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1.
The effect of fungal infection on the reproductive potential of two-spotted spider mite, Tetranychus urticae, was evaluated as part of the full biocontrol potential of three entomopathogenic fungi by modeling of fecundity probability.
Female mites (≤2-day-old) on leaves were exposed to the sprays of Beauveria bassiana, Paecilomyces fumosoroseus and Metarhizium anisopliae at the concentrations of 1.13 × 103, 1.55 × 103 and 0.95 × 103 deposited conidia mm−2 and then individually reared at 25°C and 12:12 L:D for oviposition. Mite mortalities 10 days after spraying were 73.1, 75.4
and 67.9% in the fungal treatments versus 15.5% in control. On average, females infected by the three fungal species survived
5.8, 6.2 and 6.3 days, and laid 3.1, 4.0 and 4.0 eggs per capita, respectively. These were 3–4 fold lower than the control
fecundity at 12.3. The cumulative probabilities [P(m ≤ N)] for the counts of infected and non-infected (control) females laying m eggs per capita (m ≤ N) during 10 days fit very well the equation P(m ≤ N) = 1/[1 + exp(a + bm)] (r
2 ≥ 0.98), yielding a solution to the probability for the female mites to achieve a specific fecundity {P(m ≤ N)−P[m ≤ (N − 1)]}. Consequently, the infected mites had 71–78% chance to lay ≤5 eggs per capita but only 5–8% to deposit >10 eggs despite
some variation among the tested fungi. In contrast, the chances for the non-infected mites to achieve the low and high fecundities
were 23 and 55%. The fitted probabilities provide a full coverage of the fecundity potential of infected versus non-infected
mites and are more informative than the mean fecundities. 相似文献
2.
Jan E. Janečka M. E. Tewes L. L. Laack L. I. GrassmanJr A. M. Haines R. L. Honeycutt 《Conservation Genetics》2008,9(4):869-878
Threatened populations are vulnerable to the effects of genetic drift and inbreeding, particularly when gene flow is low and
the effective population size is small. Estimates of effective population size (N
e
) provide important information on the status of endangered populations that have experienced severe fragmentation and serve
as indicators of genetic viability. Genetic data from microsatellite loci were used to estimate N
e
for the 2 remaining populations of the endangered ocelot (Leopardus pardalis albescens) occurring in the United States. Several methods were used to calculate N
e
, resulting in estimates ranging from N
e
= 8.0 (95% CI: 3.2–23.1) to 13.9 (95% CI: 7.7–25.1) for the population located at the Laguna Atascosa Wildlife Refuge in
Cameron County, Texas. The ocelot population in Willacy County, Texas, had N
e
estimates of 2.9 (95% CI: 1.7–5.6) and 3.1 (95% CI: 1.9–13.5), respectively. Estimates of N
e
in both populations were below the critical value recommended for short-term viability. 相似文献
3.
Population subdivision due to habitat loss and modification, exploitation of wild populations and altered spatial population
dynamics is of increasing concern in nature. Detecting population fragmentation is therefore crucial for conservation management.
Using computer simulations, we show that a single sample estimator of N
e based on linkage disequilibrium is a highly sensitive and promising indicator of recent population fragmentation and bottlenecks,
even with some continued gene flow. For example, fragmentation of a panmictic population of N
e = 1,000 into demes of N
e = 100 can be detected with high probability after a single generation when estimates from this method are compared to prefragmentation
estimates, given data for ~20 microsatellite loci in samples of 50 individuals. We consider a range of loci (10–40) and individuals
(25–100) typical of current studies of natural populations and show that increasing the number of loci gives nearly the same
increase in precision as increasing the number of individuals sampled. We also evaluated effects of incomplete fragmentation
and found this N
e-reduction signal is still apparent in the presence of considerable migration (m ~ 0.10–0.25). Single-sample genetic estimates of N
e thus show considerable promise for early detection of population fragmentation and decline. 相似文献
4.
