Mimulus sookensis (Phrymaceae), a new Allotetraploid Species Derived from Mimulus guttatus and Mimulus nasutus

2012·11.9 MB·English

by  Beverly G Benedict

Madrono, Vol. 59, No. 1, pp. 29-43, 2012
MIMULUS SOOKENSIS (PHRYMACEAE), A NEW ALLOTETRAPLOID SPECIES
DERIVED FROM MIMULUS GUTTATUS AND MIMULUS NASUTUS
Beverly G. Benedict
Connell Herbarium, University of New Brunswick, 10 Bailey Drive, Fredericton, N.B.,
Canada E3B 5A3
Jennifer L. Modliszewski'
Department of Biology, Duke University, Campus Box 90338, Durham, NC 27708
[email protected]
Andrea L. Sweigart
Department of Genetics, University of Georgia, Fred C. Davison Life Sciences Complex,
GA
Athens 30602
NoLAND H. Martin
Department of Biology, Texas State University-San Marcos, 601 University Drive, San
TX
Marcos, 78666
Fred R. Ganders
Department of Botany, University of British Columbia, 3529-6270 University Blvd.
Vancouver B.C., Canada V6T 1Z4
John H. Willis
Department of Biology, Duke University, Campus Box 90338, Durham NC 27708
Abstract
A new species ofmonkeyflower, Mimulussookensis, is described. This species is found throughout
the southernportion ofVancouver Island, theGulfIslands ofBritish Columbia, the San Juan Islands
ofWashington state, the Willamette and Umpqua RiverValleys in Oregon, and has been collected at
one location in Mendocino County, California. Mimulus sookensis is a tetraploid species (/? = 28)
derived from the predominately outcrossing Miumlus guttatus DC. (/? = 14) and the predominately
self-pollinating Miumlus uasutus Greene {u = 14). Mimulus sookensis is similar phenotypically to the
small-flowered M. uasutus, but differs in chromosome number, height, and by a slightly more
narrowedcorollatubethan thatofM. uasutus. It iscommonlyfound onwet hillsides, seeps,cutbanks,
and in roadside ditches, often co-occuring with M. guttatus but infrequently with M. uasutus.
Key Words: Allotetraploid speciation, Miuudus, Miumlus guttatus, Miumlus uasutus, monkeyflower,
new species, Oregon, Vancouver Island.
A small-flowered monkeyflower similar to heterozygous, sinall-flowered monkeyflowers
Mimulus uasutus Greene was first observed on were known to be highly selfing, given their floral
VancouverIsland, Canada, by Fred Ganders, and structure, small flower size, and often cleistoga-
later collected for scientific study in May 1991 by mous nature (Ritland and Ritland 1989; Dole
Beverly Benedict. Although phenotypically simi- 1992; Willis 1993). Morphological analysis of M.
lar to M. uasutus (Fig. 1), allozyme analysis guttatus, and the two small-flowered inonkey-
revealed that some ofthe small-floweredmonkey- flowers (M uasutus and the species described
flowers on Vancouver Island were always hetero- here, M. sookensis) revealed that while M. uasutus
zygous at allozyme markers. This was in contrast and M. sookensis overlapped a great deal in floral
to allozyme data from another small-flowered morphology, subtlemorphological differencesdid
monkeyflower found on the island, M. uasutus exist (Fig. 1,e.g., pistil length,corollatubewidth).
(snouted monkeyflower), and thecommon yellow Because of fixed heterozygosity in some of the
monkeyflower, M. guttatus DC. These results small-flowered Mimulus on Vancouver Island,
were intriguing because while the large-flowered, and slight differences in floral morphology, F.
chasmogamous M. guttatus is known to be Ganders suspected that the heterozygous mon-
highly outcrossing, both M. uasutus and the keyflowers in question were actually a distinct
j taxon of allopolyploid origin (Benedict 1993).
Chromosome squashes conducted at the time
'Author for correspondence revealed that these new monkeyflowers, M.
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Fig. 1. Photographs of M. sookensis and its progenitor species. Side profile photographs are taken on
approximately the same scale. A. M. sookensis, B. M. guttatus, C. M. sookensis, D. M. nasutus.
sookensis, had more than n = \4 chromosomes, species concept, e.g., Mayr 1996) but has
but an exact count was not obtained. contributed significantly to angiosperm evolution
Following the work of B. G. Benedict, flow (Stebbins 1971; Grant 1981; Masterson 1994;
cytometry data from three M. sookensis collec- Otto and Whitton 2000).
