CROSSING‐DISTANCE EFFECTS IN DELPHINIUM NELSONII : OUTBREEDING AND INBREEDING DEPRESSION IN PROGENY FITNESS

Abstract

Abstract. -Depending on its genetic causes, outbreeding depression in quantitative characters may occur first in the free-living F, generation produced by a wide cross. In 1981-1985, we generated F, progenies by hand-pollinating larkspurs (Delphinium nelsoniii with pollen from l-m, 3-m, lOrn, or 30-m distances. From the spatial genetic structure indicated by previous electrophoretic and reciprocal transplantation studies, we estimate that these crosses range from being inbred (f "" 0.06) to outbred. We planted 594 seeds from 66 maternal sibships under natural conditions. As of 1992, there was strong evidence for both inbreeding depression and outbreeding depression. Progeny from intermediate crossing distances grew approximately twice as large as more inbred or outbred progeny in the first 5 yr after planting (P = 0.013, repeated measures ANOVA), and survived almost 1 yr longer on average (contrast of 3-m and l Ovm treatments versus I m and 30 m; P = 0.028, ANOVA). Twenty maternal sibships produced flowering individuals; only four and two of these represented l-m and 30-m crossing distances, respectively (P = 0.021, G-test). The cumulative fitness of intermediate distance sibships averaged about twice that of l-rn sibships, and five to eight times that of 30-m sibships (P = 0.017, ANOVA). Thus, even though progeny of I-m crosses were inbred to a degree only about one-eighth that ofselfing, inbreeding depression approximated 50%,and outbreeding depression equaled or exceeded50%for all fitnesscomponents.Key words.-Crossing distance, Delphinium nelsonii, inbreeding depression, larkspur, outbreeding depression, plant population structure, progeny fitness.Received December 29, 1992. Accepted July 30, 1993.Outbreeding depression refers to a reduction in character means following crosses between genetically dissimilar individuals belonging to a single species (Dobzhansky

Molecular and quantitative signatures of biparental inbreeding depression in the self-incompatible tree species Prunus avium

“…Outbreeding depression at very early lifestages could indeed explain that fixation index tended to be lower in seeds. Offspring fitness might show an optimum over the whole parental dissimilarity range as reported in Ranunculus reptans (Willi and Van Buskirk, 2005), but our results are surprising because outbreeding depression rarely occurs within-population (Waser and Price, 1994;Grindeland, 2008), usually because of low environmental heterogeneity within stands (Frankham et al, 2011). This result might also be an artefact resulting from the high variation of kinship within families (Supplementary Material 1).…”

“…Yet, absence of heterozygote excess within adults suggests no biparental inbreeding depression effects from seedlings to adults, although the number of loci used in our study might be too low to allow a correlation between inbreeding and heterozygosity (Balloux et al, 2004). Environmental stress could also lead to different expression levels of inbreeding (Waser and Price, 1994;Paschke et al, 2005). The nursery was located in a region differing from the region of origin of the stand for soil, water and climate conditions.…”

“…Isolation of this P. avium population may have thus resulted in loss of genetic diversity and homozygote excess in seed and seedlings, as a consequence of low pollen immigration (Hanson et al, 2008;Sebbenn et al, 2010), significant spatial genetic structure (see Supplementary File 3; We analysed eight nuclear microsatellite loci and the gametophytic incompatibility locus. Waser and Price, 1994;Isagi et al, 2007;Grindeland, 2008;Hasegawa et al, 2009;Takeuchi et al, 2010), inbreeding (see Supplementary Material 1) or generation overlapping (Litrico et al, 2005). Seed sampling and seed germination resulted in loss of genetic diversity in the stand Bayern only.…”

Spatial patterns of seed dispersal, their determinants and consequences for recruitment

“…Among tropical trees, seed production is highest in years of high insolation that follow several years of lower insolation, because these conditions increase the plant resources available for fruitset and also favor pollinators 29 . Local genetic structure and self-incompatibility systems can determine the degree of inbreeding and outbreeding depression, and thus the number and quality of seeds produced 30 . Predispersal losses of seeds as a result of abortion or predation also vary among individuals and between years; no factors that consistently explain the variation have been identified 31 .…”

Spatial and temporal genetic structure in a hybrid cordgrass invasion

“…These seeds then spread on the tide and established as vigorous seedlings throughout the tidal flat, over time dominating this environmentally harsh habitat. Producing offspring in this way may greatly increase the rate of the colonization of new and challenging environments by maximizing the effects of selective forces on highly adapted genotypes, and so avoiding both inbreeding and outbreeding depression during this difficult phase of invasion (Lynch, 1991;Waser and Price, 1994;Sloop et al, 2009).…”