Our basic knowledge of the ecology, especially the age and growth of polar deep-sea biota is still scarce. This study provides
first data about the age and growth of the two abundant Arctic fish species Lycodes frigidus and Lycodes squamiventer (Zoarcidae). Lycodes frigidus was caught at the deeper parts (1,546–3,576 m depth) of the HAUSGARTEN observatory (HG), west of Svalbard. The congener Lycodes squamiventer was caught at two HG stations (1,273–1,546 m) and at the H?kon Mosby Mud Volcano (HMMV, ~1,250 m), a cold seep in the southwestern
Barents Sea. Age was determined by sagittal otolith increment analysis. Growth performance was assessed by fitting age–length
data to a von Bertalanffy growth equation. Our data suggest that L. frigidus and L. squamiventer attain maximum ages of 33 and 21 years, respectively. Lycodes squamiventer from the HMMV had significantly higher growth rates and their maximum age and length was slightly lower compared to conspecifics
from the shallow HG stations. Von Bertalanffy growth equations were L
t
= 58.9 ∗ (1 − e(−0.042*t)) for L. frigidus, and L
t
= 25.3 ∗ (1 − e(−0.074*t)) and L
t
= 24.2 ∗ (1 − e(−0.099
*
t)) for L. squamiventer from HG and the HMMV, respectively. A comparison of these data with those of eight other zoarcids indicates that growth performances
are correlated with temperature: the higher the annual mean temperatures experienced, the higher the growth rates. However,
maximum ages decrease with increasing temperatures. 相似文献
5.
Electrophoretic variants for 11 isozyme systems were examined by horizontal polyacrilamide gel electrophoresis in natural
populations of Larrea ameghinoi and L. nitida (section Larrea). The two taxa presented fixed alternative allelic variants at loci Adh-1, Gdh-1 and Mdh-1. Genetic variability estimates showed no statistically significant differences among populations of
section Larrea (He: 0.097–0.167). However, these values were significantly lower than those reported for species of section Bifolium (L. divaricata, diploid L. tridentata) in a previous contribution (He: 0.17–0.29). Positive and highly significant Wright's fixation indices are in agreement with higher amounts of inbreeding
for nitida and L. ameghinoi, as suggested on the basis of floral morphology by previous authors. Moreover, the higher levels of genetic differentiation
obtained for conspecific populations of section Larrea as compared to those of section Bifolium are also consistent with these
observations. Nei's genetic identity values obtained for sympatric (I=0.80) and allopatric (I=0.63–0.73) L. ameghinoi – L. nitida population pairs are concordant with those expected for different, but closely related congeneric species.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
Bavi RS Kamble AD Kumbhar NM Kumbhar BV Sonawane KD 《Cell biochemistry and biophysics》2011,61(3):507-521
Conformational preferences of the modified nucleosides N2-methylguanosine (m2G) and N2, N2-dimethylguanosine (m22G) have been studied theoretically by using quantum chemical perturbative configuration interaction with localized orbitals
(PCILO) method. Automated complete geometry optimization using semiempirical quantum chemical RM1, along with ab initio molecular
orbital Hartree–Fock (HF-SCF), and density functional theory (DFT) calculations has also been made to compare the salient
features. Single-point energy calculation studies have been made on various models of m2G26:C/A/U44 and m22G26:C/A/U44. The glycosyl torsion angle prefers “syn” (χ = 286°) conformation for m2G and m22G molecules. These conformations are stabilized by N(3)–HC2′ and N(3)–HC3′ by replacing weak interaction between O5′–HC(8).
The N2-methyl substituent of (m2G26) prefers “proximal” or s-trans conformation. It may also prefer “distal” or s-cis conformation that allows base pairing with A/U44 instead of C at the hinge region. Thus, N2-methyl group of m2G may have energetically two stable s-trans m2G:C/A/U or s-cis m2G:A/U rotamers. This could be because of free rotations around C–N bond. Similarly, N2, N2-dimethyl substituent of (m22G) prefers “distal” conformation that may allow base pairing with A/U instead of C at 44th position. Such orientations of
m2G and m22G could play an important role in base-stacking interactions at the hinge region of tRNA during protein biosynthesis process. 相似文献
7.
