The scaling of reproductive variability in trees

Seed output in perennial plant populations is temporally variable and often synchronous over large regions. The similarly complex spatiotemporal dynamics of animal populations have been characterized by the power‐law scaling of the variance in population numbers with mean abundance. Here we show that a large compilation of published reproductive time series exhibits largely invariant mean–variance scaling properties across both angiosperm and conifer tree species. A simple model of seed production in tree stands shows that observed values of the scaling exponent reflect very general aspects of plant ecology and life history as well as the temporal dynamics of seed production. Together, these results suggest that the continuum of reproductive variability and synchrony observed in trees may reflect the influence of a common set of ecological processes.     

The evolution of the pheromonal signal system and its potential role for reproductive isolation in heterothallic neurospora

Comparative sequencing studies among a wide range of taxonomic groups, including fungi, provide the overall pattern that reproductive genes evolve more rapidly than other genes, and this divergence is believed to be important in the establishment of reproductive barriers between species. In this study, we investigated the molecular evolution of the pheromone receptor genes pre-1 and pre-2 of strains belonging to 12 and 13 heterothallic taxa, respectively, of the model genus Neurospora. Furthermore, we examined the regulatory pattern of both pheromone precursor and receptor genes during sexual crosses of Neurospora crassa and Neurospora intermedia, for which reinforcement of interspecific reproductive barriers in sympatry previously has been documented. We conclude that the part encoding the C-terminal intracellular domain of pre-1 and pre-2 genes evolves rapidly. Both stochastic and directional processes drive this divergence; both genes contain neutrally evolving codons, and in addition, pre-1 contains codons evolving under positive selection, whereas in pre-2 we found highly variable regions with numerous repeats encoding glycine, threonine, or aspartic acid. In addition, we found regulatory changes of the pheromone and receptor genes during crosses between N. crassa and N. intermedia with different reproductive success. Gene expression levels are higher in the interspecific sympatric crosses with low reproductive success than in their intraspecific and/or allopatric equivalents, both at the stage of initial communication and contact and later at postfertilization stages. Taken together, our data indicate that pheromones and receptors are important key players during reproductive isolation between Neurospora species, and this study provides a general framework for future studies on the role of reproductive proteins for reproductive isolation.     

The cytological basis for reproductive variability in the Anoetidae (Sarcoptiformes: Acari)

Meiosis is described in a thelytokous strain of the anoetid mite Histiostoma feroniarum (Dufour) and in both sexes of the arrhenotokous strain of this species. Oogenesis in the thelytokous strain is accomplished by ameiotic mitosis with only one pseudo-maturation division. During this division one or more chromosomes may move to the poles precociously and while in this position can be mistaken for centrioles. Fourteen chromosomes are found at metaphase of the pseudo-maturation division and in cleaving eggs of this strain. In the arrhenotokous strain, male meiosis consists of a single mitotic division. Oogenesis is regular and 7 bivalents are observed at the first maturation division. Metaphases of the first cleavage division in fertilized eggs show 14 chromosomes and 7 chromosomes in unfertilized eggs.It is postulated that the thelytokous strain has arisen from the arrhenotokous strain. This assumption is in agreement with that suggested for several insect species previously reported. The evolution in the Acari and the variability in the modes of reproduction in this suborder are discussed in light of the findings in this paper on the Anoetidae.     

The role of extracellular vesicles in endometrial receptivity and their potential in reproductive therapeutics and diagnosis

Extracellular vesicles (EVs) are small, nanometre sized, membrane-enclosed structures released by cells and are thought to be crucial in cellular communication. The cargo of these vesicles includes lipids, proteins, RNAs and DNA, and control various biological processes in their target tissues depending on the parental and receiver cell’s origin and phenotype. Recently data has accumulated in the role of EVs in embryo implantation and pregnancy, with EVs identified in the uterine cavity of women, sheep, cows, horses, and mice, in which they aid blastocyst and endometrial preparation for implantation. Herein is a critical review to decipher the role of extracellular vesicles in endometrial receptivity and their potential in reproductive therapies and diagnosis. The current knowledge of the function of embryo and endometrial derived EVs and their cargoes, with regards to their effect on implantation and receptivity are summarized and evaluated. The findings of the below review highlight that the combined knowledge on EVs deriving from the endometrium and embryo have the potential to be translated to various clinical applications including treatment, a diagnostic biomarker for diseases and a drug delivery tool to ultimately improve pregnancy rates.     