tions revealed that the small-flowered monkey- Here, we present evidence that M. sookensis is
flowers from Vancouver Island and surrounding historically taxonomically unrecognized, and
areas, as well as the valleys of western Oregon provide new chromosome data that provide
and northern California, had approximatey twice conclusive evidence that M. sookensis is a
the DNA content ofM. guttatus and M. nasutus, cytologically distinct species, which has previous-
suggesting again that this taxon was oftetraploid ly been shown (Sweigart et al. 2008) to be of
origin (Sweigart et al. 2008). Sequence data from polyploid origin, and reproductively isolated
two nucleargenes confirmed that this new species from its diploid progenitors, as well as a
was a hybrid tetraploid derived from M. guttatus description of this hitherto unnamed species of
and M. nasutus. Furthermore, crossing data monkeyflower.
revealed that the allotetraploids were reproduc-
tively isolated from their diploid progenitors due Review of Previously Published
to failure ofseed development, a result consistent MiMULUS Taxa
with the triploid block that is commonly ob-
served in interploidy crosses (Sweigart et al. Mimulus guttatus is an herbaceous wildflower
2008). Although M. sookensis is a cryptic species distributed throughout much of western North
due to its phenotypic similarity to M. nasutus, the America (Vickery 1978), while Mimulus nasutus
fact that it is reproductively isolated from its has a restricted range relative to M. guttatus
diploid progenitors illustrates the concept of (Kiang and Hamrick 1978; Vickery 1978).
instant or rapid speciation of polyploids, which Mimulus guttatus, M. nasutus, and M. sookensis
has long been recognized (e.g., Winge 1917; all belong to the M. guttatus speciescomplex, and
Dobzhansky 1937; Coyne and Orr 2004). Poly- are part of the Simiolus clade (Beardsley et al.
ploidy not only has the propensity to quickly 2004) of the genus Mimulus. Mimulus guttatus
create new species (according to the biological and its close relatives have been extensively
2012] BENEDICT ET AL.: SHY MONKEYFLOWER A NEW POLYPLOID MIMULUS 31
Table 1. Complete List of Previously Published Mimvlvs Taxa Which Might Have Been a
Description of M. Sookensis, With a Description of How They Are Different From M. sookensis.
Taxa are listed in alphabetical order, although subspecies and varieties are listed in parentheses if variety or
subspecies was given specific raMnk. Forsynonyms examined, three sources were used: the synonyms listed in Grant
(1924) and Pennell (1951) for nasutus, and the synonyms listed for both M. guttatus and M. mtsutus in IPNI.
Many ofthe large flowered varieties of M. guttatus were not included in this list for the purpose ofbrevity. All
references are included in the literature cited. Evidence sources refers to all herbarium specimens, drawings and
descriptions, in both the nomenclatural citation and established floras or monographs, that were used in
determining differences. For each candidate taxa, the characters that most easily illustrate the difference between
the listed taxa and M. sookensis are described for the listed taxa.
Previously
published taxa Synonym (source) Evidence sources Distinguishing characters from M. sookensis
M. arvensis M. guttatus Greene (1887); Diploid {n = 14), easily hybridizes with M. guttatus;
Greene (M. (IPNI) Grant (1924); Greenedescribes the leaves as lyrate, and the species
guttatus DC. Pennell (1951); as perhaps synonymous with M. lyratus Benth.
var. arvensis Mukherjee and Grant describes the variety ashavingan uppercalyx
Grant) Vickery (1962) tooth not markedly longer than others, elongated
internodes, teeth not usually folded over each other
at maturity
M. bakeri M. nasutus CAS 22488 CAS specimen appears to be hybrid between M.
Gandoger (Grant 1924, (isotype), NY guttatus and M. nasutus, while description doesn't
Pennell 1951) 20798 (possible match specimen, description suggests that difference
isotype); between M. nasutusand M. bakeriis the impunctate
Gandoger calyx ofM. bakeri
(1919)
M. cordatus M. nasutus Greene (1910); Corolla lacking in spotting, diploid {n 14) that
Greene (Grant 1924) Pennell (1951); hybridizes easily with M. guttatus
Mukherjee and
Vickery (1962)
M. cuspidatus M. nasutus DS 771002 M. nasutus found in wet shades exhibiting phenotypic
Greene (Grant 1924; (isotype); plasticity in a classic shade avoidance response (see
Pennell 1951) description in text for discussion)
Greene (1910)
M. decorus M. guttatus CAS 22445; Corolla large
(Grant) Suksd. (IPNI) Pennell (1951)
(M. guttatus
DC. var.