Elena V. Artyukova Marina M. Kozyrenko Peter G. Gorovoy Yury N. Zhuravlev 《Genetica》2009,137(2):201-212
Microbiota decussata Kom. (Cupressaceae) is a subalpine species endemic to the Sikhote Alin Mountains with populations scattered throughout the
range. We used sequence data for four noncoding regions of chloroplast DNA to characterize the genetic diversity in populations
sampled from different parts of M. decussata natural range. No variation was observed in the trnT–trnF region, whereas the trnH–psbA, trnS–trnfM, and trnS–trnG regions showed polymorphisms. At the species level, we found a low nucleotide diversity (π = 0.0009) and high haplotype diversity
(h = 0.981) as well as high differentiation (ΦST = 0.420). N
ST and G
ST values suggested the existence of a phylogeographic structure in M. decussata. The observed patterns of diversity could be explained in part by ecological features of the species and its long-term persistence
throughout the range with population expansion, successive fragmentation and isolation. 相似文献
8.
Kaarel Adamberg Petri-Jaan Lahtvee Kaspar Valgepea Kristo Abner Raivo Vilu 《Antonie van Leeuwenhoek》2009,95(3):219-226
Quasi steady state growth of Lactococcus
lactis IL 1403 was studied in glucose-limited A-stat cultivation experiments with acceleration rates (a) from 0.003 to 0.06 h−2 after initial stabilization of the cultures in chemostat at D = 0.2–0.3 h−1. It was shown that the high limit of quasi steady state growth rate depended on the acceleration rate used—at an acceleration
rate 0.003 h−2 the quasi steady state growth was observed until μ
crit = 0.59 h−1, which is also the μ
max value for the culture. Lower values of μ
crit were observed at higher acceleration rates. The steady state growth of bacteria stabilized at dilution rate 0.2 h−1 was immediately disrupted after initiating acceleration at the highest acceleration rate studied—0.06 h−2. Observation was made that differences [Δ(μ − D)] of the specific growth rates from pre-programmed dilution rates were the lowest using an acceleration rate of 0.003 h−2 (< 4% of preset changing growth rate). The adaptability of cells to follow preprogrammed growth rate was found to decrease
with increasing dilution rate—it was shown that lower acceleration rates should be applied at higher growth rates to maintain
the culture in the quasi steady state. The critical specific growth rate and the biomass yields based on glucose consumption
were higher if the medium contained S
0 = 5 g L−1 glucose instead of S
0 = 10 g L−1. It was assumed that this was due to the inhibitory effect of lactate accumulating at higher concentrations in the latter
cultures. Parallel A-stat experiments at the same acceleration and dilution rates showed good reproducibility—Δ(μ − D) was less than 5%, standard deviations of biomass yields per ATP produced (Y
ATP), and biomass yields per glucose consumed (Y
XS) were less than 15%. 相似文献
9.
The effect of temperature on post-feeding ammonia excretion and oxygen consumption in the southern catfish 总被引:1,自引:0,他引:1
Yiping Luo Xiaojun Xie 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2009,179(6):681-689
The post-prandial rates of ammonia excretion (TAN) and oxygen consumption in the southern catfish (Silurus meridionalis) were assessed at 2 h intervals post-feeding until the rates returned to those of the fasting rates, at 17.5, 22.5, 27.5,
and 32.5°C, respectively. Both fasting TAN and increased with temperature, and were lower than those previously reported for many fish species. The relationship between
fasting TAN (mmol NH3–N kg−1 h−1) and temperature (T, °C) was described as: fasting TAN = 0.144e
0.0266T
(r = 0.526, n = 27, P < 0.05). The magnitude of ammonia excretion and its ratio to total N intake during the specific dynamic action (SDA) tended to increase initially, and then decrease with increasing temperature. The
ammonia quotient (AQ), calculated as mol NH3–N/mol O2, following feeding decreased as temperature increased. The relationship between AQ during SDA and temperature was described
as: AQduring SDA = 0.303e
−0.0143T
(r = 0.739, n = 21, P < 0.05). Our results suggest that ammonia excretion and oxygen consumption post-feeding are operating independently of each
other. Furthermore, it appears that the importance of protein as a metabolic substrate in postprandial fish decreases with
temperature. 相似文献
10.