The rhizosheath: a potential root trait helping plants to tolerate drought stress

Plant and Soil - Experimental data concerning possible trophic relationships between phorophytes and epiphytes are contradictory. Several studies have indirectly shown that epiphytes affect the...     

Predicting coral bleaching hotspots: the role of regional variability in thermal stress and potential adaptation rates

Sea surface temperature fields (1870–2100) forced by CO₂-induced climate change under the IPCC SRES A1B CO₂ scenario, from three World Climate Research Programme Coupled Model Intercomparison Project Phase 3 (WCRP CMIP3) models (CCSM3, CSIRO MK 3.5, and GFDL CM 2.1), were used to examine how coral sensitivity to thermal stress and rates of adaption affect global projections of coral-reef bleaching. The focus of this study was two-fold, to: (1) assess how the impact of Degree-Heating-Month (DHM) thermal stress threshold choice affects potential bleaching predictions and (2) examine the effect of hypothetical adaptation rates of corals to rising temperature. DHM values were estimated using a conventional threshold of 1°C and a variability-based threshold of 2σ above the climatological maximum Coral adaptation rates were simulated as a function of historical 100-year exposure to maximum annual SSTs with a dynamic rather than static climatological maximum based on the previous 100 years, for a given reef cell. Within CCSM3 simulations, the 1°C threshold predicted later onset of mild bleaching every 5 years for the fraction of reef grid cells where 1°C > 2σ of the climatology time series of annual SST maxima (1961–1990). Alternatively, DHM values using both thresholds, with CSIRO MK 3.5 and GFDL CM 2.1 SSTs, did not produce drastically different onset timing for bleaching every 5 years. Across models, DHMs based on 1°C thermal stress threshold show the most threatened reefs by 2100 could be in the Central and Western Equatorial Pacific, whereas use of the variability-based threshold for DHMs yields the Coral Triangle and parts of Micronesia and Melanesia as bleaching hotspots. Simulations that allow corals to adapt to increases in maximum SST drastically reduce the rates of bleaching. These findings highlight the importance of considering the thermal stress threshold in DHM estimates as well as potential adaptation models in future coral bleaching projections.     

The reproductive potential of workers in slave-making ants

Summary Colonies of slave-making ants have been used repeatedly to test sex allocation theory. It was suggested that workers of slave-making ants are more strongly selected to reproduce than workers of related, non-parasitic species, because they are incapable of manipulating sex allocation and the sexualization of larvae in their colonies. I show here that in slave-making Formicoxenini, worker ovaries on average consist of significantly more ovarioles than in non-parasiticLeptothorax species. Similarly, whereas in mostLeptothorax species, workers form reproductive hierarchies and lay eggs only in orphaned colonies, slave-maker workers show antagonistic interactions already in the presence of the queen and at least in some species have been observed ovipositing in queen-right colonies. The significance of these results is discussed.     

Influence of helping and breeding experience on reproductive performance in the Seychelles warbler: a translocation experiment

