Hermaphroditism is prevalent in plants but may allow interference between male function (pollen removal and dispersal) and female function (pollen receipt and seed production) within a flower. Temporal or spatial segregation of gender within a hermaphroditic flower may evolve to reduce this interference and enhance male and female reproductive success. We tested this hypothesis using Chamerion angustifolium (Onagraceae), in which pollen removal (male) and pollen deposition (female) were measured directly on hermaphroditic and experimentally produced unisexual flowers.
This book of about 600 pages is written to provide practitioners of pollination biology with a broadly based source of methodologies as well as the basic conceptual background to aid in understanding. Thus, the book reflects the expertise of the assembled a team of internationally acclaimed scientists. Pollination biology enjoys over 200 years of scientific tradition. In recent years, the interdisciplinarity of pollination biology has become a model for integrating physics, chemistry, and biology into natural history, evolutionary and applied ecology.
Protandry, a form of temporal separation of gender within hermaphroditic flowers, may reduce the magnitude of pollen lost to selfing (pollen discounting) and also serve to enhance pollen export and outcross siring success. Because pollen discounting is strongest when selfing occurs between flowers on the same plant, the advantage of protandry may be greatest in plants with large floral displays. We tested this hypothesis with enclosed, artificial populations of Chamerion angustifolium (Onagraceae) by experimentally manipulating protandry (producing uniformly adichogamous or mixed protandrous and adichogamous populations) and inflorescence size (two-, six-, or 10-flowered inflorescences) and measuring pollinator visitation, seed set, female outcrossing rate, and outcross siring success.
In self-compatible plants, small populations may experience reduced outcrossing owing to decreased pollinator visitation and mate availability. We examined the relation between outcrossing and population size in eastern Ontario populations of Aquilegia canadensis. Experimental pollinations showed that the species is highly self-compatible, and can achieve full seed-set in the absence of pollinators via automatic self-pollination. We estimated levels of outcrossing (t) and parental inbreeding coefficients (F) from allozyme variation in naturally pollinated seed families for 10 populations ranging in size from 32 to 750 reproductive individuals.
Historically, dichogamy (the temporal separation of gender in flowering plants) has been interpreted as a mechanism for avoiding inbreeding. However, a comparative survey found that many dichogamous species are self-incompatible (SI), suggesting dichogamy evolved for other reasons, particularly reducing interference between male and female function. Here we re-examined the association between dichogamy and SI in a phylogenetic framework, and tested the hypothesis that dichogamy evolved to reduce interference between male and female function.
Clonal growth in plants can increase pollen and ovule production per genet. However, paternal and maternal reproductive success may not increase because within-clone pollination (geitonogamy) can reduce pollen export to adjacent clones (pollen discounting) and pollen import to the central ramets (pollen limitation). We investigated the relationship between clone size and mating success using clones of Malus x domestica at four orchards (blocks of 1–5 rows of trees). For each block, we measured maternal function as fruit and seed set in all rows and paternal function as siring rate in the first row of the adjacent block.
Protandry (when male function precedes female) can enhance fitness by reducing selfing and increasing pollen export and outcrossed siring success. However, responses to selection on protandry may be constrained by genetic variation and correlations among floral traits. We examined these potential constraints in protandrous Chamerion angustifolium (Onagraceae) by estimating genetic variation in male-phase duration and associated floral traits using a paternal half-sib design and selection experiment. Narrow-sense heritability of male-phase duration was estimated as 0.
Mating by outcrossing plants depends on the frequency and quality of interaction between pollen vectors and individual flowers. However, the historical focus of pollination biology on individual flowers (floricentrism) cannot produce a complete understanding of the role of pollination in plant mating, because mating is an aggregate process, which depends on the reproductive outcomes of all of a plant’s flowers. Simultaneous display of multiple flowers in an inflorescence increases a plant’s attractiveness to pollinators, which should generally enhance mating opportunities.
