Anatomy and uses of the mature leaves of three species of Sabal (Arecaceae) of the Yucatan, México

This paper describes the leaf anatomy of Sabal mauritiiformis (Karst.) Griseb. & H. Wendl., Sabal mexicana Mart. and Sabal yapa Wright ex Becc., three of the four most representative species of the Yucatán Península, in Mexico. These species are locally used: in the roofing of traditional homes, as food (fruits and apical buds), and in the production of hats, brooms and handicrafts. Leaf samples were collected in secondary growth of lower montane rainforest in the state of Quintana Roo and in two home gardens in the state of Yucatán. Herbarium samples were obtained, and samples of blade and petiole were fixed in formaline-acetic acid-alcohol. Cross incisions were made on the blade and petiole, and were dyed with safranin and toluidine blue O. The results show that S. mauritiiformis and S. yapa are morphologically alike: both are tall, slim palm trees; the leaf in S. mauritiiformis is a shorter palm-like structure compared with the other two species. The shape of the main nerve, as seen in cross section, is rectangular in the three species. The hastula in the three species is acuminate and adaxial. The foliar anatomic structure is similar in the three species, although there are some differences. The adaxial an abaxial epidermis of the blade consist of one layer and, superficially, the anticlinal walls are straight; the stomata are intercostal, of the tetracytic type, present on both surfaces in S. mexicana and S. yapa and only on the abaxial surface on S. mauritiiformis. The hypodermis is one layer thick in S. yapa and in S. mexicana and two layers thick in S. mauritiiformis. In the three species the palisade parenchyma consists of several undefined strata as the cells are similar-in shape and size--to the cells in the spongy parenchyma, so there is no marked difference between these strata and the spongy parenchyma seems almost continuous. Both fibrous and vascular bundles are distributed between the hypodermis and the palisade parenchyma; the fiber bundles can be found towards the abaxial surface while the vascular and fiber bundles are located towards the adaxial surface. The fibers, in the three species, are elongated, with the pointed tips, undivided and unseptated. One to three wide vessels of metaxilem can be seen in the vascular bundles, those in S. yapa being the widest in diameter. The vascular bundles are surrounded by thick fiber sheaths which come in pairs. The anatomic structure of the petiole is similar to that of the blade, and is characterized by the many vascular and fiber bundles dispersed in the parenchymatous tissue, and which are very resistant. The histological structure of the blade and petiole reflects strength and flexibility, qualities which make these plants adequate in the construction of roofs for rural housing and other buildings.     

Culture of Poecilia reticulata (Pisces: Poecilidae) in tropical water bodies, Veracruz, México

Poecilia reticulata, also known as guppy, is the most popular fish in the aquarium environment. Guppys are viviparous fish with high tolerance to extreme temperatures. The development of the offspring takes between 25 and 30 days. We developed a technology for raising guppys, which outlines infrastructure and devices for reproduction, nursery, feeding, and commercialization, evaluating the financial and technical feasibility of this technology in a case study. The complete reproductive cycle occured in floating cages with 1 mm mesh and the method was tested in a tropical lagoon in Mexico. Water quality was monitored throughout the study period (temperature, dissolved oxygen and pH levels). A marketing survey was carried out at all existing aquarium shops in Veracruz City. Data collected depict quantities demanded and offered for each species by season, place of origin, and resistance to handling. The hydrobiological characteristics were: average temperature 31.4 degrees C, dissolved oxygen 4.5 mgl(-1), and pH level 6.8. With these values we built a production function, and used it to evaluate profitability. We estimate a benefit/cost ratio of 1.16, with a net annual income of US$257.67. The system may provide two permanent jobs.     

