{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T04:08:46Z","timestamp":1785384526087,"version":"3.55.0"},"reference-count":62,"publisher":"Wiley","issue":"8","license":[{"start":{"date-parts":[[2025,8,10]],"date-time":"2025-08-10T00:00:00Z","timestamp":1754784000000},"content-version":"vor","delay-in-days":9,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":["bsapubs.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["American J of Botany"],"published-print":{"date-parts":[[2025,8]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:sec><jats:title>Premise<\/jats:title><jats:p>The rate of carbon assimilation in leaves (<jats:italic>A<\/jats:italic>) is a key trait central to a plant's economic strategy that has downstream impacts on the regional and global cycling of carbon and other nutrients. Most previous paleoecological studies estimate <jats:italic>A<\/jats:italic> from nearest living relatives or leaf vein density.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>We present a method for reconstructing <jats:italic>A<\/jats:italic> using gas\u2010exchange modeling that requires both measured (stomatal size and density, leaf \u03b4<jats:sup>13<\/jats:sup>C) and inferred (e.g., atmospheric CO<jats:sub>2<\/jats:sub> concentration) inputs. We apply this method to ten extant taxa and nine fossil taxa representing common angiosperms of the exquisitely preserved mid\u2010Miocene (~15.9\u2009Ma) flora at Clarkia in northern Idaho, USA.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>Application to extant taxa produces estimates of <jats:italic>A<\/jats:italic> that are near measured values on the same leaves (R<jats:sup>2<\/jats:sup>\u2009=\u20090.89 across all taxa). Median reconstructed <jats:italic>A<\/jats:italic> for fossil taxa range from 9.5\u201321.7 \u00b5mol m<jats:sup>\u20132<\/jats:sup> s<jats:sup>\u20131<\/jats:sup> with 95% confidence intervals ~+51%\/\u201338% indicating that most species are statistically indistinguishable. Sensitivity tests show that our method is most reliable when CO<jats:sub>2<\/jats:sub> is well\u2010constrained, but when that is impractical, taxa within single sampling horizons (with a presumed fixed CO<jats:sub>2<\/jats:sub> concentration) can be organized by <jats:italic>A<\/jats:italic> into a relative rank order with tighter confidence intervals (~+16%\/\u201314%).<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions<\/jats:title><jats:p>Following this relative approach at Clarkia, we reconstruct high <jats:italic>A<\/jats:italic> for taxa whose modern relatives are characterized by rapid growth and\/or riparian habitats (<jats:italic>Castanea<\/jats:italic> and <jats:italic>Platanus<\/jats:italic>) and corroborate previous interpretations on the ecology of taxa whose modern relatives are less known (<jats:italic>Quercus simulata<\/jats:italic>).<\/jats:p><\/jats:sec>","DOI":"10.1002\/ajb2.70082","type":"journal-article","created":{"date-parts":[[2025,8,11]],"date-time":"2025-08-11T05:45:05Z","timestamp":1754891105000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Estimating carbon assimilation rates from fossil leaves and application to the mid\u2010Miocene Clarkia forest"],"prefix":"10.1002","volume":"112","author":[{"ORCID":"https:\/\/orcid.org\/0009-0006-2725-4539","authenticated-orcid":false,"given":"Melanie R.","family":"Cham","sequence":"first","affiliation":[{"name":"Department of Earth and Environmental Sciences Wesleyan University Middletown 06459 Connecticut USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2514-1008","authenticated-orcid":false,"given":"Alexander J.","family":"Lowe","sequence":"additional","affiliation":[{"name":"Department of Biology University of Washington Seattle 98195 Washington USA"},{"name":"Burke Museum of Natural History and Culture University of Washington Seattle 98195 Washington USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0976-953X","authenticated-orcid":false,"given":"Dana L.","family":"Royer","sequence":"additional","affiliation":[{"name":"Department of Earth and Environmental Sciences Wesleyan University Middletown 06459 Connecticut USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sophia M.","family":"Ronan","sequence":"additional","affiliation":[{"name":"Department of Biology University of North Carolina Greensboro Greensboro 27412 North Carolina USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"William C.","family":"Rember","sequence":"additional","affiliation":[{"name":"Independent researcher Fernwood 83830 Idaho USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0612-0305","authenticated-orcid":false,"given":"Caroline A. 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