TY - JOUR T1 - Local biotic adaptation of trees and shrubs to plant neighbors. JF - Okios Y1 - 2017 A1 - Grady, K.C. A1 - Wood, T. E. A1 - Kolb, T. E. A1 - Hersch-Green, E. A1 - Shuster, S.M. A1 - Gehring, C. A. A1 - Hart, S.C. A1 - Allan, G.J. A1 - T. G. Whitham AB -

Natural selection as a result of plant–plant interactions can lead to local biotic adaptation. This may occur where species frequently interact and compete intensely for resources limiting growth, survival, and reproduction. Selection is demonstrated by comparing a genotype interacting with con‐ or hetero‐specific sympatric neighbor genotypes with a shared site‐level history (derived from the same source location), to the same genotype interacting with foreign neighbor genotypes (from different sources). Better genotype performance in sympatric than allopatric neighborhoods provides evidence of local biotic adaptation. This pattern might be explained by selection to avoid competition by shifting resource niches (differentiation) or by interactions benefitting one or more members (facilitation). We tested for local biotic adaptation among two riparian trees, Populus fremontii and Salix gooddingii, and the shrub Salix exigua by transplanting replicated genotypes from multiple source locations to a 17 000 tree common garden with sympatric and allopatric treatments along the Colorado River in California. Three major patterns were observed: 1) across species, 62 of 88 genotypes grew faster with sympatric neighbors than allopatric neighbors; 2) these growth rates, on an individual tree basis, were 44, 15 and 33% higher in sympatric than allopatric treatments for P. fremontii, S. exigua and S. gooddingii, respectively, and; 3) survivorship was higher in sympatric treatments for P. fremontii and S. exigua. These results support the view that fitness of foundation species supporting diverse communities and dominating ecosystem processes is determined by adaptive interactions among multiple plant species with the outcome that performance depends on the genetic identity of plant neighbors. The occurrence of evolution in a plant‐community context for trees and shrubs builds on ecological evolutionary research that has demonstrated co‐evolution among herbaceous taxa, and evolution of native species during exotic plants invasion, and taken together, refutes the concept that plant communities are always random associations.

VL - 126 UR - https://onlinelibrary.wiley.com/doi/full/10.1111/oik.03240 IS - 4 ER - TY - JOUR T1 - Leaf litter quality affects aquatic insect emergence: contrasting patterns from two foundation trees. JF - Oecologia Y1 - 2013 A1 - Compson,Zacchaeus G A1 - Adams,Kenneth J A1 - Edwards,Joeseph A A1 - Maestas,Jesse M A1 - Whitham,Thomas G A1 - Jane C Marks KW - Animals KW - arizona KW - Biota KW - Food Chain KW - Insecta KW - Plant Leaves KW - Populus KW - Rivers KW - Species Specificity AB -

Reciprocal subsidies between rivers and terrestrial habitats are common where terrestrial leaf litter provides energy to aquatic invertebrates while emerging aquatic insects provide energy to terrestrial predators (e.g., birds, lizards, spiders). We examined how aquatic insect emergence changed seasonally with litter from two foundation riparian trees, whose litter often dominates riparian streams of the southwestern United States: Fremont (Populus fremontii) and narrowleaf (Populus angustifolia) cottonwood. P. fremontii litter is fast-decomposing and lower in defensive phytochemicals (i.e., condensed tannins, lignin) relative to P. angustifolia. We experimentally manipulated leaf litter from these two species by placing them in leaf enclosures with emergence traps attached in order to determine how leaf type influenced insect emergence. Contrary to our initial predictions, we found that packs with slow-decomposing leaves tended to support more emergent insects relative to packs with fast-decomposing leaves. Three findings emerged. Firstly, abundance (number of emerging insects m(-2) day(-1)) was 25% higher on narrowleaf compared to Fremont leaves for the spring but did not differ in the fall, demonstrating that leaf quality from two dominant trees of the same genus yielded different emergence patterns and that these patterns changed seasonally. Secondly, functional feeding groups of emerging insects differed between treatments and seasons. Specifically, in the spring collector-gatherer abundance and biomass were higher on narrowleaf leaves, whereas collector-filterer abundance and biomass were higher on Fremont leaves. Shredder abundance and biomass were higher on narrowleaf leaves in the fall. Thirdly, diversity (Shannon's H') was higher on Fremont leaves in the spring, but no differences were found in the fall, showing that fast-decomposing leaves can support a more diverse, complex emergent insect assemblage during certain times of the year. Collectively, these results challenge the notion that leaf quality is a simple function of decomposition, suggesting instead that aquatic insects benefit differentially from different leaf types, such that some use slow-decomposing litter for habitat and its temporal longevity and others utilize fast-decomposing litter with more immediate nutrient release.

VL - 173 SN - 0029-8549 UR - http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&DbFrom=pubmed&Cmd=Link&LinkName=pubmed_pubmed&LinkReadableName=Related%20Articles&IdsFromResult=23532583&ordinalpos=3&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSumhttp://www.ncbi. IS - 2 ER - TY - JOUR T1 - Leaf ontogeny interacts with Bt modification to affect innate resistance in GM aspens JF - Chemoecology Y1 - 2011 A1 - Axelsson,EP A1 - Hjältén,J A1 - TG Whitham A1 - Julkunen-Tiitto,R A1 - Pilate,G AB - Bioassays with a non-target slug ( Deroceras spp.) and chemical analyses were conducted using leaf tissue from already existing genetically modified insect-resistant aspen trees to examine whether genetic modifications to produce Bacillus thuringiensis (Bt) toxins could affect plant phytochemistry, which in turn might influence plant–herbivore interactions. Three major patterns emerged. First, two independent modifications for Bt resistance affected the phytochemical profiles of leaves such that both were different from the isogenic wild-type (Wt) control leaves, but also different from each other. Among the contributors to these differences are substances with a presumed involvement in resistance, such as salicortin and soluble condensed tannins. Second, bioassays with one Bt line suggest that the modification somehow affected innate resistance (“Innate” is used here in opposition to the “acquired” Bt resistance) in ways such that slugs preferred Bt over Wt leaves. Third, the preference test suggests that the innate resistance in Bt relative to Wt plants may not be uniformly expressed throughout the whole plant and that leaf ontogeny interacts with the modification to affect resistance. This was manifested through an ontogenetic determined increase in leaf consumption that was more than four times higher in Bt compared to Wt leaves. Our result are of principal importance, as these indicate that genetic modifications can affect innate resistance and thus non-target herbivores in ways that may have commercial and/or environmental consequences. The finding of a modification–ontogeny interaction effect on innate resistance may be especially important in assessments of GM plants with a long lifespan such as trees. VL - 21 UR - http://link.springer.com/article/10.1007/s00049-011-0080-8 IS - 3 ER -