The large and heavy seeds of the limber pine (Pinus flexilis) lack the wings on seeds characteristic of most pines. The seeds are the primary food source for Clark’s nutcracker which harvests seeds after the cones open. It then caches thousands of seeds each summer and fall in locations far from the original tree to eat later in the year. During years when many cones and seeds are produced, the nutcracker caches 3-5x the number of seeds actually eaten. When they are present, tree squirrels remove the cone before it opens before the seeds are fully developed, and will eat the seeds immediately or cache the cone for later consumption. Question: Scientists were interested to see whether the two seed harvesters would affect seed and cone traits. They compared cone and seed traits in areas that had nutcrackers but tree squirrels were either present or absent. Where squirrels were present, cone mass was larger but there were fewer seeds per cone, and smaller kernels per seed. What do the results suggest about differences between sites in the fitness tradeoff between investment in seeds vs seed defense based on the suite of seed harvesters present?
The large and heavy seeds of the limber pine (Pinus flexilis) lack the wings on seeds characteristic of most pines. The seeds are the primary food source for Clark’s nutcracker which harvests seeds after the cones open. It then caches thousands of seeds each summer and fall in locations far from the original tree to eat later in the year. During years when many cones and seeds are produced, the nutcracker caches 3-5x the number of seeds actually eaten. When they are present, tree squirrels remove the cone before it opens before the seeds are fully developed, and will eat the seeds immediately or cache the cone for later consumption.
Question:
Scientists were interested to see whether the two seed harvesters would affect seed and cone traits. They compared cone and seed traits in areas that had nutcrackers but tree squirrels were either present or absent. Where squirrels were present, cone mass was larger but there were fewer seeds per cone, and smaller kernels per seed.
What do the results suggest about differences between sites in the fitness tradeoff between investment in seeds vs seed defense based on the suite of seed harvesters present?
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