A new species of Ceratozamia (Zamiaceae) from Tabasco and Chiapas, Mexico

Ceratozamia becerrae sp. nov. is described and illustrated. This species from Tabasco and Chiapas has affinity with C. miqueliana H. Wendl. from Veracruz and Chiapas, but differs in morphology and habit of leaves, leaflets, male and female strobili and trunk. Ceratozamia becerrae is considered part of the C. miqueliana species complex that includes C. miqueliana, C. euryphyllidia Vázq.Torres, Sabato & Stevenson and C. zoquorum Pérez-Farrera, Vovides & Iglesias. The geographical range of this species complex is southern Veracruz, Tabasco and northern Chiapas in tropical rain forests.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 123–128.     

Cladosporium fulvum (syn. Passalora fulva), a highly specialized plant pathogen as a model for functional studies on plant pathogenic Mycosphaerellaceae

Taxonomy:  Cladosporium fulvum is an asexual fungus for which no sexual stage is currently known. Molecular data, however, support C. fulvum as a member of the Mycosphaerellaceae, clustering with other taxa having Mycosphaerella teleomorphs . C. fulvum has recently been placed in the anamorph genus Passalora as P. fulva . Its taxonomic disposition is supported by its DNA phylogeny, as well as the distinct scars on its conidial hila, which are typical of Passalora , and unlike Cladosporium s.s. , which has teleomorphs that reside in Davidiella , and not Mycosphaerella .
Host range and disease symptoms:  The presently known sole host of C. fulvum is tomato (members of the genus Lycopersicon ). C. fulvum is mainly a foliar pathogen. Disease symptoms are most obvious on the abaxial side of the leaf and include patches of white mould that turn brown upon sporulation. Due to stomatal clogging, curling of leaves and wilting can occur, leading to defoliation.
C. fulvum as a model pathogen:  The interaction between C. fulvum and tomato is governed by a gene-for-gene relationship. A total of eight Avr and Ecp genes, and for four of these also the corresponding plant Cf genes, have been cloned. Obtaining conclusive evidence for gene-for-gene relationships is complicated by the poor availability of genetic tools for most Mycosphaerellaceae – plant interactions. Newly developed tools, including Agrobacterium -mediated transformation and RNAi, added to the genome sequence of its host tomato, which will be available within a few years, render C. fulvum attractive as a model species for plant pathogenic Mycosphaerellaceae.
Useful websites:  http://www.sgn.cornell.edu/help/about/index.html ; http://cogeme.ex.ac.uk     

Isolation and characterization of microsatellite loci in the highland papaya Vasconcellea × heilbornii V. Badillo (Caricaceae)

Nine polymorphic microsatellite loci were identified in the tropical plant Vasconcellea ×heilbornii and used to estimate allelic diversity in two populations of southern Ecuador. Allelic richness ranged from two to five alleles, observed heterozygosity ranged from 0.150 to 0.947 and expected heterozygosity ranged from 0.186 to 0.701. Most of these markers also amplified microsatellite loci in two other Vasconcellea species (Vasconcellea stipulata and Vasconcellea cundinamarcensis). Hence, these markers will be useful for population genetic analysis and the evaluation of genetic diversity and gene flow in these species.     

Variation in litter under individual tree crowns: Implications for scattered tree ecosystems

In forest ecosystems litter is usually assessed in terms of the average amount produced by the canopy. In scattered tree ecosystems this approach is problematic because the canopy is discontinuous and the spatial arrangement of litter highly variable. We addressed this problem by quantifying the spatial variation in litter load and litter composition associated with individual trees in a Eucalyptus melliodora – Eucalyptus blakelyi woodland. Litter was sampled under crowns and in grassland adjacent to 10 E. blakelyi and 10 E. melliodora trees ranging in diameter at breast height (dbh) from 14 to 129 cm. A total of 302 L samples were collected from these trees, at distances ranging from 0 to 42 m from main stem. The sampled litter loads ranged from 0.02 to 109.3 t ha^?1 and were significantly higher under tree crowns than in grassland for litter and each component of litter (leaves, bark, fine twigs, coarse twigs). In particular, the mean litter load under tree crowns (12.5 t ha^?1) was an order of magnitude higher than the mean litter load in grassland (1.27 t ha^?1). There was a significant (P = 0.0103) positive relationship between mean litter load under the tree crown and dbh, indicating larger trees produced more litter per unit area of ground than smaller trees. Generalized Linear Modelling produced highly significant (P < 0.0001) models predicting the spatial variation in litter load and litter composition in terms of distance from main stem and dbh. Our models demonstrate gradients in litter load and composition under tree crowns. These gradients were most pronounced for the large trees in our study. The disproportionate input of litter and variety of litter components associated with large trees in our study supports their keystone role in scattered tree ecosystems and highlights the need to maintain these structures in agricultural landscapes.     

