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1.
Seed and microsite limitations of recruitment and the impacts of post-dispersal seed predation at the within population level 总被引:1,自引:0,他引:1
María Calviño-Cancela 《Plant Ecology》2007,192(1):35-44
Seed predation may cause important seed losses in plant populations, but its impact on the dynamics of populations will depend
on the degree of seed or microsite limitations for recruitment. Seed losses will only affect recruitment if it is seed limited.
The nature of recruitment limitation (seeds or microsites) is usually ascribed to whole plant populations but it may vary
within populations among microhabitats and habitats. Thus, the potential impact of seed predation will also vary within the
population, being highest where recruitment is seed limited. The impact to the whole population will depend on the spatial
concordance between the intensity of seed predation and that of seed limitation. Recruitment limitations (with seed addition
experiments), seed predation (with seed removal experiments), and the dynamics of seed availability in the soil (with soil
samples taken both after seed dispersal and before the following dispersal event) of the shrub Corema album (Empetraceae) were investigated in dunes in NW Spain, at microhabitats ‘open ground’, ‘underneath C. album ♀’, and ‘underneath C. album ♂’ at two habitats, sparse and dense scrub. The nature of recruitment limitation (seeds vs. microsites) varied within the
population. It was seed limited in the microhabitat ‘open ground’ and microsite limited under shrub cover. The spatial patterns
of seedling recruitment were unrelated to seed availability but strongly affected by germination requirements. The spatial
discordance between seed availability and recruitment implies a crucial constraint for processes affecting seed availability
(seed predation but also e.g., dispersal) to impact recruitment. They will not affect its spatial pattern but only its quantity
as long as they act in those sites selected by seeds to germinate. Seed predation was highest underneath mother plants and lowest in open ground. Thus, its potential
impact is low, as it is centred where recruitment is not seed limited. This study shows that the analysis of seed predation
in relation to recruitment limitations at smaller spatial scales within the population provides more insight to understand
its impact. 相似文献
2.
Synopsis Coral reef fishes almost universally disperse over relatively great distances during a pelagic larval phase. Barlow (1981)
suggested that this dispersal is adaptive because adult fishes inhabit a patchy, uncertain environment. This reiterated an
older idea that the random extinction of local populations necessarily favours dispersal, since ultimately all populations
of non-dispersers will disappear. Whereas this view is based on adult survival, we emphasize a less frequent view that substantial
larval dispersal may be adaptive when offspring experience patchy and unpredictable survival in the pelagic habitat. We do
not address the question of why these animals ‘broadcast’ rather than ‘brood’, but suggest that species committed to pelagic
offspring will be under selection to disperse siblings to spread the risk of failure among members of a cohort. Our arguments
are supported by a heuristic computer simulation. 相似文献
3.
Elizabeth A. MacDougall-Shackleton Michael Clinchy Liana Zanette Bryan D. Neff 《Conservation Genetics》2011,12(5):1195-1203
Natural habitats, and the populations they sustain, are becoming increasingly fragmented by human activities. Parallels between
‘true’ islands and ‘habitat’ islands suggest that standing levels of individual genetic diversity in naturally fragmented
populations may predict the genetic fate of their anthropogenically fragmented counterparts, but this hypothesis remains largely
untested. We compared neutral-locus genetic diversity of individual song sparrows (Melospiza melodia) breeding in a naturally fragmented landscape (small coastal islands) to that of song sparrows in similar-sized ‘urban islands’
separated by roads and housing developments rather than by water. Individuals on coastal islands were more heterozygous and
less inbred than those in urban islands. Estimates of population genetic structuring (assessed by pairwise genetic differentiation
and Bayesian clustering methods) and contemporary dispersal (based on assignment tests) revealed little structure within either
landscape, suggesting that lack of connectivity at the geographic scale we investigated cannot explain the reduced heterozygosity
of urban birds. However, within-site genetic similarity was higher in the urban than the coastal landscape. Assuming that
historic genetic diversity was similar in these two environments, our findings suggest that anthropogenically fragmented populations
may lose genetic diversity faster than their naturally fragmented counterparts. 相似文献
4.
