FLORAL CORRELATES AND FITNESS CONSEQUENCES OF MATING-SYSTEM VARIATION INTURNERA ULMIFOLIA

Abstract

Abstract.-Outcrossing rates varied from 0% to 69% among Jamaican populations of Turnera ulmifolia. A correlation between increasing herkogamy and outcrossing rate occurred among populations. Predictions from sex-allocation theory were tested by estimating allocation to reproductive functions. Significant differences in allocation patterns occurred among populations, but they were not correlated with outcrossing rates. The fitness consequences of inbreeding were assessed in high-and low-density greenhouse experiments for nine populations with variable outcrossing rates. No evidence for inbreeding depression occurred in early portions of the life history, but multiplicative fitness functions provide evidence for inbreeding depression. We tested the prediction that selfing populations have lower levels of inbreeding depression than outcrossing populations but found no significant correlation.Key words.-Herkogamy, inbreeding depression, outcrossing, resource allocation, selfing.Received July 16, 1993. Accepted May 23, 1994 The study of plant mating-system evolution has provided fertile ground for the interaction of theoretical and empirical workers. Extensive empirical work began with Darwin (1876) and has continued at an ever-increasing pace that has been at least paralleled by theoretical studies. For example, a number of evolutionary models have focused particular attention on the evolution of self-fertilization (e.g., Fisher 1941;Crosby 1949;Charlesworth and Charlesworth 1979;Lloyd 1979;Holsinger et al. 1984;Lande and Schemske 1985; Uyenoyarna and Waller 1991a,b). The models span a wide range, from considerations of the population genetics of inbreeding depression (Lande and Schemske 1985; Charlesworth 1987a, 1990; Holsinger 1988;Charlesworth et al. 1991; Uyenoyama and Waller 1991a,b) to those including the ecology of reproduction and dispersal (Lloyd 1979(Lloyd , 1980(Lloyd , 1988Holsinger et al. 1984;Holsinger 1986; Schoen and Brown 1991;Wiener and Feldman 1991). Other models have considered the "secondary" effects of mating-system evolution on the allocation of resources to male, female, and attractive structures Charlesworth 1981, 1987b;Charnov 1982;Lloyd 1984; Morgan 1992a,b).Empirical studies attempting to test the theories have examined the influence of mating patterns on plant population genetics (reviewed in Brown 1979;Hamrick et al. 1979;Loveless and Hamrick 1984). Studies of inbreeding depression and often its relationship to mating patterns and/or environmental heterogeneity have been undertaken for natural plant populations, and inbreeding depression has generally been detected at one or more life-history stages (e.g., Schemske 1983; Schoen 1983;Waller 1984;Kalisz 1989;Karron 1989;Levin 1989Levin , 1991Dudash 1990;Holtsford and Ellstrand 1990;Ritland 1990a;Schmitt and Ehrhardt 1990;Barrett and Charlesworth 1991;Ashman 1992;Johnston 1992;Agren and Schemske 1993;Dole and Ritland 1993;Wolfe 1993). Studies showing variation in selfing rates within and between species as well as the influence of flor...

Pollination in Turnera subulata (Turneraceae): Unilateral reproductive dependence of the narrowly oligolectic bee Protomeliturga turnerae (Hymenoptera, Andrenidae)

“…Long-and short-styled morphs of T. subulata differ in at least 8 characteristics which are similar to the ones detected in other species of the genus (Barrett, 1978;Shore, 1985, 1987;Belaoussoff and Shore, 1995;Shore and Barrett, 1984). Short-styled flowers produce less ovules (38.5) and pollen grains (13,600) than long-styled flowers (53, 14,500).…”

Inbreeding depression and the cost of inbreeding on seed germination

“…Levin and Bulinska-Radomska, 1988;Latta and Ritland, 1994;Belaoussoff and Shore, 1995;Ferdy et al, 2001;Lofflin and Kephart, 2005) but not of others (e.g. Willis, 1993a;Eckert and Barrett, 1994;Johnston and Schoen, 1996;Goodwillie and Knight, 2006).…”

Impact of Insect Pollinator Group and Floral Display Size on Outcrossing Rate

“…Outcrossing rate increases with greater level of herkogamy or stronger protandry as it becomes more difficult for self pollen to reach the stigmas (Schoen 1982;Holtsford and Ellstrand 1992;Belaoussoff and Shore 1995;Karron et al 1997;Brunet and Eckert 1998). Outcrossing rate tends to decrease in plants with larger floral displays as pollinators visit more flowers in succession on these plants, increasing the level of geitonogamous selfing (Hodges 1995;Harder and Barrett 1996;Snow et al 1996;Karron et al 2004;Mitchell et al 2004).…”