Acetaldehyde addition and pre-adaptation to the stressor together virtually eliminate the ethanol-induced lag phase in Saccharomyces cerevisiae

AIMS: To show that the ethanol-induced lag phase in yeast can be almost eliminated by combining pre-adaptation with acetaldehyde supplementation. METHODS AND RESULTS: Pre-adaptation to noninhibitory concentrations of ethanol and supplementation of unadapted cultures with acetaldehyde each separately reduced the lag phase of ethanol-inhibited cultures by c. 70%. By combining the two methods the ethanol-induced lag phase was virtually eliminated (90% reduction in lag time). CONCLUSIONS: Pre-adaptation to ethanol and acetaldehyde supplementation appear to promote yeast growth through different mechanisms, which are additive when combined. SIGNIFICANCE AND IMPACT OF THE STUDY: The combination of the above procedures is a potentially powerful tool for reducing the lag of stressed cultures, which may have practical applications: e.g. in reducing the lag of yeasts inoculated into lignocellulosic hydrolysates employed in fuel ethanol production.     

Genotypes on the move: some things old and some things new shape the genetics of colonization during species invasions

When we set a species loose outside of its historical range, we create opportunities to test fundamental questions about how populations establish, adapt, disperse, and ultimately define range boundaries. A particularly controversial issue here is how genetic variation among and within populations contributes to the dynamics of species distributions. In this issue of Molecular Ecology, Rosenthal and colleagues (2008) seize an opportunity to examine how multiple introductions create genetically distinct establishment events and how these are incorporated into invasive spread. Their findings suggest that a particular recombinant lineage of Brachypodium sylvaticum may be responsible for most of the recent expansion of this invader, highlighting the potential importance of genetic novelty and historical context for colonization success.     

Co-evolution of cleaning and feeding morphology in western Atlantic and eastern Pacific gobies

Cleaning symbioses are mutualistic relationships where cleaners remove and consume ectoparasites from their clients. Cleaning behavior is rare in fishes and is a highly specialized feeding strategy only observed in around 200 species. Cleaner fishes vary in their degree of specialization, ranging from species that clean as juveniles or facultatively as adults, to nearly obligate or dedicated cleaners. Here, we investigate whether these different levels of trophic specialization correspond with similar changes in feeding morphology. Specifically, we model the evolution of cleaning behavior across the family Gobiidae, which contains the most speciose radiation of dedicated and facultative cleaner fishes. We compared the cranial morphology and dentition of cleaners and non-cleaners across the phylogeny of cleaning gobies and found that facultative cleaners independently evolved four times and have converged on an intermediate morphology relative to that of dedicated cleaners and non-cleaning generalists. This is consistent with their more flexible feeding habits. Cleaner gobies also possess a distinct tooth morphology, which suggests they are adapted for scraping parasites off their clients and show little similarity to other cleaner clades. We propose that evolutionary history and pre-adaptation underlie the morphological and ecological diversification of cleaner fishes.     

Photophilic behaviour in surface- and cave-dwelling Atlantic mollies Poecilia mexicana (Poeciliidae)

The phototactic behaviour of surface- and cave-dwelling Atlantic mollies Poecilia mexicana was examined. Surface-dwelling Atlantic mollies, as well as light- and dark-reared cave fish showed photophilic behaviour under all light intensities used (620, 50 and 3 lx).     

基于功能性状多维性理解外来物种入侵的达尔文归化难题

达尔文归化难题是进行外来物种入侵预测的重要理论依据,然而,达尔文归化假说和预适应假说却预测了2种截然不同的结果。事实上,达尔文归化难题争论的焦点是物种间的差异性还是相似性促进了外来物种的成功入侵,究其原因可能是忽略了功能性状的多维性。所谓功能性状的多维性,就是不同的功能性状可能代表着不同的生态功能轴,外来物种的入侵是多个维度上不同生态过程的综合结果。本研究以现代物种共存理论为基础,构建了一个基于环境过滤和适合度差异2个维度的入侵预测模型框架,不同维度对应着不同的功能性状以及不同的种间相似性关系。该预测模型表明,在环境过滤维度上与本地物种性状趋同,同时,在适合度维度上与本地物种性状趋异的外来物种是潜在的入侵物种,而其危害程度主要取决于本地群落的构建过程。该模型框架可为外来物种入侵预警提供理论依据,也可为生物多样性保护、外来物种的防治与管理等提供实践指导。     

