Outbreeding Depression Caused by Intraspecific Hybridization Between Local and Nonlocal Genotypes in Abies sachalinensis

Abstract

To evaluate the effects of intraspecific hybridization of local and nonlocal genotypes on growth traits of progeny in Abies sachalinensis, we performed reciprocal crossing between nonlocal trees in a high-elevation zone (1,100-1,200 m asl) and local trees in a low-elevation zone (530 m asl) in Hokkaido, northern Japan, in 1979 and established a common garden experiment using local × local (female × male), local × nonlocal, nonlocal × local, and nonlocal × nonlocal progeny in the low-elevation zone in 1986. Survival, height, diameter at breast height (dbh), needle nitrogen content, specific leaf area (SLA), and needle area per shoot diameter (NA) of 25-year-old progeny were measured in 2005. The survival rate was consistently high (>85% on average). Reductions in height and dbh were apparent in F1 hybrids compared with local × local progeny. Furthermore, outbreeding depression was significant in height growth of nonlocal × local F1 hybrids and in dbh of both F1 hybrids. Reductions in growth traits may be related to morphological needle traits, such as the low values of SLA and NA. Elevation guidelines for A. sachalinensis seed zones are discussed to ensure the long-term viability of both restored and native populations.

Hybridization with invasiveRosa rugosathreatens the genetic integrity of nativeRosa mollis

“…B). However, we do not know whether the low fitness is influenced by the isolation of the population, as shown in many other plant groups (Keller & Waller, ; Hensen, Oberprieler & Wesche, ; Hensen & Wesche, ; De Vere et al ., ) or by outbreeding depression caused by hybridization (Waser, Price & Shaw, ; Montalvo & Ellstrand, ; Goto et al ., ). However, hybrids between two dogrose species did not show reduced seed set (Wissemann & Hellwig, ; Werlemark, ; Ritz & Wissemann, ; Herklotz, ), but in hybrids between section Caninae and other sections, a lower number of seeds compared with the parents was observed (Gustafsson, ; Feuerhahn & Spethmann, ; Werlemark, ).…”

Incipient ecological speciation between successional varieties of a dominant tree involves intrinsic postzygotic isolating barriers

“…Early botanists recognized that ecologically differentiated plant populations represent intermediate stages in the speciation process (e.g., Clausen, ), and there is a sizeable body of the literature that examines the strengths and stages of reproductive isolating barriers within plant species, often in association with adaptation to contrasting environments. These studies of postzygotic reproductive isolation below the species boundary—or outbreeding depression (Price & Waser, )—reveal partial isolation within species across environmental gradients or ecotones (Fenster & Galloway, ; Grindeland, ; Montalvo & Ellstrand, ; Waser, Price, & Shaw, ), even in trees (Goto, Iijima, Ogawa, & Ohya, ; Stacy, ). In such cases, outbreeding depression appears to result from the disruption of local adaptation; however, partial reproductive isolation between conspecific populations can result also from physiological or intrinsic causes such as underdominance (heterozygote disadvantage), chromosomal rearrangements, or the breakup of coadapted gene complexes (Edmands, ; Price & Waser, ).…”

Inbreeding and outbreeding depression in Stylidium hispidum: implications for mixing seed sources for ecological restoration

“…; Goto et al. ). To assess the risks of outbreeding depression and the significance of local provenance, experimental evaluation of intraspecific hybrid performance is needed, as well as trials to compare hybrid performance with estimates of population divergence (Edmands ).…”