scholarly journals Frequency-dependent hybridization contributes to habitat segregation in monkeyflowers

2021 ◽  
Author(s):  
Katherine Toll ◽  
David Lowry
Keyword(s):  
Stress Tolerance ◽  
Competitive Ability ◽  
Field Experiments ◽  
Natural Populations ◽  
Seed Viability ◽  
Spatial Segregation ◽  
Closely Related Species ◽  
Frequency Dependent ◽  
Close Relatives ◽  
Competition For Resources

Spatial segregation of closely related species is usually attributed to differences in stress tolerance and competitive ability. For both animals and plants, reproductive interactions between close relatives can impose a fitness cost that is more detrimental to the rarer species. Frequency-dependent mating interactions may thus prevent the establishment of immigrants within heterospecific populations, maintaining spatial segregation of species. Despite strong spatial segregation in natural populations, two sympatric California monkeyflowers (Mimulus nudatus and M. guttatus) survive and reproduce in the other's habitat when transplanted reciprocally. We hypothesized that a frequency-dependent mating disadvantage maintains spatial segregation of these monkeyflowers during natural immigration. To evaluate this hypothesis, we performed two field experiments. First, we experimentally added immigrants in varying numbers to sites dominated by heterospecifics. Second, we reciprocally transplanted arrays of varying resident and immigrant frequency. Immigrant seed viability decreased with conspecific rarity for M. guttatus, but not M. nudatus. We observed immigrant minority disadvantage for both species, but driven by different factors- frequency-dependent hybridization for M. guttatus, and competition for resources and/or pollinators for M. nudatus. Overall, our results suggest a potential major role for reproductive interference in spatial segregation that should be evaluated along with stress tolerance and competitive ability.

Improved growth and yield of Faba beans (Vicia faba cv. Fiord) by inoculation with strains of Rhizobium leguminosarum biovar. viciae in acid soils in south west Victoria

1994 ◽  
Vol 45 (3) ◽  
pp. 613 ◽  
Author(s):  
JM Carter ◽  
WK Gardner ◽  
AH Gibson
Keyword(s):  
Vicia Faba ◽  
Rhizobium Leguminosarum ◽  
Field Experiments ◽  
Natural Populations ◽  
Acid Soils ◽  
Growth And Yield ◽  
Nitrogen Accumulation ◽  
Commercial Strain ◽  
South West ◽  
Faba Beans

The response of faba beans (Vicia faba L. cv. Fiord) to seed inoculation with eight strains of Rhizobium leguminosarum biovar. viciae was examined in field experiments at six sites on acid soils in south-west Victoria. At two of the sites, two additional strains were examined, and in 1988, 14 strains were examined at one site. Very low natural populations of R. leguminosarum bv. viciae were found at the experimental sites. Most strains resulted in improved early nodulation and increased grain yield at all sites, when compared to inoculation with the commercial strain of rhizobia (SU391). Plant dry matter production and nitrogen accumulation in the plant shoot tissue was also increased at one site during the flowering period by some strains. Large visual differences between plots inoculated with SU391 and other strains were evident at most sites. Most uninoculated treatments were not nodulated and yielded very poorly. Treatments inoculated with the strain SU391 performed similarly to the uninoculated treatments.

scholarly journals A field perspective on effects of fire and temperature fluctuation on Cerrado legume seeds

2017 ◽  
Vol 27 (2) ◽  
pp. 74-83 ◽  
Author(s):  
L. Felipe Daibes ◽  
Talita Zupo ◽  
Fernando A.O. Silveira ◽  
Alessandra Fidelis
Keyword(s):  
Temperature Fluctuation ◽  
Field Experiments ◽  
Seed Viability ◽  
Soil Surface ◽  
Temperature Fluctuations ◽  
Fire Effects ◽  
Fuel Load ◽  
Physical Dormancy ◽  
Legume Seeds ◽  
Field Perspective

