Osmotic adjustment in three succulent species of Zygophyllaceae

Three species, Zygophyllum album L., Z. coccineum L. and Z. simplex L., from family Zygophyllaceae were collected from two locations in Egypt to study their response to environmental conditions. Organic solutes (amino acids, soluble proteins and soluble sugars) and inorganic solutes (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl^?, PO₄^3? and SO₄^2?) were estimated to study their role in osmotic adjustment under the effect of drought and salinity. The study showed that Z. coccineum is most tolerant for drought and salinity than Z. simplex. Z. coccineum was dependent on soluble proteins and soluble sugars, to increase its content of bound water, to undergo water deficit in desert. Z. simplex accumulated inorganic solutes more than Z. coccineum and less organic solutes. Amino acids content increased in Z. coccineum and Z. simplex survived in saline conditions to play a role in osmotic adjustment. Under the effect of salinity, all the studied species showed a tendency and high capacity to accumulate inorganic solutes. The main inorganic salutes were Ca²⁺, Mg²⁺ and Cl^?. The role of Na⁺ was less than Ca²⁺ and Mg²⁺. Z. album and Z. simplex preferred Mg²⁺ more than Z. coccineum which preferred Ca²⁺.     

Problems of distinction among succulent Euphorbia species from eastern tropical Africa

Problems of distinction among succulent Euphorbia species from eastern tropical Africa. Identification of herbarium specimens of succulent Euphorbia species is especially difficult due to distortion of important characters upon drying. Problems encountered in collecting and preserving material result in poor representation in the herbarium, and true variation and distribution of closely related taxa are thus often established only from field studies. These problems are exposed and some solutions given in four groups of species from east and northeast Africa: the non-spiny E. schimperi-nubica group, the single-spined E. triaculeata group, the shrubby E. heterochroma-stapfii group and the tree E. nyikae-kibwezensis group.     

Ecological and evolutionary insights from species invasions

Species invasions provide numerous unplanned and frequently, but imperfectly, replicated experiments that can be used to better understand the natural world. Classic studies by Darwin, Grinnell, Elton and others on these species-invasion experiments provided invaluable insights for ecology and evolutionary biology. Recent studies of invasions have resulted in additional insights, six of which we discuss here; these insights highlight the utility of using exotic species as 'model organisms'. We also discuss a nascent hypothesis that might provide a more general, predictive understanding of invasions and community assembly. Finally, we emphasize how the study of invasions can help to inform our understanding of applied problems, such as extinction, ecosystem function and the response of species to climate change.     

Some limnological features of three lakes from Mexican neotropics

A limnological survey was conducted in three water bodies from the tropical rain forest region of southeast Veracruz, Mexico, in order to recognize their morphometric characteristics and to define their mixing patterns. These were: a temporary pond, Laguna del Zacatal (A=7.64 ha, Z _m =13.0 m); and two permanent lakes, Laguna Escondida (A =18.26 ha, Z _m = 32.5 m) and Lago de Catemaco (A = 7254 ha, Z _m = 22.0 m). Both El Zacatal and La Escondida are warm monomictic, whereas Lago de Catemaco is polymictic. Our results support the hypothesis that most tropical lakes are prone to winter overturn. Dissolved oxygen showed large variation, from almost constant epilimnetic saturation in all three lakes to hypolimetic anoxia in Laguna Escondida. Differences in mixing between lakes are determined by the joint influence of morphometry, rainfall and wind.     

Alkaloids,limonoids and furocoumarins from three Mexican Esenbeckia species

The chemical constituents of three Mexican Esenbeckia species have been determined. Rutaevin was the main limonoid present in the seeds of all three species, E. litoralis, E. flava and E. berlandieri. The husks, leaves, wood and bark contained a wide array of known furocoumarins and furoquinoline alkaloids. In addition, 1-hydroxy-3-methoxy-N-methylacridone was obtained from E. litoralis bark and a new natural 2-quinolone alkaloid, formulated as 3,3-diisopropyl-N-methyl-2,4-quinoldione, was obtained from E. flava wood. The structure was assigned from spectroscopic considerations and conversion to N-methylhaplofoline.     

