1. The Preferred Floral Traits of
Camas Pollinators
Jaime Patzer, Willamette University
Thesis submitted December 2010
Thesis Advisor: Dr. Susan R. Kephart

2. Abstract
The evolution of both plants and pollinators has been facilitated through their various diverse
interactions. Selective pressures, exerted by functional groups of pollinators as they respond to
their floral preferences, are postulated to be a major cause of floral diversification and may
contribute to plant speciation. This study sought to determine which plant traits play the greatest
role in attracting pollinators for two native species of camas lily, Camassia quamash and C.
leichtlinii. Not much is known of the trait preferences of the generalist pollinators that visit C.
quamash and C. leichtlinii in natural prairie habitats, making this species pair a good subject for
investigating the effect of manipulating trait combinations in artificial flowers. We observed
plant-pollinator interactions among natural and artificial camas flowers at Kingston Prairie
Preserve, a site of known camas occurrence and hybridization, to determine which floral trait or
trait combination had the greatest effect in attracting pollinators. We found that pollinator
functional groups were similar for C. leichtlinii and C. quamash; however, their frequencies
differed in the near and far meadows of Kingston Prairie Preserve. Honeybees (Apis mellifera),
flies, and solitary bees were the most frequent functional groups to visit C. quamash and C.
leichtlinii. Overall, Apis mellifera was the most frequent pollinator across the Kingston Prairie
Preserve. As with natural camas populations at the study site, artificial flowers most closely
resembling C. leichtlinii (having two or three C. leichtlinii traits) received more frequent
visitation than those resembling C. quamash, however, unlike natural camas populations,
visitation was not significantly different for artificial flowers, which may be due to a small
sample size. Tall height and wide petals appeared to be the preferred traits of the generalist
pollinators observed in this study, but further data are needed to confirm these preliminary
trends. The density of open camas flowers within study plots and the habitat of the plot (near or
far meadow) were also found to influence visitation. Data collected in this study allow us to
better understand the preferences of generalist pollinators that visit C. leichtlinii and C. quamash,
and will enable predictions as to whether these species will diverge or whether hybridization
between the two will allow for species merging. In generalized pollination systems, reproductive
isolation is less likely as pollinators facilitate gene flow when they move between plant species.
If C. leichtlinii and C. quamash have the potential to merge, conservation efforts to maintain
both as separate species can benefit from information gathered from studies such as these.

3. Introduction
The evolution of both plants and pollinators has been facilitated through their various diverse
interactions. Pollinator functional groups exert selection pressures on floral traits, which can
result in changes that affect an entire plant population or community (Fenster et al. 2004).
Functional groups include species whose similar behavior during plant pollination results in
similar selection pressures (Fenster et al. 2004). When specific floral traits are repeatedly
selected for in this context, convergent evolution may result (Fenster et al. 2004, Waser et al.
1996, Armbruster et al. 1999); alternatively, pollination by two or more pollinators or functional
groups may cause floral characters to evolve in response to the net selection pressures of their
pollinators (Armbruster 2001, Fenster et al. 2004, Toräng et al. 2006). Previous studies by
Cresswell and Galen (1991) have attributed changes in Polemonium viscosum to directional
selection on traits resulting from plant-pollinator interactions.
Selective pressures, exerted by functional groups of pollinators as they respond to their
preferences, are a major cause of floral diversification and may contribute to plant speciation
(Kephart and Theiss 2003, Fenster et al. 2004, Martin et al. 2008). Preference is defined as the
degree to which a pollinator is biased toward various traits during floral selectivity (Gegear and
Laverty 2005). Differences in floral morphology, color, fragrance, and reward can exploit the
diverse preferences among pollinators and increase reproductive success. For example,
pollinators are known to selectively visit plants with greater rewards (Cresswell and Galen 1990,
Fenster et al. 2004, Kasagi and Kudo 2003, Makino and Sakai 2007, Mitchell et al. 1998,
Pleasants 1981, Shykoff and Bucheli 1995). Flowers that do not have large nectar or pollen
rewards may receive fewer visits from pollinators, and therefore have less opportunity for
reproduction. By responding to their diverse preferences, pollinators select for and ensure the
survival of plants with specific floral traits within populations (Galen and Stanton 1989, Makino
and Sakai 2007). As a result, plants that rely solely on animals for pollination are more likely to
exhibit traits, such as a large floral display size, that attract pollinators due to the strong selection
pressures on the floral phenotype (Totland and Matthews 1997).
Observing plant-pollinator interactions allows us to document which pollinators visit which
flowers with the greatest constancy. Flower constancy refers to the tendency of pollinators to
restrict their visits to one flower type while disregarding other available rewarding flowers
(Waser 1986, Gegear and Laverty 2005). Gegear and Laverty (2005) observed that bees tend to
respond to flowers with unique trait combinations with higher degrees of constancy than flowers
that differ in only one trait, such as color. Additional studies are needed to determine which plant
traits play the greatest role in attracting pollinators (Séguin and Plowright 2008). Using traits
exhibited by a preferred plant species, we can design experiments to learn which floral trait or
trait combination has the greatest effect in achieving floral constancy.
In addition to preferred phenotypic traits, habitat and floral density may also influence pollinator
behavior (Steffan-Dewenter et al. 2002, Hegland and Totland 2005). Landscape context may
significantly influence pollinator diversity and abundance, and pollinator functional groups
respond differently to landscape, with some groups being more restricted to certain habitat
conditions due to nesting requirements (Steffan-Dewenter et al. 2002). As pollinators move
through their environment, they also encounter patches of varying floral density, which can
affect visitation. Dense floral patches often attract more pollinators than patches of low density