decorus Grant)
M. erosus M. nasutus Greene (1910) Corolla exserted from tube, synonym ofM. nasutus
Greene (Grant 1924)
M. g/areosus M. nasutus Greene (1889, Leavestoothed orlobed, slimy, synonym ofM. nasutus
Greene (Grant 1924; 1894)
M Pennell 1951)
guttatus DC. M. guttatus Pennell (1947) Stoloniferous variant ofM. guttatus with more linear
subsp. scouleri (IPNI) leaves (perhaps synonymous with M. tilingii Regel
M(Hook.) Pennell or M. caespitosus Greene)
lial/ii Greene M. guttatus Greene (1885); Leaves parallel-veined and almost entire, calyx highly
(M. guttatus (IPNI) Grant (1924) inflated
DC. var. ha/Hi
Grant)
M. guttatus DC. M. guttatus Pennell (1941); Leaves pinnately lobed at the base, corolla long
var. lyratus (IPNI) Pennell (1951 (2 3 cm)
(Benth.) Pennell
ex M. Peck
M. guttatus var. M. guttatus Gray (1867); Grant (1924) thought to be synonymous with M.
depauperatus (IPNI) Grant (1924); puncticaly.x and M. nu'crophy/lus, based on
Grant (M. Hitchcock and Hitchcock and Cronquist (1987) and Gray, appears
luteus var. Cronquist tobesimplyadescriptionofsmall A/, guttatusorM.
depauperatus (1987) nasutus plants with few or small flowers - a
A. Gray) condition most likely caused by environment
M. guttatus var. M. guttatus Greene (1885); Leaves glaucous, synonymous with AI. gknicescens
gkiucescens (IPNI) Jepson (1925); (Greene)
(Greene) Jeps. Pennell (1951)
{M. glaucescens)
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Table Continued.
1.
Previously
published taxa Synonym (source) Evidence sources Distinguishing characters from M. sookensis
M. guttatus var. M. guttatus CAS 23523 Campbell lumps all synonyms ofM. nasutus and M.
gracilis (A. Gray (IPNI) (isotype for nasutusitselfunderthisvariety. CAS specimenisM.
ex Torr.) M. pardalis): pardalis, corolla described as being twice as long as
Campbell Campbell the calyx, diploid {n = 14)
(1950);
ORE96554
M. guttatus var. M. nasutus Synonym ofM. nasutus
nasutus Jeps. (Pennell 1951)
M. guttatus var. M. guttatus Grant (1924) Listed as perennial, large-flowered
puberulus A. L. (IPNI)
Grant
M. inflatulus M. breviflorus CAS 152750 Calyx equal-toothed, leaves more linear and narrow,
Suksd. (Pennell 1951) (isolectotype); synonym ofM. breviflorus Piper
Pennell (1951)
M. la.xus Pennell M. guttatus CAS 329746 Variant ofM. guttatus, diploid {n = 14)
ex. M. Peck (Mukherjee and (isotype); NY
Vickery 1962) 90734 (isotype);
Mukherjee and
Vickery (1962)
M. marmoratus M. nasutus Greene (1895b) DescriptionofM. marmoratusmatchesthatofahybrid
Greene (Pennell 1951) between M. guttatus and M. nasutus, with large red
blotch on middle lower lobe, with a corolla that is
longer than M. nasutus (>3 cm)
M. micranthus A. M. guttatus, M. DS 74105; NY Narrow-range endemic ofCA; calyx even toothed and
Heller (M. nasutus (IPNI) 90746 (isotype lower teeth not curled upward and inward upon
guttatus var. Heller 7410); maturity, stemweak, lowerleavesdescribedasbeing
micranthus (A. Heller (1912); lyrate and long-petioled, calyx puberulent, diploid
Heller) G. R. Grant (1924); used in multiple genetic studies (see text)
Campb., M. Pennell (1951);
nasutus Greene Munz (1959)
var. micranthus
A. L. Grant)
M. micropJiyUus Greene (1885), Leavessmall, stemsrounded, pistilmuchexsertedfrom
Benth. (M Pennell (1941. calyx, located mostly in the mountains
guttatus var. 1951)
microphyhus
Pennell in M.
Peck)
M. minuscuhis M. nasutus Greene (1910) Perennial, shorter than M. sookensis, leaves ovate,
Greene (Grant 1924) flowers large
M. minutiflorus CAS 961575 Corolla superficially similar in appearance to M.
R. K. Vickery (isotype); sookensis, but lackingridges, and stemswiry; closely
Vickery (1997) related to M. wiensii, n = 32
M. nasutus Greene M. nasutus Howeh (1949) Howell (1949) bases his description ofthis variety on
var. eximius (IPNI) M. nasutus, but does not realize that what he
Green A. L. considersM. nasutusisactuallyahybridbetweenM.