Reproductive success of the cooperative breeding Seychelleswarbler (Acrocephalus sechellensis) increases with age. Thisage effect is not due to differential survival or increasedreproductive effort, but to accumulated helping and breedingexperience. In their first year of breeding, reproductive performanceof inexperienced warblers with neither helping nor breedingexperience was significandy lower than that of warblers of thesame age with either previous helping or breeding experience.Reproductive performance was the same for primiparae with helpingexperience and for birds with breeding experience. Female primiparaewith helping experience or breeding experience built betternests and spent more time incubating than inexperienced females,which led to increased hatching success. Male primiparae withhelping experience or males with breeding experience guardedthe clutch better than inexperienced males, which led to reducedegg predation. Even-aged warblers with different previous experienceswere transferred to unoccupied islands, where birds startedbreeding immediately in high-quality territories. The experimentshowed that birds with helping experience produced their firstfledgling as fast as experienced breeders, and significandyfaster than inexperienced birds. Breeding performance did notimprove further with experience after the first successful breedingattempt. Only birds with previous breeding experience who pairedwith inexperienced birds, were likely to change mate. The otherpair combinations remained stable. Thus, primiparous birds withhelping experience have greater lifetime reproductive successthan inexperienced primiparae of the same age. This experimentshows that helping behavior has not only been selected for inthe context of promoting an individual's indirect fitness, butalso in the context of gaining helping experience which translatesinto improved reproductive success when a helper becomes a breeder.[Behav Ecol 7: 326-333 (1996)]     

胞外ATP在男性生殖道中的作用

胞外ATP除了能广泛作为神经递质外,还被认为是一种旁分泌或自分泌因子。ATP从男性生殖道中的精子或上皮细胞中释放,在调节各种生殖生理功能中起多种作用。本文综述了ATP调节附睾上皮细胞阴离子分泌的信号通路,阐述了ATP对依赖上皮细胞的输精管平滑肌收缩的调节机制,讨论了ATP在男性生殖道中的功能和作用。     

The origin and genetic variability of the Czech sika deer population

Sika deer (Cervus nippon), native to Asia, formed two well-established free-living populations in the Czech Republic over the last century and continue to spread. Sika are also maintained in a large number of enclosures; these continue to introduce new individuals from the places of its origin as well as from other European countries. Despite extensive research into the morphology and ethology of the Czech sika deer, conducted over the last three decades, no study using genetic methods has been done. This study aimed to determine the genetic variability and the geographic origin of the Czech sika deer population. Two mitochondrial markers, the cytochrome b and the control region were analyzed in this study. Analysis of the two markers confirmed that the founder individuals of the Czech population originated from both native island (Japanese Islands) and native mainland (Far East Russia) populations. Results showed that the genetic variability of the Czech sika deer population is lower than the variability of the native Japanese population, but higher than that of the sampled part of the native Russian population. Also, the genetic variability was found to be higher within the samples from enclosures.     

The assessment of reproductive potential in Micronesian kingfisher pairs

The Micronesian kingfisher Halcyon cinnamomina cinnamomina is now extinct in the wild and survives only in U.S. zoos. Although pairs have reproduced in captivity, the captive breeding program has been plagued with inconsistencies in reproductive success. One problem has been determining whether birds housed as reproductive pairs have really established pairbonds. The behavior of newly paired birds may provide information that could be used to predict future reproductive success. Observations conducted for 90 min immediately after introduction of five new pairs at three institutions suggest that the specific behavioral combination of high nest activity and low aggression may indicate reproductive compatibility. Pairs that ultimately produced surviving offspring were less aggressive and engaged in more nest activity than pairs that were not productive. Observations conducted on four of these pairs for an additional month after introduction failed to provide additional information relevant to the assessment of pair status. Although long-term behavioral observations are also desirable, quick assessments such as these may be useful for determining the reproductive potential of more pairs than would be possible using traditional methods. The identification of sexually compatible pairs is a critical step toward the ultimate goal of re-establishing this species in the wild. Zoo Biol 17:425–432, 1998. © 1998 Wiley-Liss, Inc.     

The role of mineral surfaces in the origin of life

Adsorption of nucleoside phosphates on the surfaces of volcanic rocks has been studied. Differences in the adsorption of some nucleoside phosphates on the surface of basalt cinder have been found. Differences in the adsorption of similarmolecules on different mineral surfaces have also been shown. Different adsorptive capacities may have served as a mechanism for the selection of organic molecules during prebiotic evolution.     

