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Nesom,
G.L. 2010. See articles in Phytoneuron
Nesom, G.L. 2009.
Taxonomy of Forestiera
pubescens and Forestiera neomexicana (Oleaceae). Lundellia 12: 814.
Forestiera neomexicana is relatively constant in diagnostic features of vestiture and
leaf shape across most of its range in the southwestern USA, from California to
New Mexico and into western Texas.
Apparent intermediacy in leaf shape and vestiture with F. pubescens,
however, as well as glabrous forms of F. pubescens, have complicated
identification. The two taxa are
treated here as the eastern F. pubescens var. pubescens and the
western F. pubescens var. parviflora, comb. nov. The ranges of the two taxa are mapped and
variant forms are shown in Texas.
Synonymy and typification are provided.
Nesom, G.L. 2009.
Taxonomic overview of Ligustrum
(Oleaceae) naturalized in the United States. Phytologia 91: 467482.
A
key, morphological descriptions, and basic synonymy are provided for the eight
species of Ligustrum known to be naturalized in North America north of
Mexico: L. japonicum, L. lucidum, L. obtusifolium
(including L. amurense), L. ovalifolium, L. quihuoi, L.
sinense, L. tschonowskii, and L. vulgare. Identifications have been inconsistent
particularly between L. sinense and L. vulgare and between L.
japonicum and L. lucidum.
The occurrence of L. quihuoi outside of cultivation in Arkansas,
Mississippi, and Oklahoma is documented.
Nesom, G.L. 2009.
Taxonomic notes on acaulescent
Oxalis (Oxalidaceae) in the USA. Phytologia 91: 501526.
A
key to species and typification summaries with descriptions, notes on
variation, and geography are presented for 10 acaulescent Oxalis species
occurring in the USA, both native and naturalized: O.
articulata, O. caerulea, O. debilis, O. decaphylla,
O. drummondii, O. intermedia, O. latifolia, O.
metcalfei, O. triangularis, and O. violacea. Oxalis metcalfei (previously identified in the USA mostly as O.
alpina) occurs in Arizona, Colorado, New Mexico, and Texas. Oxalis latifolia occurs in Arizona,
New Mexico, and Texas, at the northern extremity of its range. Oxalis intermedia, native
to the West Indies, has previously been known to be naturalized in the USA in
Florida and is reported here from Louisiana and Texas. Oxalis debilis (including O. corymbosa) occurs across seven
coastal states of the southeastern USA and is reported here for California by a
voucher and for Washington by a sight record.
Nesom, G.L. 2009.
Notes on Oxalis sect. Corniculatae
(Oxalidaceae) in the southwestern United States. Phytologia
91: 527533.
Oxalis
californica, O. pilosa, and O. albicans are distinct species
of the southwestern USA and Mexico.
Geographic summaries are provided and a species key includes these as
well as O. corniculata, O. dillenii, and O. stricta, which
also occur in the area. Oxalis
californica is documented from south-central Arizona by collections from
closely adjacent sites in Pinal and Maricopa counties in the Superstition
Wilderness Area. Outside of its native
range in California, and Arizona, and southwestern New Mexico, O. pilosa
is reported from probable adventive occurrences in Nevada, Utah, and
Oregon. Oxalis albicans is
documented as an adventive in southern California.
Nesom,
G.L. 2009. Again: taxonomy of
yellow-flowered caulescent Oxalis (Oxalidaceae) in eastern North America. J. Bot. Res. Inst. Texas 3: 727738.
The taxonomy of Oxalis sect. Corniculatae is revised for
eastern North America and contrasted with previous classifications and
circumscriptions, particularly those of Eiten and Lourteig. Eight taxa, some previously recognized as
subspecies or varieties, are recognized here at species rank. Oxalis stricta L. and O.
dillenii Jacq. sensu stricto are appropriately identified in the sense that
Eiten used the names. Oxalis florida
Salisb. (= O. dillenii subsp. filipes) is a distinct species
primarily of the Atlantic states and Gulf coast, less common in more inland
regions. Oxalis priceae Small is
a distinct species of the southeastern USA without infraspecific taxa; disjunct
populations occur in northeastern Mexico.
Oxalis texana (Small) Fedde (= Oxalis priceae subsp. texana)
is treated as a distinct species of east Texas and adjacent Louisiana and
Arkansas. Oxalis texana is close
in morphology to O. dillenii sensu stricto and occurs sympatrically with
it but distinct in geography and morphology from O. priceae sensu
stricto. Oxalis illinoensis
Schwegm. is geographically and morphologically distinct from O. grandis
Small. Neotypes are designated for O.
lyonii and O. illinoensis.
