Supercooling along an Altitudinal Gradient in Espeletia schultzii, a Caulescent Giant Rosette Species

Rada, F., Goldstein, G., Azocar, A. and Torres, F. 1987. Supercoolingalong an altitudinal gradient in Espeletia schultzii, a caulescentgiant rosette species.—J. exp. Bot. 38: 491–497. Tropical high Andes plants may be exposed to sub-zero temperaturesany night of the year. These plants have to rely on mechanismswhich protect them from these environmental conditions but atthe same time allow their growth and development. Supercoolinghas been found to be the principal avoidance mechanism in leavesof the caulescent giant rosette genus Espeletia in the Andes.We report here the differences in supercooling capacity andcold injury in several Espeletia schultzii populations growingalong an altitudinal gradient. The relationships between supercooling,water potential and leaf anatomy were also investigated. Thesupercooling capacity increased and injury temperature decreasedfrom lower to higher elevation populations. These changes maybe explained in terms of physiological, morphological and anatomicalcharacteristics of the leaves. Key words: Espeletia schultzii, supercooling, freezing avoidance mechanisms     

Euplotes Cytoskeleton: Tubulin and Microtubular Systems in Interphase1,2

The Euplotes cytoskeleton obtained by treatment with Triton X-100 in a microtubule-stabilizing buffer has been studied by electron microscopy and SDS-polyacrylamide electrophoresis. An antiserum has been prepared using the tubulin band from preparative gels of Euplotes cytoskeletons as an antigen. This antiserum reacts with the tubulin from different ciliated protozoa but fails to recognize the vertebrate tubulin by immunoblotting. Immunoblotting studies have demonstrated a slower electrophoretic mobility for the α-tubulin of Euplotes and Oxytricha than that of Paramecium and Tetrahymena. A cytoplasmic microtubular network in Euplotes has been revealed by indirect immunoftuorescence using both an anti-α-tubulin monoclonal antibody directed against chick brain tubulin and an antiserum raised against the tubulin of Euplotes.     

Morphological Modifications of Oocyte Vitelline Envelope from Bufo arenarum during Different Functional States

The submicroscopic morphology of the vitelline envelope of Bufo arenarum's oocyte change significantly during the maturation and fertilization processes. The morphological changes are related to physiological activity in vivo and can be triggered in vitro by experimental procedures. It is our scope to present the ultrastructure differences of fascicular components of the vitelline envelope in coelomic, "pars recta" conditioned, oviductal, oviposited and fertilized oocytes. Our experimental results indicate that artificial "pars recta" treatment of coelomic oocytes arrange the fascicular components as those of oviposited oocyte, although differences still remain indicating that additional maturation processes take place while the egg pass througth the oviduct. Fertilized or activated oocytes which are refractary to sperm penetration, change the vitelline envelope fascicular components orientation giving a submicroscopical image quite different to those of none fertilized oocytes. These ultrastructural changes define in a clear cut manner the functional states of Bufo arenarum's oocyte.     

Morphological and molecular taxonomy of a new Daptonema (Nematoda,Xyalidae) with comments on the systematics of some related taxa

A new species of Daptonema is described based upon morphological characters and 18S rRNA sequence. Daptonema matrona sp. nov. was collected in Pina Basin (north‐eastern Brazil). It differs from all other species of the genus by the presence of reduced cephalic setae and straight spicules. These features require an adaptation of the generic diagnosis. Moreover, the females are characterized by intra‐uterine development of the offspring, considered herein as their major autapomorphic feature. Molecular systematic analyses supported Daptonema matrona sp. nov. as a distinct genetic and evolutionary lineage. The data also indicate hypotheses of taxonomic synonymies amongst some related taxa from Xyalidae as well as the paraphyly of Daptonema. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158 , 1–15.     

Texas Latino College Student Attitudes Toward Natural Resources and the Environment

Abstract: Latinos in the United States are an increasing segment of the population and are becoming important stakeholders in the management of natural resources. Although Latinos have been included in attitudinal research on environmental concerns, few studies have focused exclusively on Latino attitudes toward natural resources and the environment. We surveyed Texas college and university students of Mexican descent (n = 635) to determine their environmental concerns. Using the New Ecological Paradigm (NEP), we determined an environmental concern score for each respondent and compared this index to several demographic variables. We found that gender, a political candidate's environmental position, mother's education, combined parental income, and, to a lesser degree, the number of grandparents born in the United States and religiosity (church attendance), were important model variables. We hypothesized that acculturation would be an important factor in predicting NEP scores; however, acculturation level was not an important predictor in our study, which we attribute to both the nature of our sample (i.e., highly acculturated college students) and small sample sizes of less-acculturated college students. We recommend that future research consider determining the importance of acculturation in Latino attitudes toward natural resources and the environment.     