Wind Energy Development and Wildlife Conservation: Challenges and Opportunities

ABSTRACT Wind energy development represents significant challenges and opportunities in contemporary wildlife management. Such challenges include the large size and extensive placement of turbines that may represent potential hazards to birds and bats. However, the associated infrastructure required to support an array of turbines—such as roads and transmission lines—represents an even larger potential threat to wildlife than the turbines themselves because such infrastructure can result in extensive habitat fragmentation and can provide avenues for invasion by exotic species. There are numerous conceptual research opportunities that pertain to issues such as identifying the best and worst placement of sites for turbines that will minimize impacts on birds and bats. Unfortunately, to date very little research of this type has appeared in the peer-reviewed scientific literature; much of it exists in the form of unpublished reports and other forms of gray literature. In this paper, we summarize what is known about the potential impacts of wind farms on wildlife and identify a 3-part hierarchical approach to use the scientific method to assess these impacts. The Lower Gulf Coast (LGC) of Texas, USA, is a region currently identified as having a potentially negative impact on migratory birds and bats, with respect to wind farm development. This area is also a region of vast importance to wildlife from the standpoint of native diversity, nature tourism, and opportunities for recreational hunting. We thus use some of the emergent issues related to wind farm development in the LGC—such as siting turbines on cropland sites as opposed to on native rangelands—to illustrate the kinds of challenges and opportunities that wildlife managers must face as we balance our demand for sustainable energy with the need to conserve and sustain bird migration routes and corridors, native vertebrates, and the habitats that support them.     

How a bottom‐dweller beats the canopy: inhibition of an aquatic weed (Potamogeton pectinatus) by macroalgae (Chara spp.)

1. Bottom‐dwelling charophytes have been observed to replace canopy‐forming pondweeds within a few years in de‐eutrophied shallow lakes. Competition for bicarbonate (HCO₃^?) may explain this shift in vegetation dominance but inhibition of pondweeds by Chara spp. through direct competition has not been shown experimentally. 2. We tested whether charophytes inhibited growth of fennel pondweed (Potamogeton pectinatus) in the absence of belowground competition by growing plants in pots in mesocosms following a replacement series experimental design. To further understand the role of bicarbonate, we studied main and interactive effects of Chara, light and bicarbonate on P. pectinatus growth in a laboratory study. 3. Early in the mesocosm experiment, high charophyte densities had a negative effect on P. pectinatus cover at a time when bicarbonate levels were low. However, bicarbonate levels eventually converged to low levels in all treatments. At final harvest, both species exhibited lower biomasses at higher densities of conspecific pots, indicating that ultimately intraspecific competition was limiting. In a laboratory study, Chara inhibited P. pectinatus the most under a combination of high light and high bicarbonate concentrations, suggesting that Chara may negatively affect P. pectinatus by acting as a general nutrient sink. 4. Our results suggest that Chara growth can reduce bicarbonate levels, delaying but not preventing a P. pectinatus growth pulse. Given the recorded inhibition under ample bicarbonate supply, Chara’s ability to act as nutrient sink may contribute to the decline of P. pectinatus under Chara recovery in shallow lakes.     

Isozymes of Glutamate Dehydrogenase in Chlamydomonas reinhardi*, †

SYNOPSIS. Two electrophoretically distinct forms of glutamate dehydrogenase were found in extracts of Chlamydomonas reinhardi. The slower moving of these was detectable only when the cells were grown organotrophically. The other, more active, enzyme copurified with chloroplasts and was not electrophoretically detectable in extracts of organotrophically grown cultures of the y-2 mutant strain; this absence was not apparent in wild type or in the mutant strain y-1. Both forms of the enzyme were cofactor non-specific.     

Isolation of a Strain of Chlamydomonas reinhardi with Altered Control of Glyceraldehyde 3-Phosphate Dehydrogenase*, †

SYNOPSIS. A strain of Chlamydomonas reinhardi is described in which the control of glyceraldehyde 3-P dehydrogenase is altered; the activity of the NADP-dependent enzyme is apparently independent of chlorophyll content.     

Misclassified Resource Selection: Compositional Analysis and Unused Habitat

Abstract: During the past decade, compositional analysis (CA) has been used widely in animal—habitat and resource selection studies. Despite this popularity, CA has not been tested for potential systematic biases such as incorrect identification of preferred resources. We used computer-simulated data based on known habitat use and availability parameters to assess the potential for CA to incorrectly identify preferred habitat use. We consider in particular the situation when available habitat categories not used by all animals are included in the resource selection analysis, with substitution of a relatively small value, such as 0.01, for each 0% utilization value. Progressively larger misclassification-error*** rates in preferred habitat use resulted from substituting progressively smaller positive values for each 0% utilization of a habitat category.