Nesom, G.L. and J.O.
Sawyer. 2009. Frangula
betulifolia and F. obovata (Rhamnaceae) are distinct species. Phytologia
91: 300307.
Frangula betulifolia var. obovata occurs in northern Arizona,
Nevada, Utah, and Colorado and is geographically disjunct from var. betulifolia,
which occurs in southern Arizona, New Mexico, Texas, and northern Mexico. The
two taxa are consistently different in leaf shape and texture, and with their
genetic isolation, each is appropriately treated at specific rank. A new
combination is made: Frangula obovata (Kearney & Peebles) Nesom
& Sawyer, comb. et stat. nov.
Nesom, G.L.
2009. Taxonomic overview of Eurybia sect. Herrickia (Asteraceae: Astereae). J. Bot. Res. Inst. Texas 3: 161167.
Herrickia horrida and five closely related species are included here within Eurybia sect. Horrida. These species are E. glauca, E. horrida, E. pulchra, and E. wasatchensis, as previously treated by Nesom, and two other species recently recognized by molecular evidence as close relatives: Eurybia kingii (D.C. Eat.) G.L. Nesom, comb. nov. (including Eurybia kingii var. barnebyana (Welsh & Goodrich) G.L. Nesom, comb. nov.) and Eurybia aberrans (A. Nels.) G.L. Nesom, comb. nov. The first five of these species were treated by Brouillet as a broadened genus Herrickia; the last was segregated as the monotypic genus Triniteurybia Brouillet, Urbatsch & Roberts. Molecular data indicate that Eurybia, Herrickia, and Triniteurybia constitute a 3-taxon grade at the base of the Machaerantherinae clade but morphological distinctions of Herrickia and Triniteurybia from Eurybia are trivial or non-existent and their separation from Eurybia at generic rank is based strictly on cladistic hypotheses. Nomenclatural summaries and geographic distributions are shown for the six species of Eurybia sect. Herrickia.
Nesom, G.L. 2009.
Point of
view: Authors initials in scientific names with multiple authorities. Phytologia 91: 6263.
Insistence on extended forms of author
citations in all situations seems unnecessary, especially where brevity and
easy comprehension are concerns.
Additions of initials in citations of multiple authors load up text with
unnecessary and ponderous details.
Nesom,
G.L. 2008. Ranunculus
ficaria (Ranunculaceae), naturalized in Texas. J. Bot. Res. Inst. Texas 2:
741742.
Ranunculus ficaria is documented
to grow outside of cultivation in Tarrant County, where it is found along creek
banks in Fort Worths Overton Park.
Seeds are sterile and the plants reproduce asexually by bulbils produced
by the roots and in leaf axils.
Nesom, G.L. 2008. Classification of subtribe Conyzinae (Asteraceae: Astereae). Lundellia 11: 838.
Subtribe Conyzinae includes Erigeron, New World Conyza,
the North American genus Aphanostephus, and a small group of South
American species segregated as the genera Apopyros,
Darwiniothamnus, Hysterionica,
Leptostelma, and Neja. Erigeron is the
only genus with species native to regions outside of the New World. About 500
species are included in the subtribe. All North American, Central American, and
South American species of Erigeron are included in the present treatment
and assigned to one of the 35 sections recognized here. Ten new sections of Erigeron
are recognized: sect. Disparipili Nesom, sect. nov., sect. Filifolii (Rydb.) Nesom, comb. et
stat. nov., sect. Gyrifolium Nesom, sect. nov., sect. Lonchophylli Nesom, sect. nov., sect. Meridionales Nesom & N. Andrus, sect. nov., sect Microcephalum Nesom, sect.
nov., sect. Quercifolium Nesom, sect. nov., sect. Radicati (Rydb.) Nesom, comb. et stat. nov., sect. Rhizonexus Nesom, sect.
nov., and sect. Terranea (Colla) Nesom, comb. et stat. nov. Conyza is at least biphyletic; each of
the groups is represented in the treatment but not all of the South American
species are included. Molecular data have made it clear that traditional, North
American species of Erigeron form the basal and terminal clades in the
evolutionary topology of the subtribe, thus Conyza, Aphanostephus, and the other segregate genera have arisen from
within the branches of Erigeron. Erigeron, as currently treated
and tentatively maintained here, is paraphyletic. Broad taxonomic alternatives
that include only monophyletic taxa are (1) to treat the whole subtribe as Erigeron
or (2) to recognize Aphanostephus or Aphanostephus, Conyza,
and the other South American segregates and at least an additional 5 to 10 new
generic-level segregates from species groups traditionally treated as North
American Erigeron.