AbstractInformation from a field perspective on temperature thresholds related to physical dormancy (PY) alleviation and seed resistance to high temperatures of fire is crucial to disentangle fire- and non-fire-related germination cues. We investigated seed germination and survival of four leguminous species from a frequently burned open Neotropical savanna in Central Brazil. Three field experiments were conducted according to seed location in/on the soil: (1) fire effects on exposed seeds; (2) fire effects on buried seeds; and (3) effects of temperature fluctuations on exposed seeds in gaps and shaded microsites in vegetation. After field treatments, seeds were tested for germination in the laboratory, together with the control (non-treated seeds). Fire effects on exposed seeds decreased viability in all species. However, germination of buried Mimosa leiocephala seeds was enhanced by fire in an increased fuel load treatment, in which we doubled the amount of above-ground biomass. Germination of two species (M. leiocephala and Harpalyce brasiliana) was enhanced with temperature fluctuation in gaps, but this condition also decreased seed viability. Our main conclusions are: (1) most seeds died when exposed directly to fire; (2) PY could be alleviated during hotter fires when seeds were buried in the soil; and (3) daily temperature fluctuations in gaps also broke PY of seeds on the soil surface, so many seeds could be recruited or die before being incorporated into the soil seed banks. Thus seed dormancy-break and germination of legumes from Cerrado open savannas seem to be driven by both fire and temperature fluctuations.

Differential coloration patterns in the intertidal crab Neohelice (=Chasmagnathus) granulata

2010 ◽  
Vol 91 (5) ◽  
pp. 1041-1047 ◽  
Author(s):  
Agustina Méndez Casariego ◽  
Tomás Luppi ◽  
Oscar Iribarne
Keyword(s):  
Salt Marshes ◽  
Field Experiments ◽  
Spatial Segregation ◽  
Body Coloration ◽  
Body Regions ◽  
Intertidal Crab ◽  
Coloration Pattern ◽  
Chasmagnathus Granulata ◽  
Colour Changes ◽  
Coloration Patterns

Many crustaceans with spatial segregation may present differential body coloration depending on the habitat they inhabit. Since crustaceans are unable to synthesize carotenoids, individuals must acquire them from their diet, so diet changes can modify individual coloration. The burrowing crab Neohelice (=Chasmagnathus) granulata inhabits the intertidal, from the uppermost parts of salt marshes to the lowest mudflat zones with a spatial segregation of different size-classes. They are primarily deposit feeders in mud flats and herbivorous–detritivorous in the salt marsh. We analysed the effect of intermoult length on the carapace colour of N. granulata, and the changes in carapace colour with crab size and zone. Crab colour varied between unvegetated and vegetated areas. Some of these differences were in part caused by colour changes related to crab size. Larger crabs show less intensive colours, and given that they inhabit the upper part of the intertidal a differential coloration pattern occurred between zones. In field experiments intermoult duration affected crab colour and some body regions analysed showed differences between zones unrelated to size.

Spinetoram Is Compatible with the Key Natural Enemy of Frankliniella Species Thrips in Pepper

2008 ◽  
Vol 9 (1) ◽  
pp. 30 ◽  
Author(s):  
Mrittunjai Srivastava ◽  
Lara Bosco ◽  
Joe Funderburk ◽  
Anthony Weiss
Keyword(s):  
Frankliniella Occidentalis ◽  
Field Experiments ◽  
Natural Populations ◽  
Western Flower Thrips ◽  
Central Florida ◽  
Flower Thrips ◽  
Natural Predator ◽  
Wilt Virus ◽  
The Impact ◽  
Reduced Risk

Feeding by the western flower thrips, Frankliniella occidentalis, causes damage to the fruits of pepper, and the species is the key vector of Tomato spotted wilt virus. Effective management integrates conservation of populations of the natural predator, Orius insidiosus, with the use of reduced-risk insecticides, namely spinosad. We conducted field experiments in northern Florida in 2005 and 2006 and in central Florida in 2006 to evaluate the new reduced-risk insecticide spinetoram for control of thrips and to determine the impact on natural populations of O. insidiosus. Spinetoram at 61 g ai/ha was as effective as spinosad at 140 g ai/ha against the western flower thrips and the other common thrips in Florida, Frankliniella tritici and Frankliniella bispinosa. The mean numbers of the predator were very high in all treatments in each experiment, and their numbers relative to the numbers of thrips indicated that predation was sufficient to suppress thrips populations in all treatments. Broad-spectrum insecticides when included in the experiments provided little or no control; sometimes, they flared thrips numbers compared to untreated pepper. Accepted for publication 25 October 2007. Published 18 January 2008.

