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1. Differences in dietary composition and preference maintained despite gene flow across a woodrat hybrid zone

   https://doi.org/10.1002/ece3.7399  

   Nielsen, Danny P.; Matocq, Marjorie D. (March 2021, Ecology and Evolution)

   Abstract Ecotones, characterized by adjacent yet distinct biotic communities, provide natural laboratories in which to investigate how environmental selection influences the ecology and evolution of organisms. For wild herbivores, differential plant availability across sharp ecotones may be an important source of dietary‐based selection.We studied small herbivore diet composition across a sharp ecotone where two species of woodrat,Neotoma bryantiandN.lepida, come into secondary contact with one another and hybridize. We quantified woodrat dietary preference through trnLmetabarcoding of field‐collected fecal pellets and experimental choice trials. Despite gene flow, parentalN. bryantiandN. lepidamaintain distinct diets across this fine spatial scale, and across temporal scales that span both wet and dry conditions.Neotoma bryantimaintained a more diverse diet, withFrangula californica(California coffeeberry) making up a large portion of its diet.Neotoma lepidamaintains a less diverse diet, withPrunus fasciculata(desert almond) comprising more than half of its diet. BothF. californicaandP. fasciculataare known to produce potentially toxic plant secondary compounds (PSCs), which should deter herbivory, yet these plants have relatively high nutritional value as measured by crude protein content.Neotoma bryantiandN. lepidaconsumedF. californicaandP. fasciculata, respectively, in greater abundance than these plants are available on the landscape—indicating dietary selection. Finally, experimental preference trials revealed thatN. bryantiexhibited a preference forF. californica, whileN. lepidaexhibited a relatively stronger preference forP. fasciculata. We find thatN. bryantiexhibit a generalist herbivore strategy relative toN. lepida, which exhibit a more specialized feeding strategy in this study system.Our results suggest that woodrats respond to fine‐scale environmental differences in plant availability that may require different metabolic strategies in order to balance nutrient acquisition while minimizing exposure to potentially toxic PSCs. 

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2. Hybridization in the absence of an ecotone favors hybrid success in woodrats ( Neotoma spp.)

   https://doi.org/10.1093/evolut/qpad012  

   Klure, Dylan M.; Greenhalgh, Robert; Parchman, Thomas L.; Matocq, Marjorie D.; Galland, Lanie M.; Shapiro, Michael D.; Dearing, M. Denise (January 2023, Evolution)

   Abstract Hybridization is a common process that has broadly impacted the evolution of multicellular eukaryotes; however, how ecological factors influence this process remains poorly understood. Here, we report the findings of a 3-year recapture study of the Bryant’s woodrat (Neotoma bryanti) and desert woodrat (Neotoma lepida), two species that hybridize within a creosote bush (Larrea tridentata) shrubland in Whitewater, CA, USA. We used a genotype-by-sequencing approach to characterize the ancestry distribution of individuals across this hybrid zone coupled with Cormack–Jolly–Seber modeling to describe demography. We identified a high frequency of hybridization at this site with ~40% of individuals possessing admixed ancestry, which is the result of multigenerational backcrossing and advanced hybrid-hybrid crossing. F1, F2, and advanced generation hybrids had apparent survival rates similar to parental N. bryanti, while parental and backcross N. lepida had lower apparent survival rates and were far less abundant. Compared to bimodal hybrid zones where hybrids are often rare and selected against, we find that hybrids at Whitewater are common and have comparable survival to the dominant parental species, N. bryanti. The frequency of hybridization at Whitewater is therefore likely limited by the abundance of the less common parental species, N. lepida, rather than selection against hybrids. 

