Trends in genetic diversity among European maize cultivars and their parental components during the past 50 years

It has been claimed that the system that delivers the products of plant breeding reduces the diversity of cultivated varieties leading to an increased genetic vulnerability. The main goal of our study was to monitor the temporal trends in genetic diversity over the past five decades among maize cultivars with the largest acreage in Central Europe. Our objectives were to (1) investigate how much of the genetic diversity present in important adapted open-pollinated varieties (OPVs) has been captured in the elite flint germplasm pool, (2) examine changes in the genetic diversity among the most important commercial hybrids as well as in their dent and flint parents, (3) analyze temporal changes in allele frequencies between the dent and flint parental inbreds, and (4) investigate linkage disequilibrium (LD) trends between pairs of loci within the set of parental dent and flint lines. We examined 30 individuals of five prominent OPVs from Central Europe, 85 maize hybrids of economic importance, and their dent and flint parental components with 55 SSRs. LD was significant at probability level P=0.01 for 20.2% of the SSR marker pairs in the 82 dent lines and for 17.2% in the 66 flint lines. The dent and flint heterotic groups were clearly separated already at the beginning of hybrid breeding in Central Europe. Furthermore, the genetic variation within and among varieties decreased significantly during the five decades. The five OPVs contain numerous unique alleles that were absent in the elite flint pool. Consequently, OPVs could present useful sources for broadening the genetic base of elite maize breeding germplasm.     

Changes in needle nitrogen partitioning and photosynthesis during 80 years of tree ontogeny in Picea abies

Needle nitrogen partitioning and photosynthesis of Norway spruce were studied in a forest chronosequence in Järvselja Experimental Forest, Estonia. Current- and previous-year shoots were sampled from upper and lower canopy positions in four stands, ranging in age from 13 to 82 years. A/c _i curves were determined to obtain maximum carboxylation rate (V _cmax) and maximum rate of electron transport (J _max), whereas needle nitrogen partitioning into carboxylation (P _R), bioenergetics associated with electron transport (P _B) and thylakoid light harvesting components (P _L) was calculated from the values of V _cmax, J _max and leaf chlorophyll concentration. The greatest changes in studied needle characteristics took place between tree ages of 13 and 26 years, and this pattern was independent of needle age and canopy position. Needle mass per projected area (LMA) was lowest in the 13-year-old stand and mass-based nitrogen concentration (N^M) was generally highest in that stand. The values of LMA were significantly higher and those of N^M lower in the 26-year-old stand. Mass-based V _cmax and J _max were highest in the 13-year-old stand. Area-based photosynthetic capacity was independent of tree age. The proportion of photosynthetic nitrogen (P _R, P _B and P _L) was highest and that of non-photosynthetic nitrogen lowest in the 13-year-old stand. Current-year needles had lower LMA and P _L, but higher photosynthetic capacity compared to 1-year-old foliage. Needles from lower canopy positions exhibited lower LMA, area-based nitrogen concentration and photosynthetic capacity than needles from upper canopy. The period of substantial reductions in needle photosynthetic capacity and changes in nitrogen partitioning coincides with the onset of reproductive phase during tree ontogeny.     

Changes in the impact of anthropogenic effects on river water quality during the last 50 years in Japan

Japan’s rapid urbanisation over the last 50 years has resulted in land use and lifestyle changes, all of which are likely to have changed the quality of river water, and consequently the wetland and coastal environment. We examined changes in river water quality over this period by means of a review of previous studies. Around the 1950s, the weighted average of chloride using discharge of Japan’s 30 major rivers was 6.1 mg/l while in the 2000s it was 11.3 mg/l. Because there were no significant changes in the natural conditions, we have attributed the increase to the urbanisation of the last 50 years. Nitrate levels in the mountain streams of southern Japan have increased, particularly in the western part of the Kanto region. As this area is located on the leeward side of the Tokyo Metropolitan Area, depositions from aerosols are thought to be the main cause of the increased nitrate concentration. These two findings suggest that certain uses of land may affect river water quality differently over time, and that changes in land use may also affect river water quality in remote areas.     