Marnie H. Demandt 《Conservation Genetics》2010,11(1):249-255
Genetic drift, together with natural selection and gene flow, affects genetic variation and is the major source of changes
in allele frequencies in small and isolated populations. Temporal shifts in allele frequencies at five polymorphic loci were
used to estimate the amount of genetic drift in an isolated population of perch (Perca fluviatilis L.) and roach (Rutilus rutilus L.). Here, I used the populations from the Biotest basin at Forsmark, Sweden, to investigate genetic diversity between 1977
and 2000, during which time the population can be considered to be totally isolated from other populations. Microsatellite
data reveal stable levels of gene diversity over time for both species. Estimates of genetic differentiation (F
ST) showed a significant divergence between 1977 and 2000 for both perch and roach. A positive correlation between genetic distance
and time was found (Mantel test, perch: r = 0.724, P = 0.0112; roach: r = 0.59, P = 0.036). Estimates of effective population size (N
e) differed with a factor six between two different estimators (NeEstimator and TempoFS) applying the temporal method. Ratios
of N
e/N ranged between 10−2 and 10−3, values normally found in marine species. Despite low N
e the populations have not lost their evolutionary potential due to drift. But two decades of isolation have lead to isolation
by time for populations of perch and roach, respectively. 相似文献
11.
Interaction of maturation delay and nonlinear birth in population and epidemic models 总被引:16,自引:0,他引:16
A population with birth rate function B(N) N and linear death rate for the adult stage is assumed to have a maturation delay T>0. Thus the growth equation N′(t)=B(N(t−T)) N(t−T) e−
d
1
T−dN(t) governs the adult population, with the death rate in previous life stages d
1≧0. Standard assumptions are made on B(N) so that a unique equilibrium N
e
exists. When B(N) N is not monotone, the delay T can qualitatively change the dynamics. For some fixed values of the parameters with d
1>0, as T increases the equilibrium N
e
can switch from being stable to unstable (with numerically observed periodic solutions) and then back to stable. When disease
that does not cause death is introduced into the population, a threshold parameter R
0 is identified. When R
0<1, the disease dies out; when R
0>1, the disease remains endemic, either tending to an equilibrium value or oscillating about this value. Numerical simulations
indicate that oscillations can also be induced by disease related death in a model with maturation delay.
Received: 2 November 1998 / Revised version: 26 February 1999 相似文献
12.
