Environment versus dispersal in the assembly of western Amazonian palm communities

Aim It is a central issue in ecology and biogeography to understand what governs community assembly and the maintenance of biodiversity in tropical rain forest ecosystems. A key question is the relative importance of environmental species sorting (niche assembly) and dispersal limitation (dispersal assembly), which we investigate using a large dataset from diverse palm communities. Location Lowland rain forest, western Amazon River Basin, Peru. Methods We inventoried palm communities, registering all palm individuals and recording environmental conditions in 149 transects of 5 m × 500 m. We used ordination, Mantel tests and indicator species analysis (ISA) to assess compositional patterns, species responses to geographical location and environmental factors. Mantel tests were used to assess the relative importance of geographical distance (as a proxy for dispersal limitation) and environmental differences as possible drivers of dissimilarity in palm species composition. We repeated the Mantel tests for subsets of species that differ in traits of likely importance for habitat specialization and dispersal (height and range size). Results We found a strong relationship between compositional dissimilarity and environmental distance and a weaker but also significant relationship between compositional dissimilarity and geographical distance. Consistent with expectations, relationships with environmental and geographical distance were stronger for understorey species than for canopy species. Geographical distance had a higher correlation with compositional dissimilarity for small‐ranged species compared with large‐ranged species, whereas the opposite was true for environmental distance. The main environmental correlates were inundation and soil nutrient levels. Main conclusions The assembly of palm communities in the western Amazon appears to be driven primarily by species sorting according to hydrology and soil, but with dispersal limitation also playing an important role. The importance of environmental characteristics and geographical distance varies depending on plant height and geographical range size in agreement with functional predictions, increasing our confidence in the inferred assembly mechanisms.     

Assessing water scarcity by simultaneously considering environmental flow requirements,water quantity,and water quality

Water scarcity is a widespread problem in many parts of the world. Most previous methods of water scarcity assessment only considered water quantity, and ignored water quality. In addition, the environmental flow requirement (EFR) was commonly not explicitly considered in the assessment. In this study, we developed an approach to assess water scarcity by considering both water quantity and quality, while at the same time explicitly considering EFR. We applied this quantity–quality-EFR (QQE) approach for the Huangqihai River Basin in Inner Mongolia, China. We found that to keep the river ecosystem health at a “good” level (i.e., suitable for swimming, fishing, and aquaculture), 26% of the total blue water resources should be allocated to meet the EFR. When such a “good” level is maintained, the quantity- and quality-based water scarcity indicators were 1.3 and 14.2, respectively; both were above the threshold of 1.0. The QQE water scarcity indicator thus can be expressed as 1.3(26%)|14.2, indicating that the basin was suffering from scarcity problems related to both water quantity and water quality for a given rate of EFR. The current water consumption has resulted in degradation of the basin's river ecosystems, and the EFR cannot be met in 3 months of a year. To reverse this situation, future policies should aim to reduce water use and pollution discharge, meet the EFR for maintaining healthy river ecosystems, and substantially improve pollution treatment.     

The occurrence and frequency of 2n pollen in 2x, 4x,and 6x wild,tuber-bearing Solanum species from Mexico,and Central and South America

Summary The occurrence of 2n pollen-producing plants was investigated in 187 plant introductions (PIs) of 38 wild species of tuber-bearing Solanum. These 2x, 4x, and 6x species are from Mexico, and Central and South America. The determination of 2n pollen-producing plants was conducted using acetocarmine glycerol. Plants with more than 1% large-size pollen were regarded as 2n pollen-producing plants. 2n pollen-producing plants were identified in the following species: 10 out of 12 Mexican 2x species, seven of nine South American 2x species, seven of seven Mexican and Central American 4x species, five of five South American 4x species, and five of five Mexican 6x species. The frequency of 2n pollen-producing plants varied among species at the same ploidy level, but the range of frequency, generally between 2 and 10% among species, was similar over different ploidy levels. The general occurrence of 2n pollen in both 2x and polyploid species, which are evolutionarily related, is evidence that the mode of polyploidization in tuber-bearing Solanums is sexual polyploidization. Furthermore, the frequencies of 2n pollen-producing plants in autogamous disomic polyploid species were not markably different from those of their related diploid species. It is thought that the frequent occurrence of 2n gametes with autogamy tends to disturb the fertility and consequently reduce fitness of polyploids. Thus, we propose that the breeding behavior of polyploids and the occurrence of 2n gametes may be genetically balanced in order to conserve high fitness in polyploid species in tuberbearing Solanum.Paper No. 3114 from the Laboratory of Genetics. Research supported by the College of Agriculture and Life Sciences; International Potato Center; USDA, SEA, CGRO 84-CRCR-1-1389; and Frito Lay, Inc.     