The lek paradox states that maintaining genetic variation necessary for ‘indirect benefit’ models of female choice is difficult,
and two interrelated solutions have been proposed. ‘Genic capture’ assumes condition-dependence of sexual traits, while genotype-by-environment
interactions (GEIs) offer an additional way to maintain diversity. However, condition-dependence, particularly with GEIs,
implies that environmental variation can blur the relationship between male displays and offspring fitness. These issues have
been treated separately in the past. Here we combine them in a population genetic model, and show that predictions change
not only in magnitude but also in direction when the timing of dispersal between environments relative to the life cycle is
changed. GEIs can dramatically improve the evolution of costly female preferences, but also hamper it if much dispersal occurs
between the life history stage where condition is determined and mating. This situation also arises if selection or mutation
rates are too high. In general, our results highlight that when evaluating any mechanism promoted as a potential resolution
of the lek paradox, it is not sufficient to focus on its effects on genetic variation. It also has to be assessed to what
extent the proposed mechanism blurs the association between male attractiveness and offspring fitness; the net balance of
these two effects can be positive or negative, and often strongly context-dependent. 相似文献
5.
The damselflyMnais pruinosa costalis (Odonata: Calopterygidae) is unusual in that males are dimorphic, existing as clear-winged non-territorial ‘sneaks’ and orange-winged
territorial ‘fighters’. Here we report the results of population census data and behavioural observations in the field and
laboratory, and present estimates of emergence period, reproductive period, total lifespan, and reproductive success of each
morph. Clear-winged males are smaller and have lower daily reproductive success than orange-winged males, but live for longer
in the field and laboratory. We accounted for the difference in the ‘operational reproductive life’ of the two morphs and
estimated lifetime reproductive success: there was no difference between clear-winged and orange-winged males. We discuss
possible mechanisms for the maintenance of the two forms. 相似文献
6.
Tibisay Escalona Tag N. Engstrom Omar E. Hernandez Brian C. Bock Richard C. Vogt Nicole Valenzuela 《Conservation Genetics》2009,10(6):1683-1696
We studied the population genetics of Podocnemis unifilis turtles within and among basins in the Orinoco and Amazon drainages using microsatellites. We detected high levels of genetic
diversity in all sampled localities. However, ‘M-ratio’ tests revealed a substantial recent population decline in ten localities, in accord with current widespread exploitation.
Our results reveal a consistent pattern across multiple analyses, showing a clear subdivision between the populations inhabiting
the Amazon and Orinoco drainages despite a direct connection via the Casiquiare corridor, and suggesting the existence of
two biogeographically independent and widely divergent lineages. Genetic differentiation followed an isolation-by-distance
model concordant with hypotheses about migration. It appears that migration occurs via the flooded forest in some drainages,
and via river channels in those where geographic barriers preclude dispersal between basins or even among nearby tributaries
of the same basin. These observations caution against making generalizations based on geographically restricted data, and
indicate that geographically proximate populations may be demographically separate units requiring independent management. 相似文献
7.
The processes determining where seeds fall relative to their parent plant influence the spatial structure and dynamics of plant populations and communities. For animal dispersed species the factors influencing seed shadows are poorly understood. In this paper we test the hypothesis that the daily temporal distribution of disperser behaviours, for example, foraging and movement, influences dispersal outcomes, in particular the shape and scale of dispersal curves. To do this, we describe frugivory and the dispersal curves produced by the southern cassowary, Casuarius casuarius, the only large-bodied disperser in Australia’s rainforests. We found C. casuarius consumed fruits of 238 species and of all fleshy-fruit types. In feeding trials, seeds of 11 species were retained on average for 309 min (±256 SD). Sampling radio-telemetry data randomly, that is, assuming foraging occurs at random times during the day, gives an estimated average dispersal distance of 239 m (±207 SD) for seeds consumed by C. casuarius. Approximately 4% of seeds were dispersed further than 1,000 m. However, observation of wild birds indicated that foraging and movement occur more frequently early and late in the day. Seeds consumed early in the day were estimated to receive dispersal distances 1.4 times the ‘random’ average estimate, while afternoon consumed seeds received estimated mean dispersal distances of 0.46 times the ‘random’ estimate. Sampling movement data according to the daily distribution of C. casuarius foraging gives an estimated mean dispersal distance of 337 m (±194 SD). Most animals’ behaviour has a non-random temporal distribution. Consequently such effects should be common and need to be incorporated into seed shadow estimation. Our results point to dispersal curves being an emergent property of the plant–disperser interaction rather than being a property of a plant or species. 相似文献
8.
