The reproductive success of a Quercus petraea × Q. robur F1-hybrid in back-crossing situations

A 56 year old Quercus petraea × Q. robur F1-hybrid was back-crossed to both parental species. Pollen mixes were applied and paternity assigned to offspring based on microsatellite markers. The studied Q. petraea × Q. robur hybrid proved highly fertile and back-crossed well with both Q. robur and Q. petraea with slight but not significant preference for Q. robur. The results do not support the hypothesis about highly unidirectional gene flow between Q. robur and Q. petraea towards Q. robur as the observed back-crossing ability of the hybrid opens a route for nuclear gene flow from Q. robur to Q. petraea. However, Q. petraea × Q. robur hybrids may be rare in nature and the results do not tell us if the (probably more common) reciprocal hybrid also back-crosses easily to Q. petraea.     

CNS mastitis: nothing to worry about?

In this paper, we analyzed a very large field data set on intramammary infections (IMI) and the associated somatic cell count (SCC) in dairy cows. The objective of the study was to analyze the impact of coagulase-negative staphylococci (CNS) IMI on cow SCC, both mean and variability, and on the potential of these infections to have a major impact on the bulk milk SCC (BMSCC). Data and milk samples for bacterial culture were collected by Quality Milk Production Services (QMPS) between 1992 and March of 2007. The QMPS program services dairy farms in New York State and other states in the Northeastern USA and operates in conjunction with Cornell University. Only records from cows where SCC and milk production data were available, and where only one organism was isolated from bacterial cultures of milk samples (or where culture was negative) were used for this analysis. A total of 352,614 records from 4200 whole herd mastitis screening sampling qualified for this study. Within herds an average of 15% (S.D. 12%) of cows sampled were infected with CNS, ranging between 0 and 100%. Average within herd prevalence of cows with a CNS IMI and an SCC over 200,000 cells/ml was 2% (S.D. 4%) with a minimum of 0% and a maximum of 50%. Results of linear mixed models showed three distinct populations of IMI statuses: negative cultures with the lowest SCC; CNS and Corynebacterium bovis with a moderate increase in SCC, and Streptococcus agalactiae, Streptococcus spp. and Staphylococcus aureus showing an important increase in SCC. Surprisingly, milk production was slightly but significantly higher in CNS infected cows compared to culture-negative cows, whereas it was strongly reduced in cows with a major pathogen IMI. The percentage contribution of CNS infections to the BMSCC was 17.9% in herds with a BMSCC less than 200,000 cells/ml. This value decreased to 11.9 and 7.9% in herds with bulk milk SCC between 200,000 and 400,000 and over 400,000 cells/ml, respectively. We concluded that very few herds with milk quality problems would have an important increase in BMSCC that could be mostly attributed to CNS infections. On the other hand, in herds with low BMSCC, CNS infections may be an important contributor to the total number of somatic cells in the bulk milk.     

Biochemical genetics of oxidative resistance to diazinon in the house fly

The genetics and biochemistry of oxidative resistance to diazinon were investigated in a diazinon-resistant strain of the house fly, Musca domestica L. The resistant strain was crossed with a multimarker susceptible strain and substrains containing portions of the resistant strain genome were prepared. Resistance, microsomal oxidase, and cytochrome P-450 spectral characteristics were then compared in the different strains. The major gene for resistance to diazinon is semidominant and is located on chromosome II, 13 crossing over units from the recessive mutant stubby wing. Additional resistance genes occur on chromosome II and on other chromosomes as well. Resistance to diazinon was introduced into a susceptible mutant-marked strain via genetic crossing over. Increases in parathion oxidase, total and P-450-specific N- and O-demethylase activity, and resistant strain type I binding spectrum were introduced along with resistance, indicating genes controlling these parameters and resistance are either identical or closely linked. No increase in activity of cytochrome P-450 itself was introduced into the mutant strain. Additional genes controlling the amount of cytochrome P-450 and several spectral changes characteristic of the resistant strains are apparently controlled by genes located at different loci on chromosome II. Resistance factors on other chromosomes are also present, but were not characterized.     

Ecological consequences of variation in standard metabolism and dominance among salmon parr

Abstract – Standard metabolic rate (SMR, closely related to basal and resting metabolism) varies by up to threefold among juvenile Atlantic salmon, Salmo salar L., of similar size at common temperature. Here, consequences of this variation are predicted by combining empirically derived relationships between SMR, specific dynamic action, energy budgets, water velocity, food level in the environment and food availability to fish. The range of velocities across which growth is predicted to occur is inversely related to a fish’s SMR. Growth is positively related to SMR at high but negatively related to it at low‐food levels. The relationship between food level and the range of velocities over which lower SMR fish can grow but higher SMR fish cannot is asymmetrically bi‐phasic and peaked. It is predicted that maternal manipulation of offspring SMR would generate fitness benefits through bet‐hedging against unpredictability in food level and increases in the overall range of velocities that the family of offspring can occupy and thrive in.     