scholarly journals Causation without correlation: parasite-mediated frequency-dependent selection and infection prevalence

2021 ◽  
Author(s):  
Curtis M Lively ◽  
Julie Xu ◽  
Frida Ben-Ami
Keyword(s):  
Genetic Diversity ◽  
Natural Populations ◽  
Infection Prevalence ◽  
Strong Positive Correlation ◽  
Frequency Dependent ◽  
Frequency Dependent Selection ◽  
Host Diversity ◽  
Host Genetic ◽  
Host Parasite

Parasite-mediated selection is thought to maintain host genetic diversity for resistance. We might thus expect to find a strong positive correlation between host genetic diversity and infection prevalence across natural populations. Here we used computer simulations to examine host-parasite coevolution in 20 simi-isolated clonal populations across a broad range of values for both parasite virulence and parasite fecundity. We found that the correlation between host genetic diversity and infection prevalence can be significantly positive for intermediate values of parasite virulence and fecundity. But the correlation can also be weak and statistically non-significant, even when parasite-mediated frequency-dependent selection is the sole force maintaining host diversity. Hence correlational analyses of field populations, while useful, might underestimate the role of parasites in maintaining host diversity.

scholarly journals Balancing selection maintains polymorphisms at neurogenetic loci in field experiments

2017 ◽  
Vol 114 (14) ◽  
pp. 3690-3695 ◽  
Author(s):  
Eija Lonn ◽  
Esa Koskela ◽  
Tapio Mappes ◽  
Mikael Mokkonen ◽  
Angela M. Sims ◽  
...  
Keyword(s):  
Reproductive Success ◽  
Population Density ◽  
Arginine Vasopressin ◽  
Field Experiments ◽  
Balancing Selection ◽  
Regulatory Region ◽  
Natural Populations ◽  
Myodes Glareolus ◽  
Sexual Antagonism ◽  
Reproductive Behaviors

Most variation in behavior has a genetic basis, but the processes determining the level of diversity at behavioral loci are largely unknown for natural populations. Expression of arginine vasopressin receptor 1a (Avpr1a) and oxytocin receptor (Oxtr) in specific regions of the brain regulates diverse social and reproductive behaviors in mammals, including humans. That these genes have important fitness consequences and that natural populations contain extensive diversity at these loci implies the action of balancing selection. In Myodes glareolus, Avpr1a and Oxtr each contain a polymorphic microsatellite locus located in their 5′ regulatory region (the regulatory region-associated microsatellite, RRAM) that likely regulates gene expression. To test the hypothesis that balancing selection maintains diversity at behavioral loci, we released artificially bred females and males with different RRAM allele lengths into field enclosures that differed in population density. The length of Avpr1a and Oxtr RRAMs was associated with reproductive success, but population density and the sex interacted to determine the optimal genotype. In general, longer Avpr1a RRAMs were more beneficial for males, and shorter RRAMs were more beneficial for females; the opposite was true for Oxtr RRAMs. Moreover, Avpr1a RRAM allele length is correlated with the reproductive success of the sexes during different phases of reproduction; for males, RRAM length correlated with the numbers of newborn offspring, but for females selection was evident on the number of weaned offspring. This report of density-dependence and sexual antagonism acting on loci within the arginine vasopressin–oxytocin pathway explains how genetic diversity at Avpr1a and Oxtr could be maintained in natural populations.

High seed viability recorded in an endangered endemic species, 'Isoplexis isabelliana' (Scrophulariaceae), after more than 30 years of storage in a conservation seed bank

2021 ◽  
Vol 42 ◽  
pp. e69341
Author(s):  
Miguel Ángel González Pérez ◽  
Nereida Cabrera-García ◽  
Isabel Cayon-Fernández
Keyword(s):  
Seed Bank ◽  
Germination Rate ◽  
Genetic Material ◽  
Natural Populations ◽  
Seed Viability ◽  
Seed Storage ◽  
Botanical Garden ◽  
Storage Conditions ◽  
Seed Banks ◽  
Ex Situ

