Photoadaptation, photoinhibition and productivity in the blue-green alga, Spirulina platensis grown outdoors

Two Spirulina platensis strains, SP-G and SP-RB, resistant and sensitive to photoinhibition of photosynthesis, respectively, were grown outdoors in dense cultures and under different photon fluxes provided by shading. Cultures of both strains grown under full sunlight were more resistant to photoinhibition than those grown under nets with 15–50% decreases in the incident photon flux. Cultures grown outdoors were more resistant to photoinhibition than the laboratory ones. At noon, the photosynthetic activity, as expressed by O₂ evolution, was higher for cultures grown under 50% shade, as compared with unshaded cultures. Productivity of the shaded cultures, in terms of biomass produced per day, was always higher when the cultures were protected from photoinhibition.     

Enhanced assimilation rate and water use efficiency with latitude through increased photosynthetic capacity and internal conductance in balsam poplar (Populus balsamifera L.)

In outdoor common gardens, high latitude populations of deciduous tree species often display higher assimilation rates ( A ) than low latitude populations, but they accomplish less height. To test whether trends in A reflect adaptation to growing season length or, alternatively, are garden growth artefacts, we examined variation in height increment and ecophysiological traits in a range-wide collection of Populus balsamifera L. populations from 21 provenances, during unconstrained growth in a greenhouse. Rooted cuttings, maintained without resource limitation under 21 h photoperiod for 90 d, displayed increasing height growth, A , leaf mass per area and leaf N per area with latitude whereas stomatal conductance ( g _s) showed no pattern. Water-use efficiency as indicated by both gas exchange and δ ¹³C increased with latitude, whereas photosynthetic nitrogen-use efficiency decreased. Differences in δ ¹³C were less than expected based on A/g _s, suggesting coextensive variation in internal conductance ( g _m). Analysis of A – C _i curves on a subset of populations showed that high latitude genotypes had greater g _m than low-latitude genotypes. We conclude that higher peak rates of height growth in high latitude genotypes of balsam poplar are supported by higher A , achieved partly through higher g _m, to help compensate for a shorter growing season.     

Effects of floods on fish assemblages in an intermittent prairie stream

1. Floods are major disturbances to stream ecosystems that can kill or displace organisms and modify habitats. Many studies have reported changes in fish assemblages after a single flood, but few studies have evaluated the importance of timing and intensity of floods on long‐term fish assemblage dynamics. 2. We used a 10‐year dataset to evaluate the effects of floods on fishes in Kings Creek, an intermittent prairie stream in north‐eastern, Kansas, U.S.A. Samples were collected seasonally at two perennial headwater sites (1995–2005) and one perennial downstream flowing site (1997–2005) allowing us to evaluate the effects of floods at different locations within a watershed. In addition, four surveys during 2003 and 2004 sampled 3–5 km of stream between the long‐term study sites to evaluate the use of intermittent reaches of this stream. 3. Because of higher discharge and bed scouring at the downstream site, we predicted that the fish assemblage would have lowered species richness and abundance following floods. In contrast, we expected increased species richness and abundance at headwater sites because floods increase stream connectivity and create the potential for colonisation from downstream reaches. 4. Akaike Information Criteria (AIC) was used to select among candidate regression models that predicted species richness and abundance based on Julian date, time since floods, season and physical habitat at each site. At the downstream site, AIC weightings suggested Julian date was the best predictor of fish assemblage structure, but no model explained >16% of the variation in species richness or community structure. Variation explained by Julian date was primarily attributed to a long‐term pattern of declining abundance of common species. At the headwater sites, there was not a single candidate model selected to predict total species abundance and assemblage structure. AIC weightings suggested variation in assemblage structure was associated with either Julian date or local habitat characteristics. 5. Fishes rapidly colonised isolated or dry habitats following floods. This was evidenced by the occurrence of fishes in intermittent reaches and the positive association between maximum daily discharge and colonisation events at both headwater sites. 6. Our study suggests floods allow dispersal into intermittent habitats with little or no downstream displacement of fishes. Movement of fishes among habitats during flooding highlights the importance of maintaining connectivity of stream networks of low to medium order prairie streams.     

Timing of photoperiodic competency causes phenological mismatch in balsam poplar (Populus balsamifera L.)

Plant phenology is expected to be sensitive to climate warming. In boreal trees, spring flush is primarily temperature driven, whereas height growth cessation and autumn leaf senescence are predominantly controlled by photoperiod. Cuttings of 525 genotypes from the full range of balsam poplar were planted into two common gardens (Vancouver and Indian Head, Canada) at similar latitudes, but with differing winter temperatures and growing seasons. There was clinal variation in spring and, particularly, summer and fall phenology. Bud flush and, despite milder climate, bud set and leaf drop were earlier at Vancouver than at Indian Head by 44, 28 and 7 d, respectively. Although newly flushed growth is insensitive to photoperiod, many genotypes at both sites became competent before the summer solstice. At Vancouver, high‐latitude genotypes set dormant terminal buds in mid‐spring. Most other genotypes grew until midsummer or set bud temporarily and then experienced a second flush. In both gardens and in a growth chamber experiment, earlier bud set was associated with reduced height growth and higher root/shoot ratios. Shoots attained competency ～5 weeks after flushing, which would normally prevent dormancy induction before the solstice, but may be insufficient if spring advances by more than a few weeks.     

