Fitness and Genetic Architecture of Parent and Hybrid Willows in Common Gardens

Fritz, Robert S.; Hochwender, Chris G.; Albrectsen, Benedicte Riber; Czesak, Mary Ellen

doi:10.1111/j.0014-3820.2006.tb01200.x

Cited by 35 publications

(23 citation statements)

References 55 publications

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“…European aspen grew faster than the backcross hybrid aspen in all treatments, similar to observations of backcross and parent generations of Salix (Fritz et al 2006). Compared with F 1 hybrids, further hybrids of Populus are generally slower growing (Karim and Hawkins 1999).…”

Section: Discussionsupporting

confidence: 80%

Growth and frost hardening of European aspen and backcross hybrid aspen as influenced by water and nitrogen

Nikula¹,

Manninen²,

Pulkkinen³

2011

Annals of Forest Science

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& Introduction The interactive effects of water and nitrogen (N) on frost hardiness are not well known in broad-leaved trees. Furthermore, new environmental conditions may favour naturally generated hybrids between native and introduced tree species over native species. & Methods A greenhouse experiment with freezing tests was carried out to study how water (low, medium, high) and N (low, high) supply influence the growth, bud phenology and frost hardening of seven young European aspen (Populus tremula) and backcross hybrid aspen ([P. tremula × Populus tremuloides] × P. tremula) families. & Results The native European aspen grew faster, whereas hybrid aspen × aspen frost hardened faster and exhibited better overall frost hardiness and earlier budburst. Hybrid aspen × aspen also showed intraspecific variation in frost hardiness. The two species showed similar responses to different water and N supplies, and both species were more affected by changes in N supply than in water supply. Higher N supply-especially when combined with droughtdelayed frost hardening, an effect that was more pronounced in European aspen. & Conclusions The results suggest that backcross hybrid aspen may in some respects be better adapted to a range of environmental conditions than the native species.

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Section: Discussionsupporting

confidence: 80%

Growth and frost hardening of European aspen and backcross hybrid aspen as influenced by water and nitrogen

Nikula¹,

Manninen²,

Pulkkinen³

2011

Annals of Forest Science

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“…All else being equal, subsequent generations would be expected to decline in fitness due to a decay in any dominance variation underlying heterosis, as well as due to the appearance of deleterious epistatic interactions if coadapted gene complexes had been disrupted [22]. There is ample evidence that epistasis contributes to population differentiation in plants [114], [115], [116], [117], but little empirical evidence for forest trees [118], [119]. Epistatic differentiation may accumulate through randomly changing the genetic background, such as when periods of isolation (i.e.…”

Section: Discussionmentioning

confidence: 99%

Heterosis May Result in Selection Favouring the Products of Long-Distance Pollen Dispersal in Eucalyptus

2014

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Using native trees from near the northern and southern extremities of the relatively continuous eastern distribution of Eucalyptus globulus in Tasmania, we compared the progenies derived from natural open-pollination (OP) with those generated from within-region and long-distance outcrossing. Controlled outcrossing amongst eight parents - with four parents from each of the northern and southern regions - was undertaken using a diallel mating scheme. The progeny were planted in two field trials located within the species native range in southern Tasmania, and their survival and diameter growth were monitored over a 13-year-period. The survival and growth performances of all controlled cross types exceeded those of the OP progenies, consistent with inbreeding depression due to a combination of selfing and bi-parental inbreeding. The poorer survival of the northern regional (♀N♂N) outcrosses compared with the local southern regional outcrosses (♀S♂S) indicated differential selection against the former. Despite this mal-adaptation of the non-local ♀N♂N crosses at both southern sites, the survival of the inter-regional hybrids (♀N♂S and ♀S♂N) was never significantly different from that of the local ♀S♂S crosses. Significant site-dependent heterosis was detected for the growth of the surviving long-distance hybrids. This was expressed as mid-parent heterosis, particularly at the more northern planting site. Heterosis increased with age, while the difference between the regional ♀N♂N and ♀S♂S crosses remained insignificant at any age at either site. Nevertheless, the results for growth suggest that the fitness of individuals derived from long-distance crossing may be better at the more northern of the planting sites. Our results demonstrate the potential for early-age assessments of pollen dispersal to underestimate realised gene flow, with local inbreeding under natural open-pollination resulting in selection favouring the products of longer-distance pollinations. Indeed, heterosis derived from long-distance pollinations may be sufficient to counter local mal-adaptation, at least in the first generation.

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“…2005; Lexer et al . 2005; Fritz et al . 2006), although it is still possible that fitness reduction of hybrids would show up at a later stage.…”

Section: Discussionmentioning

confidence: 99%

Differential performance of reciprocal hybrids in multiple environments

2008

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1.Closely related taxa may be maintained as distinct species by a variety of reproductive isolating mechanisms. These include: inability to produce hybrid offspring, endogenous selection against hybrids in the form of genomic incompatibilities, and exogenous selection observable in genotypeby-environment interactions. To understand the relative importance of these three isolating mechanisms, we performed hand-pollination and reciprocal transplant experiments in a natural plant hybrid zone. 2. We measured reproductive isolation by making crosses between two parent species of Penstemon and naturally occurring hybrids. Inclusion of reciprocal hybrid crosses allowed us to determine whether fitness components differed depending on the identity of the mother. 3. Hybrid performance was evaluated in the greenhouse and in a reciprocal transplant experiment in the field. We measured fruit set, seed set, seed weight, time required for fruits to mature and seedling growth for potted plants. To test for exogenous isolation, we planted pure parents, reciprocal F 1 hybrids and later generation hybrids in a reciprocal transplant experiment, and measured survival. 4. On average, interspecific crosses produced as many seeds as conspecific crosses. Hybrid performance was also equal to or greater than parents in all environments, including the greenhouse and all field gardens, indicating a lack of endogenous isolation. Parent species and reciprocal F 1 hybrids differed in many traits measured. In each field garden, the hybrid with the native cytoplasm had a higher survival rate, suggesting local adaptation to different elevations. 5. Synthesis . Exogenous factors that differ along elevational gradients can be more important than intrinsic genetic incompatibilities in determining the fitness of plant hybrids. Our results illustrate the importance of studying hybrid performance in multiple environments and in generating reciprocal hybrids to test for isolating mechanisms in natural hybrid zones.

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Fitness and Genetic Architecture of Parent and Hybrid Willows in Common Gardens

Cited by 35 publications

References 55 publications

Growth and frost hardening of European aspen and backcross hybrid aspen as influenced by water and nitrogen

Growth and frost hardening of European aspen and backcross hybrid aspen as influenced by water and nitrogen

Heterosis May Result in Selection Favouring the Products of Long-Distance Pollen Dispersal in Eucalyptus

Differential performance of reciprocal hybrids in multiple environments

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