Pollinator sharing in dioecious figs (Ficus: Moraceae)

As one of the most specialized pollination syndromes, the fig (Ficus)–fig wasp (Agaonidae) mutualism can shed light on how pollinator behaviour and specificity affect plant diversification through processes such as reproductive isolation and hybridization. Pollinator sharing among species has important implications for Ficus species delimitation and the evolutionary history of the mutualism. Although agaonid wasp pollinators are known to visit more than one host species in monoecious figs, pollinator sharing has yet to be documented in dioecious figs. The present study investigated the frequency of pollinator sharing among sympatric, closely‐related dioecious figs in Ficus sections Sycocarpus and Sycidium. Molecular and morphological species identification established the associations between pollinating agaonid wasp species and host fig species. Cytochrome oxidase I was sequenced from 372 Ceratosolen pollinators of Ficus section Sycocarpus and 210 Kradibia pollinators of Ficus section Sycidium. The association between fig species and morphologically distinct clades of pollinator haplotypes was predominantly one‐to‐one. In Ceratosolen, six of 372 pollinators (1.5%) visited fig species other than the predominant host. No pollinator sharing was detected between the two Sycidium host species, although a rare hybrid shared Kradibia pollinators with both parental species. These findings point to low rates of pollinator sharing among closely‐related dioecious fig species in sympatry, and perhaps lower rates than among monoecious figs. Such rare events could be evolutionarily important as mechanisms for gene flow among fig species. Differences in rates of pollinator sharing among fig lineages might explain the conflicting phylogenetic patterns inferred among monoecious figs, dioecious figs, and their respective pollinators. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 546–558.     

The dynamic pipeline: hydraulic capacitance and xylem hydraulic safety in four tall conifer species

Recent work has suggested that plants differ in their relative reliance on structural avoidance of embolism versus maintenance of the xylem water column through dynamic traits such as capacitance, but we still know little about how and why species differ along this continuum. It is even less clear how or if different parts of a plant vary along this spectrum. Here we examined how traits such as hydraulic conductivity or conductance, xylem vulnerability curves, and capacitance differ in trunks, large‐ and small‐diameter branches, and foliated shoots of four species of co‐occurring conifers. We found striking similarities among species in most traits, but large differences among plant parts. Vulnerability to embolism was high in shoots, low in small‐ and large‐diameter branches, and high again in the trunks. Safety margins, defined as the pressure causing 50% loss of hydraulic conductivity or conductance minus the midday water potential, were large in small‐diameter branches, small in trunks and negative in shoots. Sapwood capacitance increased with stem diameter, and was correlated with stem vulnerability, wood density and latewood proportion. Capacitive release of water is a dynamic aspect of plant hydraulics that is integral to maintenance of long‐distance water transport.     

Somatic and genetic factors in sun and shade population differentiation in Plantago lanceolata and Anthoxanthum odoratum

Differences between individuals collected from sun and shade populations could result from either somatic or genetic differences, particularly in populations of perennial plants. Our objective in this study was to separate somatic from genetic differences. We collected Anthoxanthum odoratum and Plantago lanceolata from sun and shade populations and made measurements on both vegetatively propagated clones and seed progeny from each clone. The parental populations differed in a wide range of physiological and morphological traits. However, only photosynthetic capacity was significantly different between both the original sun and shade populations and their seed progeny. In both species, plants from the sun population had higher photosynthetic capacities than those from the shade population when grown in a common environment. This demonstrates that there was genetic differentiation between the sun and shade populations. Photosynthetic capacity of parents and offspring also differed, suggesting a somatic effect. Since many of the original clones were virus-infected, but all but one of the offspring were virus-free, this might have been a result of virus infection. However, in spite of the fact that the parents and offspring clones were propagated vegetatively so that the plants were at the same developmental stage at the time of measurement, we cannot rule out the possibility that differences in age of cell lines could also have been a factor.     

THE GENUS GIGANTASPIS HEINTZ, 1962 (VERTEBRATA, HETEROSTRACI) FROM THE LOWER DEVONIAN OF SPITSBERGEN

Abstract:  Material collected in 1969 by the CNRS-MNHN expedition to Spitsbergen includes a new species of Gigantaspis , G. minima , which is the smallest known species of this genus. The revision of Gigantaspis leads to the inclusion of Zascinaspis laticephala Blieck and Goujet in this genus. The phylogenetic analysis presented herein suggests that Gigantaspis is close to Zascinaspis , as suggested by Blieck. Moreover, it is also close to generalized representatives of the Protaspididae. Their shared character states allow the definition of a possible ancestral morphotype for the Protaspididae.     