Role of chemical cues and natal rearing effect on host recognition by the parasitic wasp Melittobia digitata

Parasitoids are expected to have the ability to find, recognize, and perhaps to discern potential hosts that can best support the development of their progeny. Melittobia Westwood (Hymenoptera: Eulophidae) are gregarious ectoparasitoids, which primarily attack mud daubers (Hymenoptera: Sphecidae). How Melittobia females locate their host is not well known, but the process may involve host‐related chemical signals. In this study, we investigated the roles of host chemical cues and natal rearing effect in host recognition by Mel. digitata Dahms. In an olfactometer that contained prepupae of Trypoxylon politum Say (Hymenoptera: Sphecidae), Megachile rotundata (Fabricius) (Hymenoptera: Megachilidae), puparia of Neobellieria bullata (Parker) (Diptera: Sarcophagidae), empty or intact host cocoons, or nest mud, Mel. digitata females spent significantly more time in air fields that contained T. politum (prepupae + cocoon) and Meg. rotundata (prepupae + cocoon) than in N. bullata and control fields. Nest mud and natal host had no attraction for parasitoid host choice. Most first and last choices of Mel. digitata females in the olfactometer were not consistent, suggesting an initial random dispersion, although they responded positively towards hosts in cocoons.     

Bird community composition across an Andean tree‐line ecotone

Few studies have found strong evidence to suggest that ecotones promote species richness and diversity. In this study we examine the responses of a high‐Andean bird community to changes in vegetation and topographical characteristics across an Andean tree‐line ecotone and adjacent cloud forest and puna grassland vegetation in southern Peru. Over a 6‐month period, birds and vegetation were surveyed using a 100 m fixed‐width Distance Sampling point count method. Vegetation analyses revealed that the tree‐line ecotone represented a distinctive high‐Andean vegetation community that was easily differentiated from the adjacent cloud forest and puna grassland based on changes in tree‐size characteristics and vegetation cover. Bird community composition was strongly seasonal and influenced by a pool of bird species from a wider elevational gradient. There were also clear differences in bird community measures between tree‐line vegetation, cloud forest and puna grassland with species turnover (β‐diversity) most pronounced at the tree‐line. Canonical Correspondence Analysis revealed that the majority of the 81 bird species were associated with tree‐line vegetation. Categorizing patterns of relative abundance of the 42 most common species revealed that the tree‐line ecotone was composed primarily of cloud forest specialists and habitat generalists, with very few species from the puna grassland. Only two species, Thlypopsis ruficeps and Anairetes parulus, both widespread Andean species more typical of montane woodland vegetation edges, were categorized as ecotone specialists. However, our findings were influenced by significant differences in species detectability between all three vegetation communities. Our study highlights the importance of examining ecotones at an appropriate spatial and temporal scale. Selecting a suitable distance between sampling points based on the detection probabilities of the target bird species is essential to obtain an unbiased picture of how ecotones influence avian richness and diversity.     

Isolation of seven polymorphic microsatellite loci,using an enrichment protocol,in the high Andean Asteraceous Chaetanthera pusilla

We report the development of seven microsatellite markers in the high Andean Asteraceae Chaetanthera pusilla. An enrichment protocol was used to isolate microsatellite loci, and polymorphism was explored with samples from two natural populations collected in the high Andes at La Parva and Valle Nevado (Chile). We found a high level of polymorphism, heterozygote deficiency and strong differentiation among populations. Four of the seven loci successfully cross‐amplified in other Chaetanthera species.     

Effect of thermal acclimation on preferred temperatures in two mygalomorph spiders inhabiting contrasting habitats

Variations in the preferred temperatures during the rest periods of Grammostola rosea Walckenaer and Paraphysa parvula Pocock, two mygalomorph spiders occupying different habitats in central Chile, are analyzed. The former inhabits arid and semi‐arid lowland near plant communities, composed of shrubs (evergreens with small leathery leaves) and small trees; the latter is found in the central mountains of the Chilean Andes, above 2000 m.a.s.l. The preferred temperatures of these spiders at different times of day and exposure to cold (15 °C) and warm (25 °C) acclimation temperatures are compared. Body mass does not affect the preferred temperature of the larger spider G. rosea, although P. parvula, a spider with half of the body mass of G. rosea, shows a decrease in preferred temperature with body mass. This can be explained by a higher plasticity and thermal sensitivity of the smaller species as result of increased surface : volume ratio. The preferred temperature increases with the hour of the day under both acclimation conditions in P. parvula and in cold‐acclimated G. rosea, which is likely associated with crepuscular and nocturnal behaviour in both species. Grammostola rosea shows temperature preferences lower than those of P. parvula under both acclimation conditions. The increase of the acclimation temperature from 15 to 25 °C results in an increment of 2–3 °C in the preferred temperature of P. parvula but only 0.2 °C in that of G. rosea. Two contrasting lifestyle strategies are found: a small mygalomorph spider with phenotypic plasticity and adaptation to the fluctuating environment of high altitude, and a large mygalomorph spider with higher thermal inertia adapted to the more stable environment of lowlands.