Grant ex J. T. guttatus and M. nasutus, also appears to be
Howell synonymous with M. nasutus var. insignis
M. nasutus M. nasutus Grant (1924); Flowersizeoutsidethe rangeofM. sookensisandlarge
Greene var. (IPNI) and Pennell blotch ofanthocyanin spotting on lower corolla
insignis A. L. (1941) lobe, both suggest that descriptionmatches that ofa
Grant hybrid between M. guttatus and M. nasutus
M. guttatus DC. M. guttatus JEPS 2938 (the Large flowered, hybrid between M. guttatus and M.
var. insignis (IPNI) very type!) nasutus
Greene
M. parishii Gand. M. nasutus Gandoger (1919) Leaves deeply cut or laciniate; only a single specimen
(Grant 1924; was examined in the naming
Pennell 1951)
M. puheruhis Greene (1910) Corolla large (>3 cm), stem round and viscidly
Greene puberulent
M. puberulus M. nasutus Gandoger (1919) Only distinguishing feature from typical M. nasutus is
Gand. (Grant 1924; that it is minutely pubescent; only a single specimen
Pennell 1951) was examined, a synonym ofM. nasutus
)
2012] BENEDICT ET AL.: SHY MONKEYFLOWER A NEW POLYPLOID MIMULUS 33
Table Continued.
\.
Previously
published taxa Synonym (source) Evidence sources Distinguishing characters from M. sookensis
M. pwicticalyx M. nasutus ORE96654 Leaves tiny upper tooth hardly more prominent than
Gand. (Pennell 1951) (isotype); others; only a single specimen was examined in the
ORE96655; naming
Gandoger
(1919)
M. suhreniformis M. nasutus UC 27111 Appears to be a diminuitive variant ofM. nasutus, but
Greene (Grant 1924; (holotype); without anthocyanin spotting on corolla
Pennell 1951) Greene (1895a
M. washingtonensis CAS 152669 Calyx equal-toothed, flowers large
Gand. (isotype);
Gandoger
(1919)
collected and examined throughout western available), and drawings and descriptions in
North America, by both early botanists and other references to determine if a previously
contemporary botanists and geneticists. Histori- published name could be applied to M. sookensis
cally, M. guttatiis and its close relatives have been (Table 1). We did not find a previously published
subject to extraordinarily divergent taxonomic taxon that satisfied every aspect ofthe morphol-
treatments by different authors. Pennell (1951) ogy and cytology ofM. sookensis (Table 1), and
recognized 28 taxa closely alHed with M. guttatus thus, despite the abundance of synonyms within
from the Pacific Northwest, and in a recent the M. guttatus species complex, no previously
treatment ofCalifornia, Thompson (1993) recog- published names can be applied to M. sookensis.
nized only five. In contemporary times, the genus Throughout the course of our examination
Mimulus has seen a proliferation of scientific of M. sookensis candidates, we found that the
interest: a Google Scholar search for articles reasons why candidate taxa were not representa-
published between 1980-2011 including the word tive of M. sookensis fell into one or more
Mimulus in the title found 436 articles, with 194 categories. First, pronounced differences in habit,
written on M. guttatus alone. Although many of leaf, and even floral morphology existed (e.g.,
these recent publications do not necessarily perenniality, lyrate leaves, even-toothed calyx).
include field work, it is safe to assert that more Second, in some cases the species described was
has been learned of the genetics, ecology, likely either a hybrid between M. guttatus and M.
distribution, and taxonomic status ofM. guttatus nasutus, or M. nasutus. In the field, M. guttatus
and its close relatives, since the publications of and M. nasutusare known to hybridizewhen they
Grant (1924), Pennell (1951) and even Thompson co-occur (Kiang 1973; Martin and WiUis 2007).
(1993), see Wu et al. (2008). By combining Hybrids between M. guttatus and M. nasutus
knowledge from contemporary studies with have flowers that aremuch more similar in size to
historical taxonomic wisdom, we found that M. M. guttatus, due to dominance ofthe M. guttatus
sookensis is truly a previously overlooked species floral genes (Fishman et al. 2002). In the field, a
in this intensely studied group, in part due to its prominent red blotch has often been observed on
cryptic nature. the lower middle corolla lobe ofboth M. nasutus
To determine if M. sookensis was previously (e.g., Pennell 1951; Kiang 1973) and some
taxonomically recognized, we first identified monkeyflowers with larger flowers than those of
synonyms ofM. guttatus (only the small-flowered typical M. nasutus, but bearing resemblance to
or obscure taxa) and M. nasutus, from those M. nasutus in shoot architecture and leaf
hsted in Pennell (1951), Grant (1924), and morphology. This prominent red blotch has not
Campbell (1950), and from lists of synonyms been observed on M. sookensis flowers. The fact
derived from IPNI (International Plant Names that the species described often had both larger
Index). We also searched in Pennell (1951) and flowers and a large red blotch suggests that they
Grant (1924) for descriptions of small, yellow- are either M. nasutus or hybrids between M.