The increasing use of genetically modified (GM) plants has raised concerns about the escape of transgenes to conventional
populations. To counteract possible fitness advantages of GM plants, an advantageous ‘primary transgene’ may be linked to
a ‘mitigation’ transgene that is selectively disfavored. A risk related to this technique is the possible break-up of the
transgenes. This may lead to the establishment of genotypes that only express the primary transgenic trait and are therefore
selectively favored over both conventional and GM genotypes. We study here how the establishment of break-up genotypes in
tree populations depends on life history, pollen dispersal kernels, and the linkage between transgenes. To this end, we model
the dynamics of an initially homozygous GM population and a conventional population growing next to each other. The simulations
are based on a spatially explicit simulation model for population-genotype dynamics. Pollen and seed dispersal are described
by fat-tailed dispersal kernels. Break-up of transgenes is due subsequent crossing of GM and conventional genotypes. The spatial
pattern of pollen and seed dispersal causes break-up and establishment of new invasive genotypes to occur mostly in the conventional
population. The amount of individuals of these genotypes established in the conventional population depends on the interaction
between life-history traits, pollen dispersal distances and the linkage of the transgenes. Thus, risk assessment of transgene
break-up requires information on the genetics, local dynamics, and dispersal of GM and conventional varieties. The approach
presented here provides a tool for combining these different sources of information, and it contributes to the formulation
of general rules for the management of GM tree populations. 相似文献
9.
Genetic variability and structure of natural and domesticated populations of Caribbean pine (Pinus caribaea Morelet) 总被引:1,自引:0,他引:1
Y.-Q. Zheng R. A. Ennos 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,98(5):765-771
Isozyme analysis of seed samples derived from natural and managed populations of the tropical pine Pinus caribaea vars ‘bahamensis’ and ‘caribaea’ was used to assess population genetic structure in its native range and to detect changes
occurring during early domestication of the species. Baseline data from natural populations of the two varieties showed that
populations sampled as seed are characterized by high gene diversity (mean He=0.26) and a low level of inbreeding ( mean Fis=0.15). A UPGMA tree of genetic relatedness among populations indicates that the two varieties represent distinct evolutionary
units. Within each variety there is significant differentiation among populations, and this is greater for the more fragmented
populations of var ‘bahamensis’ (Fst=0.08) than for var ‘caribaea’ (Fst=0.02). Seed from a seed orchard population of var ‘caribaea’ established within its natural range showed no change in genetic
diversity but did show a reduced inbreeding coefficient (Fis=0.09) compared with its progenitor populations, suggesting a decrease in selfing and/or biparental inbreeding. A bulked seed
sample from an exotic plantation of var ‘bahamensis’ in Australia displayed a large increase in the inbreeding coefficient
(Fis=0.324) compared with that found in natural populations, possibly due to elevated self-fertilization. Finally, a bulked seed
sample from an exotic plantation population of var ‘caribaea’ from China showed enhanced genetic diversity, an increase in
the inbreeding coefficient and more linkage disequilibrium than its presumed progenitor populations. It was also genetically
divergent from them. RFLP analysis of chloroplast DNA variation in the Chinese sample suggested that seeds of the related
taxa P. elliottii and P. taeda, or seeds derived from hybridization with these taxa growing in the seed production area, had been included in the seed crop
during harvesting. We conclude that monitoring of appropriate genetic markers may be an effective means of identifying potentially
deleterious genetic changes occurring during forest tree domestication.
Received: 10 August 1998 / Accepted: 8 September 1998 相似文献
10.
