scholarly journals Architectural traits constrain the evolution of unisexual flowers and sexual segregation within inflorescences: an interspecific approach

2018 ◽  
Author(s):  
Rubén Torices ◽  
Ana Afonso ◽  
Arne A. Anderberg ◽  
José M. Gómez ◽  
Marcos Méndez
Keyword(s):  
Resource Availability ◽  
Sex Allocation ◽  
Sexual Segregation ◽  
Sequential Development ◽  
Size Number ◽  
Sexual Specialization ◽  
Resource Decline ◽  
Flower Density ◽  
Unisexual Flowers ◽  
The Difference

ABSTRACTMale and female unisexual flowers have repeatedly evolved from the ancestral bisexual flowers in different lineages of flowering plants. This sex specialization in different flowers often occurs within inflorescences. We hypothesize that inflorescence architecture may impose a constraint on resource availability for late flowers, potentially leading to different optima in floral sex allocation and unisexuality. Under this hypothesis we expect that inflorescence traits increasing the difference in resource availability between early and late flowers would be phylogenetically correlated with a higher level of sexual specialization. To test this hypothesis, we performed a comparative analysis of inflorescence traits (inflorescence size, number of flowers and flower density) in the sunflower family, which displays an extraordinary variation in floral sexual specialization at the inflorescence level, i.e. hermaphroditic, gynomonoecious and monoecious species. We found that species with a complete sex separation in unisexual flowers (monoecy) had significantly denser inflorescences. Furthermore, those species arranging their flowers in denser inflorescences also showed greater differences in the size of early and late fruits, a proxy of resource variation between flowers. Our findings support the idea that floral sexual specialization and consequently sexual segregation may be the consequence of different floral sex allocation optima driven by the sequential development of flowers that results in a persistent resource decline from earlier to later flowers.

scholarly journals Electronic Resource Availability Studies: An Effective Way to Discover Access Errors

2015 ◽  
Vol 10 (3) ◽  
pp. 30 ◽  
Author(s):  
Sanjeet Mann
Keyword(s):  
Resource Availability ◽  
Information Seeking ◽  
Research Method ◽  
Initial Study ◽  
Electronic Resource ◽  
Technical Problems ◽  
Systems Research ◽  
Before And After ◽  
The Difference ◽  
Student Information

Abstract Objective – The availability study is a systems research method that has recently been used to test whether library users can access electronic resources. This study evaluates the availability study’s effectiveness as a troubleshooting tool by comparing the results of two availability studies conducted at the same library before and after fixing access problems identified by the initial study. Methods – The researcher developed a six-category conceptual model of the causes of electronic resource errors, modified Nisonger’s e-resource availability method to more closely approximate student information-seeking behaviour, and conducted an availability study at the University of Redlands Armacost Library to estimate how many resources suffered from errors. After conducting troubleshooting over a period of several months, he replicated the study and found increased overall availability and fewer incidences of most error categories. He used Z tests for the difference of two proportions to determine whether the changes were statistically significant. Results – The 62.5% availability rate in the first study increased after troubleshooting to 86.5% in the second study. Z tests showed that troubleshooting had produced statistically significant improvements in overall availability, in the number of items that could be downloaded from the library’s online collection or requested through interlibrary loan (ILL), and in three of six error categories (proxy, target database and ILL). Conclusion – Availability studies can contribute to successful troubleshooting initiatives by making librarians aware of technical problems that might otherwise go unreported. Problems uncovered by an availability study can be resolved through collaboration between librarians and systems vendors, though the present study did not demonstrate equally significant improvements across all types of errors. This study offers guidance to librarians seeking to focus troubleshooting efforts where they will have the greatest impact in improving access to full-text. It also advances the availability research method and is the first attempt to quantify its effectiveness as a troubleshooting tool.

scholarly journals Breeding stage, not sex, affects foraging characteristics in masked boobies at Rapa Nui

