Microbial populations and activities in the rhizoplane of rock-weathering desert plants. I. Root colonization and weathering of igneous rocks

Dense layers of bacteria and fungi in the rhizoplane of three species of cactus (Pachycereus pringlei, Stenocereus thurberi, Opuntia cholla) and a wild fig tree (Ficus palmeri) growing in rocks devoid of soil were revealed by bright-field and fluorescence microscopy and field emission scanning electron microscopy. These desert plants are responsible for rock weathering in an ancient lava flow at La Purisima-San Isidro and in sedimentary rock in the Sierra de La Paz, both in Baja California Sur, Mexico. The dominant bacterial groups colonizing the rhizoplane were fluorescent pseudomonads and bacilli. Seven of these bacterial species were identified by the 16S rRNA molecular method. Unidentified fungal and actimomycete species were also present. Some of the root-colonizing microorganisms fixed in vitro N(2), produced volatile and non-volatile organic acids that subsequently reduced the pH of the rock medium in which the bacteria grew, and significantly dissolved insoluble phosphates, extrusive igneous rock, marble, and limestone. The bacteria were able to release significant amounts of useful minerals, such as P, K, Mg, Mn, Fe, Cu, and Zn from the rocks and were thermo-tolerant, halo-tolerant, and drought-tolerant. The microbial community survived in the rhizoplane of cacti during the annual 10-month dry season. This study indicates that rhizoplane bacteria on cacti roots in rock may be involved in chemical weathering in hot, subtropical deserts.     

The role of the use of different host plants in the maintenance of the inversion polymorphism in the cactophilic Drosophila buzzatii

Abstract. Inversion polymorphisms often have been associated with fitness variation. Cactophilic Drosophila buzzatii has been used widely for the study of the maintenance of chromosomal variation. The purpose of this paper is to address the relative importance of variable selection regimes associated with the use of three different host cacti and antagonistic pleiotropy in the maintenance of chromosomal variation. Using homokaryotypic stocks derived from several lines homozygous for four second-chromosome arrangements, we show that inversions significantly affect first-instar larva to adult viability (VT), developmental time (DT) and adult thorax length (TL). We also show that the effects of inversions on DT and VT are dependent on the cactus rearing media. The effects of polymorphic gene arrangements on life-history traits suggest the existence of trade-offs between early and late fitness components. The dosage of arrangement 2st , the ancestral gene order, was negatively correlated with DT and TL, whereas flies carrying the derived arrangements 2j and 2jq⁷ had longer DTs and larger TLs. Arrangements 2st and 2jq⁷ increased viability, at least in one of the cactus media tested. Our results suggest that environmental heterogeneity, as represented by the use of different cactus hosts and the trade-off between DT and TL, may be involved in the maintenance of the polymorphism. In addition, our data suggest that the chromosomal phylogeny may be decoupled from the evolution of the genes affecting life-history traits linked to the inversion system.     

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 2845km², 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.     

Detectability and Response Rates of Ferruginous Pygmy-Owls

Abstract: Survey techniques that are both reliable and efficient are necessary to accurately estimate population parameters, especially for rare species. Cactus ferruginous pygmy-owls (Glaucidium brasilianum cactorum; hereafter pygmy-owls) have declined in southwestern North America and are surveyed often to comply with federal law. We studied owl responses to broadcasted calls to quantify how detectability and response rates (owls/station/transect) vary with environmental, spatial, temporal, and weather-related factors. We surveyed owls along 392 transects (1,113 km) throughout Sonora, Mexico, including a subset of 14 transects (47.2 km) that we surveyed repeatedly to assess factors that affected response rates. We challenged 17 adults and 23 juveniles that were radiomarked, adults attending 50 occupied nests, and adults attending 6 groups of radiomarked juveniles to respond to broadcasted calls to assess factors that affected detectability. Across Sonora, response time averaged 2.6 ± 0.1 minutes (xM ± SE, n = 520), with 99 ± 0.4% of owls detected in ≤8 minutes; response distance averaged 251 ± 7 m, with 91 ± 1% of owls detected at ≤400 m. Response time decreased by an average of 4 ± 2% and response distance decreased by 12 ± 3 m with each half-month period from early courtship through brooding (P ≤ 0.035). Response time averaged 39 ± 24% faster during morning than midday at occupied nests. Detectability was 1.0 ± 0.0 when surveyors were 100 m from occupied nests and decreased to 0.78 ± 0.10 when surveyors were 500 m from occupied nests. Detectability was higher during incubation, brooding, and natal dispersal (0.89 ± 0.05-1.0 ± 0.0) than during fledgling-dependency (0.50 ± 0.20-0.67 ± 0.19). Response rates of males did not vary from early courtship to brooding (P = 0.84), yet those of females decreased systematically to zero across the same period (P < 0.001). Because detectability of pygmy-owls remains consistently high during nesting, response rates generated from carefully designed surveys can provide reliable estimates of occupancy and abundance.     