flower Mimulus that were not listed as synonyms guttatus and M. nasutus. Third, there were some
ofM. guttatusor M. nasutus, but were considered cases in which floral morphology differences were
to be closely related to the Simiolus clade subtle, but differences in chromosome number
(candidate taxa. Table 1). For these 31 candidate existed, based on crossing studies and chromo-
taxa, in which the author might have potentially some counts of Vickery (Campbell 1950; Mu-
described M. sookensis, we referred to herbarium kherjee and Vickery 1962). In the special case
specimens, the original species descriptions, of Mimulus micranthus A. Heller, it is defined in
crossing data and chromosome counts (when part by its endemism (Munz 1959). Mimulus
MADRONO
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Table 2. Listof Collections Usedin Meiotic Chromosome Countsandinthe Previously Published
FlowCytometryAnalysesPresentedin Sweigartetal. (2008). Abbreviations: MCC, meioticchromosome
count; FC, flow cyometry.
Collection Taxon Locale Longitude Latitude Analyses
DRN (DEX) M. sookensis Dexter's Reservoir, OR, USA -122.756 43.917 FC
LSN M. sookensis Lowell, OR, USA -122.784 43.930 MCC, FC
NHI M. sookensis Nanoose Hill, VI, BC, CAN -124.160 49.273 MCC
ROG M. sookensis ca. 12 mi SE ofMarial, (as the -123.644 42.657 MCC, FC
crow flies) OR, USA
TRT M. nasutus near Troutdale, OR, USA -122.368 45.520 MCC
micranthus is a diploid that has been used in was transferred to 70% ethanol after 24 hr and
multiple genetic analyses, and has been success- stored at —20°C until ready for use. Flower buds
fully crossed with other known diploids (Fenster were then partially dissected in a 70% ethanol
and Ritland 1992, 1994; Ritland et al. 1993; solution. The partially-dissected floral material
Fenster et al. 1995). Last, we believe that the was then transferred to a half-strength aceto-
species described in some cases were possibly carmine solution, where all non-anther material
representative of phenotypic plasticity, the most was removed. Anthers were then transferred to a
noteable being M. cuspidatus Greene, found drop of aceto-carmine on a sHde, and were
growing in shaded spots, with elongated inter- eviscerated to release the pollen mother cells
nodes, and lack of anthocyanin spotting. In from the anthers. After thorough evisceration,
Impatiens capensis Meerb., this phenotype is the tissuewas removed from the solution, and the
known to be an adaptive plastic response slide was placed on a warming plate to facilitate
(Schmitt et al. 1995; Dixon et al. 2001) that is staining. A drop of Hoyer's solution (Anderson
characteristic of the classic shade avoidance 1954) was then added and the chromosomes were
syndrome (Smith 1982; Smith and Whitelam squashed by placing a coverslip over the solution
1997). While it is not possible to directly test for and pressing down. Stained cells were examined
plasticity in previously collected specimens, it with brightfield microscopy at 630-1000X mag-
seems highlyplausible that many ofthe candidate nification using a Zeiss Axioplan 2 microscope,
taxa that we examined are representative ofeither and photographed at lOOOx with a mounted
phenotypic variation or plasticity in M. nasutus Axiovision HR camera.
or M. guttatus. Grant (1924) noted that M. Meiotic chromosome counts revealed 28 dis-
nasutusappeared to be quite a plastic species, and tinct chromosome pairs in M. sookensis and 14
thus the taxa's earlier designations (e.g.. Grant distinct chromosome pairs in diploid M. nasutus
1924; Pennell 1951) as synonyms are appropriate. (Fig. 2). Although the sister chromatids are not
Additionally, Kiang (1973) demonstrated that easily distinguishable, it is clear from the
Mimulus nasutus is an exceptionally plastic chromosome squashes that there are twice as
species, as the flower size is dependent upon both many of the chromosomes in M. sookensis as
external environmental conditions, and the posi- there are in diploid M. nasutus. Thischromosome
tion of the flower along the stem. It is also well count constitutes the first published count for M.
known that M. guttatus harbors a great deal of sookensis. Using these chromosome numbers as a
Wu
phenotypic variation (reviewed in et al. calibration, we were able to confirm that the
2008). specimens used in the flow cytometry analysis of
Sweigart et al (2008, Table 2) were indeed
Cytological Analysis allotetraploid.
Meiotic counts ofchromosomes were conduct-
Taxonomic Treatment
ed to corroborate the previous indications of
polyploidy as evidenced by flow cytometry Mimulus sookensis B. G. Benedict, J. L. Modlis-
(Table 2), crossing barriers, (Sweigart et al. zewski, A. L. Sweigart, N. H. Martin, F. R.