Kiørboe T 《Oecologia》2006,148(1):181-50
I examine how the population biology of pelagic copepods depends on their mating biology using field data and a simple demographic model. Among calanoid copepods, two distinct patterns emerge. Firstly, copepods that lack seminal receptacle and require repeated mating to stay fertilized have near equal adult sex ratios in field populations. Winter population densities are orders of magnitude less than the critical population density required for population persistence, but populations survive winter seasons as resting eggs in the sediment. Population growth in these species is potentially high because they have on average a factor of 2 higher egg production rates than other pelagic copepods. Secondly, other copepods require only one mating to stay fertile, and populations of these species have strongly female-skewed adult sex-ratios in field populations. Resting eggs have not been described within this group. Winter population sizes are well predicted by the critical density required for population persistence which, in turn, is closely related to the body-size-dependent mate-search capacity. Thus, the different requirements for mating lead in the first case to a more opportunistic reproductive strategy that implies rapid colonization of the pelagic during productive seasons, and in the second case to a strategy that allows maintenance of a pelagic populations during unproductive seasons. Positive density dependent population growth during periods of low population density (‘Allee effect’) amplifies population density variation during winter into the subsequent summer, thus explaining why summer densities appear to depend more on winter densities than on current growth opportunities in pelagic copepods. 相似文献
11.
Julien Cucherousset Gordon H. Copp Michael G. Fox Erik Sterud Hein H. van Kleef Hugo Verreycken Eva Záhorská 《Biological invasions》2009,11(9):2171-2180
To evaluate the potential invasiveness of pumpkinseed Lepomis gibbosus introduced to northwestern European inland waters, growth and reproduction traits were examined in ten populations along
a trajectory spanning northwestern Europe (Norway, England, Holland, Belgium and France) and evaluated in light of published
dataset from Europe. In the 848 pumpkinseed captured, maximum age was 3–4 years, with a sex ratio near unity in all but one
population. Significant variations with increasing latitude were observed in adult growth (age 2–3 increment in total length,
TL) and mean age at maturity (A
M), with non-significant variations observed in juvenile growth (TL at age 2), sex ratio and gonado-somatic index. As observed
elsewhere in Europe, mean A
M decreased significantly with increasing TL at age 2. Using this relationship, which has been proposed elsewhere as a potential
predictive model of pumpkinseed invasiveness, eight of the ten populations could be provisionally categorized as ‘non-invasive’
(five populations), ‘transitional’ (one population) and ‘potentially invasive’ (two populations), with two populations not
categorized due to insufficient data. Based on the available knowledge on each population, the relationship between juvenile
growth and age at maturity appeared to predict reasonably the status of pumpkinseed in northwestern Europe and its applicability
to other species should be tested. 相似文献
12.
To date, despite decades of investigations and the relative abundance of mortality data, our understanding of the phenomenon
of ‘mortality crossover’ remains inadequate. We propose a methodology for transforming mortality data from the ‘age-domain’
to the ‘time-domain’. We then introduce a model of selection partially offset by mobility, to simulate the dynamics of vulnerability
in a population cohort that is heterogeneous in health and death. Using our model of vulnerability simulating the dynamics
of mortality in the time-domain, we compare the mortality experience of the Black and White populations of the United States,
identify the significance of selection and mobility as potential factors producing the crossover phenomenon, and make diagnostic
use of them. 相似文献
13.
Christophe Piscart Jaimie T. A. Dick David McCrisken Calum MacNeil 《Biological invasions》2009,11(9):2141-2145
Invasive species and environmental change often occur simultaneously across a habitat and therefore our understanding of their
relative roles in the decline of native species is often poor. Here, the environmental mediation of a critical interspecific
interaction, intraguild predation (IGP), was examined between invasive (Gammarus pulex) and native (G. d. celticus) freshwater amphipods. In the laboratory, IGP asymmetries (males preying on congeneric females) were examined in river water
sourced from zones where: (1) the invader has completely displaced the native; (2) the two species currently co-exist, and
(3) the native currently persists uninvaded. The invader was always a more effective IG predator, but this asymmetry was significantly
weaker moving from ‘invader-only water’ through ‘co-existence water’ to ‘native-only water’. The constituent of the water
that drives this mediation of IGP was not identified. However, balancing the rigour of laboratory experiments with field derived
‘environment’ has advanced understanding of known patterns in a native species decline, and its co-existence and persistence
in the face of an invader. 相似文献
14.