Molecular identification of phytoplasmas in fasciated cacti and succulent species and associated hormonal perturbation

Fasciation, a frequent phenomenon in Cactaceae, has been attributed to various causes. The present study reports on phytoplasma-induced fasciation in Euphorbia coerulescens (Euphorbiaceae), Orbea gigantea (Asclepiadaceae), Opuntia cylindrica (Cactaceae), and Senecio stapeliiformis (Asteraceae). DNA was extracted from symptomless and fasciated tissues and amplified by nested PCR using universal primers P1/P7 followed by R16F2n/R16R2 produced amplicons of 1.2 Kb. The nucleotide sequence analyses of the amplicons indicated that fasciated plants were infected by phytoplasma. Phylogenetic analysis placed the cacti fasciation phytoplasmas in 16SrII group. The hormonal content of symptomless and fasciated tissues including indole-3-acetic acid (IAA), kinetin (Kin), N⁶-benzyladenine (BA), abscisic acid (ABA), and gibberellic acid (GA₃) was quantified by high performance liquid chromatography (HPLC). The results indicated that fasciation in O. gigantea was correlated with the accumulation of Kin and IAA increasing five and two times, respectively, as compared to symptomless tissue. However, there was no consistent pattern of hormones in other fasciated species (E. coerulescens, O. cylindrica, and S. stapeliiformis), suggesting that different plant species might have different mechanism to develop fasciation associated with phytoplasma infection.     

Spatial-temporal population dynamics across species range: from centre to margin

Understanding the boundaries of species' ranges and the variations in population dynamics from the centre to margin of a species' range is critical. This study simulated spatial-temporal patterns of birth and death rates and migration across a species' range in different seasons. Our results demonstrated the importance of dispersal and migration in altering birth and death rates, balancing source and sink habitats, and governing expansion or contraction of species' ranges in changing environments. We also showed that the multiple equilibria of metapopulations across a species' range could be easily broken following climatic changes or physical disturbances either local or regional. Although we refer to our models as describing the population dynamics across whole species' range, they should also apply to small-scale habitats (metapopulations) in which species abundance follows a humped pattern or to any ecosystem or landscape where strong central-marginal (C-M) environmental gradients exist. Conservation of both central and marginal populations would therefore be equally important considerations in making management decisions.     

Fundamental biogeographic patterns across the Mexican Transition Zone: an evolutionary approach

Transition zones, located at the boundaries between biogeographic regions, represent events of biotic hybridization, promoted by historical and ecological changes. They deserve special attention, because they represent areas of intense biotic interaction. In its more general sense, the Mexican Transition Zone is a complex and varied area where Neotropical and Nearctic biotas overlap, from southwestern USA to Mexico and part of Central America, extending south to the Nicaraguan lowlands. In recent years, panbiogeographic analyses have led to restriction of the Mexican Transition Zone to the montane areas of Mexico and to recognize five smaller biotic components within it. A cladistic biogeographic analysis challenged the hypothesis that this transition zone is biogeographically divided along a north‐south axis at the Transmexican Volcanic Belt, as the two major clades found divided Mexico in an east‐west axis. This implies that early Tertiary geological events leading to the convergence of Neotropical and Nearctic elements may be younger (Miocene) than those that led to the east‐west pattern (Paleocene). The Mexican Transition Zone consists of five biogeographic provinces: Sierra Madre Occidental, Sierra Madre Oriental, Transmexican Volcanic Belt, Sierra Madre del Sur, and Chiapas. Within this transition zone, at least four cenocrons have been identified: Paleoamerican, Nearctic, Montane Mesoamerican, and Tropical Mesoamerican. Future studies should continue refining the identification of cenocrons and the reconstruction of a geobiotic scenario, as well as integrating ecological biogeographic studies, to allow a more complete understanding of the patterns and processes that have caused the biotic complexity of this transition zone.     