Territoriality and Survivorship of the Sierra Madre Sparrow in La Cima,México

We studied the life-history of the Sierra Madre sparrow (Xenospiza baileyi) in a subalpine grassland-agriculture mosaic south of Mexico City. From March to early September 1999 we captured and color-banded 53 adults with mist-nets and mapped the breeding territories of 21 males. We again mapped territories in the same spot in April and May 2000. The number of breeding territories was found to be the same in the two consecutive years and interannual survivorship was found to be relatively high. Breeding territories were restricted to the bunchgrass-covered areas. We used the density of territories and the amount of remaining habitat to estimate a total population size of 5,380–6,150 adults for this species. Using this and other recent data, we recommend raising the Sierra Madre sparrow to the status of critically endangered using BirdLife International criteria.     

Antibiotic resistance and plasmid pattern of enterotoxigenic ST-a strains of Escherichia coli isolated in Puebla, México

Antibiotic susceptibilities of 22 strains of Escherichia coli isolated from children from 0 to 3 years old at the University Hospital of Puebla were determined. Almost all strains were resistant to ampicillin, tetracycline, streptomycin, and kanamycin. Gel electrophoresis of DNA from 10 clinical strains of E. coli revealed a heterogeneous plasmid population. Plasmid DNA, ranging in molecular mass from 1.8 to 120 megadaltons, was demonstrated in 10 strains. Moreover, the frequency of antibiotic transfer ranged from 1.6/10(8) to 2/10, and the simultaneous transfer of the gene encoding heat-stable enterotoxin was also determined. Six out of 10 strains tested were able to cotransfer ST-a as demonstrated by the suckling mouse test. It is possible that antibiotic selective pressure may increase the isolation of enterotoxigenic E. coli strains.     

Frequency of antibodies to Toxoplasma gondii in stray dogs of Oaxaca, México

We studied the frequency of antibodies against Toxoplasma gondii in stray dogs in the city of Oaxaca, Mexico through the evaluation of 154 sera by indirect ELISA. A frequency of 61.7% was found; it was higher in males (45 of 65, 69.2%) than in females (49 of 89, 55.0%), although this difference was not statistically significant. An increase in frequency was observed with age, the lowest being among animals younger than 1 yr (4 of 20, 20.0%) and the highest in dogs older than 7 yr (21 of 25, 84.0%). This is the first study in dogs of this region of Mexico and revealed high T. gondii transmission and evidence of early exposure in animals that are in close contact with contaminated water or raw meat, or both. Further studies are needed in order to understand the role of T. gondii infection in public health.     

Interruption of Transmission of Onchocerca volvulus in the Southern Chiapas Focus,México

Background

The Southern Chiapas focus of onchocerciasis in Southern Mexico represents one of the major onchocerciasis foci in Latin America. All 559 endemic communities of this focus have undergone semi-annual mass treatment with ivermectin since 1998. In 50 communities of this focus, ivermectin frequency shifted from twice to four times a year in 2003; an additional 113 communities were added to the quarterly treatment regimen in 2009 to achieve a rapid suppression of transmission.

Methodology/Principal findings

In-depth epidemiologic and entomologic assessments were performed in six sentinel communities (which had undergone 2 rounds of ivermectin treatment per year) and three extra-sentinel communities (which had undergone 4 rounds of ivermectin treatment per year). None of the 67,924 Simulium ochraceum s.l. collected from this focus during the dry season of 2011 were found to contain parasite DNA when tested by polymerase chain reaction-enzyme-linked immunosorbent assay (PCR-ELISA), resulting in an upper bound of the 95% confidence interval (95%-ULCI) of the infective rate in the vectors of 0.06/2,000 flies examined. Serological assays testing for Onchocerca volvulus exposure conducted on 4,230 children 5 years of age and under (of a total population of 10,280 in this age group) revealed that 2/4,230 individuals were exposed to O. volvulus (0.05%; one sided 95% confidence interval = 0.08%).

Conclusions/Significance

The in-depth epidemiological and entomological findings from the Southern Chiapas focus meet the criteria for interruption of transmission developed by the international community.     

