A directed network analysis of heterospecific pollen transfer in a biodiverse community

Ecology ◽  
2013 ◽  
Vol 94 (5) ◽  
pp. 1176-1185 ◽  
Author(s):  
Qiang Fang ◽  
Shuang-Quan Huang
Keyword(s):  
Network Analysis ◽  
Directed Network ◽  
Pollen Transfer ◽  
Heterospecific Pollen

Unilateral incompatibility and the effects of interspecific pollination for Erythronium americanum and Erythronium albidum (Liliaceae)

1993 ◽  
Vol 71 (2) ◽  
pp. 353-358 ◽  
Author(s):  
Lawrence D. Harder ◽  
Mitchell B. Cruzan ◽  
James D. Thomson
Keyword(s):  
Seed Production ◽  
Pollen Tubes ◽  
The Self ◽  
Pollen Transfer ◽  
Interspecific Incompatibility ◽  
Unilateral Incompatibility ◽  
Heterospecific Pollen ◽  
Interspecific Pollen Transfer ◽  
Erythronium Americanum ◽  
Incompatibility Reaction

To determine whether interspecific pollen transfer could reduce seed production by two sympatric lilies, Erythronium albidum and Erythronium americanum, we hand-pollinated flowers with mixtures of conspecific and heterospecific pollen. These species exhibited typical unilateral interspecific incompatibility, i.e., pollen tubes from the self-infertile species (E. americanum) grew apparently unimpeded in styles of the self-fertile species (E. albidum), whereas the reverse cross resulted in an incompatibility reaction. Because of this asymmetrical relation and faster growth by heterospecific pollen tubes in E. albidum stigmas than by conspecific tubes, pollination with abundant heterospecific pollen reduced fruit and seed production by E. albidum, but not by E. americanum, as long as the stigma also received some conspecific pollen. Unilateral incompatibility could benefit self-infertile species in reproductive interactions with closely related self-fertile species; however, this benefit remains to be demonstrated for naturally pollinated plants. Key words: Erythronium albidum, Erythronium americanum, interspecific pollen transfer, pollination, unilateral incompatibility.

Connectivity and Centrality Characteristics of the Epileptogenic Focus Using Directed Network Analysis

2019 ◽  
Vol 27 (1) ◽  
pp. 22-30 ◽  
Author(s):  
Joshua A. Adkinson ◽  
Bharat Karumuri ◽  
Timothy N. Hutson ◽  
Rui Liu ◽  
Omar Alamoudi ◽  
...  
Keyword(s):  
Network Analysis ◽  
Directed Network ◽  
Epileptogenic Focus

A directed network analysis of the cardiome identifies molecular pathways contributing to the development of HFpEF

2020 ◽  
Vol 144 ◽  
pp. 66-75
Author(s):  
Georg Summer ◽  
Annika R. Kuhn ◽  
Chantal Munts ◽  
Daniela Miranda-Silva ◽  
Adelino F. Leite-Moreira ◽  
...  
Keyword(s):  
Network Analysis ◽  
Directed Network ◽  
Molecular Pathways

scholarly journals The impact of latent confounders in directed network analysis in neuroscience

2013 ◽  
Vol 371 (1997) ◽  
pp. 20110612 ◽  
Author(s):  
Rebecca Ramb ◽  
Michael Eichler ◽  
Alex Ing ◽  
Marco Thiel ◽  
Cornelius Weiller ◽  
...  
Keyword(s):  
Network Analysis ◽  
Nonlinear System ◽  
Granger Causality ◽  
Directed Network ◽  
Vector Autoregressive Models ◽  
Vector Autoregressive ◽  
Physiological Pathways ◽  
The Impact ◽  
The Brain ◽  
Past Activity

In the analysis of neuroscience data, the identification of task-related causal relationships between various areas of the brain gives insights about the network of physiological pathways that are active during the task. One increasingly used approach to identify causal connectivity uses the concept of Granger causality that exploits predictability of activity in one region by past activity in other regions of the brain. Owing to the complexity of the data, selecting components for the analysis of causality as a preprocessing step has to be performed. This includes predetermined—and often arbitrary—exclusion of information. Therefore, the system is confounded by latent sources. In this paper, the effect of latent confounders is demonstrated, and paths of influence among three components are studied. While methods for analysing Granger causality are commonly based on linear vector autoregressive models, the effects of latent confounders are expected to be present also in nonlinear systems. Therefore, all analyses are also performed for a simulated nonlinear system and discussed with regard to applications in neuroscience.