4. (Totland and Matthews 1997, Thomson 1981). To minimize the amount of energy expended
when traveling between patches, generalist pollinators may seek out patches where floral density
is high (optimal foraging), regardless of the particular flower species present (Thomson 1981).
Neither floral density, habitat, nor individual floral traits fully explain pollinator selectivity, but
understanding their roles in pollinator attraction can help explain observed visitation frequencies
to specific plant species, allowing us to infer future patterns in population distributions.
Artificial systems allow for the study of isolated and joint effects of plant traits on pollinator
visitation (Internicola et al. 2007). Further, artificial flowers permit trait manipulation, including
trait combinations not found in nature; thus, they provide a good testing system for pollinator
response (Blarer et al. 2002, Heuschen et al. 2005, Makino and Sakai 2007). Previous studies
using artificial flowers have shown pollinator preference for specific floral traits including nectar
reward (Blarer et al. 2002, Makino and Sakai 2007), petal arrangement (Séguin and Plowright
2008), and flower color (Heuschen et al. 2005). However, constancy may not be the result of a
single trait. Gegear and Laverty (2005) observed stronger floral constancy with greater floral trait
variation: artificial flowers with two traits added to a color had higher constancy than those with
a single trait combined with a color. Unfortunately, only rarely do studies involving artificial
flowers use models that resemble real flowers, and most experiments take place in a lab setting.
Often the model flowers used are made from paper squares, disks, or centrifuge tubes that are
then supplemented with sucrose solutions. Using artificial flowers that appear similar to real
flowers and conducting experiments in a natural setting may more accurately reflect the innate
preferences of pollinators (Yoshioka et al. 2007).
Species in the genus Camassia provide a good study system for examining pollinator trait
preferences. Four of the six North American species of Camassia (C. cusickii, C. howellii, C.
quamash, and C. leichtlinii) occur in western North America (Ranker and Hogan 2002, Sultany
et al. 2007). Two species found in Oregon (C. quamash and C. leichtlinii) are widespread,
abundant, and distinct from one another (Gould 1942, Sultany et al. 2007, Fishbein et al. 2010).
In the Willamette Valley, plants of Camassia quamash are shorter in stalk height (10-30 inches),
have floral displays in a bilateral arrangement, and relatively narrow petals. Plants of Camassia
leichtlinii are taller in height (36 inches or greater), show radial floral symmetry, and have wider
petals (Gould 1942, Ranker and Hogan 2002). Both plants also co-occur in several known
locations in Oregon’s Willamette Valley.
Not much is known of the trait preferences of the generalist pollinators that visit C. quamash and
C. leichtlinii, and prior research conducted on the relationships between Camassia and its
pollinators (Parachnowitsch and Elle 2005, Kephart, Palmer, and Sultany, unpublished), make
this species a good subject for investigation using trait combinations in artificial flowers. Pilot
studies suggest that pollinators may prefer C. leichtlinii (e.g., Kotaich 2009, unpublished), but it
is not yet known why. Thus, the availability of native C. quamash and C. leichtlinii, their varied
morphologies and ability to hybridize (Uyeda and Kephart 2006), and their generalist pollinators
make these two species a valuable system for determining which individual floral traits or trait
combinations might generate the greatest response among pollinators. The use of artificial
flowers with modifiable traits, which resemble the phenotypes of the two native camas species
and their hybrids, allows us to examine pollinator preference of various trait combinations and
infer potential changes within these parent populations and their hybrid offspring. As fruit set

