DOI: 10.5061/dryad.x95x69pdj
title: Morphological, molecular, and biogeographic evidence for specific recognition of Euthamia hirtipes and Euthamia scabra (Asteraceae, Astereae)

description: The number and identity of species in the North American genus Euthamia
 (Asteraceae, Astereae) have varied considerably among taxonomic
 treatments. Euthamia graminifolia (L.) Nutt. is often treated to broadly
 include plants from the northern and eastern United States and Canada,
 including the Atlantic and Gulf Coasts. Broad-leaved, largely glabrous
 plants from New Jersey to the Florida Panhandle have been inconsistently
 treated as E. graminifolia, E. graminifolia var. hirtipes (Fernald) C.E.S.
 Taylor & R.J. Taylor E. hirtipes (Fernald) Sieren , or a hybrid
 between E graminifolia and E. caroliniana (L.) Greene ex Porter &
 Britton . Similarly, plants from the Florida Panhandle to eastern
 Louisiana have been incorporated into either E. graminifolia or E.
 graminifolia var. hirtipes, with only Greene in 1902 recognizing southern
 plants as a distinct species, E. scabra Greene . To determine the identity
 and proper rank of these entities, morphological and phylogenetic analyses
 were performed to evaluate relationships within Euthamia. Plants from the
 Atlantic Coast are most morphologically similar to those from the Gulf
 Coast, which morphologically resemble E. gymnospermoides Greene, a largely
 midwestern prairie species. The Gulf Coast plants and E. gymnospermoides
 share similar DNA sequences while those of the Atlantic Coast plants are a
 more distantly related clade. Neither the Gulf Coast nor the Atlantic
 Coast plants’ ribosomal DNA sequences are highly polymorphic, indicating
 that they are not likely of hybrid origin. Occasional plants found within
 southernmost Alabama and the Florida Panhandle have polymorphic sequences
 and intermediate morphological features however, suggesting that putative
 hybrids exist between the Gulf Coast and Atlantic Coast plants. This study
 concludes that entities deserve species rank as E. scabra Greene for
 scabrous plants occurring in the central Gulf Coast region and E. hirtipes
 (Fernald) Sieren for the largely glabrous plants mostly along the Atlantic
 Coast. Ecological niche modeling indicates that precipitation, especially
 during the summer months, and soils featuring coarse fragments and
 elevated sand content, drive the distribution of these organisms, largely
 restricted to either side of the Apalachicola River that often serves as a
 distributional barrier.
description: Morphological data was collected by evaluating five parts of each
 feature measured (i.e., five leaves to determine leaf width and length for
 one specimen) and averaging the results (or taking the mean for features
 solely with integers, such as floret numbers).
 Molecular data was acquired by Sanger Sequencing two loci - ITS
 (using Hoshi primers) and ETS (using 18S-ETS primers). The
 ".bipartitions" file refers to the RAxML maximum likelihood tree
 with fast bootstrap support values, and the ".nex.con.tre" file
 refers to the MrBayes output with posterior probabilities.
 Coordinate data were extracted from specimens or augmented with
 field collections/documentation.