Abstract P214: Social Network Analysis of a Community Aphasia Group Pre- And Post-Covid: Implications for Future Planning

Stroke ◽  
2021 ◽  
Vol 52 (Suppl_1) ◽  
Author(s):  
Tom Sather ◽  
Anna Livera
Keyword(s):  
Social Network ◽  
Social Network Analysis ◽  
Network Analysis ◽  
Time Frame ◽  
Directed Network ◽  
Negative Consequences ◽  
Network Graph ◽  
Future Planning ◽  
Network Characteristics ◽  
The Impact

Introduction: Among the many negative consequences of aphasia is an altered social network. Social network analysis supports an objective, quantitative evaluation of social networks among individuals with aphasia along with potential impacts of social programming and interventions on an individual’s social network. Social network analysis may also support better understanding of the impact of Covid on individuals with aphasia. Aims: This pilot evaluation utilized social network analysis via R to evaluate the social network characteristics of a community-based aphasia network across a 12-month pre-Covid period. Social network aphasia group data for a standard duration of time pre- and post-Covid were also compared to identify potential social implications of Covid in a population already at higher risk for reduced social interactions. This presentation will also provide fundamental concepts relevant to social network analysis for those interested in pursuing such analysis in further depth. Methods: Twelve months of pre-Covid aphasia group program attendance data were examined using the visNetwork R package. An additional six months of Covid-era time frame data were also analyzed.The primary relationship function of “ a attended b” (where a = individual participant and b = event/setting) was used in the analysis. Multiple social network characteristics were analyzed and displayed including node, edgeness, directionality, weight, and centrality indices across individuals with aphasia, care partners and community members and settings. Results and Conclusions: Network analysis reveals a directed network graph with primarily unidirectional relationships. There is an emergence of several aphasia group participant behavior types, both pre- and post-Covid, relevant for future planning including: communities of individuals who have similar behaviors in terms of type of event attendance; key individuals who are "heavy users" of various services in terms of frequency and breadth of event attendance; and peripheral users who use only one service. Post-Covid social network implications are discussed including supports to mitigate negative impacts of Covid on social network composition.

scholarly journals Pollen on stigmas as proxies of pollinator competition and facilitation: complexities, caveats and future directions

2020 ◽  
Vol 125 (7) ◽  
pp. 1003-1012 ◽  
Author(s):  
Tia-Lynn Ashman ◽  
Conchita Alonso ◽  
Victor Parra-Tabla ◽  
Gerardo Arceo-Gómez
Keyword(s):  
Pollen Transfer ◽  
Future Directions ◽  
Indirect Measure ◽  
Heterospecific Pollen ◽  
Complex Processes ◽  
Flower Visitation ◽  
Fitness Consequences ◽  
Functional Aspects ◽  
Broad Variety ◽  
Plant Pollinator

Abstract Background Pollen transfer via animals is necessary for reproduction by ~80 % of flowering plants, and most of these plants live in multispecies communities where they can share pollinators. While diffuse plant–pollinator interactions are increasingly recognized as the rule rather than the exception, their fitness consequences cannot be deduced from flower visitation alone, so other proxies, functionally closer to seed production and amenable for use in a broad variety of diverse communities, are necessary. Scope We conceptually summarize how the study of pollen on stigmas of spent flowers can reflect key drivers and functional aspects of the plant–pollinator interaction (e.g. competition, facilitation or commensalism). We critically evaluate how variable visitation rates and other factors (pollinator pool and floral avoidance) can give rise to different relationships between heterospecific pollen and (1) conspecific pollen on the stigma and (2) conspecific tubes/grain in the style, revealing the complexity of potential interpretations. We advise on best practices for using these proxies, noting the assumptions and caveats involved in their use, and explicate what additional data are required to verify interpretation of given patterns. Conclusions We conclude that characterizing pollen on stigmas of spent flowers provides an attainable indirect measure of pollination interactions, but given the complex processes of pollen transfer that generate patterns of conspecific–heterospecific pollen on stigmas these cannot alone determine whether competition or facilitation are the underlying drivers. Thus, functional tests are also needed to validate these hypotheses.

scholarly journals Pollen transfer networks reveal alien species as main heterospecific pollen donors with fitness consequences for natives

2020 ◽  
Author(s):  
Víctor Parra‐Tabla ◽  
Conchita Alonso ◽  
Tia‐Lynn Ashman ◽  
Robert A. Raguso ◽  
Cristopher Albor ◽  
...  
Keyword(s):  
Alien Species ◽  
Pollen Transfer ◽  
Heterospecific Pollen ◽  
Fitness Consequences
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