic cacti, forming more than 3 m long curtains, hanging from the canopy of the Atlantic Rainforest in eastern Brazil. At the apex of thin, pendant shoots, green-brownish berries are formed. We report here as a novelty for the Cactaceae that these berries are strongly scented, and present an odour analysis along with an olfactoric survey of fruits of about 50 species and varieties of the cactus tribe Rhipsalideae. The volatile blend of berries of R. juengeri is dominated by ketones, some of which are responsible for the characteristic blackcurrant-like scent, as is shown by GC-olfactometry. The odour and inconspicuous colour stand out among fruits of other epiphytic cacti that are thought to be consumed by birds. Fruit characters of R. juengeri and the flagellicarpic presentation indicate adaptation to chiropterochory.