2a0n0d8),seaqnudencfeidxednuhcelteearrozylogcoisit(yBenaetdiacltloz1y9m9e3s; CGaAnNdeArDs,A,andBriJt.isHh.CWoillulimsb,ias,p.onnova. s—oTutYhPweEs:t
Sweigart et al. 2008). Three individuals, each facing, open, wet hillside in Sooke Potholes
sffoorrookmtehnesdiicfsfhe(rrToeanmbtolescoo2lm,leeLcSctoiNuo,nnstNs.HcoIAn,sisRdiOengrGlee)ddwitpoelroebiedusMMe..d P7Bre5onvemidni,ccita4l288P2aV4r2'k0N7b9e71s62i3d^(eh4o3tl'hoetyWSp,oeo:k1UeBCMRi)av.yer,1e9l9e1v,.
nasutus individual (TRT) was also counted, for
the purpose of comparing chromosome sizes. Herba annua obligata, a Mimulusguttatus DC.
Immature flowerbudswerecollected in a 3:1 95% Pistillo 5-13 mm longo, corolla 6-20 mm longa
ethanohglacial acetic acid solution. The tissue et pistillo calycem aequante vel paulo longiore
2012] BENEDICT ET AL.: SHY MONKEYFLOWER-A NEW POLYPLOID MIMULUS 35
B
D
f
Fig. 2. Meioticchromosomecountsin Mimulus. A. M. sookensis(LSN),with28 bivalentsasseeninprophaseI of
meiosis. B. M. sookensis(NHI), shownwithtwo daughtercellsatlatetelophaseI. Uppercell has28distinguishable
univalents, while the lower cell has ca. 28 univalents. C. M. nasutus (TRT), with 14 bivalents at prophase I of
meiosis. D. M. sookensis (ROG) as seen at late telophase I of meiosis,with two daughter cells each possessing
28 univalents.
differ; a foliis non bullatu, et caulus non alatis long, green-white to red-white; glabrous. Stems
differ; planta tetraploidea. tending to quadrangular but not winged, <2 mm
Annual or winter annual herb, bearing oppo- wide. Inflorescence few flowered to racemose,
site pedicillate basal leaves graduating into sessile terminal, with 1 primary raceme, occasional
cauline leaves, 5-25 cm high, glabrous to secondary racemes arising from leafaxils, flowers
mm
minutely pubescent. Roots fibrous. Leaves with opposite in leafaxils. Pedicel 3-22 long, red,
mm
leafblade palmately veined, regularly denticulate, glabrous. Calyx 5 13 long, central adaxial
widely ovate, apex obtuse to acute, 0.5-3 X 0.5- calyx lobe longer than other four, green, often
2.5 cm becoming gradually reduced up the stem; with anthocyanic spotting, white hairs on margin,
leaf blade above adaxially green, frequently with somewhat inflated upon maturity. Corolla bila-
anthocyanic spotting, glabrous to minutely pu- biate or sometimes cleistogamous, 5 22 X 2-
bescent, veins often purplish red near leafbase; 13 mm, yellow, corolla lobes subequal, palate
leaf surface below abaxially silver-green to densely hairy, red spotted, extending into tubes
purple, glabrous, veins green. Petiole 0-2 cm as two ridges, tube narrowly funnel shaped.
MADRONO
36 [Vol. 59
4-13 mm long. Stamens didynamous, upper VWictoria, 4 March 1912, Henry s.n. (UBC 80455);
stamens shorter, long stamens 4-12 mm. Pistil slope ofMount Maxwell, Saltspring Island, 15
5-13 mm; style white, minutely pubescent; stigma May 1963, Young 159 (UBC 221634); Vancouver
yellow, usually slightlyexserted fromcalyx; ovary Island, 5 km N ofCowichan Lake, 19 May 1990,
2-5 mm, green; stipe 0-1 mm; stigma lobes may Benedict 4 (UBC 207937); Vancouver Island,
be thigmotropic. Capsule dehiscing by longitudi- Nanoose Hill, N of Nanaimo, 1 May 1990,
nal sUts with persistent style, crowned by a Benedict 1 (UBC 207934); Vancouver Island,
persistent calyx; lower calyx lobes curved up- Finlayson Arm Road, near Goldstream Provin-
wards toward upper calyx lobe upon maturity. cial Park, 17 May 1990, Benedict 2 (UBC
Seeds up to 300 per capsule, oval, brown, 0.5 X 207910); Vancouver Island, south slope of
0.2 mm. Chromosome number tetraploid, n = 28. Observatory Hill, Saanich Peninsula,1 May
Found on wet, sunny, hillsides, cutbanks, and 1991, Benedict 27 (UBC 207935). USA. ORE-
ditches on Vancouver Island and the Gulf WGON. Josephine Co.: above Rogue River 0.7 km
Islands, British Columbia, on the San Juan ofentrance to Indian Mary Park, 3 May 1993,
Islands of Washington state, in the Willamette Strayley 7506 (UBC 208478); N of Grant's Pass
and Umqua River Valleys in Oregon, and also in near South Hill summit, 13 Apr 1991, Benedict23
one known site in Dos Rios, Mendocino Co., (UBC 208138). Lane Co.: S facing road cut on N
California, from sea level to 600 m. Flowers from side of Dorena Lake, 6 Apr 1991, Benedict 11
late March to May. (UBC 207932); Douglas Co.: Umpqua River
The species is named after Sooke Potholes Valley, 6 Apr 1991, Benedict 26 (UBC 207995);
Provincial Park on Vancouver Island where it Umpqua Valley, Roseburg Quadrangle, July
was found to grow abundantly and where the 1914 Cusick 4178a, (UBC 149306); Umpqua
type specimen was collected. The common name River, 21 mi below Umpqua, 20 May 1954,
shy monkeyflower is suggested, because this Steward 6641, (UBC 197132). WASHINGTON.