THE MORAL OBLIGATION TO CREATE CHILDREN WITH THE BEST CHANCE OF THE BEST LIFE

According to what we call the Principle of Procreative Beneficence (PB), couples who decide to have a child have a significant moral reason to select the child who, given his or her genetic endowment, can be expected to enjoy the most well-being. In the first part of this paper, we introduce PB, explain its content, grounds, and implications, and defend it against various objections. In the second part, we argue that PB is superior to competing principles of procreative selection such as that of procreative autonomy. In the third part of the paper, we consider the relation between PB and disability. We develop a revisionary account of disability, in which disability is a species of instrumental badness that is context- and person-relative. Although PB instructs us to aim to reduce disability in future children whenever possible, it does not privilege the normal. What matters is not whether future children meet certain biological or statistical norms, but what level of well-being they can be expected to have.     

Partial local mate competition in the wasp Trichogramma euproctidis: the role of emergence sex ratio on female mating behaviour

1. Parasitic wasps with structured populations are generally assumed to follow the local mate competition (LMC) model: females lay only the minimal number of sons necessary to inseminate all daughters in the emergence patch, and increase this number when faced with additional broods from unrelated females. After emergence, daughters mate with local males before dispersing for host location and oviposition. The main predictions from the model have been verified for many species. 2. Conflicting evidence exists on the status of the egg parasitoids Trichogramma regarding their on‐patch versus off‐patch mating. Although the life‐history traits of several species indicate that mating must occur on the emergence patch, recent data suggest that mating could occur outside the natal patch. 3. In this study, we measured the level of off‐patch mating in the egg parasitoid Trichogramma euproctidis using two isofemale lines in a greenhouse experiment. The impact of the sex ratio on the level of off‐patch mating was also tested. 4. The overall off‐patch mating proportion was 40.5% with a range between 0 and 85.7%, and was influenced by the sex ratio on the emergence patch: the more males available at emergence, the less off‐patch mating occurring. 5. The mating structure of this species can be described as partial LMC.     

Comparing and contrasting life history variation in four aphid hyperparasitoids

1. In primary parasitoids, significant differences in life history and reproductive traits are observed among parasitoids attacking different stages of the same host species. Much less is known about hyperparasitoids, which attack different stages of primary parasitoids. 2. Parasitoids exploit hosts in two different ways. Koinobionts attack hosts that continue feeding and growing during parasitism, whereas idiobionts paralyse hosts before oviposition or attack non‐growing host stages, e.g. eggs or pupae. 3. Koino‐/idiobiosis in primary parasitoids are often associated with different expression of life history trade‐offs, e.g. endo‐ versus ectoparasitism, high versus low fecundity and short versus long life span. 4. In the present study, life history parameters of two koinobiont endoparasitic species (Alloxysta victrix; Syrphophagus aphidivorus), and two idiobiont ectoparasitic species (Asaphes suspensus; Dendrocerus carpenteri) of aphid hyperparasitoids were compared. These hyperparasitoids attack either the parasitoid larva in the aphid before it is killed and mummified by the primary parasitoid or the parasitoid prepupa or pupa in the dead aphid mummy. 5. There was considerable variation in reproductive success and longevity in the four species. The idiobiont A. suspensus produced the most progeny by far and had the longest lifespan. In contrast, the koinobiont A. victrix had the lowest fecundity. Other developments and life history parameters in the different species were variable. 6. The present results reveal that there was significant overlap in life history and reproductive traits among hyperparasitoid koinobionts and idiobionts, even when attacking the same host species, suggesting that selection for expression of these traits is largely association specific.     

Habitat use by breeding Tree Sparrows Passer montanus

Tree Sparrows Passer montanus showed a strong preference for nest-sites adjacent to wetland habitats, and avoidance of sites on intensively managed mixed farmland distant from Rutland Water. A variety of wetland edge habitats were frequently used by foraging adult birds when provisioning nestlings, and invertebrate prey of aquatic origin was frequently recorded in chick diet. We suggest that the wetland edge habitats at the study sites played a key role in providing adequate diversity and availability of suitable invertebrate prey to allow successful chick rearing throughout the long breeding season of this multi-brooded passerine. It is possible that large areas of formerly occupied farmland in the UK no longer provide these invertebrate resources due to the effects of intensification in the late 20th century. There was no evidence that the availability of supplementary seed food within 1 km of the nest-site influenced nest-site choice, or affected productivity. It is probable that the importance of seed food resources to the persistence of Tree Sparrow populations operates on a larger spatial scale than that tested in this study, due to the greater mobility of Tree Sparrows in the non-breeding season, when seed resources are most likely to be a key limiting factor. When considering conservation management aimed at recovering breeding populations of Tree Sparrows, the key resources of seed food, invertebrate food and nest-sites must be made available at appropriate spatial scales.     

Isolation and cross‐familial amplification of 41 microsatellites for the brook charr (Salvelinus fontinalis)

The brook charr (Salvelinus fontinalis; Osteichthyes: Salmonidae) is a phenotypically diverse fish species inhabiting much of North America. But relatively few genetic diagnostic resources are available for this fish species. We isolated 41 microsatellites from S. fontinalis polymorphic in one or more species of salmonid fish. Thirty‐seven were polymorphic in brook charr, 15 in the congener Arctic charr (Salvelinus alpinus) and 14 in the lake charr (Salvelinus namaycush). Polymorphism was also relatively high in Oncorhynchus, where 21 loci were polymorphic in rainbow trout (Oncorhynchus mykiss) and 16 in cutthroat trout (Oncorhynchus clarkii) but only seven and four microsatellite loci were polymorphic in the more distantly related lake whitefish (Coregonus clupeaformis) and Atlantic salmon (Salmo salar), respectively. One duplicated locus (Sfo228Lav) was polymorphic at both duplicates in S. fontinalis.