Inbreeding depression under a competitive regime in Mimulus guttatus: consequences for potential male and female function

Abstract

The effects of one generation of selfing and outcrossing on six life history characters were examined in the greenhouse for two populations of the mixed-mating species Mimulus guttatus. Inbreeding depression was not detected in the mass of seed produced by maternal plants, but selfing significantly reduced germination success by 13-20 per cent relative to outcross seeds. Seedlings produced by self-pollination were 26-3 1 per cent smaller than outcross progeny. Late life history stages were examined under varied competitive regimes in which each plant was grown with a neighbour of either an inbred or outbred individual. Progeny resulting from seif-pollinations showed a 14-30 per cent reduction in ovule number per locule, and their pollen production per flower was reduced by 28-33 per cent. Adult above-ground biomass showed the greatest inbreeding depression, ranging from 24-50 per cent depending on the competitive conditions. Thus progeny resulting from selfing are smaller as adults and contribute significantly fewer potential gametes into the gene pooi as pollen grains and ovules. The multiplicative effects of these characters is calculated. For all traits except ovule number, outcross progeny from parents of the same population did not differ significantly from outcross progeny produced by parents that came from populations separated by 10 km, suggesting relatively little differentiation between populations. The relative performance of self and outcross progeny in later life history stages was independent of the relative performance observed in earlier stages.Keywords: competition, inbreeding depression, mating system, Mimulus guttatus, ovule production, pollen production.Although inbreeding depression has been estimated in many species (e.g. Schemske, 1983;Schoen, 1983; reviewed by Charlesworth & Charlesworth, 1987;Ritland & Ganders, 1987;Svensson, 1988;Griffing, 1989;Levin, 1989;Dudash, 1990; Holtsford & Elistrand, 1990;Fenster, 1991b;Johnston, .1992;Agren & Schemske, 1993) more information is needed on how the genetic makeup of immediate neighbours can affect the relative performance of self and outcross progeny and how the expression of inbreeding depression varies across life history traits.

INBREEDING DEPRESSION IN GYNODIOECIOUSLOBELIA SIPHILITICA: AMONG-FAMILY DIFFERENCES OVERRIDE BETWEEN-MORPH DIFFERENCES

“…The prediction of a negative correlation between the level of inbreeding depression and the degree of inbreeding has been tested by comparing plant species with different mating systems or comparing populations within a species with different degrees of selfing. The majority of these studies provide support for the prediction (Holtsford and Ellstrand 1990;Dole and Ritland 1993;Husband andSchemske 1995, 1996;Carr and Dudash 1996;Johnston and Schoen 1996;Affre and Thompson 1997).Recent theoretical studies have emphasized that familylevel variation in inbreeding depression is not equal to the inbreeding depression in the population as a whole (Holsinger 1988(Holsinger , 1991 Uyenoyama and Waller 1991a,b,c;Uyenoyama et al 1993). According to these models, variation in inbreeding depression at the family level is produced by associations that develop between loci determining the mating system and loci determining the probability of survival (inbreeding depression).…”

“…The prediction of a negative correlation between the level of inbreeding depression and the degree of inbreeding has been tested by comparing plant species with different mating systems or comparing populations within a species with different degrees of selfing. The majority of these studies provide support for the prediction (Holtsford and Ellstrand 1990;Dole and Ritland 1993;Husband andSchemske 1995, 1996;Carr and Dudash 1996;Johnston and Schoen 1996;Affre and Thompson 1997).…”

Inbreeding Alters Resistance to Insect Herbivory and Host Plant Quality in Mimulus Guttatus (Scrophulariaceae)

“…Estimates of inbreeding depression taken from plants with spittlebug nymphs were 1.5 to 3.0 times greater than estimates from control plants. Interestingly, estimates of inbreeding depression for natural populations of M. guttatus based on changes in inbreeding coefficients (Dole and Ritland 1993) are much higher (␦ ϭ 81%) than estimates from greenhouse studies (e.g., Willis 1993a,b;Carr and Dudash 1995).…”

Male–male competition magnifies inbreeding depression in wild house mice

“…Second, they cannot reveal the effects of conditionally deleterious alleles (6,28), whose effects will be revealed only in the presence of natural stresses, such as harsh climates, food shortages, competition, predation, and parasitism. Experimental studies of invertebrates and plants reveal that inbreeding depression may be greater when measured under stressful environments (29)(30)(31); therefore, we need to determine the effects of inbreeding for vertebrates under natural conditions. Surprisingly, there has been no experimental measurement of the effects of inbreeding on both adult survival and reproduction for any vertebrate living in the wild or even under stressful conditions designed to mimic nature.…”