Submission Type
Poster
Abstract
For perennial plants, the optimal timing of flowering is a tradeoff between survivorship and fecundity, a classic example of bet-hedging. For many monocarpic perennials, there is an advantage in delaying flowering until the plant reaches a larger size and is thus capable of a higher fecundity. However, in delaying flowering, there is a risk that the plant will die before reproducing at all. Here, we investigate this fitness trade-off in the imperiled dune thistle, Cirsium pitcheri. Using a long-term, spatially-explicit demographic data set with yearly censuses, we found that C. pitcheri individuals on the foredune flowered at a younger age compared to other dune habitats. We tested two alternative hypotheses: (1) younger-flowering plants had ample nutrients, causing them to be able to reach a flowering threshold size more quickly, or (2) these plants experienced a deficit of resources and thus a higher likelihood of dying, resulting in early reproduction at a smaller size. Our results support the former hypothesis: plants in all areas of the dune did not differ in size the year prior to flowering. Therefore we conclude that the foredune microenvironment where plants flowered at younger ages facilitates rapid growth and reproduction for this species, and represents optimal habitat. This result provides insight into the demographic patterns of C. pitcheri that may inform the conservation and recovery of this threatened species.
Spatial variation in flowering age in Cirsium pitcheri: does this imperiled dune thistle hedge its bets?
For perennial plants, the optimal timing of flowering is a tradeoff between survivorship and fecundity, a classic example of bet-hedging. For many monocarpic perennials, there is an advantage in delaying flowering until the plant reaches a larger size and is thus capable of a higher fecundity. However, in delaying flowering, there is a risk that the plant will die before reproducing at all. Here, we investigate this fitness trade-off in the imperiled dune thistle, Cirsium pitcheri. Using a long-term, spatially-explicit demographic data set with yearly censuses, we found that C. pitcheri individuals on the foredune flowered at a younger age compared to other dune habitats. We tested two alternative hypotheses: (1) younger-flowering plants had ample nutrients, causing them to be able to reach a flowering threshold size more quickly, or (2) these plants experienced a deficit of resources and thus a higher likelihood of dying, resulting in early reproduction at a smaller size. Our results support the former hypothesis: plants in all areas of the dune did not differ in size the year prior to flowering. Therefore we conclude that the foredune microenvironment where plants flowered at younger ages facilitates rapid growth and reproduction for this species, and represents optimal habitat. This result provides insight into the demographic patterns of C. pitcheri that may inform the conservation and recovery of this threatened species.
Comments
E. Binney Girdler, Department of Biology, Kalamazoo College