Nesom,
G.L. 2008. Taxonomic
review of Solidago petiolaris and S. wrightii (Asteraceae:
Astereae). Phytologia 90: 2135.
Solidago
petiolaris is treated to include three morpho-geographic entities.
Plants east of the Mississippi River are var. petiolaris; those west of
the Mississippi are var. angusta and var. wardii. Phyllaries of
var. angusta (in the eastern part of the western range) are glandular;
phyllaries of var. wardii (in the western part are eglandular and finely
strigose. Solidago wrightii is closely similar to S. petiolaris,
especially where their ranges approach each other, and they show parallel
trends of variation in leaf shape and involucral vestiture. Within S.
wrightii, glandular plants apparently are populational variants without
geographic coherence and are treated here as S. wrightii forma adenophora
(Blake) Nesom, comb. et stat. nov. A narrow-leaved race near the
southeastern corner of the range of the species (in Chaves Co. and Eddy Co.,
N.M., and Culberson Co., Tex.) is recognized as S. wrightii var. guadalupensis
Nesom, var. nov.
Lipscomb, B.L. and G.L.
Nesom. 2007. Galium parisiense (Rubiaceae) new for Texas, and notes on its taxonomy. J. Bot.
Res. Inst. Texas 1: 12371300.
Galium
parisiense var. leiocarpum is documented as a first record for
Texas and South Carolina. Other
localities in the eastern U.S.A. are mapped for the glabrous-fruited expression
of G. parisiense (var. leiocarpum), bristly-fruited G.
parisiense (var. parisiense), and the closely related,
glabrous-fruited G. divaricatum.
All taxa are European natives. In both North America and Europe, var. parisiense
and var. leiocarpum have distinct geographic ranges and occur
sympatrically in some areas. Galium
divaricatum occurs sympatrically at least with var. leiocarpum. We suggest that specific rank is appropriate
for each of the three taxa, as G. parisiense L., G. divaricatum Pourret
ex Lam., and G. anglicum Hudson (= G. parisiense var. leiocarpum).
Nesom, G.L. 2007.
Distribution of Gamochaeta (Asteraceae: Gnaphalieae) in
Texas, Oklahoma, Arkansas, and Louisiana. J. Bot. Res. Inst. Texas 1: 11251130.
Distributions
of seven species of Gamochaeta are mapped at county level in Texas,
Oklahoma, Arkansas, and Louisiana: G. antillana, G. argyrinea, G.
calviceps, G. chionesthes, G. coarctata, G. pensylvanica,
and G. purpurea. Gamochaeta
purpurea is the only species known from pre-1900 collections. Gamochaeta coarctata and G.
chionesthes are known only from collections made after 1967; the latter
apparently is spreading rapidly but has not reached Texas and Oklahoma.
Nesom, G.L. 2007. Notes on the
disarticulation of Xylothamia (Asteraceae: Astereae). J. Bot. Res. Inst. Texas 1: 145148.
The primarily Mexican genus Xylothamia was originally described with
nine species, but molecular evidence subsequently indicated that these species
are divided into two separate evolutionary lineages. One of these groups
(four species) was transferred to the Caribbean genus Gundlachia,
while the other (five species) was split into four separate new genera.
An alternative and reasonable taxonomic solution proposed here is to maintain
the group close to Gundlachia as the genus Xylothamia and
treat the remaining five species within a single genus.
Nesom, G.L. and B.L. Turner. 2007.
Taxonomic
review of the Xanthisma spinulosum
complex (Asteraceae: Astereae).
Phytologia 89: 371389.
Xanthisma
incisifolium, X. glaberrimum, X. paradoxum (Turner &
Hartman) Turner & Nesom, comb. et stat. nov., and X. scabrellum (Greene)
Turner & Nesom, comb. nov., do not intergrade with other taxa of the
complex and are treated at specific rank. In regions of sympatry, X.
spinulosum var. spinulosum, var. gooddingii, var. chihuahuanum,
and var. austrotexanum intergrade and are maintained at varietal rank. Xanthisma
spinulosum var. hartmanii Turner & Nesom, var. nov., is
described from northern Coahuila. County-level dot maps document distribution
of the taxa.
Nesom, G.L. 2006.
Taxonomic overview of
the Heterotheca villosa complex
(Asteraceae: Astereae). Sida 22: 376380.