5. may be pollen limited (Vietmeier and Kephart, unpublished), it is important to understand the
pressures exerted on plant fitness as generalist pollinators respond to their innate preferences.
Several questions must be addressed in order to understand the interactions between Camassia
and its pollinators. First, are pollinators similar for C. leichtlinii and C. quamash, and if so, do
particular insect species show preference toward one species or differ in their visitation
frequency to C. leichtlinii or C. quamash? I want to determine if specific individual pollinators
or functional groups are more frequent on C. quamash or C. leichtlinii, potentially as a result of
floral trait preference. If pollinators overall prefer one camas species to the other, I expect to see
a greater number of insect visits per observation time to that species. Since traits such as tall
height (Schaffer and Schaffer 1977, Donnelly et al. 1998), radial floral symmetry (Kalisz et al.
2006, Gong and Huang 2009) and wide petal width (Ashman et al. 2000) are known to affect
insect visitation levels, and Kotaich (2009, unpublished) observed higher visitation to C.
leichtlinii than C. quamash at Kingston Prairie, I predict greater overall visitation to C.
leichtlinii. If different pollinators or functional groups vary in their attraction to the traits
displayed by the two camas species, I expect to see differences in the relative frequencies of the
most common pollinators on these species. Second, are the preferences observed in artificial
flower visitation congruent with visitation to natural camas species? If trait preferences exist,
artificial flowers with trait combinations similar to C. quamash and C. leichtlinii are expected to
receive similar visitation as observed in natural populations. When individual traits are separated
out of trait combinations, I expect that the traits most responsible for the increased visitation will
be those of C. leichtlinii, such as height. In a preliminary study (Patzer 2009, unpublished), I
found that when individual traits were analyzed based on visits to artificial flowers; tall height
was more frequently selected for than traits pertaining to petal width or petal arrangement. In
addition, pollinators often chose floral displays and petals that are large, viewing the size as a
signal of reward size (Ashman et al. 2009, Blarer et al. 2002, Heiling and Herberstein 2004);
therefore, the larger petal size of C. leichtlinii over C. quamash may play a role in the increased
visitation to C. leichtlinii. While a taller height and larger flower size are distinct C. leichtlinii
traits, bilateral symmetry, a trait inherent to C. quamash, may be acting to attract pollinators to
the smaller, native camas species. Rodríguez et al. (2004), for example, found that bumblebees
(Bombus terrestris) with no experience on symmetric or asymmetric flowers show innate
preferences for bilateral symmetry.
Understanding the preferences of the generalist pollinators that visit C. leichtlinii and C.
quamash will enable predictions as to whether these species will diverge or whether
hybridization between the two will allow for species merging (Kimball 2008). In generalized
pollination systems, floral reproductive isolation is less likely as pollinators facilitate gene flow
as they move between plant species. If C. leichtlinii and C. quamash have the potential to merge,
conservation efforts to maintain both as separate species can benefit from information gathered
from studies such as these.

6. Methods
Study species and site
Both C. quamash and C. leichtlinii are abundant in the region from British Columbia to
California (Gould 1942). These two species have distinct differences that are easy to observe
without visual aid, and they hybridize in nature giving many trait combinations (Uyeda and
Kephart 2006). This study was conducted at The Nature Conservancy’s Kingston Prairie
Preserve (Figure 1). This 152 acre site is located three miles southeast of Stayton, Oregon, near
the North Santiam River in the Willamette Valley, a region in northwest Oregon that surrounds
the Willamette River from mountains near Eugene to the Columbia River at Portland
(Willamette Valley Agriculture 2009). Habitat varies from wet meadow to dry uplands and
native plant species thrive as a result of restoration efforts by The Nature Conservancy of Oregon
(The Nature Conservancy 2010). The abundance of camas across Kingston Prairie makes it an
ideal location to study artificial camas flowers alongside natural camas populations.
Furthermore, sympatric populations of C. leichtlinii and C. quamash give rise to plants that
appear to be putative hybrids in the spring and summer.
Two distinct meadows, referred to in this paper as the “near meadow” and the “far meadow”
were used for this study (Figures 1 and 2). Each meadow had large natural populations of both
camas species, and similar coflowering species and pollinators, but the flowering time was later
in the far meadow for all plants, causing us to distinguish between these two meadows (Jensen et
al., unpublished data). The earlier flowering time of C. quamash also allows us to compare insect
trait preferences in the presence and absence of the putatively preferred floral resource, C.
leichtlinii, over the course of the flowering season.
Data collection began in May 2010, during the start of floral onset in native camas, and
continued through summer until natural camas populations were no longer blooming (July 2010).
Continuous collection through the flowering season allowed for the observation of any
differences in pollinator preference for artificial camas flowers in the presence or absence of
natural camas. In addition, by continuing the study after natural camas populations bloomed, I
could note the effect of floral background on visitation rate as co-flowering species changed
throughout the season.
Visitation to C. leichtlinii and C. quamash and pollinator preference
The collection of observational data on the behaviors of pollinators toward plants available in
their natural habitat allows inferences as to whether specific pollinators show preference to one
camas species over the other. To infer whether pollinators exhibited preference for C. leichtlinii
or C. quamash, we collected observational data on pollinators in the field for 10 minute intervals
in 1 m2
plots with natural camas flowers only or in plots with artificial camas flowers
supplemented (Figure 3). All observers recorded the plant species visited, duration of time spent
in the plot (in seconds), and total number of artificial and natural flowers visited by each
pollinator while in the plot. In addition to species and floral trait differences, we tracked habitat
and floral density, as both variables are known to influence visitation by pollinators. To compute
floral density, we counted the number of camas stems and open flowers per plot, as well as the
presence of co-flowering associates. Ambient temperature and wind speed were also collected
with a pocket Kestral 2000 hand-held weather meter. Pollinator responses were documented as a
visit if the pollinator probed for nectar, gathered pollen, or directly landed on a flower.