Susceptibility to mercurials of clinical Pseudomonas aeruginosa isolated in México

Susceptibility to inorganic mercuric ions and to organomercurials of 237 Pseudomonas aeruginosa clinical strains isolated in Mexico was determined by agar dilution tests. Resistant strains fell into two classes: i) narrow-spectrum resistant strains (27% of total isolates) resistant only to mercuric ions and to merbromin, and most grouped in pyocin type 1; and ii) broad-spectrum resistant strains (5%) with additional resistances to thimerosal, phenylmercury, methylmercury and p-hydroxymercuribenzoate, that belonged mostly to pyocin type 10. Mercurial resistant isolates showed a higher proportion of resistance to antibiotics and metals than did mercurial sensitive isolates, and broad-spectrum resistant strains had the highest frequency of resistance to antibiotics and to tellurite and arsenate.     

From Isozymes to Genomics: Population Genetics and Conservation of Agave in México

Mexico is a megadiverse country, but less than 54 % of its original vegetation still remains. In particular Mexican deserts and arid and semiarid ecosystems harbor a large number of endemic taxa, and the genus Agave is an outstanding example. Agave is one of the largest genera of the Mexican flora, including a total estimated number of 200 species, 74 % of them endemic to the country. Agave is also one of the Mexican plant genera with more population genetic studies. We describe here studies in 22 Agave species using different genetic markers. For the genus we found on average a high level of genetic variation, H _s ?=?0.19, and a low genetic differentiation, F _st ?=?0.15. We identify some species that should be subject to special conservation genetic efforts, in particular the endangered A. victoriae-reginae and both wild populations and landraces of A. angustifolia, including the cultivated A. tequilana.     

Monogeneans in introduced and native cichlids in México: evidence for transfer

We examined 2 cichlid fish species native to México, Cichlasoma callolepis and C. fenestratum, and 2 introduced African cichlids, Oreochromis aureus and O. niloticus, from 3 localities in southeastern México for monogeneans. Six monogenean species infected the African cichlids: Cichlidogyrus haplochromii, C. dossoui, C. longicornis longicornis, C. sclerosus, C. tilapiae, and Enterogyrus malmbergi. We found all these parasite species, except C. haplochromii and C. dossoui, on the native C. fenestratum and C. callolepis. Prevalences of Cichlidogyrus spp. were 3-10% and abundances ranged from 0.03 +/- 0.2 to 0.1 +/- 0.3 for native cichlids. We only recovered a single E. malmbergi from 1 C. callolepis. We found Sciadicleithrum bravohollisae, a monogenean of native Cichlasoma spp., on the gills of the introduced O. aureus from Lake Catemaco (prevalence 3%, abundance 0.03 +/- 0.2). Although prevalence and abundance in atypical hosts were fairly low, the present findings provide evidence of monogenean transfer from African to American cichlids and vice versa. This is the first record of exotic monogeneans in the genus Cichlidogyrus and Enterogyrus infecting native American cichlid fish. It is also the first record from southeastern México of a native American monogenean infecting introduced African cichlids.     

Climate refugia for Pinus spp. in topographic and bioclimatic environments of the Madrean sky islands of México and the United States

Climate refugia, or places where habitats are expected to remain relatively buffered from regional climate extremes, provide an important focus for science and conservation planning. Within high-priority, multi-jurisdictional landscapes like the Madrean sky islands of the United States and México, efforts to identify and manage climate refugia are hindered by the lack of high-quality and consistent transboundary datasets. To fill these data gaps, we assembled a bi-national field dataset (n?=?1416) for five pine species (Pinus spp.) and used generalized boosted regression to model pine habitats in relation to topographic variability as a basis for identifying potential microrefugia at local scales in the context of current species’ distribution patterns. We developed additional models to quantify climatic refugial attributes using coarse scale bioclimatic variables and finer scale seasonal remote sensing indices. Terrain metrics including ruggedness, slope position, and aspect defined microrefugia for pines within elevation ranges preferred by each species. Response to bioclimatic variables indicated that small shifts in climate were important to some species (e.g., P. chihuahuana, P. strobiformis), but others exhibited a broader tolerance (e.g., P. arizonica). Response to seasonal climate was particularly important in modeling microrefugia for species with open canopy structure and where regular fires occur (e.g., P. engelmannii and P. chihuahuana). Hotspots of microrefugia differed among species and were either limited to northern islands or occurred across central or southern latitudes. Mapping and validation of refugia and their ecological functions are necessary steps in developing regional conservation strategies that cross jurisdictional boundaries. A salient application will be incorporation of climate refugia in management of fire to restore and maintain pine ecology. Una versión en español de este artículo está disponible como descarga.