2020 ◽  
Vol 74 (12) ◽  
Author(s):  
Miriam Lerma ◽  
Nina Dehnhard ◽  
Guillermo Luna-Jorquera ◽  
Christian C. Voigt ◽  
Stefan Garthe
Keyword(s):  
Prey Availability ◽  
General Pattern ◽  
Sexual Segregation ◽  
Food Distribution ◽  
Rapa Nui ◽  
Breeding Stage ◽  
Horizontal Competition ◽  
Show Evidence ◽  
Competition For Food ◽  
The Difference

Abstract Sexual segregation in foraging occurs in some species and populations of boobies (Sulidae), but it is not a general pattern. Sexual segregation in foraging may occur to avoid competition for food, and this competition may intensify during specific stages of breeding. We examined sexual segregation in foraging in relation to breeding stage in masked boobies Sula dactylatra at Rapa Nui by tracking simultaneously incubating and chick-rearing birds using GPS recorders (n = 18) and collected a total of 11 regurgitate samples. Stable isotope analyses (δ13C and δ15N) of whole blood samples were carried out in 20 birds. There were no differences in foraging trip parameters or diet between females and males. Both sexes traveled farther and for longer while incubating than while rearing chicks. Isotopic niches (δ13C and δ15N) overlapped to some degree among all groups at all times, but the lowest overlap between sexes occurred during incubation. While preying on ephemerally distributed flying fish, vertical or horizontal competition avoidance may be almost impossible, and thus females and males share their foraging grounds. Since birds were tracked simultaneously, shorter foraging trips of chick-rearing birds must be an effect of the constraints of provisioning the chick. Differences observed in δ15N and δ13C values between sexes may be caused by subtle differences in their foraging behaviors, or by differences in physiology linked to breeding. Our findings suggest that local oceanography and its inherent food distribution are determinants for sexual segregation in foraging patterns in masked boobies and possibly also other booby species. Significance statement In some animals, females and males forage on different areas or prey on different species to avoid competition for food resources. In boobies (Sula sp.), some studies show evidence of sexual segregation in foraging and others do not. Here, we tested if sexual segregation in foraging occurred in masked boobies on the Pacific island of Rapa Nui by studying simultaneously incubating and chick-rearing birds. We found no evidence of sexual segregation on foraging behavior or diet. We discuss that the difference between this and other studies in boobies may be an effect of the local prey availability. When the prey community is more diverse and heterogeneously distributed, each sex may access different resources and thus sexual foraging segregation will occur. In contrast, in areas like Rapa Nui where prey resources are distributed ephemerally, sexual segregation in foraging will not be useful and is thus less likely to occur.

Performance simulations for categorical mediation: Analyzing khb estimates of mediation in ordinal regression models

2019 ◽  
Vol 19 (4) ◽  
pp. 913-930 ◽  
Author(s):  
E. Keith Smith ◽  
Michael G. Lacy ◽  
Adam Mayer
Keyword(s):  
Logistic Regression ◽  
Nonlinear Regression ◽  
Regression Models ◽  
Binary Logistic Regression ◽  
Experimental Conditions ◽  
Logistic Regression Models ◽  
Nonlinear Regression Models ◽  
Size Number ◽  
Confidence Interval Coverage ◽  
The Difference

Standard mediation techniques for fitting mediation models cannot readily be translated to nonlinear regression models because of scaling issues. Methods to assess mediation in regression models with categorical and limited response variables have expanded in recent years, and these techniques vary in their approach and versatility. The recently developed khb technique purports to solve the scaling problem and produce valid estimates across a range of nonlinear regression models. Prior studies demonstrate that khb performs well in binary logistic regression models, but performance in other models has yet to be investigated. In this article, we evaluate khb‘s performance in fitting ordinal logistic regression models as an exemplar of the wider set of models to which it applies. We examined performance across 38,400 experimental conditions involving sample size, number of response categories, distribution of variables, and amount of mediation. Results indicate that under all experimental conditions, khb estimates the difference (mediation) coefficient and its associated standard error with little bias and that the nominal confidence interval coverage closely matches the actual. Our results suggest that researchers using khb can assume that the routine reasonably approximates population parameters.