monkeyflower disguises itself as M. nasutus, and San Juan Co.: rock outcropping on Orcas IsL, 13
the flowers are small, in contrast to the 'gay' and Apr 1975, Gates 4, (UBC 263239).
gregarious flowers ofM. guttatus (Vickery 1952). Gabriola Island, 21 May 1951, Raymer s.n.
(UBC 5603135).
Additional M. sookensis Specimens Examined
Features Distinguishing M. sookensis and
CANADA. B.C.: Lasqueti Island, Trematon M. nasutus
Mountain, 19 May 1985, Ceska 19167 (V
144698); N. Pender Island, Oak Bluffs, 4 Apr Minmlus sookensis is exceedingly similar in
1983, Ceska and Olgilve 14245 (V 133335); floral morphology to M. nasutus (Fig. 1). All
Saltspring Island, 5 1/2 km SW of Ganges, Lot characters overlap to a degree with M. nasutus,
34, 18 April 1976, Douglas 9716 (V 136977); but under favorable growth conditions, the
Saltspring Island, clearing at the end of Isabella following structures tend to be more reduced
Road,18 May 1980, Benedict 3 (UBC 207936); in M. sookensis (M. nasutus measurements are
Mayne Island, Heck Hill, open bluff, 13 March presentedhereinparentheses): smtmemwidth <1 mm
1980, Janszen 1532 (V 107521) and 6 Apr 1979, (<4 mm), calyx length 5-13 (6-16.5 mm),
Janszen 978 (V 98035); Galiano Island, 12 May leaves 0.5 3 x 0.5-2.5 mm (0.5-10 X 0.5-
1975, Wood 13 (V 97333); Galiano Island, west- 7.5 mm), hmeimght 3-25 cm (5-50 cm), pedimceml
facing slope overlooking ocean, Bluffs Park, 19 length 3-22 (4-26 mm), stipe length 0-1
May 1993, Benedict 35 (UBC 207931); Gabriola (0.5-2 mm). Minmlus sookensis tends to have a
Island, 21 May 1951, Raymer 5603135 (UBC longerpistil relative to its calyx and the differemncme
70999); Vancouver Island, Gonzales Hill near in calyx and pistil lengths range from 2.5-3.5
Victoria, April 1916, Newcomhe s.n. (V 42590); (0-6 mm). The ratio of the width of the flower
Vancouver Island, Alberta Head, Newcomhe s.n. to the base in M. nasutus is usually >2 (<2).
(V 42592); Denman Island, wet cliffs facing Miniulus nasutus often tends to have a more
Hornby Island, 7 Jul 1952, Brink s.n. (UBC sharply angled and winged stem and the leaves
68843); Vancouver Island, Durrance Lake drain- are often bullate, while M. sookensis tends to
age on rock outcrop, 9 May 1963, Young 63 have anthocyanic red spotting on the calyx more
(UBC 108599); Vancouver Island, Ucluelet, frequently than M. nasutus.
rocky ledges, 23 May 1975, Rose 75-284 (UBC
177970); Vancouver Island, Anderson Hill in Relationships and Distribution
Victoria, 17 May 1950, Krajina andSpilsburv s.n.