Heterotheca villosa (as treated by Semple 1996, 2006) is a
complex species with nine varieties, most of which are sympatric in various
degrees. Heterotheca villosa var.
nana and H. villosa var. scabra are essentially allopatric
and intergrade little, but each is widely sympatric with H. villosa and
distinct from it. Recognition at
specific rank accurately reflects the status of var. nana and var. scabra,
and they are treated here, respectively, as Heterotheca horrida (Rydb.)
Harms and Heterotheca polothrix Nesom, nom. et stat. nov. Heterotheca stenophylla sensu stricto
is distinct from H. stenophylla var. angustifolia (sensu Semple)
and sympatric with it, and the latter is appropriately treated as H. villosa
var. angustifolia (Rydb.) Harms.
The New Mexico endemic Heterotheca villosa var. sierrablancensis
Semple is raised to specific rank as Heterotheca sierrablancensis (Semple)
Nesom, comb. et stat. nov.
Identifications of vars. villosa, foliosa, ballardii,
and minor (all sensu Semple) require arbitrary judgements because of
their broad sympatry and extensive intergradation. The distinction between var. pedunculata and H. zionensis
is not clear, and both taxa apparently intergrade broadly with more typical
H. villosa. Variety depressa is
maintained at specific rank as H. depressa (Rydb.) Dorn. Maps show the generalized distributions of
the taxa of the H. villosa complex sensu Semple, and a nomenclatural
summary outlines an alternative taxonomy.
Nesom,
G.L. 2006. Taxonomic review of Symphyotrichum patens (Asteraceae:
Astereae). Sida 22: 10751080.
The eastern North American Symphyotrichum patens has been treated
by Jones (1983, 1992) and other botanists to include var. patens, var. patentissimum,
and var. gracile. These taxa
have been distinguished primarily by habit, involucral size and vestiture, and
phyllary orientation. Morphological
distinctions between var. patens and var. gracile have been
viewed as overlapping and the two taxa have been interpreted as sympatric over
a wide region; the present study concludes that it is not possible to distinguish
them in an unarbitrary or evolutionarily meaningful way, and var. gracile is
not recognized. Variety patens sensu
lato apparently comprises two diploid and three or four tetraploid population
systems. Variety patentissimum is
morphologically distinct and consistently tetraploid, and it intergrades with
tetraploid var. patens where their ranges are contiguous or
overlapping. A county-level map shows
the distribution of the two infraspecific taxa of S. patens, as
interpreted in the present study. A similar
map shows ploidal distribution within the species, based on data available from
previous studies.
Nesom, G.L. 2005. Infrageneric
classification of Liatris (Asteraceae: Eupatorieae). Sida 21: 13051321.
A formal classification divides the species of Liatris (blazing
star or gayfeather) into 5 'sections,' two of which are further divided into
'series.' The classification is based on morphological similarities among
the 37 species and hypotheses regarding their evolutionary relationships.
Nesom, G.L. 2005. Broadened concept of Liatris
helleri (Asteraceae: Eupatorieae).
Sida 21: 13231333.
A much-broadened concept is documented
for a species formerly considered to be rare and narrowly endemic to a small
area in the North Carolina mountains. In the amended concept, it occurs more
broadly through North Carolina and also in Virginia and West Virginia (and is
no longer rare).
Nesom, G.L. 2004. New species of Gamochaeta
(Asteraceae: Gnaphalieae) from the eastern United States and comments on
similar species. Sida 21: 717742.
Two new species of Gamochaeta (cudweed) are described from the eastern
USA. One occurs abundantly in at least 19 states, and the other is known from 9
states. Both tend to be weeds of roadsides and other 'weedy' sites, and it is
possible that both species may be native to South America, where they also have
been previously undetected.
Nesom, G.L. 2004. New distribution records
for Gamochaeta (Asteraceae: Gnaphalieae) in the United States. Sida 21: 11751186.
Various state records are reported for species of Gamochaeta
(cudweed). Two of the species are first reported for the USA. For the 12
species of the genus known from the USA, a hypothesis of nativity is given,
with acknowledgement that because the species tend to be extremely weedy, it is
difficult to be certain of their native area.
Nesom, G.L. 2004. Notes on typification in Pluchea
(Asteraceae: Plucheeae). Sida 21:
5964.
In order to clearly establish the identity of various names used for
species of North American Pluchea (camphorweed), a particular
herbarium specimen is associated with each of the names. This is not
something that was consistently done for old names (most pre-1900), but it is
required for new ones.
Nesom, G.L. 2004. Erigeron peregrinus
and Erigeron glacialis (Asteraceae: Astereae). Sida 21: 665672.