7. Pollinators were identified as closely as possible to order or genus. In cases where identification
was not known, a description of the insect was recorded, and in some cases, individuals were
captured as voucher specimens for later identification.
All individual pollinators recorded were combined into five functional groups based on total
visitation observed during our study. The five functional groups of the most common visitors
were: Apis (honeybees), Bombus (bumble bees), solitary bees (Halictidae and Andrenidae), flies
(Syrphidae, Bombylidae, known as bee flies, and all other flies), and other visitors. To compare
the diversity and composition of the pollinator fauna visiting both species, we tabulated the
number of individuals of the five functional groups of pollinators visiting at least one plant
during a foraging bout in each 10 minute observation plot and used Chi-square tests to compare
the distributions of these groups on each species. In addition, pair wise comparisons of visitation
to each camas species and both habitat types using Chi-square and t-tests were made to
determine whether a species was preferred or if habitat altered species preference.
Preference for natural vs. artificial flowers and floral trait importance
Artificial flowers can be used to combine the traits of C. quamash and C. leichtlinii in a variety
of ways to obtain combinations possible through hybridization and study how pollinators
respond to different trait combinations. Previous studies have examined pollinator responses to
artificial flowers and found that pollinators can be trained to forage for nectar on them. Artificial
flowers can be made to suit a variety of studies, and in some prior research, the artificial flowers
used did not even visually resemble flowers of any plant species (Witjes and Eltz 2007, Makino
and Sakai 2007). Artificial flowers can be constructed for collecting data on pollinator response
to nectar reward, petal arrangement, flower color, or spatial arrangement of the flowers in test
plots. Artificial flowers provide a good testing system since they can be placed anywhere, the
bloom is open at all hours during all seasons, and the traits can easily be manipulated.
Artificial camas flowers were built to allow comparison of three chosen traits: plant height, petal
arrangement and petal width. Traits were combined to give eight different combinations (Table
1). Artificial flower stalks were constructed from green floral stakes with pointed tips, which
were 30 cm in length. Pedicels constructed from 22-gauge green floral wire, were attached to the
main stalk and were of two different lengths to account for the stalk height differences of C.
quamash and C. leichtlinii. Long pedicels (gave a total height of 70 cm when added to the stake)
were used to represent the taller stalk height of C. leichtlinii, and short pedicels (with a total
height of 35 cm when added to the stake) were used for artificial flowers which resembled the
height of natural C. quamash plants. Flowers were cut from plastic folder material selected for its
similar color to natural camas petals and tepals. The purple color was as close (to the human eye)
to the color of natural camas flower petals as possible. Petals were cut in two different widths to
represent the wide petals of C. leichtlinii and narrow petals of C. quamash, and were based on
mean values from natural populations in the Willamette Valley (C. quamash petals were 0.67 cm
in width and 2.27 cm in length, C. leichtlinii petals were 0.90 cm in width and 2.98 cm in length;
Sultany 2009, unpublished). Petals were glued to floral wire at the top of the artificial flower
stalk, with each stalk having one flower at the apex. The wires allowed for manipulation of petal
configuration to form radial or bilateral arrangement. Green floral tape served to secure the floral
wire pedicel to the floral stake. A small amount of green clay formed into a sphere (diameter ≈
0.75 to 1.0 cm) served as the ovary of each flower. The clay sphere was pressed into the center of

8. the flower between the petals at the top of the stalk. A small depression was added to each clay
center to hold 30% sucrose solution. The clay center was dosed with 30% sucrose solution using
a 1 mL plastic pipette. The pipette was squeezed lightly until one drop (about 0.0314 mL) of
sucrose solution fell on its own from the tip. By controlling the amount and concentration of the
sucrose solution added to each artificial flower, we can effectively remove the variable of
pollinator attraction based on reward.
Artificial camas plots were arranged at sites where pollinators had been observed and other
natural camas populations were flowering. Artificial camas flowers were haphazardly placed in 1
m2
plots to simulate the non-uniform arrangements in natural populations (Figure 3). Floral traits
were arranged along a gradient ranging from pure C. quamash to pure C. leichtlinii, with
intermediate types representing combinations likely in hybrids and backcross progeny (Table 1).
Each trait combination was represented twice per plot, using two sets of artificial flowers.
To ascertain whether visiting insects exhibit the same preferences for C. leichtlinii or C.
quamash between natural and artificial camas populations, I used mean visits per flower per plot
as an indication of preference for one species over the other in natural camas plots and compared
this visitation to each species with or without artificial flowers present. Mean visits per flower
per plot were standardized by open flower density of the plot, as floral density has been found to
affect pollinator visitation. The same five insect groups were used in pair wise comparisons of
the total number of visits by each functional type to natural C. leichtlinii versus C. quamash,
natural camas versus artificial camas, and among artificial camas types. Individual traits of
artificial flowers were separated out and analyzed using a χ2
analysis to determine which were
preferred.
Results
Pollinator activity on C. quamash and C. leichtlinii
At Kingston Prairie, Apis was the most frequent functional group observed on plants of C.
leichtlinii and C. quamash in 1 meter observation plots in both the near meadow and far
meadows for total observed visits by individual insect visitors to each species (Figures 4, 5).
Bumblebees were rarely observed, despite being known to be highly effective camas pollinators.
Apis comprised about half of the total observed visits to plants of C. leichtlinii in both meadows,
with flies and solitary bees making up most (or all in the case of the near meadow) of the other
half of the observed pollinators (Figure 4). As with C. leichtlinii, Bombus was not observed on C.
quamash in the near meadow (Figure 5). In the far meadow, pollinators from all five functional
groups were observed on C. quamash, with Bombus showing the greatest frequency observed
during our study (Figure 5). Flies were more frequent than solitary bees to C. quamash in both
meadows (Figures 5). Aside from the effect of habitat on insect distribution, floral density within
the plot also influenced visitation rates. In plots containing C. leichtlinii, visitation to camas
flowers increased with floral density of the plot (F = 21.030, P < 0.000, R2
= 0.200; Figure 6);
however, for C. quamash, visitation to flowers decreased with high floral densities (F = 5.886, P
= 0.017, R2
= 0.43; Figure 7).
Floral preferences for the two camas species were inferred from mean visitation rates to all
natural flowers in each plot type, including those with artificial flowers. These were standardized
for natural open flower density within study plots as it affected pollinator visitation (Figures 6,