Pollen and ovules experience diverse fates during pollination, pollen-tube growth, fertilization, and seed development, which govern the male and female potential of flowering plants. This chapter identifies these fates and many of their interactions, and considers their theoretical implications for the evolution of pollen export and the production of selfed and outcrossed seeds. This analysis clarifies the importance of pollen quantity and quality for seed production, including the opportunity for poor pollen quality to cause misidentification of pollen limitation.
Jay Odenbaugh provides an interesting article entitled: Idealized, Inaccurate but Successful: A Pragmatic Approach to Evaluating Models. He describes why models are useful to ecologists, even when they are clearly wrong.
Robert F. Kennedy, Jr. gave a speech at the Sierra Club’s National Convention and Expo on September 10, 2005 in San Francisco. The transcript is available and I recommend it highly. He describes the relations among business, politics, and the environment; making a strong case for the importance of free-markets and democracy to environmental protection.
In my investigations of ovule fates, I’ve needed to estimate regression parameters from discontinuous functions. A general term for such estimates is breakpoint regression. OFStatisticalEstimates.pdf demonstrates an approach using R for such estimates in the context of seed-ovule ratios. The code includes a mechanism for generating seed-ovule data that illustrate the types of functions that need to be considered.
Sean Rice’s Evolutionary Theory is an excellent journey through the mathematical foundations of evolutionary biology. The book covers a wide array of theory, including single locus models, drift, Price’s Theorem, game theory, and multilevel selection. Despite the often intense content, the book is written with a great, economical style that is easy to read. More importantly, the consistent presentation of such a broad collection of theory highlights the unifying principles of evolution.
I recently lost control of my email. The combination of mailing lists, alerts, table of content notifications, and actual email from friends and colleagues was reaching a few hundred emails a day. The insanity had to stop! Here’s how I regained control.
Goals Before describing my solution, let’s consider what a good email system should provide?
Notifications of relevant new messages. A process for keeping track of important and unanswered messages.
The current setup at home is that I’ve added all of our music (several thousand songs) to our Mac Mini and then send it through AirTunes to the home stereo. The complication is that the stereo and computer are at opposite ends of the house. Ideally, I can use my iBook to control the Mac Mini without needing to walk down the hall, but how?
One solution is to use VNC, which allows complete control of the Mac Mini.
Recently, I needed to combine several pdf files into one. The The Tao of Mac has a discussion of how to do this and I’m posting the code I used here so that I can find it again later.
gs -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=out.pdf -c save pop -f *.pdf Running this from a directory containing only the pdfs to be combined produces out.pdf.
I have used this diagram of evolutionary ecology in a wide variety of contexts. In the hope that it may be useful to others, I have made it available to anyone interested. The OmniGraffle source file is available as EvolEcol.graffle.
In collaboration with Jana and Steve Vamosi, I have started a new project called Plantae. The goal of this project is to create a community website for the collection of evolutionary and ecological data for plant species. An early prototype of the project is available and we welcome feedback on all aspects of the project.
Although the current implementation is rather rough. I hope to make some rapid progress on the design and function of the site in the new year.
Now that intelligent design is back in the Canadian news, we should consider (again!) the consequences of teaching intelligent design in the classroom.
Intelligent design makes two postulates:
Complexity cannot be explained by science.
Given 1, complexity comes from an intelligent designer.
Now, consider a science exam in any subject and the danger of intelligent design being taught in school becomes apparent.
Physics question: Why does the earth orbit the sun?
The Onion on Intelligent Falling theory: “David Pescovitz: The Onion brilliantly parodies Intelligent Design believers:
KANSAS CITY, KS—As the debate over the teaching of evolution in public schools continues, a new controversy over the science curriculum arose Monday in this embattled Midwestern state. Scientists from the Evangelical Center For Faith-Based Reasoning are now asserting that the long-held ‘theory of gravity’ is flawed, and they have responded to it with a new theory of Intelligent Falling.