The discovery of state transitions in photosynthesis 40 years ago

In the late 1960s, I identified an aspect of the kinetics of chlorophyll fluorescence in algal cells that I was unable to explain in terms of photochemical quenching. I proposed a novel regulatory mechanism for the distribution of light energy to photosystems I and II, which is now known by the term of “state transitions.” I also examined the “cation-dependent redistribution of light energy” to photosystems I and II and the “energy-dependent quenching” of chlorophyll fluorescence. At that time, financial constraints prevented me from measuring the emission and action spectra of chlorophyll fluorescence at liquid-nitrogen temperature and the light quality-dependent changes in the yield of chlorophyll fluorescence at room temperature. The financial problems were solved by constructing several pieces of electronic equipment using skills obtained by repairing radios when I was a high-school and college student.     

Adaptive responses in resurgent Lake Victoria cichlids over the past 30 years

Textbook examples of adaptive radiation like the Galapagos finches and the East-African cichlids form a subject of major interest in evolutionary biology. Many of these species often show rapid morphological changes in response to a perturbed environment. The dramatic ecological changes in Lake Victoria during the past three decades, e.g. Nile perch predation and eutrophication, provide a unique opportunity to study environmental effects on cichlid morphology. Preliminary research has revealed that the lake’s haplochromines tend to be extremely plastic and sensitive to these environmental changes. So far, long-term ecomorphological studies at short-term intervals are extremely rare. In this study, we examined morphological changes over a 30 year period in six haplochromine species. Geometric morphometric analyses at intervals of approximately 3 years revealed adaptive responses. Three out of four resurgent haplochromines had a smaller head surface/caudal peduncle area (HS/CPA) ratio during the upsurge of the predatory Nile perch. During the same period, all four resurgent species had a larger cheek depth and a smaller eye size. The smaller HS/CPA ratio and larger cheek depth are likely to be adaptive responses to a high predation pressure and a diet shift to larger prey. The smaller eye size seems to be the result of a trade off between the eyes and other morphological structures in the smaller head of these species. Interestingly, the direction of the morphological changes was different between the four resurgent cichlid species and two species that became extremely rare or even may have gone extinct. The HS/CPA ratio increased in the extinct species where it decreased in the resurgent species. This study suggests that predation is a major driver of these morphological changes, which may be due to either phenotypic plasticity or adaptive changes.     

A dendroclimatic analysis of regional moisture variation in the northeastern Tibetan Plateau during the past 150 years

As a transitional zone between westerlies and the Asian Monsoon system, the northeastern part of the Tibetan Plateau (NETP) is highly sensitive to climate change. The record of historical regional moisture variation in the NETP is essential for understanding climatic variation and its relationship with different climate systems in this area. Using principal component analysis, a time series was extracted from sixteen moisture-sensitive tree-ring series to investigate the regional moisture variation in the NETP over the past 150 years. We find that the first principal component (PC1) represents 46.9 % of the total variance, reflecting a common growth response to the climate factor. A spatial correlation analysis of PC1 with the gridded meteorological data demonstrated that the precipitation in May–June was the major factor in controlling tree-ring growth. Further analysis indicated that the westerlies had a sustained influence on rainfall in the NETP over the past 150 years. In addition, the rainfall in the NETP may be closely associated with the East Asian Monsoon (EAM). Severe drought years commonly correspond to years of a negative phase of the North Atlantic Oscillation and stronger EAM years over the past 150 years.     

Quantitative trait loci for yield and related traits in the wheat population Ning7840 × Clark

Grain yield and associated agronomic traits are important factors in wheat (Triticum aestivum L.) improvement. Knowledge regarding the number, genomic location, and effect of quantitative trait loci (QTL) would facilitate marker-assisted selection and the development of cultivars with desirable characteristics. Our objectives were to identify QTLs directly and indirectly affecting grain yield expression. A population of 132 F₁₂ recombinant inbred lines (RILs) was derived by single-seed descent from a cross between the Chinese facultative wheat Ning7840 and the US soft red winter wheat Clark. Phenotypic data were collected for 15 yield and other agronomic traits in the RILs and parental lines from three locations in Oklahoma from 2001 to 2003. Twenty-nine linkage groups, consisting of 363 AFLP and 47 SSR markers, were identified. Using composite interval mapping (CIM) analysis, 10, 16, 30, and 14 QTLs were detected for yield, yield components, plant adaptation (shattering and lodging resistance, heading date, and plant height), and spike morphology traits, respectively. The QTL effects ranged from 7 to 23%. Marker alleles from Clark were associated with a positive effect for the majority of QTLs for yield and yield components, but gene dispersion was the rule rather than the exception for this RIL population. Often, QTLs were detected in proximal positions for different traits. Consistent, co-localized QTLs were identified in linkage groups 1AL, 1B, 4B, 5A, 6A, and 7A, and less consistent but unique QTLs were identified on 2BL, 2BS, 2DL, and 6B. Results of this study provide a benchmark for future efforts on QTL identification for yield traits.     

