Pollinator limitation, cost of reproduction, and fitness in plants: a transition-matrix demographic approach

A model of population dynamics based on a transition-probability matrix was used to evaluate how pollinator limitation and demographic cost of reproduction interact to create a fitness surface for plants. The state variable was the size-fecundity class of an individual; in a given season, individuals were classified as having relatively high or low fecundity. Three parameters were investigated: cost of reproduction c, was the probability that high-fecundity individuals regress one size class; population pollination level, p, was the probability that reproductive individuals have a high-fecundity year; fecundity difference, d, was the relative difference in fecundity between low- and high-fecundity individuals. The main results of simulations were that 1) for any combination of c and d, there is a particular value of p that maximizes fitness, and this value can be very low or very high; 2) keeping the other parameters constant, higher c's reduce fitness and higher d's increase fitness; 3) the magnitude of the effects of c and d on fitness depends only on p and is lowest when p is lowest and highest when p is highest; and 4) increases in c and d move the optimal pollination level to the left and right, respectively. Hand-pollinations should be designed to explicitly quantify the relationship between d and c. -from Authors