A daisy fleabane widespread and common in high elevation habitats of western
North America is treated as a full species (E. glacialis). Since 1943
it has been regarded as a subspecies of E. peregrinus, but even where
the two species come into close contact, reproductive isolation holds them as
two distinct and recognizable entities.
Nesom, G.L. 2004. Pseudognaphalium
canescens (Asteraceae: Gnaphalieae) and putative relatives in western
North America. Sida 21: 781790.
Five species of cudweeds mostly centered in California have been recently
treated (in the Jepson Manual) as subspecies of a single species. Evidence is
presented for regarding each of them as a separate species. Pseudognaphalium
thermale is brought into the genus with a new combination, and
distribution maps and a key are included.
Nesom, G.L. 2004. Generic placement of Chaptalia
hintonii (Asteraceae: Mutisieae).
Sida 21: 929934.
In a 1998 publication, Argentinian botanist Katinas placed the Mexican species Chaptalia
hintonii in the otherwise Old World genus Gerbera. The author
takes issue with her judgement and gives evidence supporting the continued
treatment of C. hintonii within Chaptalia, where its closest
relatives are classified.
Nesom, G.L. 2004. Asteraceae from wool mill sites in South Carolina, including new records for North America. Sida 21: 12151224.
Documentation
is given for 73 taxa of Asteraceae collected in 19571960 from wool mill sites
in Berkeley County and Florence County, South Carolina. Twenty-eight (28) of these taxa are first
reports for the flora of South Carolina; seventeen (17) others represent the
first documentation for earlier reports for the state. Six (6) are first reports for North America:
Chevreulia sarmentosa, Gamochaeta argentina, and Panphalea
heterophylla (native to South America), and Peripleura arida, Stuartina
hamata, and Vittadinia sulcata (native to Australia). Calotis cuneifolia (native to
Australia) is reported for North America for the second time. Fifty-nine (59) of the 73 taxa are not
native to South Carolina; of these, 29 are native to continents other than
North America, while 30 are native to North America but from regions outside of
the state.
Nesom, G.L. 2001. Taxonomic review of Chrysogonum
(Asteraceae: Heliantheae). Sida 19:
811821.
Chrysogonum is a genus of the eastern USA well-known in cultivation
for its low growth and small, golden-yellow sunflowers. The author evaluates
previous taxonomy and finds that the species has three varieties (not just
two), each of which has a separate geography and morphological
appearance.
Nesom, G.L. and J.T.
Kartesz. 2000. Observations on the Ludwigia uruguayensis complex
(Onagraceae) in the United States.
Castanea 65: 123125.
Ludwigia uruguayensis is known
to comprise a decaploid entity (L. hexapetala) and a hexaploid one (L.
grandiflora, including the type of L. uruguayensis), but the two
chromosomal races differ only by quantitative, intergrading morphological
features, a large portion of their genome is hypothesized to be shared, and
they are known to produce hybrids of intermediate morphology in regions of
sympatry. Ludwigia hexapetala is
the more common, but both occur in the southeastern United States. We agree in general with earlier studies
regarding the nature of the distinction between the two entities but suggest
that a more reasonable treatment of them would be as subspecies within a single
species: L. grandiflora subsp. grandiflora and L. grandiflora
subsp. hexapetala, comb. et stat. nov.
Nesom, G.L. 1994.
Taxonomic
overview of Aster sensu lato
(Asteraceae: Astereae), emphasizing the New World species. Phytologia 77: 141297.
Nesom, G.L. 1992.
A new species of Castilleja (Scrophulariaceae) from
south-central Texas with comments on other Texas taxa. Phytologia
72: 209230.
Castilleja genevievana sp. nov. is described from
Crockett, Pecos, Upton, and Val Verde cos., Texas, and one closely adjacent
locality in Coahuila, Mexico. It is
most closely related to C. integra and C. purpurea var. citrina
but is allopatric with both and morphologically distinctive in its entire
leaves, unbranched trichomes, and yellow floral bracts and calyces. Castilleja wootonii (the type from
southeastern New Mexico) is the correct name for the species in Jeff Davis Co.,
Texas, previously known as C. ciliata and assumed to be a narrow
endemic. Castilleja elongata,
which has been recognized primarily from Brewster Co., Texas, and a proposed
but yet unpublished species endemic to Jeff Davis Co. are interpreted as merely
intergrading elements of the widespread and variable C. integra. Castilleja latebracteata (the type
from Texas) is a synonym of Castilleja rigida (the type from Chihuahua),
a species primarily distributed in northern Mexico. Castilleja tortifolia (the type from Texas) is conspecific
with the earlier named C. mexicana, also most abundant in northern Mexico.