Pollen Presentation Theory Collaboration


Participants: James D. Thomson, The University at Stony Brook (ecologist)
W. S. Armbruster, University of Alaska Fairbanks (ecologist)
Paul Wilson, California State University, Northridge (ecologist)
Andrea D. Wolfe, Ohio State University (systematist)

Funded by NSF DEB-9708332: "Collaborative research. Floral function and phylogeny in Penstemon: Tests of pollen presentation theory." (1997-2001)


Contents

Introduction

Taxon Sampling

Subg. Penstemon
Subg. Habroanthus
Subg. Saccanthera
Subg. Dasanthera
Subg. Cryptostemon
Subg. Dissecti

Focal Species

Morphometrics


Introduction: Recent advances in understanding the functions of flowers as donors and recipients of pollen have stimulated models of how variation in pollen presentation should affect the reproductive success of plants. For example, if pollinators are frequent, plants that place small, restricted doses of pollen on individual pollinators will be expected to sire more seeds than those that place all or most of their pollen on the first visitor. If pollinator visits are rare, plants that make pollen freely accessible will be more successful. Pollen presentation theory (PPT) focuses attention on ways that plants control pollen transfer, through structural features (e.g., the extent to which anthers open or stay closed), developmental features (e.g., anthers that open gradually or asynchronously), and physiological features (e.g., the amount and scheduling of nectar secretion). Such features are predicted to change adaptively with shifts in pollination mode and ecology. The principal objective is to test these prediction in the very large and diverse plant genus Penstemon, which shows great variation in anther morphology and pollination mechanism, as well as numerous apparent shifts in pollination mode (e.g., at least four independent shifts from bee to bird pollination).

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Taxon sampling: Penstemon is a North American endemic genus of about 275 species. In order to adequately test PPT, we are reconstructing the phylogeny of the genus using as many species as possible. To date, we have extracted DNAs (D) for 95 species and have leaf (L) or seed (S) material from ca 30 additional species. Leaf and/or seed material have been contributed by Andrea D. Wolfe, Shannon Datwyler, James Thomson, Paul Wilson, Paul Wolf, Amy McMullen, Dale Lindgren, Tom Ranker, Frank Stermitz, Jennifer Walker, Susan Meyer, Richard Clinebell II, Wayne Elisens, Scott Armbruster, Dan Crawford, Linnea Hanson, The Berry Botanical Garden, and the American Penstemon Society. The following table illustrates the taxon sampling as of July 10, 1998. The table is divided into subgenera, sections, and subsections with the number of species for each category in parentheses; organization is in descending order by number of taxa per category. Taxonomy follows that published by the American Penstemon Society (Bennett et al. 1987 -- see Penstemon Website for Bibliography)

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Subgenus Penstemon

Subg. Penstemon is characterized by anthers that dehisce across the connective and are divaricate or explanate at maturity. There are two exceptions to this: P. baccharifolius and P. multiflorus both have saccate anther morphologies. Groups with typical hummingbird floral morphology (red, tubular corollas) are: subsections Centranthifolii, Havardiani, Fasciculi, Campanulati, and sect. Baccharifolii