(UBCW55012); Vancouver Island, Mount Wells, The genus Minmlus contains well over 100
8 mi ofVictoria on moist rocky cliffs, 12 May species ofmonkeyflowers, and within the Simiolus
1975, Cakkr and Taylor 20776 (UBC 80960); clade, there are approximately 16-24 species, in-
Vancouver Island, Esquimalt, 17 Apr 1917, cluding M. guttatus, M. nasutus, and M. sookensis
Darling s.n. (UBC 45840); Vancouver Island, (Grant 1924; Pennell 1951). Comparable to the
2012] BENEDICT ET AL.: SHY MONKEYFLOWER A NEW POLYPLOID MIMULUS 37
rest of the genus, M. guttatus and its close allies laciniatus, M. platycalyx, M. glaucescens, M.
are an exceedingly phenotypically and ecological- cupriphilus, and M. nudatus as members of the
lydiverse group, makingthe M. guttatuscomplex M. guttatus complex at the rank of species. We
and its close relatives an attractive system for suggest theadditionofM. sookensistothisspecies
ecological and evolutionary studies (Wu et al. complex.
2008). Consequently, defining species relation- Based on present observations, it appears that
ships in this group of closely related monkey- M. sookensis is characterized by a disjunct
flowers is challenging. As defined by Vickery distribution. In the northern portion ofits range,
(1978), the M. guttatus species complex is M. sookensis is found throughout the southern
comprised ofthe common yellow monkeyflower, end of Vancouver Island, British Columbia, in
M. guttatus, anditsclose relatives, M. nasutus, M. the Gulf Islands of British Columbia, including
laciniatusA. Gray, M. platycalyx Pennell, and M. but not limited to Saltspring, Mayne, Galiano,
glaucescens Greene. Pennell (1951) included a Denman, Lasqueti, and Pender Island, and also
number of other taxa in the complex, including on the San Juan Islands of Washington (Fig. 3).
M. nudatus Curran, a linear-leaved serpentine In the southern portion ofits range, M. sookensis
endemic, and M. pardalis Pennell, a distinct form is found in the Willamette and Umpqua River
of monkeyflower with a prominently purple- Valleys of Oregon, and also in northern Califor-
spotted calyx, thought to be closely related to nia. In Oregon and California, collections are
M. nasutus (Pennell 1947). A copper mine known from as far north as Mehama, in Marion
endemic, M. cupriphilus McNair, was later Co., Oregon, and as far south as Dos Rios, in
included in the complex (McNair 1989). Wu et Mendocino Co., California (Fig. 3). It is con-
al. (2008) recognize M. guttatus, M. nasutus, M. ceivable that many more undiscovered M.
V.'
1^
MADRONO
38 [Vol. 59
—
34NJ
12,8W , 12,6W , 12,4W , 12,2W , 120W 11,8W , 11,6W
Fig. 4. Approximate location of M. misutiis, M. guttatus, and M. sookensis throughout western Washington,
western Oregon, and California. U.S. countieswhere M. sookensis but not M. nasutushas been observed are filled
in black, countieswhere M. nasutusbut not M. sookensishas been observedarefilled in grey, whilecountieswhere
both species have been observed have diagonal hatching. Counties where M. guttatus has been observed in
Washington are indicated with vertical hatching.
sookensis localities exist throughout the northern sites in Washington, neither M. nasutus nor M.
and southern portion of its range. sookensis has been observed (Fig. 4). This pattern
To illustrate the extent of field observations, suggests that both M. nasutus and M. sookensis
which suggest anabsenceorrarityofM. sookensis may be rare in Washington state, or at the very
throughout much ofCalifornia, we have recorded least, that M. guttatus and M. nasutus do not
the locations ofM. nasutuscollected in California commonly co-occur in this region, to our knowl-
(Fig. 4) that were used in either crossing, genetic, edge. If the rarity of co-occurrence of the two
or flow cytometry analyses (see Table 3 and progenitor taxa in Washington state is a real
references therein). IfM. sookensisexistedfurther phenomenon and not an artifact ofsampHng, the
south of Dos Rios, it is likely that it would have limited opportunities for hybridization between
been mistakenly collected as M. nasutus, and M. guttatus and M. nasutus in this region may in
subsequent analyses would have revealed its part explain the fact that M. sookensis is even
tetraploid nature. In mainland Washington state, more rare than M. nasutus in this region, and
no M. sookensis have been observed to date. perhaps does not occur at all.
Kiang and Hamrick (1978) were unable to find We cannot exclude the possibility that isolated
any M. nasutus in the Cascades of northern or ephemeral allotetraploids derived from M.
California, Oregon, and Washington. Additional guttatus and M. nasutus are found elsewhere
evidence, based on recent collections in Washing- where M. guttatus and M. nasutus co-occur and
ton state, suggests M. nasutus is rare in Washing- may potentially hybridize. However, determining
ton, unlike M. guttatus (D. Lowry, Univ. of the exact range limits of M. sookensis is beyond
Texas-Austin, and C. Wu, Univ. of Richmond, the scope of this paper, and we present here
personal communication). At many M. guttatus simply what is known at this time regarding the