Evidence for long-distance dispersal in a sedentary passerine, Gymnorhina tibicen (Artamidae)

Australian magpies (Gymnorhina tibicen) are group-living birds found across much of mainland Australia. Adults commonly remain in a breeding territory until death. Young of the year either remain on the natal (birth) site or are forced by their parents to disperse. Observational studies in south-eastern Australia suggest that most dispersing juveniles settle within 7 km of their natal territory. Therefore, despite potential for considerable gene flow (via flight), social organization predisposes magpies towards local population structuring. In this study, we measured genetic variation at both nuclear (allozyme) and mitochondrial loci and found evidence of substantial gene flow over very large distances (up to 1599 km). Thus, some juvenile magpies may disperse much greater distances than was previously thought. For mtDNA, geographic and genetic distance were strongly correlated, consistent with a pattern of isolation by distance. Therefore, although female gene flow is substantial it is apparently geographically restricted over large distances, in approximately a stepping-stone fashion. We conclude that a strong relationship between gene flow and geographic distance can develop even over large distances if populations have experienced no major historical disturbances to gene flow.     

Elevationally biased avian predation as a contributor to the spatial distribution of geometrid moth outbreaks in sub‐arctic mountain birch forest

1. Population dynamics and interactions that vary over a species' range are of particular importance in the context of latitudinal clines in biological diversity. Winter moth (Operophtera brumata) and autumnal moth (Epirrita autumnata) are two species of eruptive geometrids that vary widely in outbreak tendency over their range, which generally increases from south to north and with elevation. 2. The predation pressure on geometrid larvae and pupae over an elevational gradient was tested. The effects of background larval density and bird occupancy of monitoring nest boxes on predation rates were also tested. Predation on larvae was tested through exclusion treatments at 20 replicate stations over four elevations at one site, while pupae were set out to measure predation at two elevations at three sites. 3. Larval densities were reduced by bird predation at three lower elevations, but not at the highest elevation, and predation rates were 1.9 times higher at the lowest elevation than at the highest elevation. The rate of predation on larvae was not related to background larval density or nest box occupancy, although there were more eggs and chicks at the lowest elevation. There were no consistent differences in predation on pupae by elevation. 4. These results suggest that elevational variation in avian predation pressure on larvae may help to drive elevational differences in outbreak tendency, and that birds may play a more important role in geometrid population dynamics than the focus on invertebrate and soil predators of previous work would suggest.     

The Effects of Temperature and Daylength on the Rate of Development of Pigeonpea

Eleven cultivars of pigeonpea, representing five different maturitygroups, were grown under controlled conditions to determinehow the rate of development from sowing to flower bud initiation(FBI) and sowing to flowering was affected by temperature anddaylength, the two environmental variables thought to have mostinfluence on reproductive development. Both temperature and daylength had substantial effects overthe range 16–32 C and 10–14 h respectively. Comparisonswithin the 12 h daylength treatment showed no consistent patternwith mean temperature. A discrete-rate analysis was used todetermine the effect on development of each of the temperaturesmaking up the various treatment combinations of day and nighttemperature. The rate of development from sowing to FBI varied among cultivars.The responses to temperature were all strongly curvilinear withoptima between 20 and 24 C. The rate of development from sowingto flowering showed a similar pattern. The effect of daylengthon the rate of development was the greatest between sowing andFBI, with the greatest sensitivity between 12 and 14 h. For the range of conditions considered, temperature had at leastas great an influence as daylength on the rates of developmentfrom sowing to FBI and from sowing to flowering. Some of theresponses to time of planting that have previously been attributedto daylength effects may, in fact, have been due to temperature.The responses to temperature of reproductive and vegetativedevelopment are very different. Phenology, Cajanus cajan     

The distributions of a wide range of taxonomic groups are expanding polewards

Evidence is accumulating of shifts in species' distributions during recent climate warming. However, most of this information comes predominantly from studies of a relatively small selection of taxa (i.e., plants, birds and butterflies), which may not be representative of biodiversity as a whole. Using data from less well‐studied groups, we show that a wide variety of vertebrate and invertebrate species have moved northwards and uphill in Britain over approximately 25 years, mirroring, and in some cases exceeding, the responses of better‐known groups.     