Correlates of geographic range size in New Zealand Chionochloa (Poaceae) species

Aim To test for correlations between plant traits and geographic range size. Location: New Zealand. Methods Trait data were derived from comparative experiments, in which plants were grown in pots or in a common garden, that tested for intrinsic differences among the species in traits relating to growth, reproduction and dispersal. Controlled experiments were used to test for differences in responses to drought and waterlogging stress. Geographic range size was measured as the number of 10 km grid squares in the New Zealand region containing at least one occurrence of the species. Results Growth rate, dispersal capacity and environmental tolerance were all positively related to geographic range size. Geographically restricted species tended to have more variable flowering between years. Flowering intensity, reproductive allocation, seed set, diaspore size, and responses to single environmental factors were not related to geographic range size. Main conclusions The differences between range‐restricted and widespread Chionochloa species appear to represent alternative strategies of coping with environmental change in a dynamic landscape. Range‐restricted species are specialized to temporally persistent habitats that are of limited geographic extent. As a consequence, they have evolved traits that conflict with persistence in widespread habitats. The implication for conservation management is that the conservation of rare plants will frequently depend on protection of their habitats. The widespread Chionochloa species possess traits that enable them to disperse to and occupy a greater range of habitats. These traits have allowed some of these species to expand their ranges following environmental changes that favoured an increase in grassland extent.     

An insect introduction to the maritime Antarctic

Although several invertebrates have been introduced by Man into the Antarctic, no holometabolous insects have survived to colonize terrestrial habitats successfully. Data are presented on the survival of populations of a chironomid midge, together with an enchytraeid worm, for 17 years in a maritime Antarctic site at Signy Island, South Orkney Islands. Both species are thought to have been introduced on plant material transplanted from either South Georgia or the Falkland Islands or both in 1967. Population densities average 25718m^-2 for the dipteran larvae and 3243 m^-2 for the worms. Successful completion of the midge's life cycle was indicated by emergence of brachypterous adults and oviposition (the population is parthenogenetic with only females present). Although both taxa are capable of supercooling to between -13 and -26°C, this capacity may not be sufficient in a severe winter to avoid lethal freezing. Four potential cryoprotectants were found in insect extracts, but in concentrations (< 1 % fresh weight) unlikely to influence cold hardiness. Both invertebrates appear to be pre-adapted for survival in much harsher conditions than they normally experience, by the extension of existing physiological mechanisms. It is concluded that the main limitations to invertebrate colonization of suitable Antarctic land areas by soil-dwelling species are geographical.     

Impact of nest sanitation behavior on hosts’ egg rejection: an empirical study and meta-analyses

Egg rejection in birds is a specific adaptation toward avian brood parasitism, whereas nest sanitation is a general behavior for cleaning the nest and avoiding predation. However, both behaviors refer to the action of ejecting objects out of the nest, and nest sanitation has been proposed as a pre-adaptation for egg rejection. Here, we tested the eliciting effect of nest sanitation on egg rejection in the red-whiskered bulbul Pycnonotus jocosus, a potential host species that are sympatric with parasitic cuckoos. We conducted meta-analyses of previous studies on both nest sanitation and egg rejection, in order to evaluate the consistency of our conclusions. Our results showed that nest sanitation did not elicit egg rejection in P. jocosus. The conclusions concerning such an eliciting effect from previous studies were mixed, whereas the methodologies were inconsistent, making the studies unsuitable for comparisons. However, the ejection frequency of nest sanitation was consistently higher than the frequency of egg rejection across different host species or populations. These results suggest that nest sanitation, which is an ancient behavior, is more fundamental than egg rejection, but the effect of the former on the latter is complex and needs further study. Standardized methodologies and the integration of behavior, physiology, and modeling may provide better opportunities to explore the relationship between nest sanitation and egg rejection.     

How are the life history strategies of Antarctic terrestrial invertebrates influenced by extreme environmental conditions?

1. 1. Features of life history strategies of Antarctic terrestrial invertebrates are reviewed and compared with the predictions of two widely-used general life history models.

2. 2. Many features observed are consistent with the predictions of “adversity-” or “stress-selected” life histories, although “ruderal” characteristics are also observed.

3. 3. Many features are plesiotypic for the taxonomic groups concerned, suggesting a lack of evolved adaptations within the Antarctic biota.

4. 4. A large degree of flexibility is found in the life histories; this flexibility itself may allow passage of environmentally-imposed selective filters limiting colonisation and development in isolated and extreme terrestrial habitats.

5. 5. In general, Antarctic terrestrial invertebrates may be regarded as pre-adapted for survival of the various stresses imposed by their extreme environment.