Could the intrinsic rate of increase represent the fitness in terrestrial ectotherms?

The intrinsic rate of increase (r_m) has been considered as an important indicator of fitness in terrestrial ectotherms since long. It is actually an equivalent to the instantaneous growth rate of the exponential equation for describing the density-independent population growth. In terrestrial ectotherms, r_m has been demonstrated to be temperature-dependent. The temperature at which r_m was maximal, was considered to be the “optimal” temperature for fitness in Amarasekare and Savage (2012), but this definition needs further analysis. Only r_m cannot provide thorough representation of fitness. Because body size can affect the competitive abilities in many terrestrial ectotherms, both population size and body size should be considered in measuring the fitness of ectotherms. The rule of “bigger is better” requires relatively low temperature to increase in body size, whereas relatively high temperature is required for a rapid increase in population size. Thus, there is presumably a trade-off in temperature for adjusting individual body size and population size to achieve maximum fitness. We hypothesized that this temperature could be reflected by the intrinsic optimum temperature for developmental rate in the Sharpe–Schoolfield–Ikemoto model, and it led to a temperature estimate around 20 °C. However, the traditional viewpoint based on the temperature corresponding to the maximal intrinsic rate of increase provides a temperature estimate around 30 °C. This study suggests that a low temperature around 20 °C might authentically represent the optimal ambient temperature for fitness in terrestrial ectotherms. It implies that thermal biologists who are interested in the effect of temperature on the fitness in terrestrial ectotherms should pay more attention to their performance at low temperature rather than high temperature.     

Changes in the background losses of woody plant foliage to insects during the past 60 years: are the predictions fulfilled?

The existing scenarios generally predict that herbivory will increase with climate warming. An analysis of the published data on the background foliar losses of woody plants to insects in natural ecosystems across the globe from 1952 to 2013 provided no support for this hypothesis. We detected no temporal trend in herbivory within the temperate climate zone and a significant decrease in herbivory in the tropics. From 1964 to 1990, herbivory in the tropics was 39% higher than in the temperate region, but these differences disappeared by the beginning of the 2000s. Thus, environmental changes have already disturbed one of the global ecological patterns—the decrease in herbivory with latitude—by affecting ecosystem processes differently in tropical and temperate climate zones.     

Natural genetic variation in photosynthesis: an untapped resource to increase crop yield potential?

Raising crop yield potential is a major goal to ensure food security for the growing global population. Photosynthesis is the primary determinant of crop productivity and any gain in photosynthetic CO₂ assimilation per unit of leaf area (A) has the potential to increase yield. Significant intraspecific variation in A is known to exist in various autotrophic organs that represent an unexploited target for crop improvement. However, the large number of factors that influence photosynthetic rates often makes it difficult to measure or estimate A under dynamic field conditions (i.e. fluctuating light intensities or temperatures). This complexity often results in photosynthetic capacity, rather than realized photosynthetic rates being used to assess natural variation in photosynthesis. Here we review the work on natural variation in A, the different factors determining A and their interaction in yield formation. A series of drawbacks and perspectives are presented for the most common analyses generally used to estimate A. The different yield components and their determination based on different photosynthetic organs are discussed with a major focus on potential exploitation of various traits for crop improvement. To conclude, an example of different possibilities to increase yield in wheat through enhancing A is illustrated.     

Assessment of ecosystem health during the past 40 years for Lake Taihu in the Yangtze River Delta,China

An assessment of the ecosystem health of Lake Taihu in eastern China from 1960 to 2005 was conducted using separate and aggregated chemical and biological indicators. The chemical oxygen demand, the total nitrogen, total inorganic nitrogen and total phosphorus concentrations, and the molar ratio of TN to TP (N/P) have all significantly increased (P < 0.05) since 1980. The trophic state index increased from 35.0 in 1960 to >60.0 in 1990, confirming that Lake Taihu changed from being oligotrophic to being eutrophic. These changes in water quality have led to corresponding changes in species composition and in the densities and biomasses of many aquatic species. Algal blooms have occurred frequently since the late 1980s, leading to the dominance of small zooplankton and benthic invertebrates. About 41 fish, 65 zooplankton and 16 macrophyte species were estimated to have disappeared from the lake since the late 1980s. Buffer capacity increased for phytoplankton and zooplankton but decreased for zoobenthos. These results suggest that the Lake Taihu ecosystem was in better health in 1960, and has deteriorated since 1980.     

