Dissecting Factors Responsible For Individual Variation in Plant Fecundity

Abstract

Abstract. This paper analyses, on an individual plant basis, the various components determining seed production in the evergreen shrub Lavandula latifolia (Labiatae), in order to estimate their relative contributions to individual differences in fecundity. The relationships between fecundity and age, size, and growth rate are also examined. Experimental pollination and watering were done in an attempt to alter natural patterns of partial fecundity components. Fecundity of individual plants is partitioned into its absolute (number of inflorescences, number of flowers per inflorescence) and relative (fruits/flower and seeds/ fruit) partial components, and the following questions are addressed: (1) Are there individual differences in relative components of fecundity? (2) What are the proportional contributions of relative and absolute components of fecundity to individual variation in seed production? (3) Are relative measures of reproductive success reliable predictors of individual differences in fecundity? (4) When induced experimentally, do changes in partial fecundity components translate into modifications of the population's ranking of absolute fecundities?Fecundity depended more on plant size than age, was unrelated to growth rate, and was limited by water, but not pollen, availability. Individual plants differed in all components of fecundity examined, and differences were consistent among years. The proportional contributions of the various components to individual differences in fecundity were very unequal. Almost all variation among plants in seed production (-90% of variance) was explained by the variances and covariances of number of inflorescences and number of flowers per inflorescence. Variation among plants in the two relative components (fruit and seed set), even though statistically significant, had a negligible influence on individual differences in fecundity. These patterns remained invariant despite significant modification of flower production and fruit set induced by artificially watering a part of the study population. Fruit and seed set alone are unreliable indicators of individual differences in the maternal component of fitness in L. latifolia, and a review of relevant literature indicates that this probably applies to other polycarpic plants as well. Plant reproductive biology studies may make erroneous inferences if they consider exclusively data on relative fruit and seed set, and neglect the absolute components of individual differences in fecundity. It is proposed that, to circumvent these potential problems, demographic aspects and absolute estimates of seed output on a per individual basis should be examined in addition to the customarily employed fruit and seed set measures.Key words: fecundity components; flower production; fvuit set; individual variation; Lavandula latifolia; Mediterranean scrublands; plant demography; reproductive biology; seed production; size hierarchy; water limitation. contributions in Bentley and Elias 1983, Jones andRecent studies on plant reproductive ...

Reproductive ecology of Pinus nigra in an invasive population: individual- and population-level variation in seed production and timing of seed release

“…Our data supports this for New Zealand populations, with two very high coning years recorded in 1996 (at Lake Ruataniwha) and 2009 (at Mt Barker) and a very low coning year in 1997 (at Lake Ruataniwha). In support of previous work (Cook and Lyons 1983;Scheiner 1987;Bullock 1989;Herrera 1991;Herrera and Jovani 2010), at both Mt Barker and Lake Ruataniwha, most trees produced relatively few cones and a few trees produced many (distribution was right skewed). Despite high variability in the average number of cones produced between years, the best supported within-year fecundity distribution was consistently a negative binomial or gamma + exp.…”

“…The distribution of fecundities within many plant populations is often right skewed, with a few highly fecund individuals producing most of the seed (Cook and Lyons 1983;Scheiner 1987;Bullock 1989;Herrera 1991;Herrera and Jovani 2010). Further, in perennial plants fecundity hierarchies can persist through time, i.e.…”

Invasive Alien Plants Elicit Reduced Production of Flowers and Fruits in Various Native Forest Species on the Tropical Island of Mauritius (Mascarenes, Indian Ocean)

“…Flower bud and flower production in plants is generally limited by resources available [30], and direct competition for resources is one of the mechanisms by which IAP may affect native plant species [31]. In some cases, IAP can even utilize available resources more effectively than natives [32][33].…”

Differentiating between the Adverse Effects of Nutrient-Limitation and Direct-Cold-Limitation on Tree Growth at High Altitudes

“…First, soil available nutrients are limited by the slow decomposition rate (Herrera, 1991;Radwan, 1992;Schulze et al, 1994;Hobbie and Chapin, 1998;Hobbie et al, 2002;Crosti et al, 2006). Nutrient absorption activity also depends on temperature (Karlsson and Nordell, 1996;Weih and Karlsson, 2001).…”

“…This would mean that a plant growing at high altitude would exhibit a higher NSC concentration than a plant growing at low altitude, even though the leaves of the former contained a higher concentration of nitrogen. In addition, some fertilization studies have recorded an increase in nitrogen content in plants, particularly at high altitudes (Herrera, 1991;Sveinbjö rnsson et al, 1992;van Miegroet et al, 1993). Plants may experience nutrient-limitation at high altitudes, even though their leaves have higher nitrogen concentrations than plants from lower altitudes.…”