Andromonoecy and fruit set in three genera of the Proteaceae

It has been suggested by some authors that the low fruit to flower ratio in some Proteaceae is due to andromonoecy, while others, looking particularly at Banksia , have not been able to find evidence for male flowers in the inflorescences. Stirlingia latifolia, Xylomelum occidentals and X. angustifolium are clearly andromonoecous, while no evidence for this condition could be found in Brabejum stellatifoliutn. Production of fertile fruit is related to andromonoecy in Xylomelum and S. latifolia but not in Brabejum. It is unlikely that all-encompassing solutions will be found to what initially seem to be widespread traits in the family, especially in regard to pollination biology, as the genera in the family occupy widely different environments and have very diverse ecological ranges.     

A comparative study of breeding seasonality and litter size in eleven taxa of captive lemurs (Lemur andVarecia)

Breeding records of 11 taxa of captive lemurs housed at the Duke University Primate Center (DUPC), North Carolina, were analyzed for differences in the timing of births, for the relationship between breeding season and photoperiod, and for differences in litter size. At DUPC there are significant differences in the timing of births among certain taxa, including differences among some subspecies of Lemur fulvus.However, changes in latitude result in changes in the timing of the breeding season. Lemurs moved to higher latitudes mate at lower light-dark ratios than on Madagascar. The data presented here are consistent with the following model: a photoperiodic cue initiating reproductive activity, presumably a light-dark threshold, precedes the actual mating season by approximately 2 months, with an intervening period of physiological and social preparation. On Madagascar, selection may have favored births that coincide with the end of dry seasons and the beginning of wet seasons, which results in lactation and weaning during times of resource abundance. Taxa from the north and east have the highest mean litter sizes; those from the west have the lowest.     

An Extreme Value Analysis of Pollutant Concentrations in Surface Soils Due to Atmospheric Deposition

Risk assessments often rely on deterministic models using long-term averages or “steady-state” values of input variables. Such models do not provide the information needed to estimate acute exposures. This study uses extreme value theory to examine the frequency and magnitude of daily pollutant concentrations in surface soils predicted at six U.S. locations. Concentrations are predicted using a deposition-leaching model and 50 years of historical precipitation data. A stochastic model also is used to generate 1000 years of precipitation data as modeling inputs for each location. The annual maximum concentrations at each site are fitted to a Gumbel type I distribution to estimate occurrence probability. For soluble pollutants, the predicted concentration varied substantially with precipitation, and the maximum daily concentrations exceeded annual averages by 4 to 8 times. Observed and synthetic precipitation data produced similar results at most study locations, though the synthetic data provided a slightly better fit to the Gumbel type I distribution. The precipitation model allows the generation of representative precipitation data that extend limited historical records. The extreme value analysis facilitates the evaluation of maximum pollutant concentrations, return periods, and other statistics that are important in evaluating acute exposures.     

Environmental and genetic control of crassulacean acid metabolism in two crassulacean species and an F1 hybrid with differing biomass δ13C values

Abstract The growth, biomass δ¹³C values, and ability to accumulate titratable acidity at night were compared in eight environmental treatments for Cremnophila linguifolia, Sedum greggii, and their F₁ hybrid. In the phytotron, differences in treatment daylength, day/night temperature and water availability were all found to have effects on total plant dry weight, nocturnal accumulation of titratable acidity and biomass δ¹³C value of at least some of the genotypes. However, there were differences between the genotypes both in the magnitude and direction of response of the phenotypic properties to the treatment variables. The phytotron δ¹³C values ranged from -12.9 to -19.2‰ for C. linguifolia, from -22.2 to -33.4‰ for S. greggii, and from -19.2 to -24.9‰ for the hybrid. After with-holding water for 76 h both C. linguifolia and the hybrid had midday Ψ_leaf values of -0.23 MPa; however, S. greggii had a value of -1.05 MPa. In contrast to past observations of other species, the daily watered plants of C. linguifolia had less negative δ¹³C values than did the plants watered only weekly.     

Isolation and characterization of microsatellites in Pacific white shrimp Penaeus (Litopenaeus) vannamei

Five polymorphic microsatellite loci were characterized for Penaeus (Litopenaeus) vannamei. Loci were isolated using a partial Sau3A1 genomic library by the sequencing of randomly selected clones and by a biotinylated (CT)₁₀ and (GT)₁₀ probes screening procedure. The last strategy resulted in the most useful data. About 40% of the clones showed a previously reported satellite/microsatellite (PVS1), reducing the chance of finding new microsatellite regions. Whereas two of the microsatellite loci with more than 10 alleles will be useful for mating analysis in a breeding program, the others might prove useful for population genetic studies.     

Optimal reproductive phenology under size‐dependent cannibalism

Intra‐cohort cannibalism is an example of a size‐mediated priority effect. If early life stages cannibalize slightly smaller individuals, then parents face a trade‐off between breeding at the best time for larval growth or development and predation risk from offspring born earlier. This game‐theoretic situation among parents may drive adaptive reproductive phenology toward earlier breeding. However, it is not straightforward to quantify how cannibalism affects seasonal egg fitness or to distinguish emergent breeding phenology from alternative adaptive drivers. Here, we devise an age‐structured game‐theoretic mathematical model to find evolutionary stable breeding phenologies. We predict how size‐dependent cannibalism acting on eggs, larvae, or both changes emergent breeding phenology and find that breeding under inter‐cohort cannibalism occurs earlier than the optimal match to environmental conditions. We show that emergent breeding phenology patterns at the level of the population are sensitive to the ontogeny of cannibalism, that is, which life stage is subject to cannibalism. This suggests that the nature of cannibalism among early life stages is a potential driver of the diversity of reproductive phenologies seen across taxa and may be a contributing factor in situations where breeding occurs earlier than expected from environmental conditions.