Can changes in the distributions of resident birds in China over the past 50?years be attributed to climate change?

The distributions of bird species have changed over the past 50 years in China. To evaluate whether the changes can be attributed to the changing climate, we analyzed the distributions of 20 subspecies of resident birds in relation to climate change. Long‐term records of bird distributions, gray relational analysis, fuzzy‐set classification techniques, and attribution methods were used. Among the 20 subspecies of resident birds, the northern limits of over half of the subspecies have shifted northward since the 1960s, and most changes have been related to the thermal index. Driven by climate change over the past 50 years, the suitable range and latitude or longitude of the distribution centers of certain birds have exhibited increased fluctuations. The northern boundaries of over half of the subspecies have shifted northward compared with those in the 1960s. The consistency between the observed and predicted changes in the range limits was quite high for some subspecies. The changes in the northern boundaries or the latitudes of the centers of distribution of nearly half of the subspecies can be attributed to climate change. The results suggest that climate change has affected the distributions of particular birds. The method used to attribute changes in bird distributions to climate change may also be effective for other animals.     

Changes in the decapod fauna of an Arctic fjord during the last 100 years (1908–2007)

Whereas Arctic benthic decapods are not a species-rich group, they can dominate the local epifauna and play important roles in the ecosystem. We studied the decapod fauna from Isfjorden (Svalbard, Norway, 78°N) by sampling from 22 stations and comparing with 50 and 100-year-old data from the same localities. Our data provide no evidence of changes in the species composition of decapods during the last 50 years. Hence, we do not observe the poleward shift of species found in several pelagic communities in the North Atlantic. However, there is statistical evidence for changes in the community structure between 1908 and both 1958 and 2007. The main change is a shift towards communities more dominated by the spider crab Hyas araneus and the hermit crab Pagurus pubescens in 2007, and with a corresponding decrease in the two shrimp species Lebbeus polaris and Spirontocaris spinus. These shrimps are specialist predators compared to the more opportunistic, scavenging crabs. We argue that increased disturbance levels may be a causal factor behind the observed community change, with likely sources of disturbance including trawling and climatic fluctuations.     

Nutrient fluxes and water quality in the drainage network of the Scheldt basin over the last 50 years

and use and urban activity in the catchment of the Scheldt river system have deeply changed during the last 50 years, modifying in turn the water quality of the drainage network and the fluxes of nutrient transferred to the estuary and to the sea. Based on the RIVERSTRAHLER model, developed for establishing the link between the biogeochemical functioning of large river systems and the constraints set by the meteorology, the morphology of the drainage network and the human activity in the watershed, we reassembled the data available to document these constraints in the Scheldt basin since the last half of the XXth century and we used them to reconstruct the variations of nutrient and oxygen concentrations at the outlet of the Scheldt drainage network. We compared the results with the water quality data at the entrance of the estuarine zone available since the 1960s. Both model results and observational data show a very severe deterioration of water quality (with deep oxygen depletion) in the beginning of the 1960s, while a clear trend to improvement is apparent since the late 1980s. The budget of nutrient loadings from the watershed, retention within the drainage network and delivery to the estuarine zone is established on an annual basis for the 50 last years. The yearly fluxes of nutrient delivered by the river to the estuary and the sea show a severe depletion of silica with respect to nitrogen compared with the requirements of diatoms, and a clear shift from the early 1990s from nitrogen to phosphorus potential limitation. Seasonal variations of nutrient delivery are however much more pronounced for nitrogen, with much less inputs during the dry seasons, while phosphorus inputs, mainly from point sources are more constant, so that nitrogen limitation can still occur during summer. Compared with similar budget estimations carried out for the Seine river system, the Scheldt basin, in spite of its much higher population density, does not deliver higher specific fluxes of nutrient (presently about 2000 kgN/km²/yr, 80 kgP/km²/yr and 1000 kgSi/km²/yr), owing to very efficient processes of nutrient retention.     

