Consistency in seed-deposition patterns and the distribution of mistletoes among its host trees in an Amazonian savanna

2009 ◽  
Vol 57 (8) ◽  
pp. 640 ◽  
Author(s):  
Rodrigo Ferreira Fadini ◽  
Danielly Caroline Miléo Gonçalves ◽  
Rúbia Patrícia Fernandes Reis
Keyword(s):  
Spatial Distribution ◽  
Field Experiment ◽  
Host Size ◽  
Host Quality ◽  
Deposition Patterns ◽  
Seed Disperser ◽  
Crown Diameter ◽  
Host Trees ◽  
Cashew Tree ◽  
To Receive

The present paper describes the spatial distribution of the mistletoe Psittacanthus plagiophyllus Eichl. (Loranthaceae) on its host, the cashew tree Anacardium occidentale L., in a Brazilian Amazonian savanna. Our aim was to understand the roles of bird-seed dispersers and host quality in determining the mistletoe distribution among its host trees. In 2006, we marked 118 cashews in a 4.5-ha plot and counted the number of mistletoes and the presence of seeds attached to host branches in 2006, 2007 and 2008. On average, 36% of the hosts were infected each year. The infection load and the probability of being infected increased significantly with host crown diameter. On average, 25% of the hosts received at least one mistletoe seed in each year, being taller and previously infected hosts more prone to receive seeds in all 3 years. Elaenia cristata was the main seed disperser, visiting P. plagiophyllus 48 times in 35 h of focal records. Additionally, in a field experiment, we used the presence of an infection and the host size as surrogates for host quality and tested their effect on mistletoe survivorship. After 9 months, 16.5% of seeds survived and 14% had established, but neither host conditions nor host size influenced seed survivorship. Therefore, we suggest that mistletoe distribution is a consequence of a consistent dispersal of seeds onto larger and previously parasitised hosts across years.

scholarly journals Does Exposure to Gender Role Models Increase Women’s Political Ambition? A Field Experiment with Politicians

2019 ◽  
Vol 7 (3) ◽  
pp. 157-166
Author(s):  
Florian Foos ◽  
Fabrizio Gilardi
Keyword(s):  
Field Experiment ◽  
Gender Gap ◽  
Role Models ◽  
Female Students ◽  
Election Campaign ◽  
Political Ambition ◽  
Female Politicians ◽  
Political Office ◽  
To Receive ◽  
Positive Effect

AbstractThere is a persistent gender gap in motivations to run for political office. While exposure to role models is widely believed to increase women’s political ambition, there is little field experimental evidence on whether exposure to female politicians in realistic settings can increase political ambition. We conducted a field experiment in which a sample of 612 female students was randomly assigned to receive emails inviting them to an event that included career workshops with female politicians, or no email. The treatment increased interest in the ongoing national election campaign, but, against expectations, did not have any positive effect on political ambition. Our results suggest that female politicians who discuss their experience bluntly, instead of following a motivational script, may fail to motivate other women to pursue a political career. These results highlight the need for more research into the type of events and messages that bring more women into politics.

Living on a catfish: nested occupation of ectosymbiotic chironomids on host body

2018 ◽  
Vol 96 (7) ◽  
pp. 692-699
Author(s):  
Renato B. Dala-Corte ◽  
Adriano S. Melo
Keyword(s):  
Spatial Distribution ◽  
Body Surface ◽  
Preferential Attachment ◽  
Body Part ◽  
Host Size ◽  
Host Body ◽  
Attachment Sites

Symbiotic species often have preferential attachment sites on their host body and thus some sites may only be occupied if the supposed best sites are already occupied. Alternatively, colonization may be similar in all sites, but removal may differ among them. Both mechanisms might generate a nested pattern. Moreover, the host size can alter the quality of the site for symbiotic occupation; for instance, by increasing the area and anchorage structures or reducing removal. We predicted that the spatial distribution of the ectosymbiotic chironomid Ichthyocladius lilianae Mendes, Andersen and Sæther, 2004 on their host, the armored catfish Pareiorhaphis hypselurus (Pereira and Reis, 2002), would present a nested pattern with regards to body-part preference and variation according to host size. We found that (i) suboptimal sites on the host body were usually only occupied by a symbiont when the optimal sites were already occupied and (ii) sites occupied by larvae on small host body surface were a subset of the sites occupied on large hosts. Our results indicate a nested distribution, yet the mechanisms generating this pattern are unclear. One possibility is that symbionts have preferential sites for attachment on the host body surface and compete for these sites. As an alternative, symbionts may present no preference and colonize equally all sites, but they remain attached to sites that offer better resources or protection from removal.

