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).