Post-embryonic development of Lithobius erythrocephalus C. L. Koch (Chilopoda: Lithobiidae)

1978 ◽  
Vol 9 (4) ◽  
pp. 241-246 ◽  
Author(s):  
Göran Andersson
Keyword(s):  
Embryonic Development ◽  
Male And Female ◽  
Size Number ◽  
The Difference ◽  
Cephalic Shield

AbstractExamined Swedish specimens of Lithobius erythrocephalus belong to the nominate subspecies. The variation during development in size, number of coxal pores, ocelli, antennal articles, teeth on forcipular coxosternite, projections on tergites 9, 11 and 13, spinulation, accessory apical claw on the 15th pair of legs, genitalia and the pattern on the cephalic shield are described. Also the difference between male and female and correlation with size within each stadium are given. There are probably 8 post-larval stadia in Sweden.

scholarly journals Does resource availability affect host manipulation? – an experimental test with Schistocephalus solidus

2015 ◽  
Vol 1 ◽  
Author(s):  
NINA HAFER ◽  
DANIEL P. BENESH
Keyword(s):  
Resource Availability ◽  
Parasite Transmission ◽  
Host Manipulation ◽  
Food Treatment ◽  
Schistocephalus Solidus ◽  
Trade Offs ◽  
Common Strategy ◽  
Food Conditions ◽  
The Difference ◽  
Host Behaviour

SUMMARYHost manipulation is a common strategy of parasites employed to increase their fitness by changing the phenotype of their hosts. Whether host manipulation might be affected by environmental factors such as resource availability, has received little attention. We experimentally infected laboratory-bred copepods with the cestodeSchistocephalus solidus, submitted infected and uninfected copepods to either a high or a low food treatment, and measured their behaviour. Infection reduced host activity and speed in both feeding treatments. However, the difference between the infected and uninfected copepods was smaller under low food conditions, because uninfected, but not infected, copepods moved slower under these conditions. We suggest that these differences are mediated by the physical condition of copepods rather than changes in how strongly the parasite manipulated host behaviour. Additionally, we measured three fitness-relevant traits (growth, development and infection rate in the next host) of the parasite to identify potential trade-offs with host manipulation. The largest parasites in copepods appeared the least manipulative, i.e. their hosts showed the smallest behavioural alterations, but this may again reflect variation in copepod condition, rather than life history trade-offs between parasite growth and host manipulation. Our results point to the possibility that parasite transmission depends on environmental conditions.

scholarly journals STAR AND POOR FUND PHENOMENA IN ISLAMIC- AND CONVENTIONAL-FOCUSED FAMILIES: EMERGING COUNTRY EVIDENCE

2021 ◽  
Vol 7 (2) ◽  
pp. 263-284
Author(s):  
Anas Ahmad Bani Atta ◽  
Ainulashikin Marzuki
Keyword(s):  
Mutual Funds ◽  
Negative Relationship ◽  
Panel Regression ◽  
The Novel ◽  
Total Risk ◽  
Independent Variables ◽  
Size Number ◽  
Emerging Country ◽  
The Difference ◽  
The Impact

The aim of this study is to investigate star and poor phenomena and their impact on the flows of Islamic-focused family (IFF) and conventional-focused family (CFF). The sample includes the four emerging countries with the largest number of Islamic mutual funds from 2007 to 2018 (Saudi Arabia, Malaysia, Indonesia, and Pakistan). Panel regression analysis was used to examine the impact of dummy star and poor as independent variables, and family age, size, number of funds, past returns, and total risk as control variables for fund family flows. The results show that the dummy star has a significantly positive relationship with family flows. Family managers have succeeded in attracting more investors by using the strategy of advertising the best performing funds. However, in both, all families and IFF, the dummy poor has a negative relationship, but is insignificant. On the other hand, for CFFs, the dummy poor is significantly negative. This is because investors in IFFs, unlike those in CFFs, have more loyalty due to their moral and religious goals in addition to traditional goals. The novel finding of the study is the difference in the star phenomenon between the IFF and CFF. The findings are important for managers, as they will help them to create appropriate strategies to attract more flows and increase the assets under their management. In addition, the findings will help investors to direct their money to appropriate families.