Marine incursions,cryptic species and ecological diversification in Amazonia: the biogeographic history of the croaker genus Plagioscion (Sciaenidae)

Aim We propose a phylogenetic hypothesis for the marine‐derived sciaenid genus Plagioscion in the context of geomorphology and adaptation to freshwaters of South America, and assess the extent to which contemporary freshwater hydrochemical gradients influence diversification within a widely distributed Plagioscion species, Plagioscion squamosissimus. Location Amazon Basin and South America. Methods Using nuclear and mitochondrial DNA sequence data, phylogenetic analyses were conducted on the five nominal Plagioscion species, together with representatives from Pachyurus and Pachypops, using character and model‐based methods. Genealogical relationships and population genetic structure of 152 P. squamosissimus specimens sampled from the five major rivers and three hydrochemical settings/‘colours’ (i.e. white, black and clear water) of the Amazon Basin were assessed. Results Phylogenetic analyses support the monophyly of Plagioscion in South America and identify two putative cryptic species of Plagioscion. Divergence estimates suggest that the Plagioscion ancestor invaded South America via a northern route during the late Oligocene to early Miocene. Within P. squamosissimus a strong association of haplotype and water colour was observed, together with significant population structure detected between water colours. Main conclusions Our analyses of Plagioscion are consistent with a biogeographic scenario of early Miocene marine incursions into South America. Based on our phylogenetic results, the fossil record, geomorphological history and distributional data of extant Plagioscion species, we propose that marine incursions into western Venezuela between the late Oligocene and early Miocene were responsible for the adaptation to freshwaters in Plagioscion species. Following the termination of the marine incursions during the late Miocene and the establishment of the modern Amazon River, Plagioscion experienced a rapid diversification. Plagioscion squamosissimus arose during that time. The formation of the Amazon River probably facilitated population and range expansions for this species. Further, the large‐scale hydrochemical gradients within the Amazon Basin appear to be acting as ecological barriers maintaining population discontinuities in P. squamosissimus even in the face of gene flow. Our results highlight the importance of divergent natural selection through time in the generation and maintenance of sciaenid diversity in Amazonia.     

Nuttallia balearicae sp. n., an Avian Piroplasm from Crowned Cranes (Balearica spp.)

An avian piroplasm, Nuttallia balearicae sp. n., is described from captive Balearica p. pavonina and B. p. gibbericeps. Other avian piroplasms and their validity and taxonomic status are discussed. The possible route of transmission of these parasites is also considered.     

Nothacrobeles,n. gen., with Descriptions of Four New Species (Nematoda: Cephalobidae)

A new nematode genus, Nothacrobeles, is proposed in the subfamily Acrobelinae. Four new species are described and one new combination made. The five species exhibit a progression from short-to-long, bifurcate, elaborately fringed labial probolae, the longest probolae resembling those of species of Acrobeles.     

A new longirostrine dyrosaurid (Crocodylomorpha,Mesoeucrocodylia) from the Paleocene of north‐eastern Colombia: biogeographic and behavioural implications for New‐World Dyrosauridae