9. 7). In addition, the combined visitation of the five functional groups differed significantly
between the near and far meadows, so we compared the data obtained in each meadow separately
(χ2
= 132.76, df = 4, P ≤ .005; Figure 8). Additionally, while the same pollinator functional
groups occur on camas in both the near and far meadow, visitation by the five functional groups
differed significantly on C. leichtlinii versus C. quamash (χ2
= 117.06, df = 4, P ≤ 0.005; Figures
9, 10). Interestingly, using data standardized for open flower density within plots, which was also
based on mean flower visits per plot, Apis was not the most frequent visitor in both meadows
(Figures 9, 10) as was true for the frequency of insect visits to plants in each observation plot
without accounting for floral density (Figures 4, 5).
Mean visitation per 10 minute observation was highest in the near meadow for all plot types
(CALE, CAQU, CALE+AF, CAQU+AF; χ2
= 132.76, df = 4, P < 0.05; Figure 8). Variation in
the mean number of pollinator visits to natural camas flowers for the near and far meadows was
somewhat explained by flower density. When visitation was standardized for floral density in
plots, the data revealed significantly more visits to natural flowers of C. leichtlinii than to C.
quamash in both the near and far meadow (χ2
= 117.06, df = 4, P < 0.05; Figure 8). While
visitation was significantly different for plots containing natural C. quamash versus C. leichtlinii,
it was not significantly different for plots with artificial flowers between either meadow, or
between either plot type (CAQU+AF or CALE+AF; near meadow χ2
= 0.203, df = 1, P > 0.05;
far meadow χ2
= 0.144, df = 1, P > 0.05; Figure 8).
The same functional groups were observed on both C. leichtlinii and C. quamash within each
meadow, and visitation was highest to C. leichtlinii in both meadows for all groups except Apis
in the near meadow. In the near meadow, Apis was most frequent on C. quamash while all other
functional groups observed showed the greatest frequency on C. leichtlinii; however, visitation
only significantly differed for flies (Figure 9; Table 2). In the far meadow, all functional groups
visited C. leichtlinii more often than C. quamash; however, visitation only significantly differed
for Apis (Figure 10; Table 2).
Artificial flower visitation and trait preference
As with natural camas visitation, artificial flowers exhibiting C. leichtlinii traits received more
frequent visitation than those that resembled C. quamash: however, visitation was not
significantly different for artificial flower types (CAQU+relatives or CALE+relatives) within the
plot types (CAQU+AF or CALE+AF; near meadow χ2
= 0.203, df = 1, P > 0.05; far meadow χ2
=
0.144, df = 1, P > 0.05; Figure 11). Not only was visitation greater to artificial flowers, which
were more similar to C. leichtlinii (Figure 13), but visitation increased when artificial flowers
were added to plots containing natural C. leichtlinii (Figure 12). Visitation to hybrid types was
not significantly different from pure types (Figure 12). When individual trait combinations were
compared, the four artificial flowers with the most frequent visitation each had “wide petal
width” in common (Figure 13). Wide petal width was the most frequently visited trait, followed
by tall height (Figure 14). Visits to artificial flowers with wide petals differed significantly from
artificial flowers with narrow petals in CALE+AF plots (χ2
= 4.78, df = 1, P < 0.05), but
visitation to all other traits in pair wise comparisons was not significantly different (Figure 14).
Functional groups observed on artificial flowers were similar to those visiting natural camas
populations, however, Bombus was not observed on any artificial flower type in the near or far