scholarly journals THE ANTHRACNOSES OF CITRUS FRUITS, MANGO AND AVOCADO

1969 ◽  
Vol 10 (2) ◽  
pp. 25-63
Author(s):  
J. A. B. Nolla
Keyword(s):  
Culture Medium ◽  
Aerial Mycelium ◽  
Distinct Species ◽  
Citrus Fruits ◽  
Cultural Characteristics ◽  
Size Number ◽  
Fruit Spot ◽  
The Difference ◽  
A New Species ◽  
Growth Characters

(1) Colletotrichum glocosporioides Penz. appears to be the cause of the anthracnose diseases of mango, orange, grapefruit, lemon, avocado, and sometimes of lime. (2) Lime wither-tip may be caused by either G. gloeosporioides or Glocosporium limetticolum Clausen. (3) Collelotrichum gloeosporioides Penz. frequently causes spotting of lime blossoms and the wither-tip. It is also the cause of the spots on lime thorns. The latter is demonstrated by cultures L 9- L, 13, inclusive, which behaved like other G. gloeosporioides cultures and very distinct from cultures of G. limetticolum. (4) Glocosporium limetticolum Clausen is the cause of wither-tip· ancl leaf spot of limes. (5) G. limetticolum appears to be the only cause of fruit canker or fruit spot of limes. (6) Under artificial conditions the various cultures of G. gloeosporioides and G. limetticolum exhibit distinct cultural characteristics. (7) Cultures from the avocado differ somewhat from cultures obtained from other hosts in cultural characteristics. The difference may not furnish enough evidence for their separation into a new species. (8) There are such differences between most cultures from the lime and all cultures from the other hosts that Clausen's (5) separation of the former into a distinct species appears to be justified. (9) The four most salient growth characters in which cultures of C. gloeosporioides varied from cultures of G. limetticolum or such cultures among themselves are: (a) size, number, and arrangement of acervuli; (b) color of acervuli and substratum; (c) character of aerial mycelium; (d) size of colonies. (10) C. gloeosporioides can resist slightly more acid or alkaline concentrations than G. limetticolum. (11) Setae are occasionally present in C. gloeosporioides and absent in G. limetticolum. (12) Variation in spore size is induced by the culture medium. (13) There is great morphological similarity between G. limetticolum and C. gloeosporioides. (14) Environment induces variation in form and shape of spores. (15) The character of conidia appears to be rather uncertain for distinguishing between Gloeosporium limetticolum gloeosporioides.

Post-embryonic development of Lithobius forficatus (L.), (Chilopoda: Lithobiidae)

1976 ◽  
Vol 7 (3) ◽  
pp. 161-168 ◽  
Author(s):  
Göran Andersson
Keyword(s):  
Embryonic Development ◽  
Male And Female ◽  
Size Number ◽  
The Difference ◽  
Lithobius Forficatus

AbstractThe larval stadia of L. forficatus are easily distinguished by the number of legs and are separated from all other Scandinavian species in having more than 2+2 teeth on the forcipular coxosternite. The variation during development in size, number of coxal pores, ocelli, antennal articles, teeth on forcipular coxosternite, spinulation, projections on tergites 9, 11 and 13, accessory apical claw on the 15 th pair of legs and genitalia are described. Also the difference between male and female and correlation with size within each stadium are given. The number of coxal pores is the best feature for separating the post-larval stadia of L. forficatus. There are probably 9 post-larval stadia in Sweden. The larva media (sensu Verhoeff) is an accidental stadium and only occasionally included in development.

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