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3. Large and small herbivores have strong effects on tundra vegetation in Scandinavia and Alaska

   https://doi.org/10.1002/ece3.7977  

   Lindén, Elin; Gough, Laura; Olofsson, Johan (August 2021, Ecology and Evolution)

   Abstract Large and small mammalian herbivores are present in most vegetated areas in the Arctic and often have large impacts on plant community composition and ecosystem functioning. The relative importance of different herbivores and especially how their specific impact on the vegetation varies across the Arctic is however poorly understood.Here, we investigate how large and small herbivores influence vegetation density and plant community composition in four arctic vegetation types in Scandinavia and Alaska. We used a unique set of exclosures, excluding only large (reindeer and muskoxen) or all mammalian herbivores (also voles and lemmings) for at least 20 years.We found that mammalian herbivores in general decreased leaf area index, NDVI, and abundance of vascular plants in all four locations, even though the strength of the effect and which herbivore type caused these effects differed across locations. In three locations, herbivore presence caused contrasting plant communities, but not in the location with lowest productivity. Large herbivores had a negative effect on plant height, whereas small mammalian herbivores increased species diversity by decreasing dominance of the initially dominating plant species. Above‐ or belowground disturbances caused by herbivores were found to play an important role in shaping the vegetation in all locations.Synthesis:Based on these results, we conclude that both small and large mammalian herbivores influence vegetation in Scandinavia and Alaska in a similar way, some of which can mitigate effects of climate change. We also see important differences across locations, but these depend rather on local herbivore and plant community composition than large biogeographical differences among continents. 

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4. Different tools for different trades: contrasts in specialized metabolite chemodiversity and phylogenetic dispersion in fruit, leaves, and roots of the neotropical shrubs Psychotria and Palicourea (Rubiaceae)

   https://doi.org/10.1111/plb.70013  

   Schneider, G F; Beckman, N G (August 2025, Plant Biology)

   Abstract Plants produce an astonishingly diverse array of specialized metabolites. A crucial step in understanding the origin of such chemodiversity is describing how chemodiversity manifests across the spatial and ontogenetic scales relevant to plant–biotic interactions.Focusing on 21 sympatric species ofPsychotriaandPalicourea sensu lato(Rubiaceae), we describe patterns of specialized metabolite diversity across spatial and ontogenetic scales using a combination of field collections, untargeted metabolomics, and ecoinformatics. We compare α, β, and γ diversity of specialized metabolites in expanding leaves, unripe pulp, immature seed, ripe pulp, mature seed, and fine roots.Within species, fruit tissues from across ontogenetic stages had ≥α diversity than leaves, and ≤β diversity than leaves. Pooled across species, fruit tissues and ontogenetic stages had the highest γ diversity of all organs, and fruit tissues and ontogenetic stages combined had a higher incidence of organ‐specific mass spectral features than leaves. Roots had ≤α diversity than leaves and the lowest β and γ diversity of all organs. Phylogenetic correlations of chemical distance varied by plant organ and chemical class.Our results describe patterns of specialized metabolite diversity across organs and species and provide support for organ‐specific contributions to plant chemodiversity. This study contributes to the growing understanding within plant evolutionary ecology of the biological scales of specialized metabolite diversification. Future studies combining our data on specialized metabolite diversity with biotic interaction data and experiments can test existing hypotheses on the roles of ecological interactions in the evolution of chemodiversity. 

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5. Intraspecific correlations between growth and defence vary with resource availability and differ within and among populations

   https://doi.org/10.1111/1365-2435.13878  

   Hahn, Philip G.; Keefover‐Ring, Ken; Nguyen, Linh M. N.; Maron, John L. (July 2021, Functional Ecology)

   Abstract A paradigm in the plant defence literature is that defending against herbivores comes at a cost to growth, resulting in a growth–defence trade‐off. However, while there is strong evidence for growth–defence trade‐offs across species, evidence is mixed within species.Several mechanisms can account for this equivocal support within species, but teasing them apart requires examining growth–defence relationships both within and among populations, an approach seldom employed.We examined correlations between plant biomass (growth) and terpene production (defence) within and among populations ofMonarda fistulosa, a perennial herb. We sampled populations from Montana and Wisconsin, regions that differ in resource availability characterized by different summer precipitation and associated abiotic conditions that influence plant productivity.We found negative, neutral and positive growth–defence correlations, depending on the scale examined. Negative correlations occurred across populations originating from divergent regions, positive correlations occurred across populations originating from within the high‐resource region and neutral correlations were found within single populations.Collectively, these results challenge the general expectation of ubiquitous trade‐offs and support emerging views that resource availability (as it affects productivity) shapes the evolution of defence at different scales. A freePlain Language Summarycan be found within the Supporting Information of this article. 

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