Bridget Bickner
OEB Graduate Student
Hopkins Lab

Title: The evolution and maintenance of reproductive investment strategies in Phlox: evaluating patterns of phenotypic and environmental correlation

Abstract: Seed size and number are fundamental measures of maternal reproductive fitness in plants. However, the negative correlation between seed size and number within and between species suggests a fundamental tradeoff exists between investment in offspring quality (i.e. seed size) and offspring quantity (ie. seed number). While spatial variation in the abiotic environment is expected to play a central role in determining optimal seed packaging strategies, little empirical work has directly investigated seed packaging variation or what abiotic variables may be responsible for driving reproductive strategy divergence. Further, fundamental genetic correlations with other floral traits (ex. flower size) may limit the independent evolution of seed number variation due to pleiotropy. In this talk, I will highlight preliminary results from two ongoing projects that explore the potential roles of genetic correlation and environmental adaptation as drivers of seed packaging variation in the Phlox genus. In the first project, I use a quantitative trait loci (QTL) mapping approach to understand the genetic architecture of the flower size/number and seed size/number tradeoffs in a sister species pair, P. drummondii and P. roemeriana, with highly divergent reproductive strategies. And in the second project, I explore the geographic distribution of a unique, naturally-occurring polymorphism in P. longifolia, in which some individuals always produce one seed per chamber and others produce multiple seeds per chamber that are correspondingly smaller in size. Together, these projects provide some of the first empirical evidence to test long-standing hypotheses on the genetic and evolutionary mechanisms governing the seed size/number tradeoff.

Join via Zoom livestream: https://harvard.zoom.us/meeting/register/tJYscemsqTMqHtxHMbWzmkYAeoSU7ZWmF391 (registration required)