The spider mite Tetranychus urticae shows variation in its dispersal capacity (i.e., the leaf quality at which a female decides to disperse). We were able to
artificially select mites that had either a high or a low dispersal capacity, indicating that this trait was genetically controlled.
We then compared correlated responses to this selection. Mites with a genetically high dispersal capacity (‘HD’ strains) had
a higher diapause incidence and a lower performance compared to mites with a low dispersal capacity (‘LD’ strains). A possible
effect of random genetic drift during the selection was negligible. Our results suggest that differential dispersal capacity
is associated with contrasting life history patterns as a result of natural selection.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
U. Kumar A. K. Joshi S. Kumar R. Chand M. S. R?der 《Molecular breeding : new strategies in plant improvement》2010,26(3):477-491
Spot blotch caused by Bipolaris sorokiniana is a destructive disease of wheat in warm and humid wheat growing regions of the world. To identify quantitative trait loci
(QTLs) for spot blotch resistance, two mapping populations were developed by making the crosses between common susceptible
cultivar ‘Sonalika’ with the resistant breeding lines ‘Ning 8201’ and ‘Chirya 3’. Single seed descent derived F6, F7, F8 lines of the first cross ‘Ning 8201’ × ‘Sonalika’ were evaluated for resistance to spot blotch in three blocks in each of
the 3 years. After screening of 388 pairs of simple sequence repeat primers between the two parents, 119 polymorphic markers
were used to genotype the mapping population. Four QTLs were identified on the chromosomes 2AS, 2BS, 5BL and 7DS and explained
62.9% of phenotypic variation in a simultaneous fit. The QTL on chromosome 2A was detected only in 1 year and explained 22.7%
of phenotypic variation. In the second cross (‘Chirya 3’ × ‘Sonalika’), F7 and F8 population were evaluated in three blocks in each of the 2 years. In this population, five QTLs were identified on chromosomes
2BS, 2DS, 3BS, 7BS and 7DS. The QTLs identified in the ‘Chirya 3’ × ‘Sonalika’ population explained 43.4% of phenotypic variation
in a simultaneous fit. The alleles for reduced disease severity in both the populations were derived from the respective resistant
parent. The QTLs QSb.bhu-2B and QSb.bhu-7D from both populations were placed in the same deletion bins, 2BS1-0.53-0.75 and 7DS5-0.36-0.61, respectively. The closely
linked markers Xgwm148 to the QTL on chromosome 2B and Xgwm111 to the QTL on chromosome 7D are potentially diagnostic markers for spot blotch resistance. 相似文献
16.
M. J. Lofts 《Human Evolution》1995,10(2):145-151
The physical differences between major non-African ethnic, groups can be explained as admixture of migrating African modernHomo sapiens with existing archaicHomo populations. Evidence from mitochondrial DNA claiming no admixture is dismissed as there is no confidence in claimed phylogenies.
Racial characteristics can be explained by linking present day non-African humans with sympatric archaic populations. Neanderthals
are linked with Caucasians, the Solo population with Australian Aborigines and ‘Peking Man’ with modern Mongoloids. Fossil,
geographic and anthropometric evidence for dihybrid origins are considered. As a result, Asiatic Negritos are hypothesized
to be remnant groups of ‘morphologically pure’ migrating modern Africans. It is suggested that paleoanthropologists attempting
to reconstruct human origins should consider the dihybrid theory as a plausible alternative to the irreconcilable ‘complete
replacement’ and ‘multiregional’ theories. 相似文献
17.
