Héctor M. Hernández

Phylogenetic relationships and evolution of growth form in Cactaceae (Caryophyllales, Eudicotyledoneae)

PREMISE OF THE STUDY Cactaceae is one of the most charismatic plant families because of the extreme succulence and outstanding diversity of growth forms of its members. Although cacti are conspicuous elements of arid ecosystems in the New World and are model systems for ecological and anatomical studies, the high morphological convergence and scarcity of phenotypic synapomorphies make the evolutionary relationships and trends among lineages difficult to understand. METHODS We performed phylogenetic analyses implementing parsimony ratchet and likelihood methods, using a concatenated matrix with 6148 bp of plastid and nuclear markers (trnK/matK, matK, trnL-trnF, rpl16, and ppc). We included 224 species representing approximately 85% of the familys genera. Likelihood methods were used to perform an ancestral character reconstruction within Cactoideae, the richest subfamily in terms of morphological diversity and species number, to evaluate possible growth form evolutionary trends. KEY RESULTS Our phylogenetic results support previous studies showing the paraphyly of subfamily Pereskioideae and the monophyly of subfamilies Opuntioideae and Cactoideae. After the early divergence of Blossfeldia, Cactoideae splits into two clades: Cacteae, including North American globose and barrel-shaped members, and core Cactoideae, including the largest diversity of growth forms distributed throughout the American continent. Para- or polyphyly is persistent in different parts of the phylogeny. Main Cactoideae clades were found to have different ancestral growth forms, and convergence toward globose, arborescent, or columnar forms occurred in different lineages. CONCLUSIONS Our study enabled us to provide a detailed hypothesis of relationships among cacti lineages and represents the most complete general phylogenetic framework available to understand evolutionary trends within Cactaceae.

DNA Isolation and Amplification from Cacti

The cacti family is a morphologically heterogeneous group comprising 100 genera and about 1500 species (Hernandez and Barcenas, 1996). With the exception of one genus, all members of this family are native to America (Hernandez and Barcenas, 1996). There are three subfamilies, Opuntioideae, Cactoideae, and Pereskioideae (Gibson and Nobel, 1986). DNA isolation from cacti is notoriously difficult because they contain high amounts of polysaccharides and secondary metabolites which form insoluble complexes with nucleic acids during extraction (Guillemaut and Marechal-Drouard, 1992). Like in other groups of plants, the secondary metabolites and polysaccharides in cacti inhibit enzyme action (Porebski et al., 1997). The polysaccharides are visually evident by their viscous, glue-like texture and they make the DNA unmanageable when pipeting and hard to amplify by the polymerase chain reaction (PCR) (Poresbski et al., 1997). We report an easy and inexpensive protocol to isolate DNA from cacti. We used this method to isolate DNA from 85 species (170 individuals) of 39 genera of the subfamilies Pereskioideae, Opuntioidea, and Cactoideae. This procedure is a modification of a protocol described by De la Cruz et al. (1995) for the Cacti family. It requires only a few grams of tissue and does not require destruction of the whole plant to produce high molecular weight genomic DNA. The DNA from this procedure can be amplified consistently by PCR and used for RAPD analysis.

Diversity, spatial arrangement, and endemism of Cactaceae in the Huizache area, a hot-spot in the Chihuahuan Desert

We studied several aspects of the cactus diversity in the Huizache, an area located in the southern extreme of the Chihuahuan Desert Region, in San Luis Potosí, Mexico. Fieldwork was conducted in a square-shaped polygon (22°30′–23°00′ N, 100°00′–100°30′ W), where a total of 80 systematically-chosen localities were sampled for cactus species. Results showed that the Huizache is an important focal point for the conservation of the Cactaceae, due to the remarkably high diversity of members of this plant family in the area. With 75 species recorded, this area has the highest concentration of cactus species in the American Continent, in comparison with other comparably-sized regions. The outstanding diversity of cactus species in the Huizache area may be explained by the relatively favorable climate of this desert area, its environmental heterogeneity, and its location in a transitional position between three regions with distinct cactus floras: Chihuahuan Desert Region, Queretaroan-Hidalgoan Arid Zone, and Tula-Jaumave Valleys. Species richness is not distributed evenly in the area; the zones of highest species concentration are primarily located in the lowland valleys, in the northwestern portion of the grid square, where typical Chihuahuan Desert conditions prevail. Of the 75 cactus species found in the area, 63% are endemic to the Chihuahuan Desert. Among these, ten species are outstanding for being endemic or nearly endemic to the Huizache area. The Huizache grid square is part of a recently declared natural reserve, The Real de Guadalcázar Natural Reserve.

Diversity, geographical distribution, and conservation of Cactaceae in the Mier y Noriega region, Mexico

We carried out an inventory of the cactus species occurring in the Mier y Noriega region. The study was conducted in a square-shaped area of approximately 2845 km2, located in the southeastern segment of the Chihuahuan Desert region, between 23°00′ – 23°30′ lat. N and 100°00′ – 100°30′ long. W, including parts of the states of Nuevo León, Tamaulipas, and San Luis Potosí, Mexico. In order to know the cactus diversity, we developed an intensive method of botanical collecting; a total of 80 sites were sampled. With 54 species recorded, of which 28 were new area records and 14 new state records, the Mier y Noriega region is considered moderately rich in cactus species. Cactus diversity is distributed unevenly in the area, and the greatest species concentration occurs in its southwestern portion. The analysis of geographical distribution of individual species showed that the highest proportion (82%) are endemic to the Chihuahuan Desert Region, six of them having extremely narrow distributions. In addition, 19 species are considered endangered. With the aid of a complementarity analysis, we propose a strategy for the optimal conservation of the species and their habitats.