10. meadows (Figures 15, 16). The most frequent functional group to artificial flowers, Apis, was
also the most frequent functional group on natural populations. Aside from receiving no visits
from Bombus, artificial flowers received visits from the same functional groups as natural camas
(Figures 4-5; 15, 16).
Discussion
Even for similar flower types pollinated by generalist visitors, both habitat and species
differences can potentially influence pollinator visitation, leading to reinforcement of species
boundaries. For example, functional groups often respond to habitat attributes differently, with
Bombus preferring areas near wooded habitat due to their nesting requirements, and solitary bees
tending to be more restricted to seminatural habitats than Apis, which forage across many habitat
types (Steffan-Dewenter et al. 2002). In this study, functional groups of putative pollinators were
similar for both C. leichtlinii and C. quamash, yet visitation levels varied with habitat and camas
species. In the far meadow, all functional groups of insects showed greater frequency to C.
leichtlinii, and visitation across habitat types (near and far meadows) differed significantly, with
highest mean visitation for observation periods in the near meadow (χ2
= 132.76, df = 4, P
<0.05). Bombus was more frequent in the far meadow than the near meadow, and though
frequent on camas species in the near meadow (Patzer 2010, unpublished), was not observed on
camas species in our study plots within the near meadow. This lack of observation contributes to
the significant difference we found in visitation by the five functional groups between the near
and far meadows. Habitat adjacent to the far meadow consists of an oak grove with many fallen
logs, rocks and overgrown plants including bedstraw, nettle, blackberries, and some patches of
camas. Such variety in nesting resources allows for individuals within the genus Bombus to find
suitable nesting sites (Goulson et al. 2008) close to the far meadow camas populations. While
bumblebees are known to prefer more dense habitat for nest sites, such as that near the oak grove
in the far meadow (Goulson et al. 2008), Apis have been found to be present in greater
abundances further from forested areas, which is speculated to be due to the ability of new
queens to disperse far from their original hive and the ability of workers to forage up to 13 km
away from a hive (Brosi et al. 2007, Gould and Gould 1988).
Overall, Apis was the most frequent visitor to both camas species in both meadows. However,
when mean flower visits and open flower density within study plots were taken into account, not
just the number of individual visitor bouts to camas flowers in a plot, solitary bees were more
frequent in the near meadow and flies were more common in the far meadow. In all, these data
give us a better sense of which pollinators may be more important in potentially delivering
pollen to flowers of a particular species. While Apis was found to be the most frequent visitor
overall, after taking open flower visits and density into account, we are able to determine which
insect functional groups tend to visit more flowers within a plot. In the meadows where solitary
bees or flies appear to be more frequent visitors after factoring floral density into pollinator
visitation, it appears that these pollinators could be more important to camas species as more
individual flowers have a chance at pollination than by pollinators that visit fewer flowers per
plot. Total counts of pollinators allow for comparison of functional group diversity on each
camas species and the detection of potential insect functional group preferences for one camas
species over the other, yet they do not provide an accurate representation of pollinator
effectiveness. More importantly, an insect functional group may be more frequently observed on
a plant, it may not be as effective as another functional group when gathering and transferring

11. pollen. Factors such as insect body size and contact with anthers and stigma when visiting a
flower contribute to pollinator effectiveness. Bumblebees (Bombus) have been found to be the
most effective pollinators that visit camas species in the Willamette Valley, in part due to the
larger body size (relative to other generalist camas pollinators) which results in greater pollen
transfer after anther contact (Sultany et al. 2009, unpublished). Recent studies by Vietmeier et al.
(2010, unpublished) demonstrate that both solitary and social bees can carry significant amounts
of camas pollen on their bodies, unlike bombylid and syrphid flies.
Across habitats, pollinators were more frequently observed in C. leichtlinii, however, Apis
showed greater frequency to C. quamash than to C. leichtlinii in the near meadow. This
difference is likely due to the small sample size of CALE plots in the near meadow where only
six CALE plots were observed versus 19 CAQU plots. In the far meadow, we observed 29
CALE plots and 42 CAQU plots. Incompatible weather earlier in the camas flowering season
allowed less observation of C. leichtlinii plots as C. leichtlinii flowers later than C. quamash in
both the near and far meadow. Flowering times in the far meadow for both camas species occurs
later than the near meadow (Patzer and Jensen, 2010 unpublished), and this later flowering time
permitted greater observation of C. leichtlinii and C. quamash plots as the weather improved
later in the season. Increased observation likely allows for more accurate detection of trends in
pollinator preference. Future studies should include a greater number of plot observations in the
near meadow to detect any possible differences in pollinator preference.
In addition to variation of functional group distribution and visitation across habitats, plot floral
density was important to consider, as this is known to influence pollinator visitation (Internicola
2007, Grindeland et al. 2005, Sih and Baltus 1987). Increasing floral density yields higher
visitation, to a point. At high floral densities, lower per flower visitation occurs as flowers
compete for insect visits (Sih and Baltus 1987). Among plot types, C. leichtlinii plots received
greater visitation per observation period when standardized for floral density. This is in line with
my hypothesis. Based on evidence from prior studies, C. leichtlinii, with its larger floral display,
taller height and radially symmetric flowers were predicted to be preferred by pollinators
(Schaffer and Schaffer 1977, Donnelly et al. 1998, Kalisz et al. 2006, Ashman et al. 2000).
Numerous studies recognize the importance of floral display size and height in attracting
pollinators (Johnson et al. 1995, Robertson and Macnair 1995, Aarssen 1995); taller plants offer
greater visibility and tend to have a greater number of flowers; these traits tend to convey greater
nectar or pollen reward, which in turn serves to attract pollinators (Lortie and Aarssen 1999).
However, the effect of floral symmetry on visitation is still under debate (West and Laverty
1998, Rodríguez et al. 2004). West and Laverty (1998) found no preference for bilateral
symmetry while Rodríguez et al. (2004) reported that bumblebees show an innate preference for
symmetrical flowers. There have also been reports of generalist pollinators, such as those that
visit camas species, preferring radial petal arrangement, while specialist pollinators prefer more
complex arrangements, such as the bilateral petal arrangement of C. quamash (Kalisz et al. 2006,
Gong and Huang 2009). While floral symmetry may not be an innate preference, it is not fully
understood (Plowright et al. 2010). There is potential that symmetric flowers are more rewarding
(Møller and Eriksson 1995), and this may contribute to the preference.
As predicted based on natural camas populations, artificial flower populations had greater
visitation to C. leichtlinii traits as well. Though trait combinations representing hybrid