Spatial and host related genomic variation in partially sympatric cactophagous moth species

Surveys of patterns of genetic variation in natural sympatric and allopatric populations of recently diverged species are necessary to understand the processes driving intra- and interspecific diversification. The South American moths Cactoblastis cactorum, Cactoblastis doddi and Cactoblastis bucyrus are specialized in the use of cacti as host plants. These species have partially different geographic ranges and differ in patterns of host plant use. However, there are areas that overlap, particularly, in northwestern Argentina, where they are sympatric. Using a combination of genome-wide SNPs and mitochondrial data we assessed intra and interspecific genetic variation and investigated the relative roles of geography and host plants on genetic divergence. We also searched for genetic footprints of hybridization between species. We identified three well delimited species and detected signs of hybridization in the area of sympatry. Our results supported a hypothetical scenario of allopatric speciation in the generalist C. cactorum and genetic interchange during secondary geographic contact with the pair of specialists C. bucyrus and C. doddi that probably speciated sympatrically. In both cases, adaptation to new host plants probably played an important role in speciation. The results also suggested the interplay of geography and host plant use as drivers of divergence and limiting gene flow at intra and interspecific levels.     

仙人掌多糖提取过程中脱蛋白方法的研究

用水提取的仙人掌多糖常含有蛋白质C,实验以多糖损失率和脱蛋白率为衡量指标,选用了Sevag法、三氯乙酸法和酶法对仙人掌多糖提取物进行脱蛋白处理。实验结果表明,酶法、三氯乙酸法和Sevag法的脱蛋白率分别为89.67%、56.20%和45.65%,多糖损失率分别为7.19%、9.49%和13.75%。因此,酶提取法是替代常规方法的一种有效方法。     

Callus formation and plant regeneration from tubercles of Coryphantha elephantidens (Lem.) Lem.

Summary Callus cultures were established from pith tissue of Coryphantha elephantidens (Lem.) Lem. on Murashige and Skoog (MS) basal medium supplemented with 9.05 μM 2,4-dichlorophenoxyacetic acid (2,4-D) and 2.3 μM kinetin. Highest shoot regeneration frequency was observed on a medium containing 6.9 μM kinetin and 2.3 μM 2,4-D under 30 μE m⁻² s⁻¹ light intensity with a 16-h photoperiod. Calluses retained organogenic potential throughout several passages of subculture (18 mo.). Shoots were rooted on MS medium without plant growth regulators. All (100%) plantlets transplanted to soil survived acclimatization. Regenerated plants showed good overall growth and were morphologically similar to the mother plants.     

食用仙人掌的营养成分分析

对新近引进的菜用品种－米邦塔仙人掌进行了营养成分（维生素Ｃ、β－胡萝卡素、矿物质、水溶性氨基酸、粗蛋白、中性洗涤纤维、有机酸、可溶性糖等）的分析,并与经常食用的结球甘蓝、生菜及黄瓜作了比较。结果表明：米邦塔仙人掌中的钾、钙、铜、铁、锰、锶及硅的含量较高,尤以钙、钾的含量明显高于其它蔬菜,且不含草酸;水溶性氨基酸以酷氨酸为主;另外还含有丰富的黄酮类物质。     

胭脂虫养殖方式初探

2003～2005年在四川凉山彝族自治州西昌市、宁南县,对胭脂虫进行大棚养殖试验、大棚仙人掌悬挂养殖试验和野外养殖试验,结果表明大棚养殖和大棚仙人掌悬挂养殖胭脂虫效果比较好;野外养殖受气候影响较大,胭脂虫难以成活.