Abstract: Fossils of dyrosaurid crocodyliforms are limited in South America, with only three previously diagnosed taxa including the short‐snouted Cerrejonisuchus improcerus from the Paleocene Cerrejón Formation of north‐eastern Colombia. Here we describe a second dyrosaurid from the Cerrejón Formation, Acherontisuchus guajiraensis gen. et sp. nov., based on three partial mandibles, maxillary fragments, teeth, and referred postcrania. The mandible has a reduced seventh alveolus and laterally depressed retroarticular process, both diagnostic characteristics of Dyrosauridae. Acherontisuchus guajiraensis is distinct among known dyrosaurids in having a unique combination of craniomandibular characteristics, and postcranial morphology that suggests it may have occupied a more placid, fluvial habitat than most known Old‐World dyrosaurids. Results from a cladistic analysis of Dyrosauridae, using 82 primarily cranial and mandibular characters, support an unresolved relationship between A. guajiraensis and a combination of New‐ and Old‐World dyrosaurids including Hyposaurus rogersii, Congosaurus bequaerti, Atlantosuchus coupatezi, Guarinisuchus munizi, Rhabdognathus keiniensis and Rhabdognathus aslerensis. Our results are consistent with an African origin for Dyrosauridae with multiple dispersals into the New World during the Late Cretaceous and a transition from marine habitats in ancestral taxa to more fluvial habitats in more derived taxa.     

Cytotoxic diterpenes from roots of Crossopetalum gaumeri,a Celastraceae species from Yucatan Peninsula

Four new diterpenes, crossogumerins A–D (1–4) along with six known ones (5–10) were isolated from the root bark of Crossopetalum gaumeri, an endemic medicinal plant from the Yucatan Peninsula. Their structures were elucidated on the basis of 1D and 2D NMR techniques, including HMQC, HMBC, and ROESY experiments. Compounds 1–5, 8–10 were evaluated for cytotoxicity against HeLa (carcinoma of the cervix) and Hep-2 (lung carcinoma) human tumor cells lines and against normal Vero cells (African green monkey kidney) in lag and log phase of growth. Podocarpane diterpenes, crossogumerin B (2) and nimbiol (10), exhibited the highest activity against HeLa cells (IC₅₀ values of 3.1 and 8.1 μM, respectively), but also selectivity on Vero cells (SI 22.6 and 7.5, respectively). The preliminary SAR studies suggest that an epoxy moiety in ring B and a hydrogen bond-donor group strategically positioned in the diterpene core are important requirements for cytotoxicity and selectivity.     

New Family,Genus, and Species of Microsporida (Protozoa: Microsporida) from the Tropical Fire Ant,Solenopsis geminata (Fabricius) (Insecta: Formicidae)*

SYNOPSIS. A new species of Microsporida, Burenella dimorpha sp. n., representing a new family, Burenellidae fam. n. and genus, is described on the basis of light- and electron-microscope observations. The family is characterized by 2 sequences of sporogony, each sequence having morphologically different sporonts and spores. The parasite infects the tropical fire ant, Solenopsis geminata (Fabricius), producing distinct pathologic manifestations (clearing of the cuticle and eye malformation) and death in the pupal stage of development. Transmission of the infection per os to healthy S. geminata, to the Southern fire ant, Solenopsis xyloni McCook, and to the red and black imported fire ants, Solenopsis invicta Buren and Solenopsis richteri Forel, is reported.     

Activation of fatty acids by non-glyoxysomal peroxisomes

Ethylene treatment (approx. 20 l ·1^-1 in air for 2 d) of tobacco (Nicotiana tabacum L. cv. Havana 425) plants markedly increases the endo--1,3-glucanase (EC 3.2.1.39) content of leaves. The antigenic form of the enzyme induced is the same one whose production is blocked by treating cultured cells with combinations of auxin (1.1 · 10^-5 M -naphthaleneacetic acid) and cytokinin (1.4 · 10^-6 M kinetin). Evidence is presented that cultured tobacco cells require ethylene for -1,3-glucanase accumulation: i) ethylene treatment increased the accumulation of \-1,3-glucanase in callus tissues >10 d after subculturing and in cell-suspension cultures; ii) callus tissues can produce ethylene; iii) conditions known to inhibit ethylene production (1 mM CoCl₂; 33° C treatment) or ethylene action (approx. 1.6 mmol · 1^-1 norbornadiene in air) inhibited -1,3-glucanase accumulation by callus tissues treated for 4 d following subculturing; and, these inhibitory effects were prevented by exogenous ethylene. Combinations of auxin and cytokinin blocked ethylene-induced accumulation of -1,3-glucanase by cell-suspension cultures. The results favor a model in which ethylene induces results favor a model in which ethylene induces 1,3-glucanase accumulation, and auxin and cytokinin inhibit this induction process.Abbreviations NAA -naphthaleneacetic acid - NDE norbornadiene