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Alpine, but not montane, seed plants constitute a biogeographically and climatically distinct species pool across the Americas.
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  • Hector Figueroa,
  • Hannah Marx,
  • Maria Beatriz de Souza Cortez,
  • Charles Grady,
  • Nicholas J. Engle-Wrye,
  • Jim Beach,
  • Aimee Stewart,
  • Ryan Folk,
  • Douglas Soltis,
  • Pamela Soltis,
  • Stephen Smith
Hector Figueroa
University of Michigan
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Hannah Marx
University of New Mexico Department of Biology
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Maria Beatriz de Souza Cortez
University of Florida
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Charles Grady
University of Kansas Department of Ecology and Evolutionary Biology
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Nicholas J. Engle-Wrye
Mississippi State University Department of Biological Sciences
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Jim Beach
University of Kansas College of Liberal Arts and Sciences
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Aimee Stewart
University of Kansas College of Liberal Arts and Sciences
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Ryan Folk
Mississippi State University Department of Biological Sciences
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Douglas Soltis
University of Florida
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Pamela Soltis
University of Florida
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Stephen Smith
University of Michigan
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Abstract

Aim Higher elevation habitats contribute substantially to global biodiversity. Nevertheless, we know comparatively little about how diversity patterns differ among alpine and montane communities across different mountain ranges. Here, we characterized the realized niche space of American seed plants to ask whether or not montane or alpine community compositions define climatically distinct species pools at this regional scale. Location Americas. Time Period Contemporary. Major taxa studied Seed plants. Methods We assembled a niche model dataset of 72,372 American seed plants based on digitized and georeferenced specimen records. We used this dataset to quantify occupied abiotic niche space with regards to temperature, precipitation, and elevation. This approach further permitted differentiation of higher-elevation specialists (i.e., ranges centered at high elevations) from generalists (i.e., ranges centered at lower elevations but extending into mountain areas). Results Montane communities did not differ from the regional species pool in terms of richness patterns, occupied climatic niche space, or niche breadth. In contrast, alpine communities were characterized by a bimodal latitudinal diversity gradient, drastically reduced climatic niche space, and broader temperature but narrower precipitation niche breadth. Alpine generalists further showed statistically significant differences in temperature, but not precipitation, niche breadth from both alpine specialists and lowland taxa. We also highlight non-alpine species whose climatic niche space otherwise overlapped with that of alpine plants. These species were geographically concentrated in the southern US and Mexico, tended to have a greater fraction of their ranges in frost-exposed mountain foothills, and less of their range in lowland, frost-free, areas, compared to other non-alpine species. Main conclusions These results suggest that ecological and physiological barriers, rather than dispersal limitation might better explain alpine community assembly and that alpine, but not montane, communities form a climatically distinct species pool in the Americas.

Peer review status:IN REVISION

19 Apr 2021Submitted to Ecology and Evolution
20 Apr 2021Assigned to Editor
20 Apr 2021Submission Checks Completed
29 Apr 2021Reviewer(s) Assigned
27 May 2021Review(s) Completed, Editorial Evaluation Pending
02 Jun 2021Editorial Decision: Revise Minor