Marzena B. Fitzpatrick Roman S. Czernuszewicz 《Journal of biological inorganic chemistry》2009,14(4):611-620
Metal-substituted blue copper proteins (cupredoxins) have been successfully used to study the effect of metal-ion identity
on their active-site properties, specifically the coordination geometry and metal–ligand bond strengths. In this work, low-temperature
(77 K) resonance Raman (RR) spectra of the blue copper protein Alcaligenes xylosoxidans azurin I and its Ni(II) derivative are reported. A detailed analysis of all observed bands is presented and responsiveness
to metal substitution is discussed in terms of structural and bonding changes. The native cupric site exhibits a RR spectrum
characteristic of a primarily trigonal planar (type 1) coordination geometry, identified by the ν(Cu–S)Cys markers at 373, 399, 409, and 430 cm−1. Replacement of Cu(II) with Ni(II) results in optical and RR spectra that reveal (1) a large hypsochromic shift in the main
(Cys)S → M(II) charge-transfer absorption from 622 to 440 nm, (2) greatly reduced metal–thiolate bonding interaction, indicated
by substantially lower ν(Ni–S)Cys stretching frequencies, (3) elevation of the cysteine ν(C
β
–S) stretching, amide III, and ρ
s(C
β
H2) scissors vibrational modes, and (4) primarily four-coordinated, trigonally distorted tetrahedral geometry of the Ni(II)
site that is marked by characteristic ν(Ni–S)Cys stretching RR bands at 347, 364, and 391 cm−1. Comparisons of the electronic and vibrational properties between A. xylosoxidans azurin I and its closely structurally related azurin from Pseudomonas aeruginosa are made and discussed. For cupric azurins, the intensity-weighted average M(II)–S(Cys) stretching frequencies are calculated
to be ν(Cu–S)iwa = 406.3 and 407.6 cm−1, respectively. These values decreased to ν(Ni–S)iwa = 359.3 and 365.5 cm−1, respectively, after Ni(II) → Cu(II) exchange, suggesting that the metal–thiolate interactions are similar in the two native
proteins but are much less alike in their Ni(II)-substituted forms. 相似文献
13.
Sal (Shorea robusta Gaertn., Dipterocarpaceae) is a wind-pollinated tropical tree species found in southern Asia. We investigated the genetic
diversity and structure at four microsatellites of 15 populations comprising continuous-peripheral and disjunct-peripheral
populations in Nepal. Estimates of genetic diversity (N
A = 8.98, H
O = 0.62, H
E = 0.69) were similar when compared with those of other tropical tree species. A higher level of genetic diversity was observed
in continuous-peripheral populations (N
A = 9.61, H
O = 0.67, H
E = 0.72) as compared to disjunct-peripheral (N
A = 8.04, H
O = 0.55, H
E = 0.64). Population differentiation was higher among disjunct-peripheral populations (F
ST = 0.043) than among continuous peripherals (F
ST = 0.012). There was a significant association between gene flow distances and genetic differentiation (r
2 = 0.128, P ≤ 0.007). No spatial arrangement of populations according to their geographical locations was found. Based on observed genetic
diversity protection of some populations in continuous-peripheral range are suggested for the sustainable conservation of
genetic resources of the species while protection of some disjunct-peripheral populations are also recommended for conserving
rare alleles. 相似文献
14.
Barua S Tripathi S Chakraborty A Ghosh S Chakrabarti K 《Indian journal of microbiology》2011,51(3):369-376
The effect of fluctuations of salinity in three different seasons on diazotrophic populations and N2 fixation in six mono cropped rice field soils of the coastal region of the Gangetic delta of West Bengal, India, was studied.
The average pH, ECe, organic carbon and total nitrogen of the soils ranged from 4.99–7.08, 2.02–19.58 dSm−1, 4.68–12.03 g kg−1 and 0.44–1.70 g kg −1, respectively. The average log colony forming units of the bacterial populations and N2-fixation in the soils varied from 4.61 to 5.86 and 2.74 to 4.52 mg N2 fixed 50 ml −1 culture media respectively, with the lowest value recorded in summer. Recovery of microorganisms and N2- fixation gradually decreased with extraneous addition of NaCl in the culture media. All the eight isolates were Gram positive,
spore and capsule formers. They could utilize glucose, sucrose, mannitol, starch, citrate and nitrate, and were catalase and
gelatinase positive, but indole, methyl red and Vogues Proskauer reaction negative. The organisms produced alkaline reaction
on TSI agar slant. The acetylene reduction assay of the isolates at 0 and 1% NaCl in the culture media were 4.51–164.52 and
1.72–100.6 nmole C2H4 ml−1 culture media in 72 h, respectively. The isolates could fix 2.42–4.45 and 2.04–4.08 mg N2 fixed 50 ml−1 culture media at 0 and 1% NaCl in the culture media respectively. 16S rDNA sequences of the isolates were similar to the
species: Bacillus sp. isolate 28A, Bacillus sp. MOLA 87, Bacillus sp. By113 (B)Ydz-dh, Bacillus sp. PN13, Bacillus licheniformis strain RH101, Bacterium Antarctica 14, Bacillus sp. PN13 and Bacillus megaterium. 相似文献
15.