The Quest for a Suitable Host: Size Distributions of Host Trees and Secondary Hemiepiphytes Search Strategy

Biotropica ◽  
2011 ◽  
Vol 44 (1) ◽  
pp. 19-26 ◽  
Author(s):  
María P. Balcázar-Vargas ◽  
María C. Peñuela-Mora ◽  
Tinde R. van Andel ◽  
Pieter A. Zuidema
Keyword(s):  
Search Strategy ◽  
Host Size ◽  
Size Distributions ◽  
Suitable Host ◽  
Host Trees

scholarly journals “Outside Lobbying” over the Airwaves: A Randomized Field Experiment on Televised Issue Ads

2021 ◽  
pp. 1-7
Author(s):  
JOSHUA L. KALLA ◽  
DAVID E. BROOCKMAN
Keyword(s):  
Public Opinion ◽  
Field Experiment ◽  
Interest Groups ◽  
Interest Group ◽  
Group Influence ◽  
Randomized Field Experiment ◽  
Persuasive Power ◽  
To Receive ◽  
Organized Interest ◽  
Interest Group Influence

We present the first field experiment on how organized interest groups’ television ads affect issue opinions. We randomized 31,404 voters to three weeks of interest group ads about either immigration or transgender nondiscrimination. We then randomly assigned voters to receive ostensibly unrelated surveys either while the ads aired, one day after they stopped, or three days afterwards. Voters recalled the ads, but three ads had a minimal influence on public opinion, whereas a fourth’s effects decayed within one day. However, voters remembered a fact from one ad. Our results suggest issue ads can affect public opinion but that not every ad persuades and that persuasive effects decay. Despite the vast sums spent on television ads, our results are the first field experiment on their persuasive power on issues, shedding light on the mechanisms underpinning—and limits on—both televised persuasion and interest group influence.

Effect of host size and temporal exposure on metacercarial infection levels in the intertidal cockle Cerastoderma edule

2008 ◽  
Vol 88 (3) ◽  
pp. 613-616 ◽  
Author(s):  
David W. Thieltges
Keyword(s):  
Field Experiment ◽  
Field Survey ◽  
Age Groups ◽  
Total Sample ◽  
Host Size ◽  
Relative Importance ◽  
Host Age ◽  
Main Determinant ◽  
Cerastoderma Edule ◽  
Positive Correlations

In a field survey and a field experiment the relative importance of host size and temporal exposure in determining metacercarial infection levels in an intertidal bivalve was investigated. While cockles (Cerastoderma edule) of different age (indicated by winter rings on shells) collected at the same site showed strong positive correlations between host size and infection levels over the total sample, correlations were weak or absent within the age groups. Mean infection levels in cockles strongly increased with age suggesting temporal exposure and not size to be the main determinant of infection levels in the cockles. This was supported by a field experiment in which small and large cockles were exposed for one or two months on a tidal flat. While infection levels significantly increased with temporal exposure, host size had no significant effect. This suggests that bivalve hosts on temperate tidal flats accumulate parasites during a distinctive infection window during summer more or less independent of their size. With every additional year of exposure, infection levels of the parasites increase. Hence, it is important to take host age into account when comparing individual infection levels within and among different host populations.

Spatial distribution of oviposition sites determines variance in the reproductive rate of European bitterling (Rhodeus amarus)

Behaviour ◽  
2007 ◽  
Vol 144 (11) ◽  
pp. 1403-1417 ◽  
Author(s):  
Mirosław Przybylski ◽  
Carl Smith ◽  
Martin Reichard ◽  
Rowena Spence
Keyword(s):  
Spatial Distribution ◽  
Field Experiment ◽  
Laboratory Experiment ◽  
Reproductive Rate ◽  
Site Distribution ◽  
Unionid Mussels ◽  
Mating System Evolution ◽  
The Mean ◽  
Oviposition Sites ◽  
Unio Pictorum

AbstractWe investigated reproductive rate in relation to oviposition site distribution and quality in the European bitterling, Rhodeus amarus, a freshwater fish that spawns on the gills of living unionid mussels. In a laboratory experiment male bitterling led females to groups of four mussels at a significantly higher rate than single mussels, irrespective of mussel species. Females spawned significantly more frequently on the gills of mussels in groups than on solitary mussels, and showed a preference for spawning on the gills of Unio pictorum in comparison with Anodonta anatina. In a field experiment the total number of eggs spawned on the gills of four mussels was significantly higher than that of single mussels, though the mean number of eggs per mussel was equivalent within species. There was a significant effect of species on the number of eggs spawned in mussels; U. pictorum and U. tumidus received more eggs than A. anatina and A. cygnea. We discuss these results in the context of mating system evolution.

Resynthesized lines and cultivars of Brassica napus L. provide sources of resistance to the cabbage stem weevil (Ceutorhynchus pallidactylus (Mrsh.))