Subg. Penstemon (185 spp.)Sect. Penstemon (61 spp.)Subsect. Penstemon (18 spp.)SpeciesMaterial
P. calycosusS
P. canescensS
P. digitalisD, L, S
P. gracilisD,S
P. hirsutusD, L, S
P. laevigatusD, L, S
P. laxiflorusD, L
P. oklahomensisD, L
P. pallidusD, L, S
P. smalliiD, L
Subg. Penstemon (185 spp.)Sect. Penstemon (61 spp.)Subsect. Proceri (17 spp.)SpeciesMaterial
P. attenuatus var. attenuatusD, L, S
P. attenuatus var. militarisD, L
P. attenuatus var. palustrisD, L
P. confertusD, L, S
P. euglaucusD, L
P. globosusD, L
P. heterodoxusD, L
P. peckiiD, L, S
P. procerus var. procerusD, L, S
P. procerus var. brachyanthusD, L
P. procerus var. formosusD, L
P. rydbergii var. rydbergiiD, L, S
P. rydbergii var. oreocharisD, L
P. spatulatusD, L
Subg. Penstemon (185 spp.)Sect. Penstemon (61 spp.)Subsect. Humiles (17 spp.)SpeciesMaterial
P. albertinusD, L, S
P. anguineusD, L
P. aridusS
P. humilisD, L
P. ovatusD, L, S
P. pruinosusS
P. rattaniiD, L, S
P. subserratusD, L, S
P. virensD, L, S
P. whippleanusD, L
P. wilcoxiiD, L, S
Subg. Penstemon (185 spp.)Sect. Penstemon (61 spp.)Subsect. Deusti (3 spp.)SpeciesMaterial
P. deustus var. deustusD, L. S
P. deustus var. variabilisD, L
Subg. Penstemon (185 spp.)Sect. Penstemon (61 spp.)Subsect. Gairdneriani (2 spp.)SpeciesMaterial
P. gairdneri var. oreganusD, L
Subg. Penstemon (185 spp.)Sect. Penstemon (61 spp.)Subsect. Arenarii (2 spp.)SpeciesMaterial
P. albomarginatusD, L
Subg. Penstemon (185 spp.)Sect. Penstemon (61 spp.)Subsect. Harbouriani (1 spp.)SpeciesMaterial
still needstill need
Subg. Penstemon (185 spp.)Sect. Penstemon (61 spp.)Subsect. Multiflori (1 spp.)SpeciesMaterial
P. multiflorusD, S
Subg. Penstemon (185 spp.)Sect. Penstemon (61 spp.)Subsect. Tubaeflori (1 spp.)SpeciesMaterial
P. tubaeflorusS
Subg. Penstemon (185 spp.)Sect. Peltanthera (29 spp.)Subsect. Spectabiles (15 spp.)SpeciesMaterial
P. clevelandii var. clevelandiiD, L, S
P. clevelandii var. connatusD, L, S
P. cluteiD, L, S
P. floridusS
P. grinnellii var. grinnelliiD, L, S
P. grinnellii var. scrophularioidesD, L, S
P. incertusD
P. palmeriD, L, S
P. pseudospectabilisD, S
P. spectabilisD, L, S
Subg. Penstemon (185 spp.)Sect. Peltanthera (29 spp.)Subsect. Centranthifolii (10 spp.)SpeciesMaterial
P. centranthifoliusD, L, S
P. confususD
P. parryiD, S
P. superbusD, S
P. utahensisD
P. wrightiiS
Subg. Penstemon (185 spp.)Sect. Peltanthera (29 spp.)Subsect. Havardiani (3 spp.)SpeciesMaterial
P. havardiiS
P. murryanusD
Subg. Penstemon (185 spp.)Sect. Peltanthera (29 spp.)Subsect. Petiolati (1 spp.)SpeciesMaterial
P. petiolatusS
Subg. Penstemon (185 spp.)Sect. Aurator (28 spp.)
(no subsections)
SpeciesMaterial
P. albidusS
P. cobaeaS
P. gormaniiS
P. moffattiiD, L
Subg. Penstemon (185 spp.)Sect. Fasciculus (27 spp.)Subsect. Fasciculi (11 spp.)SpeciesMaterial
P. hartwegiiD, S
P. pinifoliusD, L, S
Subg. Penstemon (185 spp.)Sect. Fasciculus (27 spp.)Subsect. Campanulati (8 spp.)SpeciesMaterial
P. campanulatusD, S
P. kunthiiS
Subg. Penstemon (185 spp.)Sect. Fasciculus (27 spp.)Subsect. Perfoliati (3 spp.)SpeciesMaterial
P. perfiolatusS
Subg. Penstemon (185 spp.)Sect. Fasciculus (27 spp.)Ser. Racemosi (4 spp.)SpeciesMaterial
still needstill need
Subg. Penstemon (185 spp.)Sect. Fasciculus (27 spp.)Ser. Coriacei (1 spp.)SpeciesMaterial
still needstill need
Subg. Penstemon (185 spp.)Sect. Anularius
(no subsections)
SpeciesMaterial
P. acuminatusD, L
P. angustifoliusD, L, S
P. bracteatusD, L
P. carnosusL
P. cyathophorusL
P. fendleriS
P. grandiflorusD, L, S
P. harringtoniiL
P. immanifestusL
P. lentus var. lentusD
P. osterhoutiiL
P. pachyphyllusS
P. secundiflorusD, L, S
Subg. Penstemon (185 spp.)Sect. Ericopsis (16 spp.)Subsect. Caespitosi (10 spp.)SpeciesMaterial
P. caespitosus var. caespitosusD, L
P. caespitosus var. desertipictiD, L
P. crandallii var. crandalliiD, L
P. crandallii var. atratusD, L
P. teucrioidesD, L
Subg. Penstemon (185 spp.)Sect. Ericopsis (16 spp.)Subsect. Linarioides (3 spp.)SpeciesMaterial
P. linarioides var. linarioidesD, L
P. linarioides var. coloradoensisD, L
Subg. Penstemon (185 spp.)Sect. Ericopsis (16 spp.)Subsect. Ambigui (2 spp.)SpeciesMaterial
P. ambiguusD, L, S
Subg. Penstemon (185 spp.)Sect. Ericopsis (16 spp.)Subsect. Ericopsis (1 spp.)SpeciesMaterial
P. laricifoliusD, L, S
Subg. Penstemon (185 spp.)Sect. Dentanthera (4 spp.)
(no subsections)
SpeciesMaterial
still needstill need
Subg. Penstemon (185 spp.)Sect. Baccharifolii (1 spp.)
(no subsections)
SpeciesMaterial
still needstill need