12. individuals did not receive greater visitation than those resembling pure species, artificial flowers
resembling C. leichtlinii received more frequent visits in plots regardless of whether the plot
contained natural C. leichtlinii or natural C. quamash. Of the four trait combinations preferred,
wide petal width was present on each, and may be preferred even over tall stalk height. Though
trends were observed for greater visitation to artificial flowers when they were in plots with C.
leichtlinii, and when they had C. leichtlinii traits, further data collection is necessary to see if
these trends are significant at greater sample sizes. The only significant difference observed
among visitation to specific traits tested with artificial flowers was for wide petal width in
CALE+AF plots, with wide petals receiving significantly more visits than artificial flowers with
narrow petals (χ2
= 4.78, df = 1, P <0.05). The wide petal width of artificial flowers may be
preferred as it offers a landing platform, more easily accessible from a variety of directions,
while the bilateral arrangement is more difficult to approach for a visit (Kalisz et al. 2006).
The lack of significance for differences observed in visits to artificial flowers more similar to C.
leichtlinii or C. quamash may be affected by our choice to keep sucrose solution concentration
and volume equal for all artificial flower types and the use of only one blossom per artificial
flower stalk. While natural camas flowers have varying numbers of blossoms per inflorescence,
the floral display of each artificial flower was very small (one flower) by camas species
standards. Additionally, C. leichtlinii has greater nectar volumes than C. quamash (Sultany 2009,
unpublished), which serves as an attractant for pollinators within the natural populations. By
choosing not to use these variables within artificial camas flowers, our data may not resemble
visitation to natural camas if floral display and nectar reward have large effects on pollinator
preference.
It seems evident that the generalist pollinators that visit Camassia leichtlinii and C. quamash
prefer C. leichtlinii (due to the greater visitation observed to natural and artificial flowers).
However, additional data collection yielding a larger sample size would be useful in sorting out
preferences among traits that were not apparent in this study. As both camas species are able to
hybridize, understanding which traits are preferred by the generalist pollinators on camas will
allow us to infer whether these two species may merge or diverge in future generations. Such
information is useful in conservation efforts if species merging at sites of camas hybridization
may result in the loss of the species that is less frequently visited.
Acknowledgements
I would like to thank Katherine II Bisbee II Fund of Oregon Community Foundation and the M.
J. Murdock Trust and Willamette University for funding this research, The Nature Conservancy
for access permission to Kingston Prairie Preserve, and Dr. Susan Kephart for her assistance with
data collection, analysis and guidance throughout this research project. I also thank Jennifer
Butler for helpful comments on the thesis and Emilie Jensen, Alex Peters, Jonnie Dunne and
Hannah Vietmeier for their help in data collection at Kingston Prairie Preserve.

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16. Tables
Table 1. Artificial camas flower trait combinations. Traits are associated with naturally occurring
C. leichtlinii and C. quamash. Plant height is recorded as short (S) or tall (T), petal arrangement
is bilateral (B) or radial (R), petal width is wide (W) or Narrow (N). Camassia quamash is
abbreviated CAQU, and C. leichtlinii, CALE.
Flower # Short (S) / Tall
(T)
Bilateral (B)
/ Radial (R)
Narrow (N)
/ Wide (W)
# CAQU
traits
# CALE
traits
Morphological Affinity
1 S B N 3 0 Pure C. quamash
2 S B W 2 1 C. quamash backcross
3 S R N 2 1 C. quamash backcross
4 T B N 2 1 C. quamash backcross
5 S R W 1 2 C. leichtlinii backcross
6 T B W 1 2 C. leichtlinii backcross
7 T R N 1 2 C. leichtlinii backcross
8 T R W 0 3 Pure C. leichtlinii
Table 2. T-test results, visitation by insect functional groups to natural C. leichtlinii and C.
quamash in both meadows. Camassia quamash is abbreviated CAQU, and C. leichtlinii, CALE.
N/A indicates areas where visits were insufficient or no visits occurred.
Habitat Species Apis Bombus Solitary Bees Flies Other
Near CAQU
vs
CALE
t-test = 0.34
P ≤ 0.735
N/A t-test = 1.03
P ≤ 0.307
t-test = 2.85
P ≤ 0.006
N/A
Far CAQU
vs
CALE
t-test = 3.21
P ≤ 0.001
t-test = 1.28
P ≤ 0.218
t-test = 0.79
P ≤ 0.432
t-test = 0.38
P ≤ 0.704
N/A

17. Figures
Figure 1. Kingston Prairie (N 44° 46.822 W 122° 44.58). Near meadow (NM) and far meadow
(FM) outlined in yellow, unburned meadow (UM) in blue.
Figure 2. The far meadow (left), and the oak grove that separates the far meadow and near
meadows. Camassia quamash blooms in a damp, marshy setting. The near meadow (right),
facing the unburned section of Kingston Prairie. A mixed transect of C. leichtlinii, C. quamash,
Potentilla and Saxifrage is surveyed by Jaime Patzer, Emilie Jensen, and Hannah Vietmeier.
Figure 3. A 1 m2
study plot supplemented with 16 artificial flowers (AF), each numbered
according to floral trait combination, and placed haphazardly in AF plots.

