skip to main content

Explore Research Products in the NSF-PAR

Title: Heterozygous Trees Rebound the Fastest after Felling by Beavers to Positively Affect Arthropod Community Diversity
Although genetic diversity within stands of trees is known to have community-level consequences, whether such effects are present at an even finer genetic scale is unknown. We examined the hypothesis that genetic variability (heterozygosity) within an individual plant would affect its dependent community, which adds a new dimension to the importance of genetic diversity. Our study contrasted foliar arthropod community diversity and microsatellite marker-derived measures of genetic diversity of cottonwood (Populus fremontii) trees that had been felled by beavers (Castor canadensis) and were resprouting, relative to adjacent standing, unfelled trees. Three patterns emerged: 1. Productivity (specific leaf area), phytochemical defenses (salicortin), and arthropod community richness, abundance, and diversity were positively correlated with the heterozygosity of individual felled trees, but not with that of unfelled trees; 2. These relationships were not explained by population substructure, genetic relatedness of the trees, or hybridization; 3. The underlying mechanism appears to be that beaver herbivory stimulates increased productivity (i.e., 2× increase from the most homozygous to the most heterozygous tree) that is the greatest in more heterozygous trees. Salicortin defenses in twigs were also expressed at higher concentrations in more heterozygous trees (i.e., 3× increase from the most homozygous to the most heterozygous tree), which suggests that this compound may dissuade further herbivory by beavers, as has been found for other mammalian herbivores. We suggest that high stress to trees as a consequence of felling reveals a heterozygosity–productivity linkage, which in turn is attractive to arthropods. Although experiments are required to demonstrate causality, these results link the genetic diversity of individual trees to community diversity, supporting the hypothesis that interactions among foundation species (beavers and trees) have community-level effects, and underscores the importance of genetic diversity for biodiversity, conservation, and restoration.  more » « less
Award ID(s):
1914433
NSF-PAR ID:
10282321
Author(s) / Creator(s):
; ; ; ;
Date Published:
Journal Name:
Forests
Volume:
12
Issue:
6
ISSN:
1999-4907
Page Range / eLocation ID:
694
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; ( , Forests)
    null (Ed.)
    The North American beaver (Castor canadensis Kuhl) and cottonwoods (Populus spp.) are foundation species, the interactions of which define a much larger community and affect a threatened riparian habitat type. Few studies have tested the effect of these interactions on plant chemistry and a diverse arthropod community. We experimentally examined the impact of beaver foraging on riparian communities by first investigating beaver food preferences for one cottonwood species, Fremont cottonwood (P. fremontii S. Watson), compared to other locally available woody species. We next examined the impact of beaver foraging on twig chemistry and arthropod communities in paired samples of felled and unfelled cottonwood species in northern Arizona (P. fremontii) and southwestern Colorado (narrowleaf cottonwood, P. angustifolia James, and Eastern cottonwood, P. deltoides W. Bartram ex Marshall). Four major patterns emerged: (1) In a cafeteria experiment, beavers chose P. fremontii six times more often than other woody native and exotic species. (2) With two cottonwood species, we found that the nitrogen and salicortin concentrations were up to 45% greater and lignin concentration 14% lower in the juvenile resprout growth of felled trees than the juvenile growth on unfelled trees (six of seven analyses were significant for P. fremontii and four of six were significant for P. angustifolia). (3) With two cottonwood species, arthropod community composition on juvenile branches differed significantly between felled and unfelled trees, with up to 38% greater species richness, 114% greater relative abundance and 1282% greater species diversity on felled trees (six of seven analyses with P. fremontii and four of six analyses with P. angustifolia were significant). The above findings indicate that the highest arthropod diversity is achieved in the heterogenous stands of mixed felled and unfelled trees than in stands of cottonwoods, where beavers are not present. These results also indicate that beaver herbivory changes the chemical composition in 10 out of 13 chemical traits in the juvenile growth of two of the three cottonwood species to potentially allow better defense against future beaver herbivory. (4) With P. deltoides, only one of five analyses in chemistry was significant, and none of the four arthropod community analyses were significant, suggesting that this species and its arthropod community responds differently to beaver. Potential reasons for these differences are unknown. Overall, our findings suggest that in addition to their impact on riparian vegetation, other mammals, birds, and aquatic organisms, beavers also may define the arthropod communities of two of three foundation tree species in these riparian ecosystems. 
    more » « less
  2. ; ; ( , PLOS Climate)
    Ahmed, Ferdous (Ed.)
    We addressed the hypothesis that intraspecific genetic variation in plant traits from different sites along a distance/elevation gradient would influence the communities they support when grown at a new site. Answers to this hypothesis are important when considering the community consequences of assisted migration under climate change; i.e., if you build it will they come?. We surveyed arthropod communities occurring on the foundation riparian tree species Populus angustifolia along a distance/elevation gradient and in a common garden where trees from along the gradient were planted 20–22 years earlier. Three major patterns were found: 1) In the wild, arthropod community composition changed significantly. Trees at the lower elevation site supported up to 58% greater arthropod abundance and 26% greater species richness than more distant, high elevation trees. 2) Trees grown in a common garden sourced from the same locations along the gradient, supported arthropod communities more similar to their corresponding wild trees, but the similarity declined with transfer distance and elevation. 3) Of five functional traits examined, leaf area, a trait under genetic control that decreases at higher elevations, is correlated with differences in arthropod species richness and abundance. Our results suggest that genetic differences in functional traits are stronger drivers of arthropod community composition than phenotypic plasticity of plant traits due to environmental factors. We also show that variation in leaf area is maintained and has similar effects at the community level while controlling for environment. These results demonstrate how genetically based traits vary across natural gradients and have community-level effects that are maintained, in part, when they are used in assisted migration. Furthermore, optimal transfer distances for plants suffering from climate change may not be the same as optimal transfer distances for their dependent communities. 
    more » « less
  3. ; ; ; ( , Restoration Ecology)