     

Diversity, abundance and icthyofaunistic groups of the Chantuto-Panzacola lagoon-estuarine system, Chiapas, México

In the Chantuto-Panzacola system, Chiapas, México, a study of a fish community was carried out between March and November of 1997. From a total of 1456 fish collected, 31 species, 25 genera and 19 families had been identified. The diversity and abundance were high in March with H'= 2.67 bits/ind, D = 3.89 sp/ind, biomass 1.88 g/m2. density 0.25 ind/m2 and average weight 7.55 g/ind. Significant differences were found between the ecological parameters and the environmental variables of the ecosystem in the months of study (ANOVA and Tukey, p < 0.05). The multiple discriminant analysis showed that the temperature and the salinity was the most important factors in the variation of the community. The frequency analysis and spatial distribution of the fish allowed to define fish assemblages formed by several groups of species that inhabits the system. Nine dominant species were defined for the ecosystem, representing the 71% in number and the 76.4% in weight of the total catch, Achirus mazatlanus, Caranx hippos, Cathorops fuerthi, Centropomus robalito, Cichlasoma macracanthum, Cichlasoma trimaculatum, Gobiomorus maculatus, Gobionellus microdon and Lile gracilis.     

Gastropods and bivalves of commercial interest from the continental shelf of Jalisco and Colima,México

The distribution and abundance with respect to depth and type of substratum of 20 species of gastropods and four species of bivalves of economic importance were examined in the continental shelf of Jalisco and Colima, México. These species were taken with net trawls at depths from 24 to 83 m in August, 1988. Most individuals and species of gastropods were collected in stations with sandy silt substratum. Bivalves were collected in sandy silt and medium sand substrata. The six most abundant species represented 81.2% of all gastropods and bivalves collected. These species are: Cantharus pallidus, Fusinus dupetittouarsi, Ficus ventricosa, Hexaplex brassica, Harpa conoidalis and Arca pacifica.     

Interferon-γ release assays for the diagnosis of tuberculosis and tuberculosis infection in HIV-infected adults: a systematic review and meta-analysis

Background

Despite the widespread use of interferon-γ release assays (IGRAs), their role in diagnosing tuberculosis and targeting preventive therapy in HIV-infected patients remains unclear. We conducted a comprehensive systematic review to contribute to the evidence-based practice in HIV-infected people.

Methodology/Principal Findings

We searched MEDLINE, Cochrane, and Biomedicine databases to identify articles published between January 2005 and July 2011 that assessed QuantiFERON®-TB Gold In-Tube (QFT-GIT) and T-SPOT®.TB (T-SPOT.TB) in HIV-infected adults. We assessed their accuracy for the diagnosis of tuberculosis and incident active tuberculosis, and the proportion of indeterminate results. The search identified 38 evaluable studies covering a total of 6514 HIV-infected participants. The pooled sensitivity and specificity for tuberculosis were 61% and 72% for QFT-GIT, and 65% and 70% for T-SPOT.TB. The cumulative incidence of subsequent active tuberculosis was 8.3% for QFT-GIT and 10% for T-SPOT.TB in patients tested positive (one study each), and 0% for QFT-GIT (two studies) and T-SPOT.TB (one study) respectively in those tested negative. Pooled indeterminate rates were 8.2% for QFT-GIT and 5.9% for T-SPOT.TB. Rates were higher in high burden settings (12.0% for QFT-GIT and 7.7% for T-SPOT.TB) than in low-intermediate burden settings (3.9% for QFT-GIT and 4.3% for T-SPOT.TB). They were also higher in patients with CD4⁺ T-cell count <200 (11.6% for QFT-GIT and 11.4% for T-SPOT.TB) than in those with CD4⁺ T-cell count ≥200 (3.1% for QFT-GIT and 7.9% for T-SPOT.TB).