Communication in bottlenose dolphins: 50 years of signature whistle research

Bottlenose dolphins (Tursiops truncatus) produce individually distinctive signature whistles that broadcast the identity of the caller. Unlike voice cues that affect all calls of an animal, signature whistles are distinct whistle types carrying identity information in their frequency modulation pattern. Signature whistle development is influenced by vocal production learning. Animals use a whistle from their environment as a model, but modify it, and thus invent a novel signal. Dolphins also copy signature whistles of others, effectively addressing the whistle owner. This copying occurs at low rates and the resulting copies are recognizable as such by parameter variations in the copy. Captive dolphins can learn to associate novel whistles with objects and use these whistles to report on the presence or absence of the object. If applied to signature whistles, this ability would make the signature whistle a rare example of a learned referential signal in animals. Here, we review the history of signature whistle research, covering definitions, acoustic features, information content, contextual use, developmental aspects, and species comparisons with mammals and birds. We show how these signals stand out amongst recognition calls in animals and how they contribute to our understanding of complexity in animal communication.     

QTL mapping for grain filling rate and yield-related traits in RILs of the Chinese winter wheat population Heshangmai × Yu8679

A set of 142 winter wheat recombinant inbred lines (RILs) deriving from the cross Heshangmai x Yu8679 were tried in four ecological environments during the seasons 2006 and 2007. Nine agronomic traits comprising mean grain filling rate (GFR(mean)), maximum grain filling rate (GFR(max)), grain filling duration (GFD), grain number per ear (GNE), grain weight per ear (GWE), flowering time (FT), maturation time (MT), plant height (PHT) and thousand grain weight (TGW) were evaluated in Beijing (2006 and 2007), Chengdu (2007) and Hefei (2007). A genetic map comprising 173 SSR markers and two EST markers was generated. Based on the genetic map and phenotypic data, quantitative trait loci (QTL) were mapped for these agronomic traits. A total of 99 putative QTLs were identified for the nine traits over four environments except GFD, PHT and MT, measured in two environments (BJ07 and CD07), respectively. Of the QTL detected, 17 for GFR(mean), 16 for GFR(max), 21 for TGW and 10 for GWE involving the chromosomes 1A, 1B, 2A, 2D, 3A, 3B, 3D, 4A, 4D, 5A, 5B, 6D and 7D were identified. Moreover, 13 genomic regions showing pleiotropic effects were detected in chromosomes 1A, 1B, 1D, 2A, 2B, 2D, 3A, 3B, 4B, 4D, 5B, 6D and 7D; these QTL revealing pleiotropic effects may be informative for a better understanding of the genetic basis of grain filling rate and other yield-related traits, and represent potential targets for multi-trait marker aided selection in wheat.     

Is the rate of photosynthesis under blue light altered in the 7B-1 tomato mutant?

Changes of photosynthesis under blue light were examined in the ABA-overproducing 7B-1 mutant in tomato. Net photosynthetic rate (P _N), stomatal conductance (g _s), intrinsic water-use efficiency (WUE_i) and chlorophyll (a+b) [Chl (a+b)] content in leaves of different insertion (1^st, 4^th and 9^th ones) were measured in 5-, 7- and 9-week-old plants. P _N, g _s, and Chl (a+b) content were mostly similar in young leaves of 7B-1 and wild type (WT) plants. With the aging of leaves, a blue-light-induced increase in P _N and g _s to steady-state was delayed and steady-state values of P _N and g _s were lower in 7B-1 plants compared with WT. Steady-state values of WUE_i were increased in 4^th and 9^th leaves of 7B-1 plants compared with WT. The results can be explained by the higher endogenous level of ABA in 7B-1 plants and their lower sensitivity to ABA in earlier growth stage.     

Do helminths increase the vulnerability of released pheasants to fox predation?

The success of ring-necked pheasant (Phasianus colchicus) restocking in Asturias, northern Spain was assessed, and the role of parasites and predators in the mortality of released birds was studied. The experimental release of 56 radio-tagged pheasants showed that 98% of birds died within 12 days. As soon as 72 h after release, 67.5% of males and 55.0% of females were found dead. Foxes (Vulpes vulpes) killed 63% of the birds. The survival of those birds killed by foxes was lower than for birds which died due to other causes, and pheasants depositing eggs of the nematode Eucoleus contortus (Creplin, 1839) survived less than those apparently non-parasitized. No impact of the parasite on the pheasants' condition was found, but foxes preyed upon parasitized birds more than expected by random. The results suggest that: (i) the current pheasant releases in this area are unsuccessful and need to be improved; (ii) this is mainly due to intense predation by red foxes; and (iii) parasites could have some influence on the predation of released birds by foxes. However, the way parasites affect pheasant vulnerability remains unclear.