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The New Mexico Jumping Mouse (Zapus luteus) is a federally endangered granivore active for only 3 to 5 months annually. Knowledge of diet can help guide habitat recovery and yet despite calls for restoration of its riparian habitat, the diet of Z. luteus remains largely unknown. To date, only 8 plant species have been described in the diet—whereas insectivory, mycophagy, and dietary shifts have only been hypothesized. In the late summer, Z. luteus rapidly accumulates fat for a 9-month hibernation and restoration may fail if seasonal variation in the diet is overlooked. We used DNA metabarcoding on fecal DNA (n = 165) to resolve dietary taxa within multiple trophic levels of the diet and investigate monthly patterns of consumption. Seldom studied in metabarcoding frameworks, we also investigated exogenous contamination in Sherman live-capture traps. Potential contamination among feces, pelage, and trap surfaces was detectable but low (median = 0% to 2%), with fecal communities distinct from exogenous sources. The diet of Z. luteus was varied and most frequently (frequency of occurrence) of graminoids, forbs, lepidopterans, dipterids, and false-truffles. For plant foods, dietary diversity increased throughout their season of activity, shifting from sedges and woody vegetation in the early season (June to July) to forbs and grasses in the late season (August to September). Insect consumption was consistently detected throughout the season, whereas mycophagy was more frequently detected in August, when hypogeous fungi are typically more abundant. The breadth of dietary taxa suggests plasticity in resource use, potentially accommodating diverse patterns of seed availability throughout their active period. Shifts in plant consumption may reflect a dietary adaptation to the phenological patterns of their plant communities, a synchrony that might benefit both pre- and post-hibernation survival. Our work substantially improves our understanding of the diet of Z. luteus (241 dietary taxa) and will be useful for guiding habitat recovery. It also offers scalable methods to further investigate the diet under disturbance contexts (e.g., grazing, wildfire, drought).

 

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. 

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.