Conclusions/Significance

IGRAs have suboptimal accuracy for confirming or ruling out active tuberculosis disease in HIV-infected adults. While their predictive value for incident active tuberculosis is modest, a negative QFT-GIT implies a very low short- to medium-term risk. Identifying the factors associated with indeterminate results will help to optimize the use of IGRAs in clinical practice, particularly in resource-limited countries with a high prevalence of HIV-coinfection.     

Medicinal plants in the southern region of the State of Nuevo León,México

Background

Although the flora of the State of Nuevo León is well known, there are few records of ethnobotancial information. An ethnobotanical study was undertaken in order to know the medicinal plants used by people living at the scrublands and oak-pine forest areas in the southern Nuevo León. Collection of plants specimens and interviews were carried out among the people of the municipalities of Aramberri, Galeana, and Zaragoza. Since former studies in the region are scarce, the aim of this work was to record the medicinal species and their uses in the scrublands and oak-pine forest areas, of southern Nuevo León, Mexico, and also to know if there are differences in the number of species and number of uses knowledge by people.

Methods

Field work was carried out over a 2 years period; useful plants were collected and a total of 105 people from 46 different villages were interviewed. A database was compiled using data collected by means of semi structured interviews. The data were analyzed by means of non-parametric statistics, using goodness-of-fit test (Chi-squared) (number of species known by people of each municipality, number of uses known by people of each municipality), Chi-squared modified to incorporate the Yates Correction (number of species known by people living at scrublands and oak-pine forest); the Kruskall-Wallis test (number of species known by women and men of the three municipalities), and the Spearman’s rank correlation coefficient (age and number of species known, and age and number of uses).

Results

A total of 163 medicinal plant species were recorded in the study area, comprising 108 wild and 55 cultivated plants. A total of 117 species were recorded in the oak-pine forest, and 111 in the scrublands area, a total of 68 were recorded in both areas; 68 medicinal species are used in all three municipalities, 40 wild and 28 cultivated. We documented 235 different medicinal uses. The most common plant parts used for medicinal purposes were found to be leaves (123 species), stems (55), fruits (28), roots (17), and bark (14). No differences were noted in the number of medicinal plant species identified among people, but differences were significant in their knowledge with respect to the number of uses among people of the three municipalities studied; people from both, scrublands and oak-pine forest know similar number of species and number of uses. Men and women of the three different municipalities knew statistically the same number of species and number of uses. There was no correlation between resident’s age and number of species known and resident’s age and number of uses either in Galeana or in Aramberri, but, there was high correlation among these variables in Zaragoza.

Conclusion

In southern Nuevo León people use at least 5% of the total State flora as medicinal plants, and most of these species are included in few plant families. Most of medicinal species are wild and indigenous to the region. The two most important major plant communities, scrublands and oak-pine forest provide almost the same number of medicinal species. A third of the medicinal flora recorded are used in all three municipalities, most of them are wild. Leaves, stems and fruits are the plant parts most commonly used for healing, and boiling is the most common method used for this purpose. Men and women from the three municipalities are familiar with nearly the same number of species; however, their knowledge of the number of uses varies significantly. In Galeana and Aramberri there was no correlation between a person’s age and number of species recognized, however, in Zaragoza, there existed a high correlation between these two factors.