The Occurrence and Development of Plasmodium mexicanum in the Western Fence Lizard Sceloporus occidentalis

SYNOPSIS. From various localities in California, 81 (21%) of 381 Sceloporus occidentalis were found infected with Plasmodium mexicanum. Variations in asexual reproduction and host response during the acute period of development are discussed.
Appearance of initial infections in early March and the subsequent increase in natural incidence of the parasite, the absence of infections in hatchlings, and the persistence of numerous gametocytes in hibernating lizards suggest a period of spring transmission.     

Influence of Elevated CO2 and Temperature on the Photosynthesis and Respiration of White Clover Dependent on N2 Fixation

Single clonal plants of white clover (Trifolium repens L) grownfrom explants in a Perlite rooting medium, and dependent fornitrogen on N₂ fixation in root nodules, were grown for severalweeks in controlled environments which provided two regimesof CO₂, and temperature 23/18 °C day/night temperaturesat 680 µmol mol^–1 CO₂, (C680), and 20/15 °Cday/night temperatures at 340 µmol mol^–1 CO₂ (C340)After 3–4 weeks of growth, when the plants were acclimatedto the environmental regimes, leaf and whole-plant photosynthesisand respiration were measured using conventional infra-red gasanalysis techniques Elevated CO₂ and temperature increased ratesof photosynthesis of young, fully expanded leaves at the growthirradiance by 17–29%, despite decreased stomatal conductancesand transpiration rates Water use efficiency (mol CO₂ mol H₂O^–1)was also significantly increased Plants acclimated to elevatedCO₂, and temperature exhibited rates of leaf photosynthesisvery similar to those of C340 leaves ‘instantaneously’exposed to the C680 regime However, leaves developed in theC680 regime photosynthesised less rapidly than C340 leaves whenboth were exposed to a normal CO₂, and temperature environmentIn measurements where irradiance was varied, the enhancementof photosynthesis in elevated CO₂ at 23 °C increased graduallyfrom approx 10 % at 100 µmol m^–1 s^–1 to >27 % at 1170 µmol m^–2 s^–1 In parallel, wateruse efficiency increased by 20–40 % at 315 µmolm^–2 s^–1 In parallel, water use efficiency increasedby 20–40 % at 315 µmol m^–2 s^–1 In parallel,water use efficiency increased by 20–40 % at 315 µmolm^–2 s^–1 In parallel, water use efficiency increasedby 20–40 % at 315 µmol m^–2 s^–1 to approx100 % at the highest irradiance Elevated CO₂, and temperatureincreased whole-plant photosynthesis by > 40 %, when expressedin terms of shoot surface area or shoot weight No effects ofelevated CO₂ and temperature on rate of tissue respiration,either during growth or measurement, were established for singleleaves or for whole plants Dependence on N₂, fixation in rootnodules appeared to have no detrimental effect on photosyntheticperformance in elevated CO₂, and temperature Trifolium repens, white clover, photosynthesis, respiration, elevated CO₂, elevated temperature, water use efficiency, N₂ fixation     

Effects of diet and host access on fecundity and lifespan in two fruit fly species with different life‐history patterns

The reproductive ability of female tephritids can be limited and prevented by denying access to host plants and restricting the dietary precursors of vitellogenesis. The mechanisms underlying the delayed egg production in each case are initiated by different physiological processes that are anticipated to have dissimilar effects on lifespan and reproductive ability later in life. The egg‐laying abilities of laboratory‐reared females of the Mediterranean fruit fly (Ceratitis capitata Wiedmann) and melon fly (Bactrocera cucurbitae Coquillett) from Hawaii are delayed or suppressed by limiting access to host fruits and dietary protein. In each case, this is expected to prevent the loss of lifespan associated with reproduction until protein or hosts are introduced. Two trends are observed in each species: first, access to protein at eclosion leads to a greater probability of survival and a higher reproductive ability than if it is delayed and, second, delayed host access reduces lifetime reproductive ability without improving life expectancy. When host access and protein availability are delayed, the rate of reproductive senescence is reduced in the medfly, whereas the rate of reproductive senescence is generally increased in the melon fly. Overall, delaying reproduction lowers the fitness of females by constraining their fecundity for the remainder of the lifespan without extending the lifespan. © 2013 The Royal Entomological Society