The in vivo reproductive potential of density separated cells

Murine ascites cells (L1210, L5178Y, Ehrlich ascites) were labelled with ¹³¹I-iododeoxyuridine and subjected to buoyant density centrifugation on a continuous, linear Ficoll gradient. Cell losses sustained during density centrifugation were evaluated by recording the amount of ¹³¹I recovered in the final cell fractions. The viability and proliferative capacity of the density separated cells were tested by monitoring the rate of ¹³¹I excretion following inoculation of the recovered cells into new, non-radioactive hosts.Density separation in Ficoll appeared to cause few, if any, adverse effects. Cell recovery under properly regulated experimental conditions was virtually complete (97% or higher). The reproductive potential of density-separated cells was identical to that of control cells. However, considerable cell mortality could be induced by permitting cellular aggregation in medium free of antiagglutinin or by exposure of excessive quantities of cells to a density gradient.Viability indices obtained with trypan blue proved unsuitable for predicting long-term survival. In some experiments the trypan blue data provided a 90–100% viability reading when in fact the entire cell population had been inactivated by irradiation or heat incubation. Since the trypan blue test also did not reveal the full extent of mortality among aggregated cells or cells recovered from overloaded gradients, it was concluded that the dye exclusion test, in spite of its utility for monitoring immediate cell death and membrane destruction, was of limited value for evaluating the reproductive potential of mammalian cells.     

Soil flushing: a review of the origin of efficiency variability

Soil flushing using aqueous solutions is employed to solubilise contaminants. As water solubility is the controlling mechanism of dissolution, additives (surfactants, cosolvents, etc.) are used to enhance efficiencies and reduce the treatment time compared to the use of water alone. The use of surfactant alone gives efficiencies of about 80–85 % in laboratory experiments, but the amounts of product to be injected are very important, which does not seem to be economically sustainable. Studies indicate that when soil flushing is applied in the field, efficiency is very variable; it can vary from almost 0 % to almost 100 %. This illustrates the importance of knowledge of the field (soil heterogeneities, type of contamination, etc.). Using only one product (surfactant, cosolvent, cyclodextrin) often gives moderate efficiencies and needs very large amounts of products, with a product:pollutant ratio higher than 100:1. On the other hand, the use of more complex methods involving micro emulsions or several products with polymer injection lead to high efficiencies at first and a product:pollutant ratio that can be lower than 5. The importance of the initial saturation of the non-aqueous phase liquid is highlighted: the higher the initial saturation, the higher the efficiency. For initial saturations lower than 1 %, soil flushing may not be a very efficient technique. This paper provides an overview of recent studies in the area of soil and groundwater remediation, from laboratory columns scale to pilot and real sites. The research has focused on chlorinated solvents as they are extremely difficult to treat.     

The role of the hypothalamus in aging of the female reproductive system

We have investigated the role of neuroendocrine and neurochemical changes in the age-related deterioration of cyclic female reproductive function. During middle age the timing and amplitude of the proestrous and estradiol-induced LH surge is altered. We have found that the diurnal pattern of norepinephrine turnover is altered in critical hypothalamic areas known to regulate the release of LHRH. These changes may contribute to alterations in the timing and the amplitude of LH release, which may, in turn, affect the ability of rats to maintain regular estrous cycles.     

The presence of APGWamide in Octopus vulgaris: a possible role in the reproductive behavior

The concerted action of many neuropeptides has been implicated in the nervous control of specific behaviors in many molluscs. In the present study, the presence of amidated tetrapeptide Ala-Pro-Gly-Trp-NH2 (APGWamide) in those lobes that are involved in the control of reproductive behavior in Octopus vulgaris has been investigated. APGWamide immunoreactivity was mainly confined to the posterior olfactory lobule and in the inferior frontal system. These areas are involved in Octopus in the processing of either chemotactile sense or olfaction. From these lobes, immunoreactive fibers reached other lobes of the central nervous system (CNS) which could be indirectly involved in the reproductive behavior. APGWamide immunoreactivity was also present in the glandular cells of the oviducal gland in the female reproductive system. These results constitute the first detailed immunolocalization of APGWamide in cephalopods and open a new insight into the possible effects that both distant and close chemical stimuli can exert on neuropeptidergic circuitries, which may affect the reproductive behavior of cephalopods.