     

Presence, abundance and reproductive strategies of ferns in disturbed areas of Sierra Nevada, México

Diverse reproductive strategies shown by ferns and lycophytes allow them to colonize a variety of habitats, particularly after the incidence of natural or anthropogenic disturbances. This study assessed the presence, abundance and reproductive strategies of ferns growing in soils of temperate forests with different levels of disturbance at the Sierra Nevada mountain range in the State of Mexico. Vegetation, soil and environmental variables were recorded in 200 m2 permanent plots located in four forest stands. One-Way ANOVA and Canonical Correspondence Analysis resulted in the recognition of three landscape types defined by the degree of environmental alteration: low, moderate and severe. Also, from five soil samples collected in each stand, germination of ferns and lycophytes was induced. A positive relationship was found between the alteration degree and Cheilanthes abundance. Under a low landscape alteration regime, species richness is restricted to Cheilanthes bonariensis, C. marginata and Pellaea ternifolia subsp. ternifolia. The soil is a reservoir of spores of Cheilanthes and Pellaea ternifolia subsp. ternifolia because their spores can remain viable for different time intervals. Apogamy is the usual reproductive strategy of Cheilanthes species in disturbed ecosystems, although these species also show sexual reproduction in natural ecosystems with adequate water availability. Apogamy may be related to a shorter generation time in comparison with a low disturbed ecosystem. On the other hand, Pellaea ternifolia subsp. ternifolia only has sexual reproduction. Apogamy might be related to a faster generation in comparison with a low disturbed ecosystem.     

Growth and survival of seeds of the oyster Crassostrea virginica in a shrimp farm in Yucatán, México

A lot of 1600 seeds of American oyster Crassostrea virginica from the coastal lagoon La Redonda, Tabasco, Mexico was cultured in main drainage channel (S1), a secondary drainage channel (S2), the floodgate of a white shrimp Pennaeus vannamei pond (S3) and the marine water supply pond (S4). The seeds, with a total height and initial humid weight of 31.67 +/- 3.43 mm and 4.29 +/- 1.32 g, respectively, were cultured in suspended Nestier oyster boxes at 575 org/m2. Biological and environmental parameters were recorded after 296 days, the seeds in S4 reached height and weight values of 52.55 +/- 7.51 mm and 16.30 +/- 4.94 g, respectively. The index of physiologic condition along the experiment had a variation of 1.26% to 3.45%. In S4 the survival was 81.0%. In the other places the mortality was total after 90 days.     

Oceanographic conditions and diversity of sea stars (Echinodermata: Asteroidea) in the Gulf of California, México

Species richness is one of the best indicators of biodiversity. However, there are few investigations on concordance of diversity patterns and environmental settings for marine regions. The objectives of this study were to correlate species richness of shallow water (< 200 m deep) sea stars with key oceanographic factors in the Gulf of California, México, and to predict species richness of Asteroidea using multiple regressions. In these analyses the Gulf was divided into nine sections of one degree in latitude (from 23-31 degrees N), at each section we recorded: continental shelf area (at 100 and 200 m depth), temperature mean and range at three depth levels (0, 60 and 120 m), thermocline depth, surface nutrient concentrations (nitrates, phosphates and silicates), surface photosynthetic pigment concentration, and integrated productivity. Sea star species richness at each latitudinal section was estimated from literature data, new collections and museum records. Species were assigned to one of the following feeding guilds: predators of small mobile invertebrates (I), detritivores (D), predators of colonial organisms (C), generalist carnivores (G), and planktivores (P). There are 47 shallow water asteroid species in the Gulf of California (16 I, 15 D, eight C, six G, one P and one not assigned). Total species richness and guild species richness showed strong latitudinal attenuation patterns and were higher in the southernmost Gulf, an area characterized by a narrow shelf, high temperature, and low nutrient concentrations. Species diversity for each guild was correlated to a set of oceanographic parameters: temperature, nitrate concentration, and integrated productivity were linked to richness in must cases. We detected that nutrients and surface pigments always presented negative relationships with species richness, indicating that productive environments limit asteroid diversity in the study area. Finally, the postulated regression models to estimate species richness from oceanographic data were significant and highly precise. We conclude that species richness of Asteroidea in the Gulf of California is related to oceanographic conditions and can be estimated from regional oceanographic information.     