Metal cation binding by the hyperthermophilic microorganism,Archaea Methanocaldococcus Jannaschii,and its effects on silicification

Abstract: A series of experiments was conducted to determine the capacity of an archaeal strain, Methanocaldococcus jannaschii, to bind metals and to study the effects of metal binding on the subsequent silicification of the microorganisms. The results showed that M. jannaschii can rapidly bind several metal cations (Fe³⁺, Ca²⁺, Pb²⁺, Zn²⁺, Cu²⁺). Considering the lack of silicification of this strain without metal binding, these experiments demonstrate that Fe(III) ion binding to the cell wall components was of fundamental importance for successful silicification and, especially, for the excellent preservation of the cell wall. This study brings new elements to the understanding of fossilization processes, showing that the positive effect of Fe(III) on silicification, already known for Bacteria, can also apply to Archaea and that this preliminary binding can be decisive for the subsequent fossilization of these organisms. Knowledge of these mechanisms can be helpful for the search and the identification of microfossils in both terrestrial and extraterrestrials rocks, and in particular on Mars.     

Microsatellite markers for evolutionary studies in the sexually deceptive orchid genus Chiloglottis

The orchids in the genus Chiloglottis are pollinated exclusively by sexual deception. We describe 20 variable microsatellite loci that will facilitate the study of the evolution and ecology of this specialized pollination system. Two loci were isolated from Chiloglottis trilabra, with the rest derived from Chiloglottis valida. All loci were polymorphic in C. valida (H_E 0.07–0.87). Most loci amplified, and were variable within close relatives of C. valida, and a number amplified more broadly, including outside the genus.     

Methodologies for Surveying Herpetofauna Mortality on Rural Highways

Abstract: Road mortality can contribute to local and regional declines in amphibian and reptile populations. Thus, there is a need to accurately and efficiently identify hotspots of road-mortality for hazard assessment and mitigation. In 2002, we conducted walking and driving surveys throughout an extensive rural highway network in northern New York, USA, to evaluate survey methods and to quantify spatial and temporal patterns of herpetofauna road-mortality. In 2004, we repeated the surveys at a subset of locations to quantify interannual repeatability. Reptile and amphibian species had different peak periods of road-mortality because they differed in the causes of movements that resulted in crossings. Spatial locations of herpetofauna road-mortality were concentrated at a limited number of hotspots. Hotspots overlapped across species and were located at consistent locations across years. Results of walking and driving surveys were highly repeatable among survey teams, but driving surveys underestimated the density of road-mortality because many animals were missed. Detection failure was higher in some taxa (e.g., frogs) than others (e.g., turtles). Our results indicate that it is possible to design a valid, efficient methodology for locating hotspots of reptile and amphibian road-mortality along a road network and, thus, pinpoint priority sites for mitigation.     

Context‐dependent effects of mycorrhizae on herbivore density and parasitism in a tritrophic coastal study system

1. Stressful abiotic conditions and mycorrhizal fungi have both been shown to influence plant quality significantly, yet the interactive effects of these factors on relationships among plants, herbivores, and natural enemies remain unclear. 2. In this study, the results of a factorial field experiment are reported in which the effects of plant stress and mycorrhizae on density and parasitism of three herbivores of Baccharis halimifolia L. were examined. 3. Plant stress was increased by adding salt to the soil, and association with mycorrhizal fungi was increased by inoculating plant roots. 4. Inoculation with mycorrhizal fungi resulted in increased density of all three herbivore species, but the effects of mycorrhizae on parasitism varied by species and with soil salinity levels. For the gall maker Neolasioptera lathami Gagne, mycorrhizae decreased parasitism regardless of soil salinity levels. For the leaf miners Amauromyza maculosa Malloch and Liriomyza trifolii Burgess, mycorrhizae effectively negated the decrease in parasitism resulting from increased salinity. 5. The results of this study show that the effects of mycorrhizae on parasitism may be context dependent, and can be positive or negative depending upon species and environmental conditions.