Habitat fragmentation may reduce gene flow and population viability of rare species. We tested whether riparian corridors
enhanced gene flow and if human habitat modification between riparian corridors subsequently reduced dispersal and gene flow
of a wetland butterfly, the US federally endangered St. Francis’ satyr butterfly (Neonympha mitchellii francisci). We surveyed nine populations throughout the taxon’s range using five polymorphic microsatellite loci. We found that genetic
diversity of N. m. francisci was relatively high despite its restricted distribution, and that there is little evidence of population bottlenecks or extensive
inbreeding within populations. We found substantial gene flow and detectable first generation migration, suggesting that N. m. francisci is unlikely to be currently endangered by genetic factors. Pairwise population differentiation and clustering indicate some
structuring between populations on different drainages and suggest that dispersal probably occurs mainly via a stepping stone
from the closest riparian corridors. However, genetic differentiation between geographically close populations suggests that
isolation by distance is not solely responsible for population structure, and that management actions should be targeted at
maintaining connectivity of riparian and upland habitats. 相似文献
18.
Experiments were conducted to quantify parasitism of Colorado potato beetle,Leptinotarsa decemlineata (Say), by the egg parasitoid,Edovum puttleri Grissell, on 3 different cultivars of eggplant,Solanum melongena L. Levels of parasitism were higher (P<0.05) on ‘Black Pride’ than on other cultivars. The percentage of egg masses that
were parasitized was 1.2-fold higher (P<0.05) on ‘Black Pride’ than on ‘Harris Special’ and ‘White’. The number of eggs per
mass that were parasitized was 1.3- and 1.4- fold greater (P<0.05) on ‘Black Pride’ than on ‘Harris Special’ and ‘White’,
respectively. The percentage of eggs that were parasitized per mass and percentage of emerged adult parasitoids did not differ
(P>0.05) among cultivars; between 2.1- to 2.6- fold more females than males emerged from eggs on all cultivars during the
growing season.Edovum puttleri suppressed the 2nd generation ofL. decemlineata on ‘Black Pride’ and ‘Harris Special’, but did not suppress populations on ‘White’.
相似文献
19.
In the present study, we evaluated whether reproductive condition affects female reproductive behaviour in the induced ovulator
Ctenomys talarum. We also explored the effect of the interaction with a male on the reproductive condition of females. To evaluate this, we
arranged mating trials and evaluated female reproductive behaviour. Reproductive status of females was evaluated using a combined
approach of vaginal smears, urinary progesterone and oestradiol, and ovarian histology. Behaviours denoting attraction (‘male
sniff’ and ‘mount attempts’) and mutual courtship behaviours (‘spin’ and copula) were correlated with vaginal cytology before
and oestradiol and progesterone levels in urine 12 h after male–female encounter. After 24 h of the interaction, oestradiol
levels and vaginal epithelization increased while progesterone levels decreased in soliciting females. C. talarum females’ reproductive behaviour was related to its physiological reproductive state and vaginal cytology. The kind of male
interaction, whether couples copulated or remained indifferent affected the later status of females. Females are induced ovulators
by mating but male presence and interaction also affected other components of their reproductive physiology such as ovarian
hormones and vaginal cytology. 相似文献
20.
The Argentine ant, Linepithema humile, originally from South America, is now a major pest in many parts of the world with Mediterranean-like climates. Earlier research indicated that southwestern European L. humile populations are segregated into two distinct supercolonies, the ‘Main’ supercolony extending through Portugal, Spain, southern France, and Italy, and the ‘Catalonian’ supercolony in eastern Spain. Both supercolonies are unicolonial, with workers showing no aggression towards members of the same supercolony, but severe aggression towards members of the other supercolony. Here we evaluated the behavioral relationships among non-native L. humile populations on the Macaronesian islands of Madeira and the Azores and non-native populations in southwestern Europe. We conducted aggression assays among L. humile workers from Madeira, the Azores, and the two southwestern European supercolonies. We found no aggressive interactions among any combination of workers from Madeira, the Azores, and the Main supercolony. However, workers from Madeira and the Azores always fought aggressively with workers from the Catalonian supercolony. Thus, the populations of L. humile in Madeira and the Azores appear to be unicolonial and act as if they belong to the Main supercolony of southwestern Europe. This set of geographically separated but mutually compatible supercolonies, which we term a ‘metacolony,’ appears to descend from one supercolony. Historical evidence suggests that the first L. humile population in the greater Mediterranean region was established in Madeira and that propagules from the dominant supercolony in Madeira gave rise to the dominant supercolonies in to other parts of the region. 相似文献