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Subgenus Habroanthus

Subg. Habroanthus is characterized by anthers that dehisce from the distal end of the anther sac, but not across the connective. Section Elmigera consists of plants with typical hummingbird floral morphology (red, tubular corollas).

Subg. Habroanthus (46 spp)Sect. Glabri (39 spp.)(no subsections)SpeciesMaterial
P. alpinusD, L, S
P. cyananthusL, S
P. cyaneusS
P. cyanocaulisD, L
P. debilisD, L
P. glaberD, S
P. leiophyllusS
P. leptanthusL
P. mensarumD, L
P. nudiflorusS
P. payettensisD, L
P. saxosorumD, L
P. scariosusL
P. specioususD, L
P. strictiformisD, L
P. strictusD, L, S
P. virgatusL, S
Subg. Habroanthus (46 spp)Sect. Elmigera (7 spp.)(no subsections)SpeciesMaterial
P. barbatusD, L, S
P. cardinalisD, S
P. eatoniiD, L, S
P. labrosusD, L, S

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Subgenus Saccanthera

Subg. Saccanthera is characterized by anthers that dehisce across the connective but not to the distal ends. The only species with a typical hummingbird morphology (red, tubular corollas) is P. rostriflorus in sect. Emersus.

Subg. Saccanthera (26 spp.)Sect. Saccanthera (25 spp.)Subsect. Saccanthera (19 spp.)SpeciesMaterial
P. azureus var. azureusD, L
P. caesiusD, L
P. heterophyllus var. heterophyllusD, L, S
P. heterophyllus var. purdyiD, L
P. laetus var. laetusD, L, S
P. leonardiiL
P. neotericusS
P. parvulusD, L
Subg. Saccanthera (26 spp.)Sect. Saccanthera (25 spp.)Subsect. Serrulati (6 spp.)SpeciesMaterial
P. glandulosusD, L, S
P. richardsonii var. richardsoniiD, L, S
P. serrulatusD, L
P. triphyllusD, L
P. venustusD, L, S
Subg. Saccanthera (26 spp.)Sect. Emersus (1 spp.)
(no subsections)
SpeciesMaterial
P. rostriflorusD, L

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Subgenus Dasanthera

Subg. Dasanthera is characterized by anthers covered by dense, wooly hairs. All members have woody stems, which is another unique feature compared to all other species of Penstemon. Species with hummingbird flowers are P. newberryi and P. rupicola.