Predation and the evolutionary dynamics of species ranges

Gene flow that hampers local adaptation can constrain species distributions and slow invasions. Predation as an ecological factor mainly limits prey species ranges, but a richer array of possibilities arises once one accounts for how predation alters the interplay of gene flow and selection. We extend previous single-species theory on the interplay of demography, gene flow, and selection by investigating how predation modifies the coupled demographic-evolutionary dynamics of the range and habitat use of prey. We consider a model for two discrete patches and a complementary model for species along continuous environmental gradients. We show that predation can strongly influence the evolutionary stability of prey habitat specialization and range limits. Predators can permit prey to expand in habitat or geographical range or, conversely, cause range collapses. Transient increases in predation can induce shifts in prey ranges that persist even if the predator itself later becomes extinct. Whether a predator tightens or loosens evolutionary constraints on the invasion speed and ultimate size of a prey range depends on the predator effectiveness, its mobility relative to its prey, and the prey's intraspecific density dependence, as well as the magnitude of environmental heterogeneity. Our results potentially provide a novel explanation for lags and reversals in invasions.     

Observations on developmental and structural aspects of stomata in six succulent species ofSenecio (Compositae)

The development and structure of stomata on the succulent leaves of six species ofSenecio are reported. It was found that in all the species investigated the development of stomata was of the mesogenous type and the structure of the stomata was anisocytic. The constancy in the development and structure of stomata in all the species of the genus investigated agrees with the view that a stomatal type and its developmental modes are constant at the genus level. Abnormalities such as contiguous stomata, degenerated guard cells, abortive and single guard cells are also recorded as natural phenomena.     

A new genus and species of Tullbergiidae (Collembola) from the Pacific Mexican coast

The new genus Mexicaphorura, and its type species Mexicaphorura guerrerensissp. n. are described from marine littoral sand. The new genus is similar to Sensilatullbergia Thibaud & Ndiaye, 2006 in having very big sensilla on sensorial organ of antennal segment III, but of different shape, the kind of postantennal organ, with simple vesicles in Mexicaphorura versus composed vesicles in Sensilatullbergia and formulae of the pseudocelli.     

The acaulescent and succulent species of Dorstenia sect. Kosaria (Moraceae) from NE tropical Africa and Arabia

The acaulescent and succulent species of Dorstenia sect. Kosaria in NE tropical Africa include the well defined D. ellenbeckiana and the two polymorphic taxa, the D. barnimiana complex and the D. foetida complex. The D. barnimiana complex is treated as two species, D. barnimiana Schweinf. and D. tropaeolifolia (Schweinf.) Bureau. One specific name and four varietal names are reduced to synonymy. The D. foetida complex is treated as one species, D. foetida (Forssk.) Schweinf., with two subspecies, ssp. foetida and ssp. lancifolia (Rendle) Friis comb, nov., of which the former is further divided into var. foetida and var. obovata (A. Rich.) Schweinf. & Engl. Three species arc reduced to synonymy of D. foetida. The distribution of all the species is mapped.     

Interesting findings of rare geometrid species (Lepidoptera,Geometridae) in the Altai

Five rare species, Macaria halituaria (Guenée, [1858]), Chelegnophos ravistriolaria (Wehrli, 1922), Ch. tholeraria (Pungeler, 1901), Scotopteryx transbaicalica (Djakonov, 1955), and Xanthorhoe stupida (Alphéraky, 1897), are described. Chelegnophos tholeraria was found for the first time in the territory of Russia, and Ch. ravistriolaria and S. transbaicalica, in the territory of the Altai. Drawings of genitalia are given for all the species studied, and some differences from closely related species are presented. The male genitalia of X. stupida and Scotopteryx burgaria and the female genitalia of S. transbaicalica are described for the first time.     

Length–weight relationships for coastal fish species from the gillnet artisanal fishery in the central Mexican Pacific

This paper presents 43 length–weight relationships of coastal fish species of the families Carangidae, Lutjanidae and Haemulidae from the central Mexican Pacific. New maximum length values for 15 fish sepcies are included.