Acacia: The case against moving the type to Australia

Recent studies have shown that Acacia is polyphyletic and must be split into five genera. Proposal 1584 would retypify Acacia : the type of the Australian taxon A. penninervis would be conserved over the current lectotype ( A. scorpioides ) of an African taxon. We disagree with the recommendation of the Spermatophyte Committee to endorse this proposal. Contrary to Article 14.12 of the ICBN, no detailed case against conservation was presented in Proposal 1584. We maintain that there are strong arguments against conservation, such as the large number of countries that would be affected, the economic importance of the extra-Australian species, and the economic burden placed on developing countries. Acceptance of this proposal would also violate the guidelines for conservation which clearly state that the principle of priority should prevail when conservation for one part of the world would create disadvantageous change in another part of the world.

A new method to estimate areas of occupancy using herbarium data

The World Conservation Union (IUCN) Red List of Threatened Species is an important instrument to evaluate the conservation status of living organisms. However, Red List assessors have been limited by the lack of reliable methods to calculate the area of occupancy (AOO) of species, which is an important parameter for red list assessments. Here we present a new practical method to estimate AOO based on herbarium specimen data: the Cartographic method by Conglomerates (CMC). This method, which combines elements from the Areographic and Cartographic methods previously used to calculate AOO, was tested with ten cactus species from the Chihuahuan Desert Region. The results derived from this novel procedure produced in average AOO calculations 3.5 and 5.5 smaller than the Areographic and Cartographic methods, respectively. The CMC takes into account the existence of disjunctions in the distribution range of the species, producing comparatively more accurate AOO estimations. Another advantage of the CMC is that it generates results more harmonic with the current Red List criteria. In contrast, the overestimated results of the Areographic and Cartographic methods tend to artificially categorize the species, even extremely narrow endemics, in lower endangerment status.

DNA barcodes for Mexican Cactaceae, plants under pressure from wild collecting

DNA barcodes could be a useful tool for plant conservation. Of particular importance is the ability to identify unknown plant material, such as from customs seizures of illegally collected specimens. Mexican cacti are an example of a threatened group, under pressure because of wild collection for the xeriscaping trade and private collectors. Mexican cacti also provide a taxonomically and geographically coherent group with which to test DNA barcodes. Here, we sample the matK barcode for 528 species of Cactaceae including approximately 75% of Mexican species and test the utility of the matK region for species‐level identification. We find that the matK DNA barcode can be used to identify uniquely 77% of species sampled, and 79–87% of species of particular conservation importance. However, this is far below the desired rate of 95% and there are significant issues for PCR amplification because of the variability of primer sites. Additionally, we test the nuclear ITS regions for the cactus subfamily Opuntioideae and for the genus Ariocarpus (subfamily Cactoideae). We observed higher rates of variation for ITS (86% unique for Opuntioideae sampled) but a much lower PCR success, encountering significant intra‐individual polymorphism in Ariocarpus precluding the use of this marker in this taxon. We conclude that the matK region should provide useful information as a DNA barcode for Cactaceae if the problems with primers can be addressed, but matK alone is not sufficiently variable to achieve species‐level identification. Additional complementary regions should be investigated as ITS is shown to be unsuitable.

Areas of endemism of Cactaceae and the effectiveness of the protected area network in the Chihuahuan Desert

We used distribution data of 121 cactus species endemic to the Chihuahuan Desert to test the effectiveness of the regions protected area network. The analysis of species distribution using a 309 latitude 3 309 longitude grid facilitated the identification and categorization of areas of endemism. We found a low degree of coincidence between protected areas and the areas of cactus endemism, and only 63.6% of the 121 species occur in protected areas. A comple- mentarity analysis showed that 10 of the protected areas contain the 77 species that occur in protected areas. The four top priority areas protect 65 (84.4%) of these 77 species The 44 unprotected species are mainly micro-endemic and taxonomically distinctive taxa widely scattered in the region. The complementarity analysis applied to these species showed that all of them can be contained in a minimum of 24 grid squares, representing 32.9% of the total area occupied. Their strong spatial dispersion, along with their narrow endemism, is a major conservation challenge. We conclude that the current protected area network is insuffi- cient to protect the rich assemblage of cacti endemic to the Chihuahuan Desert. Conservation efforts in this region should be enhanced by increasing the effectiveness of the already existing protected areas and by the creation of addi- tional protected areas, specifically micro-reserves, to provide refuge for the unprotected species.

Characterization of microsatellite loci for the critically endangered cactus Ariocarpus bravoanus

Ariocarpus bravoanus is common in trade but critically endangered in its natural habitat. With the ultimate aim of developing a certification scheme to aid in the conservation of this species, we have isolated A. bravoanus microsatellites from a nonenriched library. Fifty‐four sequences contained a microsatellite array, of which eight were polymorphic among 23 individuals, 20 from one population and three plants from trade.

Studies on Mexican Cactaceae. IV. A new subspecies of Echinocereus palmeri Britton & Rose, first record of the species in the Chihuahuan Desert

Summary: Echinocereus palmeri subsp. mazapil, a new subspecies of Cactaceae from the Chihuahuan Desert Region, Mexico, is described and illustrated. It has only been collected from a highly specialized habitat at two remote localities in the state of Zacatecas and its range is markedly disjunct from that of the typical subspecies. In addition to divergences in geographic range and habitat preferences, E. palmeri subsp. mazapil differs from the typical subspecies by usually having relatively smaller stems with tuberculate ribs and less numerous radial spines, which usually are of unequal length.