Helminth parasites of the blue-footed booby on Isla Isabel, México

A survey of the helminth fauna of the blue-footed booby, Sula nebouxii, on Isla Isabel, off the Pacific coast of México, is presented. Eight parasite species were found: 4 digeneans (Galactosomum puffini , Mesostephanus microbursa, Opisthometra planicollis, and Renicola thapari), 3 nematodes (Contracaecum sp., Porrocaecum sp., and Tetrameres sp.), and 1 cestode (Tetrabothrius sp). All these species are reported for the first time in the blue-footed booby, and they represent 8 new locality records as well. Species accumulation curves suggest these 8 parasite species comprise the total helminth fauna of this population of boobies. The most frequent and abundant parasite was R. thapari, inhabiting the kidney of its host. In male boobies, a significant negative correlation was found between abundance of R. thapari and host body condition.     

Environmental factors that modulate the release and transport of airborne urediniospores Hemileia vastatrix (Berk. & Broome) in coffee crops in Veracruz México

The coffee leaf rust, Hemileia vastatrix, is the most destructive coffee-growing disease and the most important economically. More aggressive outbreaks of the disease were recently reported worldwide, including in Mexico, where coffee production showed a 40% decrease. This work aimed to determine the environmental conditions that favor release and air transport of the H. vastatrix urediniospores in coffee crops in Veracruz. The monitoring of airborne coffee leaf rust urediniospores was performed using three types of aerobiological traps at different heights: Hirst Spore Trap (HST, 1.5 m), Passive Spore Trap (PST 1.5, 3, 6, and 9 m), and Sedimentation Spore Sampler (SSS 1 m) from January 2014 to October 2015, in two plots in Veracruz, Mexico. The airborne urediniospores counts exhibited a bimodal distribution. Low concentrations that increase over time are evident from January to April, decreasing abruptly in May and June, only to rise again in August, reaching the highest record for airborne urediniospores during the mid-summer drought phenomenon. Dispersal of coffee rust urediniospores is mainly influenced by temperature, rain, wind, and humidity in leaves. They can reach heights in the air up to 9 m (above the canopy) in shade coffee crops. The dispersal of pathogens in the atmosphere comprises complex processes interconnected; their knowledge allows better comprehensive management of them.

     

Role of Fish in Structuring Invertebrates on Stromatolites in Cuatro Ciénegas, México

Stromatolites, the dominant Precambrian life form, declined in the Phanerozoic to occur today in only a few sites. This decline has been attributed to evolution of metazoan grazers, but stromatolites in our study site, Cuatro Ciénegas, Coahuila, México, harbor diverse macroinvertebrates. Drawing on food chain theory, we hypothesized that fish predation on invertebrates controls invertebrate populations, allowing stromatolites to flourish in Cuatro Ciénegas. Our experiment used small mesh (1 mm) cages to exclude all but larval fishes, and larger (6.5 mm) cages to exclude all larger fishes (including the molluscivorous and omnivorous endemic polymorphic cichlid, Herichthys minckleyi), but allow access to all sizes of the abundant endemic pupfish, Cyprinodon bifasciatus. No effects of treatments on invertebrate densities were noted at 6 week, but significant effects were observed on specific taxonomic groups after 3 month. In absence of fishes, hydrobiidae snails and ceratopogonids increased 3- and 5-fold, respectively, and invertebrate assemblage composition varied among treatments. Algal biomass was not affected by treatments, but algal species composition appeared to change. Overall results suggest that fish assemblages structure invertebrate assemblages, and that fishes may also be factors in determining algal communities.