    Tree plantings have the potential to increase species diversity and sequester carbon, yet planting failure and early mortality pose significant barriers to their success. Biodiversity‐ecosystem function theory suggests that diverse tree plantings could improve survival outcomes through either the portfolio or facilitation effect, yet there remain few tests of this hypothesis. Here, we use a large‐scale tree‐diversity experiment (BiodiversiTREE), with monitoring of nearly 8,000 individual trees to test whether (1) tree species diversity increases survival rates, (2) tree diversity stabilizes the risk of planting failure, and/or (3) diversity effects are important relative to other common drivers of seedling mortality (e.g. herbivory and soil moisture). We found that only species identity significantly impacted the likelihood of survival, not plant functional diversity nor plot species richness nor phylogenetic diversity. There were minor effects of elevation and soil moisture on survival, but both explained a very small amount of variation in the data (r2marg ≤ 0.011). Higher tree diversity did, however, strongly reduce variation in survival across plots, with nearly 2‐fold higher coefficients of variation in monocultures (30.4%, 28.4–32.6% 95% bootstrapped confidence interval) compared to 4‐ (16.3%, 13.8–18.7%) and 12‐species plots (12.8%, 10.8–14.7%). Ultimately, our results suggest that employing diverse species can lower the risk of planting failure (i.e. the portfolio effect), but that species selection still plays a large role in early establishment.

     
    more » « less
  4. ; ; ( , Dryad)
    Anthropogenic nitrogen (N) addition might alter the evolutionary trajectories of plant populations, in part because it alters the abiotic and biotic environment by increasing aboveground primary productivity, light asymmetry, and herbivory intensity, and reducing plant species diversity. Such evolutionary impacts could be caused by N altering patterns of natural selection (i.e., trait-fitness relationships) and the opportunity for selection (i.e., variance in relative fitness). Because at the community level N addition favors species with light acquisition strategies (e.g., tall species), we predict that N would also increase selection favoring those same traits. We also hypothesize that N could alter the opportunity for selection via its effects on mean fitness and/or competitive asymmetries.To investigate these evolutionary consequences of N, we quantified the strength of selection and the opportunity for selection in replicated populations of the annual grass Setaria faberi Herrm. (giant foxtail) growing in a long-term N addition experiment. We also correlated our measures of selection and opportunity for selection with light asymmetry, diversity, and herbivory intensity to identify the proximate causes of any N effects on evolutionary processes. N addition increased aboveground productivity, light asymmetry, and reduced species diversity. Contrary to expectations, N addition did not strengthen selection for trait values associated with higher light acquisition such as greater height and specific leaf area (SLA); rather, it strengthened selection favoring lower SLA. Increased light asymmetry was associated with stronger selection for lower SLA and lower species diversity was associated with stronger selection for greater height and lower SLA, suggesting a role for these factors in driving N-mediated selection. The opportunity for selection was not influenced by N addition (despite increased mean fitness) but was negatively associated with species diversity. Our results indicate that anthropogenic N enrichment can affect evolutionary processes, but that evolutionary changes in plant traits within populations are unlikely to parallel the shifts in plant traits observed at the community level. Data was collected in 2020 from a field experiment in a long-term ecological research site (Kellogg Biological Station LTER site in Michigan, USA). The Data folder contains 3 separate datasets as CSV files, each with accompanying .txt metadata files: 1) a dataset of individual-level data (Waterton2022_NitrogenEvolution_Individual_Data.csv); 2) a dataset of annual net primary productivity (ANPP; Waterton2022_NitrogenEvolution_ANPP_Data.csv); 3) a dataset of light measurements (Waterton2022_NitrogenEvolution_Light_Data.csv). An R script for reproducing the analyses and figures is available at https://doi.org/10.5281/zenodo.7121361. R statistical software is required to run the R script. 
    more » « less
  5. ; ( , Oecologia)
    Abstract

    Shelter building caterpillars act as ecosystem engineers by creating and maintaining leaf shelters, which are then colonized by other arthropods. Foliage quality has been shown to influence initial colonization by shelter-building caterpillars. However, the effects of plant quality on the interactions between ecosystem engineers and their communities have yet to be studied at the whole plant level. We examined how leaf tying caterpillars, as ecosystem engineers, impact arthropod communities onQuercus alba(white oak), and the modifying effect of foliage quality on these interactions. We removed all leaf tying caterpillars and leaf ties on 35Q. albasaplings during the season when leaf tying caterpillars were active (June–September), and compared these leaf tie removal trees to 35 control trees whose leaf ties were left intact. Removal of these ecosystem engineers had no impact on overall arthropod species richness, but reduced species diversity, and overall arthropod abundance and that of most guilds, and changed the structure of the arthropod community as the season progressed. There was an increase in plant-level species richness with increasing number of leaf ties, consistent with Habitat Diversity Hypothesis. In turn, total arthropod density, and that of both leaf tying caterpillars and free-feeding caterpillars were affected by foliar tannin and nitrogen concentrations, and leaf water content. The engineering effect was greatest on low quality plants, consistent with the Stress-Gradient Hypothesis. Our results demonstrate that interactions between ecosystem engineering and plant quality together determine community structure of arthropods onQ. albain Missouri.

     
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email