When and why do smallmouth bass abandon their broods? The effects of brood and parental characteristics

Abstract Variation in brood abandonment was explored by conducting partial brood removals from smallmouth bass, Micropterus dolomieu Lacepède, nests in two north temperate lakes. In both lakes, percent of the brood removed had no effect on nest failure rates. Nest failure prior to offspring swim‐up was more common, but unrelated to brood size after removal, in the lake with higher post‐spawning mortality and lower growth and fecundity. Brood size after removal was negatively related to nest failure in the lake with high survival, growth and fecundity. Nests guarded by young males failed more frequently than those of old males, and young broods failed more frequently than old broods. Dynamic programming and logistic regression models developed to predict nest fate worked better for the lake with selective pressures that theoretically favoured abandonment (e.g. high post‐spawning mortality). Both models identified male age and brood age as important factors in predicting nest fates. Because nest success is related to the age of the parent, this could have consequences for overall nest success for populations with different demographics.     

水盐胁迫对沙枣幼苗叶绿素荧光参数和色素含量的影响

在不同水分和盐分胁迫条件下测定2个种源沙枣的叶绿素含量、叶绿素荧光参数Fv/Fm和Fv/F0的变化。结果表明:随着胁迫的增加,2个种源的沙枣叶绿素含量、Fv/Fm和Fv/F0都表现出先增加后降低的趋势;在水分梯度为50%~55%和盐分梯度为0.1 mol/L时2个种源的叶绿素含量、Fv/Fm和Fv/F0值分别达到最大值;随胁迫时间增加,水分胁迫下包头种源叶绿素含量下降幅度比赤峰种源高出29.28%,而Fv/Fm值和Fv/F0值最大改变量分别为赤峰种源的1.25倍和6.62倍;盐分胁迫下包头种源沙枣的叶绿素含量下降幅度比赤峰种源高出25.26%,而Fv/Fm值和Fv/F0值最大改变量分别为赤峰种源的2.38倍和3.05倍。这说明水分和盐分胁迫对包头种源沙枣的叶绿素含量及其荧光参数的影响高于对赤峰种源的影响。     

Comparison of dietary essential amino acid requirements determined from group‐housed versus individually‐housed juvenile bluegill,Lepomis macrochirus

Two 60‐day experiments were conducted sequentially to determine (i) lysine requirement of juvenile bluegill, Lepomis macrochirus based on the dose–response method, (ii) requirements for other essential amino acids (EAAs) using whole‐body amino acid profile and (iii) whether differences in growth rates of group‐housed versus individually‐housed bluegills lead to different lysine requirement levels because of the presence and absence, respectively, of social hierarchies. Seven, semi‐purified, experimental diets (isonitrogenous, isocaloric) were prepared to contain graded levels of digestible lysine (10–31 g kg⁻¹). Experiment‐1 involved group‐housed bluegills (approximately 27 g, n = 10 fish/chamber, 4 chambers/diet) whereas experiment‐2 involved individually‐housed bluegills (approximately 30 g, n = 1 fish/chamber, 14 chambers/diet). Fish were fed twice daily to apparent satiation. Bluegill growth responses in both experiments generally improved (P < 0.05, anova ) with increasing dietary lysine levels from 10 to 16 g kg⁻¹, and then levelled off with further increase in lysine level (P > 0.05). Optimal dietary lysine level (digestible basis) was estimated to be 15 g kg⁻¹ based on broken‐line regression analyses of relative growth rate and feed conversion ratio with no differences being observed between the two rearing methods. Determined dietary requirement levels for other EAAs ranged from 2.4 g kg⁻¹ (tryptophan) to 15.3 g kg⁻¹ (leucine).     

Using DNA from museum specimens to preserve the integrity of evolutionarily significant unit boundaries in threatened species

Use of DNA from museum samples is a powerful tool to directly establish historical ESU boundaries in areas where populations of a species have been extirpated. The brush-tailed rock-wallaby (Petrogale penicillata) has suffered extensive reductions in range and population size since European settlement in Australia. Populations of this species have been grouped into three putative evolutionarily significant units (ESUs) which were likely once contiguous along the south-east coast of Australia. However, there is currently a gap of ∼320 km between extant populations of the southern and central ESUs. Conservation plans for the brush-tailed rock-wallaby include re-introductions of animals to locations within their former range. In order to preserve the historic geographic integrity of the genetic lineages within the species, it is necessary to map the boundary between the southern ESU and central ESU to allow more informed management decisions about which lineages should be used to re-stock specific geographic locations. We have extracted DNA from samples from museum specimens that come from locations between the southernmost extant colony of the central ESU and the remaining wild colony of the southern ESU. We sequenced a 177 bp interval of the left domain of the mitochondrial DNA control region and used phylogenetic analysis to group obtained sequences with previously published sequences belonging to the three ESUs. We have extended the range of the central ESU southwards and the range of the southern ESU northwards such that the gap between the ESUs is now approximately 160 km. We recommend that, where suitable historical museum collections exist, this technique be incorporated into re-introduction plans for other threatened species.