Conservation seed banks are essential for ex-situ conservation of genetic biodiversity. These institutions are especially relevant for threatened species and play a vital role in their conservation by preserving genetic material. However, samples deposited in the seed banks must germinate when necessary to use them (i.e., recovery plans, etc.). This study uses four accessions of the endemic endangered species from Gran Canaria Island (Canary Islands), Isoplexis isabelliana (Webb & Berthel.) Masf. (Scrophulariaceae). Germination tests were carried out to measure seed viability through time and the possible impact of seed storage on their viability. These accessions have been kept in the seed bank for four months to thirty years under different storage conditions. Germination results differed for seeds after 45 days of exposition using 16 hours light and 8 hours darkness at 17 °C. Accessions kept in the seed bank, independently of storage, showed a high germination percentage (89%). Whereas the accessions with rough storage conditions showed a 0% germination rate. The results highlighted the good state of conservation of the material deposited in the Seed Bank of the Botanical Garden "Viera y Clavijo" and the reliability of the temperature and humidity conditions in which the seeds of I. isabelliana have been stored. We consider these results as momentous since several natural populations of I. isabelliana has been affected by the last forest fire on the island.

scholarly journals Dominant words rise to the top by positive frequency-dependent selection

2019 ◽  
Vol 116 (15) ◽  
pp. 7397-7402 ◽  
Author(s):  
Mark Pagel ◽  
Mark Beaumont ◽  
Andrew Meade ◽  
Annemarie Verkerk ◽  
Andreea Calude
Keyword(s):  
Natural Populations ◽  
Word Choice ◽  
Random Drift ◽  
Frequency Dependent ◽  
Frequency Dependent Selection ◽  
Neutral Drift ◽  
Word Use ◽  
New Words ◽  
Core Lexicon ◽  
Positive Frequency

A puzzle of language is how speakers come to use the same words for particular meanings, given that there are often many competing alternatives (e.g., “sofa,” “couch,” “settee”), and there is seldom a necessary connection between a word and its meaning. The well-known process of random drift—roughly corresponding in this context to “say what you hear”—can cause the frequencies of alternative words to fluctuate over time, and it is even possible for one of the words to replace all others, without any form of selection being involved. However, is drift alone an adequate explanation of a shared vocabulary? Darwin thought not. Here, we apply models of neutral drift, directional selection, and positive frequency-dependent selection to explain over 417,000 word-use choices for 418 meanings in two natural populations of speakers. We find that neutral drift does not in general explain word use. Instead, some form of selection governs word choice in over 91% of the meanings we studied. In cases where one word dominates all others for a particular meaning—such as is typical of the words in the core lexicon of a language—word choice is guided by positive frequency-dependent selection—a bias that makes speakers disproportionately likely to use the words that most others use. This bias grants an increasing advantage to the common form as it becomes more popular and provides a mechanism to explain how a shared vocabulary can spontaneously self-organize and then be maintained for centuries or even millennia, despite new words continually entering the lexicon.

Review Lecture Disruptive selection

1972 ◽  
Vol 182 (1067) ◽  
pp. 109-143 ◽  
Keyword(s):  
Gene Flow ◽  
Genetic Variance ◽  
Natural Populations ◽  
Disruptive Selection ◽  
Ecological Niches ◽  
Gene Exchange ◽  
Bisexual Species ◽  
Frequency Dependent ◽  
Ecological Conditions ◽  
Intermediate Phenotypes

A population is exposed to disruptive selection if more than one phenotype has optimal fitness and intermediate phenotypes have lower fitnesses. Maintenance of the two or more optima may depend upon their relative fitnesses being frequency dependent. Such selection may be expected in two contrasting types of situation. First the two or more optimal phenotypes may depend on one another as do the two sexes in a bisexual species. Secondly the optima may be set by heterogeneity of the environment. Then we may think in terms of a mosaic of ecological niches or a clinal situation, and may expect that gene flow will tend to promote convergence of the sub-populations while disruptive selection tends to promote their divergence. Disruptive selection may therefore be relevant both to the evolution and maintenance of polymorphisms and to the divergence of parts of populations one from another, under the influence of variation of ecological conditions within the range of gametic and/or zygotic dispersal. Disruptive selection has been shown to be capable of increasing phenotypic and genetic variance, of producing and maintaining polymorphisms, of causing divergence of sub-populations between which substantial gene exchange occurs, and of splitting a population into two which are genetically isolated from one another. These results are reviewed and their relevance to natural populations discussed.

Sign in / Sign up

Export Citation Format

Share Document