Mating by outcrossing plants depends on the frequency and quality of interaction between pollen vectors and individual flowers. However, the historical focus of pollination biology on individual flowers (floricentrism) cannot produce a complete understanding of the role of pollination in plant mating, because mating is an aggregate process, which depends on the reproductive outcomes of all of a plant’s flowers. Simultaneous display of multiple flowers in an inflorescence increases a plant’s attractiveness to pollinators, which should generally enhance mating opportunities.
Clonality is very common in flowering plants, but its consequences for sexual reproduction have rarely been explored. While clonal growth can increase the number of flowers a plant produces it may also limit reproductive success through pollen discounting (reduction in pollen exported to adjacent clones) and pollen limitation (failure of outside pollen to reach the centre of a clone). Using clones of domestic apple (Malus x domestica) that ranged from 1 to 5 orchard rows wide, we found that the patterns of siring success were consistent with the presence of pollen discounting, but we failed to detect evidence for pollen limitation.
Dichogamy, the temporal separation of gender within a flower, is widespread throughout the angiosperms, occurring in over 250 families. There are two forms of dichogamy: protandry, in which male function precedes female function, and protogyny, the converse. Dichogamy has traditionally been interpreted as a mechanism to avoid inbreeding. However, recent evidence indicates that this inbreeding-avoidance hypothesis cannot completely explain the evolution of dichogamy. An alternate hypothesis is that dichogamy acts to reduce interference between gender functions.
The outcrossing rate is a fundamental attribute of plant populations that determines population genetic structure, individual plant fitness, and ultimately speciation rates. The outcrossing rate can be influenced by population size through reductions in both mate availability and pollinator service. We investigated the effect of population size on the outcrossing rate in 10 populations of Aquilegia canadensis in Southern Ontario, Canada.
Across a range of sizes from 32 to 750 reproductive individuals, we found that small populations (n 90, blue line).
As I use R for data analysis and simulations, I become more comfortable and proficient with the R/S syntax and style of programming. One important insight is the use of vector assignments in simulations. I have often read that using such assignments is the preferred method, but until recently I had not realised the importance of this statement. To illustrate the use of vector assignments and their advantages, consider two models of the style illustrated below:
A particular challenge with maintaining a weblog is the uploading and resizing of images. The process involves choosing the correct images, creating large & thumbnail sized versions, uploading these images to the webserver, and posting the appropriate code into the weblog post. In the spirit of my last few posts, image2web is an applescript I use to automate this process:
--user-specific variables property theAlbum : "Marked" --contains the images to be uploaded property theBasePath : "
The CBC has begun an experiment with podcasting. I’m impressed with the progressive approach to technology that the CBC has adopted and hope they expand the experiment to more of their programs.
This has the added effect of making my Quirks & Quarks download script obsolete.
Quirks & Quarks is the CBC’s excellent science program. I usually download the mp3 archives of the show on the weekends and listen while I walk Ceiligh.
Of course, loading up the Quirks & Quarks webpage, finding the archives, downloading the mp3s, and adding them to iTunes takes at least a few minutes. Computers are much better and handling such tedium.
Inspired by the success (for me) of the apod script, quirks.
The “Astronomy Picture of the Day” is a source of fantastic images. To take advantage of this resource, I went looking for a way to automatically set the current image as my Desktop background. A quick Google search turned up a perl script at www.haroldbakker.com. Although this was a great start, I wasn’t completely happy with the implementation of this script and decided to write my own.
The apod.pl script is written in perl and both sets the Desktop background and copies a description of the image to the Desktop as an html file.
These data measured the genetic architecture of male-phase duration in Chamerion angustifolium. There are three files in the archive used to estimate genetic variances & covariances with VCE. Format:
protandryHeritabilityData.dat: Contains the measured data for male- & female-phase duration, flower size, & display size protandryHeritabilityPedigree.ped: Contains the pedigree information for the selection experiment protandryHeritabilityVCE: Is the VCE file that configures the analysis Citation:
Routley, M.B. & B.C. Husband. 2004. Responses to selection on male-phase duration in Chamerion angustifolium.