Treesearch

European beech (Fagus sylvatica) is one of the most abundant tree species in Europe. Its genetic structure and diversity have been investigated using both molecular markers and adaptive traits as assessed in field and laboratory experimental tests looking at adaptative traits. A great deal of information also exists on the Quaternary history of the species and on plant communities associated with this keystone species. In France, the conservation of its genetic resources relies on both in situ and ex situ approaches. Some outlying populations at the margin of its distribution, that are...

Hybridization can result in the transfer of adaptations among species and may contribute to speciation processes. On the other hand, hybridization can also result in a loss of species diversity due to asymmetric gene flow between species (genetic swamping) and in low hybrid fitness. An understanding of the outcomes of interspecific hybridization is crucial for the management and conservation of tree populations. As a result of warming climates, it is expected that distribution ranges of species will shift, resulting in new zones between species and potentially new or increased hybridization...

Pinus aristata, Rocky Mountain bristlecone pine, has a narrow geographic and elevational distribution and is threatened by rapid climate change, the introduced pathogen Cronartium ribicola that causes white pine blister rust (WPBR), and bark beetles. The core distribution of P. aristata is near and at treeline in central and southern Colorado and extends into northern New Mexico with a disjunct population in northern Arizona. The combination of low genetic diversity, moderate population isolation, and a protracted regeneration dynamic puts populations at risk for extirpation by novel...

Yellowwood (Cladrastis kentukea) is an uncommon, relict, tree species with a disjunct distribution primarily in the Central Hardwoods region. Most common on rocky, sheltered slopes of the Cumberland Plateau in Tennessee and Kentucky, isolated populations occur on appropriate sites throughout the southern and central United States. In Illinois, Louisiana, and South Carolina, yellowwood is listed as endangered by state conservation agencies, but it is not federally protected. Yellowwood has increased in popularity as a street tree and is planted in or predicted to be suitable for urban...

Koa (Acacia koa) is a valuable tree species economically, ecologically, and culturally in Hawaii. A vascular wilt disease of koa, caused by the fungal pathogen Fusarium oxysporum f. sp. koae (FOXY), causes high rates of mortality in field plantings and threatens native koa forests in Hawaii. Producing seeds with genetic resistance to FOXY is vital to successful koa reforestation and restoration. The Hawaii Agriculture Research Center (HARC), with both public and private partners, operates a tree improvement program to develop koa wilt resistant populations in Hawaii. The population...

Recently, a collaboration between The Brenton Arboretum and the North Central Regional Plant Introduction Station (NCRPIS) was initiated to assemble comprehensive ex situ germplasm collections of Kentucky coffeetree, Gymnocladus dioicus. Gymnocladus dioicus was selected due to its adaptation to poor soils common to urban conditions, extreme drought tolerance, and no reported serious insect or disease problems. These factors make it a promising candidate among diverse tree genera to replace ash trees in urban environments affected by the emerald ash borer (Agrilus planipennis). Targeted...

Restoration treatments in the ponderosa pine (Pinus ponderosa P. & C. Lawson) ecosystems of the southwestern United States often include removing over 80 percent of post-EuroAmerican settlement-aged trees to create healthier forest structural conditions. These types of stand density reductions can have negative effects on genetic diversity. Allozyme analyses were used to evaluate potential impacts of restoration treatments on genetic diversity of five ponderosa pine populations located 2 to 3 km apart within the U.S. Department of Agriculture Forest Service Fort Valley Experimental Forest,...

Because of rapid global warming, it is critical for us to better understand the capacity of forest trees to adapt to a changing climate, especially species such as five-needle pines that are particularly at risk to threats because of fire suppression, population fragmentation, and pests. In this study, we used several methods to disentangle the effects of local adaptation (isolation by environment, IBE) from those of isolation by distance (IBD) and isolation by colonization (IBC) in Pinus strobus. For this reason, 153 SNPs from 103 genes, including 44 candidate genes for growth and...

Ex-situ genetic conservation focused on collection and storage of seed can play an important role in conserving the genetic diversity of species under grave threat by biotic organisms or a changing climate. However, ex-situ genetic conservation is primarily a static activity and does not allow for evolution of the species under a continuing, persistent impacting agent. Invasive insects and pathogens, once established, usually become permanent components of the ecosystem, continuously interacting with the target species. Dynamic genetic conservation seeks to actively harness the genetic...

North American native tree species in forest ecosystems, as well as managed forests and urban plantings, are being severely impacted by pathogens and insects. The impacts of these pathogens and insects often increase over time, and they are particularly acute for those species affected by non-native pathogens and insects. For restoration of affected tree species or for their continued presence in managed forests and urban plantings, genetic resistance will be key. Often, however, little or nothing is known about genetic resistance to these invaders. The U.S. Department of Agriculture...