2010 ◽  
Vol 101 (3) ◽  
pp. 287-294 ◽  
Author(s):  
M. Eickermann ◽  
B. Ulber ◽  
S. Vidal
Keyword(s):  
Brassica Napus ◽  
Field Experiment ◽  
Oilseed Rape ◽  
Screening Tests ◽  
Host Quality ◽  
Sources Of Resistance ◽  
Brassica Napus L ◽  
Key Factor ◽  
Ceutorhynchus Pallidactylus

AbstractThe cabbage stem weevil (Ceutorhynchus pallidactylus (Mrsh.)) (Col., Curculionidae) is a serious pest of winter oilseed rape (Brassica napus L. var. oleifera Metzg.) in central and northern Europe. Although host-plant resistance is a key tool in integrated pest management systems, resistant genotypes are not yet available for this species. Resynthesized rapeseed lines (B. oleracea L.×B. rapa L.) are broadening the genetic diversity and might have potential as sources of resistance to pest insects. The host quality, of nine resynthesized rapeseed lines and six genotypes of B. napus to cabbage stem weevil, was evaluated in laboratory screening tests and in a semi-field experiment. In dual-choice oviposition tests, female C. pallidactylus laid significantly fewer eggs on five resyntheses and on swede cv ‘Devon Champion’ than on the moderately susceptible oilseed rape cv ‘Express’, indicating a lower host quality of these genotypes. Results of laboratory screenings were confirmed in a semi-field experiment, in which twelve genotypes were exposed to C. pallidactylus females. The number of larvae was significantly lower in two resyntheses and in cv ‘Devon Champion’ than in oilseed rape cv WVB 9. The total, as well as individual, glucosinolate (GSL) content in the leaves differed substantially among the genotypes tested. The amount of feeding by larvae of C. pallidactylus, as measured by a stem-injury coefficient, was positively correlated with the indolyl GSL compounds 3-indolylmethyl and 4-methoxy-3-indolylmethyl, and with the aromatic GSL 2-phenylethyl, whereas it was negatively correlated with 4-hydroxy-3-indolylmethyl. Thus, the composition and concentration of GSL compounds within the plant tissue might be a key factor in breeding for pest resistance in oilseed rape.

Using effects of parasitoid size on fitness to test a host quality model assumption with the parasitoid wasp Spalangia endius

2006 ◽  
Vol 84 (11) ◽  
pp. 1678-1682 ◽  
Author(s):  
B.H. King ◽  
M.E. Napoleon
Keyword(s):  
Sexual Size Dimorphism ◽  
Parasitoid Wasp ◽  
Host Size ◽  
Female Size ◽  
Host Quality ◽  
Quality Model ◽  
Male Size ◽  
Model Assumption ◽  
Size Dimorphism ◽  
Spalangia Endius

How body size affects fitness of males relative to females is relevant to understanding the evolution of sexual size dimorphism and maternal sex-ratio manipulation. In most parasitoid wasps, mothers oviposit a greater proportion of daughters in larger hosts. The host-quality model describes how this may be adaptive. A major assumption of the model is that host size has a greater effect on the fitness of daughters than of sons. The assumption has often been tested indirectly by examining the effects of parasitoid size on fitness, because a parasitoid’s size generally increases with the size of the host on which it develops. The validity of this indirect method is examined here for the parasitoid wasp Spalangia endius Walker, 1839 parasitizing Musca domestica L., 1758. If the method is valid, effects of parasitoid size on fitness should match the effects of host size on fitness that were shown in a previous study. The effects matched in that both parasitoid size and host size affected the fitness of females but not of males. However, the aspects of female fitness that were affected differed. That female size but not male size affected fitness was consistent with the female-biased sexual size dimorphism of S. endius.

scholarly journals THE EFFECT OF BUILDING GEOMETRY ON AEOLIAN DEPOSITION AND EROSION PATTERNS: A FIELD EXPERIMENT

2020 ◽  
pp. 21
Author(s):  
Daan Poppema ◽  
Kathelijne Wijnberg ◽  
Jan Mulder ◽  
Suzanne Hulscher
Keyword(s):  
Field Experiment ◽  
Flood Protection ◽  
Sand Transport ◽  
Dune System ◽  
Deposition Patterns ◽  
Building Geometry ◽  
Dune Morphology

Buildings at the beach-dune interface, such as restaurants and (holiday) houses, affect wind-driven sand transport in their surroundings. Hereby they shape the development of the beach-dune system. This can have implications for the flood protection offered by dunes. Therefore, this research aims to understand the effect of buildings at the beach-dune interface on beach-dune morphology. In this contribution we present the results of a field experiment which focused on the effect of building size and geometry on the size and location of the deposition patterns directly around buildings.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/hlcMP7Ev1m0

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