Subg. Dasanthera (9 spp.)
(no sections)
(no subsections)
SpeciesMaterial
P. barrettiaeD, L, S
P. cardwelliiD, L, S
P. davidsonii var. davidsoniiD, L, S
P. davidsonii var. menziesiiD, S
P. davidsonii var. praeteritusD, L
P. ellipticusD, L
P. fruticosus var. fruticosusD, L, S
P. fruticosus var. scouleriS
P. fruticosus var. serratusD, L
P. lyalliiD, L, S
P. montanusD, L
P. newberryi var. newberryiD, L
P. rupicolaD, L

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Subgenus Cryptostemon

Subg. Cryptostemon is monotypic and narrowly endemic to a few locations in Plumas County, California. It is characterized by a shortened staminode and divaricate anthers.

Subg. Cryptostemon (1 spp.)
(no sections)
(no subsections)
SpeciesMaterial
P. personatusD

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Subgenus Dissecti

Subg. Dissecti is monotypic and narrowly endemic to granite formations in Georgia. It is characterized by saccate anther morphology and finely dissected leaves.

Subg. Dissecti (1 spp.)
(no sections)
(no subsections)
SpeciesMaterial
P. dissectusD

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Initial Focal Species for PPT Studies: Pennell (1935) propsed that hummingbird pollination has been derived independently in Penstemon several times. Each of the four major subgenera have taxa that are both bee- and hummingbird-pollinated. Such transitions provide essential conditions for testing PPT. Our investigation will include all groups of hummingbird-pollinated species of Penstemon for both the field studies and molecular systematics portions. From this investigation, we should be able to determine how many times hummingbird-pollination has been derived in Penstemon and whether bee- vs. hummingbird-anther morphologies differ in pollen presentation strategies for each lineage of hummingbird taxa. Furthermore, when floral morphometric, microphenological, and nectar secretion studeis are placed in a phylogenetic context, we can examine floral evolution that accompanies from the shift of one pollinator type to another (i.e., what conditions immediately preceded a shift in pollination ecology?). Thus we can as: how common is parallelism, how labile is evolution of relationships with pollinators, and what factors are responsible for these patterns?

Initial "bee-bird" species pairs selected for field studies based on preliminary data. Each species-pair represents closely related taxa from within specific clades of the Penstemon phylogenetic reconstruction (based on cpDNa restriction-site variation; Wolfe unpubl.).

"Bee species"
"Bird species"
Subgenus
Section
Study location
P. grinnelliiP. centranthifoliusPenstemonPeltantheraCalifornia
P. campanulatusP. hartwegiiPenstemonFasciculusMexico
P. strictusP. barbatusHabroanthusGlabri, ElmigeraColorado
P. heterophyllusP. rostriflorusSaccantheraSaccanthera, EmersusCalifornia
P. davidsoniiP. newberryiDasantheraCalifornia

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Morphometrics: Penstemon flowers are structurally complex with a staminode that is either glabrous or bearded, which curves over the ovary to be presented at the base of the corolla. Two pairs of stamens are presented didynamously with the upper pair fused to the corolla and the lower pair free with nectary glands located at the base of the filaments. In examining PPT and shifts from bee- to bird-pollination syndromes, we will examine changes in corolla size, taper, upper and lower lip size, and the placement of functional parts in connection with the adoption of different pollination modes. Techniques for portraying evolved shape changes in terms of spatial warp scores are in development by the Rohlf lab at Stony Brook.

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Go to:

Penstemon Website

Wolfe Homepage

Wolfe Lab Homepage


Please send your suggestions, comments, and corrections to wolfe.205@osu.edu
Last updated September 28, 1998.