The spatial and temporal genetic structure of brown trout populations from three small tributaries of Lake Hald, Denmark,
was studied using analysis of variation at eight microsatellite loci. From two of the populations temporal samples were available,
separated by up to 13 years (3.7 generations). Significant genetic differentiation was observed among all samples, however,
hierarchical analysis of molecular variance (AMOVA) showed that differentiation among populations accounted for a non-significant
amount of the genetic differentiation, whereas differentiation among temporal samples within populations was highly significant
(0.0244, P<0.001). Estimates of effective population size (N
e) using a maximum-likelihood based implementation of the temporal method, yielded small values (N
e ranging from 33 to 79). When a model was applied that allows for migration among populations, N
e estimates were even lower (24–54), and migration rates were suggested to be high (0.13–0.36). All samples displayed a clear
signal of a recent bottleneck, probably stemming from a period of unfavourable conditions due to organic pollution in the
1970–1980’s. By comparison to other estimates of N
e in brown trout, Lake Hald trout represent a system of small populations linked by extensive gene flow, whereas other populations
in larger rivers exhibit much higher N
e values and experience lower levels of immigration. We suggest that management considerations for systems like Lake Hald brown
trout should focus both on a regional scale and at the level of individual populations, as the future persistence of populations
depends both on maintaining individual populations and ensuring sufficient migration links among these populations. 相似文献
16.
Agu Laisk Eero Talts Vello Oja Hillar Eichelmann Richard B. Peterson 《Photosynthesis research》2010,103(2):79-95
Fast cyclic electron transport (CET) around photosystem I (PS I) was observed in sunflower (Helianthus annuus L.) leaves under intense far-red light (FRL) of up to 200 μmol quanta m−2 s−1. The electron transport rate (ETR) through PS I was found from the FRL-dark transmittance change at 810 and 950 nm, which
was deconvoluted into redox states and pool sizes of P700, plastocyanin (PC) and cytochrome f (Cyt f). PC and P700 were in
redox equilibrium with K
e = 35 (ΔE
m = 90 mV). PS II ETR was based on O2 evolution. CET [(PS I ETR) − (PS II ETR)] increased to 50–70 μmol e− m−2 s−1 when linear electron transport (LET) under FRL was limited to 5 μmol e− m−2 s−1 in a gas phase containing 20–40 μmol CO2 mol−1 and 20 μmol O2 mol−1. Under these conditions, pulse-saturated fluorescence yield F
m was non-photochemically quenched; however, F
m was similarly quenched when LET was driven by low green or white light, which energetically precluded the possibility for
active CET. We suggest that under FRL, CET is rather not coupled to transmembrane proton translocation than the CET-coupled
protons are short-circuited via proton channels regulated to open at high ΔpH. A kinetic analysis of CET electron donors and
acceptors suggests the CET pathway is that of the reversed Q-cycle: Fd → (FNR) → Cyt cn → Cyt bh → Cyt bl → Rieske FeS → Cyt f → PC → P700 →→ Fd. CET is activated when PQH2 oxidation is opposed by high ΔpH, and ferredoxin (Fd) is reduced due to low availability of e− acceptors. The physiological significance of CET may be photoprotective, as CET may be regarded as a mechanism of energy
dissipation under stress conditions. 相似文献
17.
