Populus Center

• Biodiversity

Woody perennials are foundation species in many ecosystems and serve as the basis for trophic interactions at multiple levels, from microbes and fungi to arthropods, birds, and mammals.

Populus, in particular, is recognized as a dominant riparian forest tree that can have significant impacts on biodiversity and ecosystem sustainability.  Riparian areas are a hotspot of biodiversity.  However, due to extensive habitat loss throughout arid areas, such as the American Southwest, riparian areas are now considered a threatened habitat type.

Populus is the only genus with documented links among genes, communities, and ecosystems.  Many Populus species hybridize readily, which often results in novel genotypes that differ significantly from either parent in important ecological traits.  Introduction of these hybrid genotypes into riparian communities may alter genetic interactions among associated species, and thus, biodiversity of the riparian habitat.

Thanks to the rich genomic resources, the Populus community is well-positioned to advance our understanding on molecular genetic mechanisms related to variation in species interactions, community formation and ecosystem sustainability.

• Climate change

Climate change impacts on animal and plant populations have been extensively documented (additional reading). There are no exceptions to Populus survival, growth and dependent communities.  Common garden studies in Utah and Arizona are showing a large shift in adaptability of source populations in which the local genotypes no longer do as well as genotypes from other source populations.  In other words, it appears that the climate change is shifting the environment out from under the local populations.  

During the recent record droughts, researchers have found that naturally occurring hybrids have 4 times higher survival rates than their parental species in reciprocal common garden trials.  Drought tolerance and other climate change-associated characteristics are among the highly desirable traits in poplar breeding programs.  Therefore, genetic and genomics tools can be applied to characterize marker-trait association for acclimation in both natural and managed forest ecosystems, not only for breeding improvements but also for climate change research.  

• Ecosystem Services

Water and nutrient cycles, below-ground carbon storage, erosion prevention, air purification and maintaining biodiversity are examples of important ecosystem services trees provide.

Approximately 50% of the variation ecosystem services are genetically based in Populus.  In addition, up to 78% of the biodiversity associated with Populus is influenced by plant genetic factors.  Importantly, much of the biodiversity inherent to ecosystems dominated by Populus is both stable and heritable.  

• Restoration

Populus researchers are actively engaged in extensive restoration projects that focus on restoring riparian habitat in the Southwestern USA.  

Restoration efforts can be guided by common garden experiments that standardize environmental conditions, in order to gain an understanding of whether marker-associated traits are heritable, and to gauge the impact of introduced species/population has on the sustainability of ecosystems and associated community members.  

Working with both Federal and local agencies, Populus common gardens containing up to 23,000 trees have been established in southwestern US.  In many cases, trees used in these projects have been propagated from local area stock.  However, trees from geographically distant areas have also been incorporated in order to assess whether local genotypes are in fact the best adapted to southwestern areas currently undergoing rapid environmental change.

• Plantation

Clonal plantations clearly have different genetic structure than natural populations, which can be a point of contention for conservation biologists.  However, selection of certain cultivars or specific genes/traits that promote biodiversity could greatly reduce the negative consequences of clonal plantations.

Hybrid pedigrees are routinely used in plantations for the biofuel, pulp and lumber industries.   Evaluating marker-trait associations in natural populations as well as commercial hybrid pedigrees constitutes an important first-step toward understanding how individual markers are transmitted and maintained in natural versus managed systems, and the influence they have on associated communities, ecosystem function and sustainability.  

A variety of genetic and genomic tools can be used in marker assisted breeding, including:
1)    gene expression studies of biochemical pathways that influence community diversity, ecosystem function and sustainability;
2)    surveys of single nucleotide polymorphism (SNP) markers that are closely tied to genes of interest and;
3)    quantitative trait locus (QTL) mapping for evaluating community and ecosystem phenotypes in plantation poplars that are genetically improved or modified.