Deyong Sun Yunmei Li Qiao Wang Heng Lv Chengfeng Le Changchun Huang Shaoqi Gong 《Hydrobiologia》2010,644(1):337-349
Light scattering, backscattering, and absorption coefficients of particles were observed at 62 locations in Lake Taihu (China)
in November 2008. A method using a priori knowledge and the measured data was proposed to partition particulate scattering
and absorption into contributions of phytoplankton and non-algal particles. The results showed that phytoplankton weakly contributed
to the particulate scattering and backscattering with the mean b
ph/b
p values usually below 10% and b
bph/b
bt values of 0.3–3.9% in the whole visible light spectrum, and an approximate relationship of b
bt ≈ b
bp ≈ b
bnap was regarded as reasonable in Lake Taihu. In contrast with scattering and backscattering, phytoplankton made more contributions
to the particulate absorption with the mean a
ph/a
p values varying in a wide range of about 20–70%. Both the scattering and absorption spectra of non-algal particles can be
modeled well by corresponding methods. A power function model was used to simulate the scattering spectra, which presented
high predictive accuracies with MAPE values usually below 5% and RMSE values below 1.5 m−1, while the spectral absorption model also performed well with mean S
nap being 0.0052 nm−1 (standard deviation, SD = 0.0010 nm−1). As to the phytoplankton absorption, a quadratic function model used was considered to have a good performance with corresponding
parameters being supported at each wavelength in the spectral range of 400–700 nm. Additionally, two basic bio-optical parameters
were determined, that is, b
nap*(550) = 0.604 m2 g−1 and a
ph*(675) = 0.0288 m2 mg−1. Overall, these results obtained in the present study supply us with new knowledge about optical properties of suspended
particulates in an inland and highly turbid lake (Lake Taihu), which are beneficial to the development of analytical models
of water color remote sensing. 相似文献
18.
Andrew J. Gregory Robb S. A. Kaler Thomas J. Prebyl Brett K. Sandercock Samantha M. Wisely 《Conservation Genetics》2012,13(2):465-474
Island populations and populations established by reintroductions are prone to extinction, in part because they are vulnerable
to deterministic and stochastic phenomena associated with geographic isolation and small population size. As population size
declines, reduced genetic diversity can result in decreased fitness and reduced adaptive potential, which may hinder short-
or long-term population viability. We used 32 microsatellite markers to investigate the conservation genetics of a newly established
population of Evermann’s Rock Ptarmigan (Lagopus muta evermanni) at Agattu Island, in the western Aleutian Archipelago, Alaska. We found low genetic diversity (observed heterozygosity = 0.41,
allelic richness = 2.2) and a small effective population size (N
e
= 28.6), but a relatively large N
e
/N ratio = 0.55, which was attributed to multiple paternity in 80% of the broods and low reproductive skew among males (λ = 0.29).
Moreover, successful breeding pairs were less related to each other than random male–female pairs. For conservation efforts
based on reintroductions, a mating system with high rates of multiple paternity may facilitate retention of genetic diversity,
thereby reducing the potential for inbreeding in small or isolated populations. Our results underscore the importance of quantifying
genetic diversity and understanding the breeding behavior of translocated populations. 相似文献
19.
Andrew R. Whiteley Kim Hastings John K. Wenburg Chris A. Frissell Jamie C. Martin Fred W. Allendorf 《Conservation Genetics》2010,11(5):1929-1943
Following glacial recession in southeast Alaska, waterfalls created by isostatic rebound have isolated numerous replicate
populations of coastal cutthroat trout (Oncorhynchus clarkii clarkii) in short coastal streams. These replicate isolated populations offer an unusual opportunity to examine factors associated
with the maintenance of genetic diversity. We used eight microsatellites to examine genetic variation within and differentiation
among 12 population pairs sampled from above and below these natural migration barriers. Geological evidence indicated that
the above-barrier populations have been isolated for 8,000–12,500 years. Genetic differentiation among below-barrier populations
(F
ST = 0.10, 95% C.I. 0.08–0.12) was similar to a previous study of more southern populations of this species. Above-barrier populations
were highly differentiated from adjacent below-barrier populations (mean pairwise F
ST = 0.28; SD 0.18) and multiple lines of evidence were consistent with asymmetric downstream gene flow that varied among streams.
Each above-barrier population had reduced within-population genetic variation when compared to the adjacent below-barrier
population. Within-population genetic diversity was significantly correlated with the amount of available habitat in above-barrier
sites. Increased genetic differentiation of above-barrier populations with lower genetic diversity suggests that genetic drift
has been the primary cause of genetic divergence. Long-term estimates of N
e based on loss of heterozygosity over the time since isolation were large (3,170; range 1,077–7,606) and established an upper
limit for N
e if drift were the only evolutionary process responsible for loss of genetic diversity. However, it is likely that a combination
of mutation, selection, and gene flow have also contributed to the genetic diversity of above-barrier populations. Contemporary
above-barrier N
e estimates were much smaller than long-term N
e estimates, not correlated with within-population genetic diversity, and not consistent with the amount of genetic variation
retained, given the approximate 10,000-year period of isolation. The populations isolated by waterfalls in this study that
occur in larger stream networks have retained substantial genetic variation, which suggests that the amount of habitat in
headwater streams is an important consideration for maintaining the evolutionary potential of isolated populations. 相似文献
20.
Christian Brümmer Nicolas Brüggemann Klaus Butterbach-Bahl Ulrike Falk Jörg Szarzynski Konrad Vielhauer Reiner Wassmann Hans Papen 《Ecosystems》2008,11(4):582-600
In a combined field and laboratory study in the southwest of Burkina Faso, we quantified soil-atmosphere N2O and NO exchange. N2O emissions were measured during two field campaigns throughout the growing seasons 2005 and 2006 at five different experimental
sites, that is, a natural savanna site and four agricultural sites planted with sorghum (n = 2), cotton and peanut. The agricultural fields were not irrigated and not fertilized. Although N2O exchange mostly fluctuated between −2 and 8 μg N2O–N m−2 h−1, peak N2O emissions of 10–35 μg N2O–N m−2 h−1 during the second half of June 2005, and up to 150 μg N2O–N m−2 h−1 at the onset of the rainy season 2006, were observed at the native savanna site, whereas the effect of the first rain event
on N2O emissions at the crop sites was low or even not detectable. Additionally, a fertilizer experiment was conducted at a sorghum
field that was divided into three plots receiving different amounts of N fertilizer (plot A: 140 kg N ha−1; plot B: 52.5 kg N ha−1; plot C: control). During the first 3 weeks after fertilization, only a minor increase in N2O emissions at the two fertilized plots was detected. After 24 days, however, N2O emission rates increased exponentially at plot A up to a mean of 80 μg N2O–N m−2 h−1, whereas daily mean values at plot B reached only 19 μg N2O–N m−2 h−1, whereas N2O flux rates at plot C remained unchanged. The calculated annual N2O emission of the nature reserve site amounted to 0.52 kg N2O–N ha−1 a−1 in 2005 and to 0.67 kg N2O–N ha−1 a−1 in 2006, whereas the calculated average annual N2O release of the crop sites was only 0.19 kg N2O–N ha−1 a−1 and 0.20 kg N2O–N ha−1 a−1 in 2005 and 2006, respectively. In a laboratory study, potential N2O and NO formation under different soil moisture regimes were determined. Single wetting of dry soil to medium soil water
content with subsequent drying caused the highest increase in N2O and NO emissions with maximum fluxes occurring 1 day after wetting. The stimulating effect lasted for 3–4 days. A weaker
stimulation of N2O and NO fluxes was detected during daily wetting of soil to medium water content, whereas no significant stimulating effect
of single or daily wetting to high soil water content (>67% WHCmax) was observed. This study demonstrates that the impact of land-use change in West African savanna on N trace gas emissions
is smaller—with the caveat that there could have been potentially higher N2O and NO emissions during the initial conversion—than the effect of timing and distribution of rainfall and of the likely
increase in nitrogen fertilization in the future. 相似文献