18. Figure 4. Apis was the most frequent pollinator at Kingston Prairie in both near and far meadows.
Bumblebees (Bombus) were infrequent, despite their effectiveness as camas pollinators.
Effect of Habitat:
Camassia leichtlinii
Far MeadowNear Meadow
Figure 5. As with C. leichtlinii in the near meadow, Bombus was not observed on C. quamash. In
the far meadow, a slightly greater diversity of pollinators was observed on both C. quamash and
C. leichtlinii, and the greatest visitation from Bombus was observed on C. quamash.
Far MeadowNear Meadow
Effect of Habitat:
Camassia quamash

19. Effect of Floral Density on Visitation in C. leichtlinii Plots
0
5
10
15
20
25
30
35
10 20 30 40 50 60 70 80 90 100 110
Floral Density
NumberofFlowersVisited
Figure 6. Visitation to C. leichtlinii plots increased with floral density (F =21.03, P <0.000, R2
=0.20).
Effect of Floral Density on Visitation in C. quamash Plots
0
10
20
30
40
50
60
70
80
10 30 50 70 90 110 130 150
Floral Density
NumberofFlowersVisited
Figure 7. Floral density of the plot did not positively influence visitation to C. quamash plots,
declining slightly with floral density (F =5.88, P ≤0.017, R2
=0.43).

20. Figure 8. Mean number of visits per 10 minute observation ( 1SE, standardized for plot floral
density), which was significantly higher in the near meadow (χ2
=132.76, P <0.05), and for C.
leichtlinii plots (CALE) relative to C. quamash plots (CAQU) (χ2
=117.06, P <0.05).
Mean Visitation by Functional Groups per 10 Minute
Observation Periods in the Near Meadow
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
CAQU
CALE
CAQU
CALE
CAQU
CALE
CAQU
CALE
CAQU
CALE
Apis Bombus Solitary Bees Flies Other
Figure 9. Mean number of flower visits/plot by each functional group  1SE, standardized by the
number of open flowers per plot. Apis had greater frequency to C. quamash; all other functional
groups were more frequent to C. leichtlinii.
MeanVisitationbyFunctional Groupsper 10Minute
Observationsinthe Far Meadow
0
0.01
0.02
0.03
0.04
0.05
0.06
CAQU CALE CAQU CALE CAQU CALE CAQU CALE CAQU CALE
Apis Bombus SolitaryBees Flies Other
Figure 10. Mean number of flower visits/plot by each functional group  1SE, standardized by
the number of open flowers per plot. All functional groups visited C. leichtlinii more frequently
than C. quamash; however, visitation only significantly differed for flies (Table 2).

21. Mean Visitation to Artificial Flower Types
per 10 Minute Observation
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
CAQU+relatives CALE+relatives
CAQU+AF
CALE+AF
Figure 11. Mean number of flower visits/plot by each functional group  1SE, standardized by
the number of open flowers per plot. Artificial flowers more closely resembling C. leichtlinii
(having two or three C. leichtlinii traits) received more frequent visitation per observation period,
and all artificial flowers types received more frequent visitation when they were in plots which
contained natural C. leichtlinii. Visitation did not significantly differ between artificial flowers
resembling C. leichtlinii (AF #5-8) and those resembling C. quamash (AF #1-4).
Mean Visitation to Artificial Flower Types per 10 Minute
Observation
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
Pure CAQU CAQU Hybrid CALE Hybrid Pure CALE
CAQU+AF
CALE+AF
Figure 12. Mean number of flower visits/plot by each functional group  1SE, standardized by
the number of open flowers per plot. Visitation was higher to plots containing natural C.
leichtlinii and to artificial flowers more closely resembling C. leichtlinii. Pure CAQU = AF#1,
CAQU hybrid = AF#2-4, CALE hybrid = AF#5-7, and pure CALE = AF#8.

22. Mean Number of Visits per 10 Minute Observation
0
0.5
1
1.5
2
2.5
SBN SBW SRN TBN SRW TBW TRN TRW
Artificial Flower Trait Combination
CAQU+AF
CALE+AF
Figure 13. Mean number of flower visits/plot by each functional group  1SE, standardized by
the number of open flowers per plot. The four trait combinations to receive the most frequent
visitation all share the trait “wide petal width,” a trait associated with C. leichtlinii.
Mean Number of Visits per 10 Minute Observation
0
1
2
3
4
5
6
7
8
Tall Short Radial Bilateral Wide Narrow
Artificial Flower Traits
CAQU+AF
CALE+AF
Figure 14. Mean number of flower visits/plot by each functional group  1SE, standardized by
the number of open flowers per plot. Visitation was more frequent to plots natural C. leichtlinii
and to traits associated with C. leichtlinii (tall height, radial petal arrangement, and wide petals).
Visitation differed significantly between wide and narrow petal width in CALE+AF plots (χ2
=
4.78, P <0.05).

23. Functional Group Visitation in a CAQU+AF Plot
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
SBN SBW SRN TBN SRW TBW TRN TRW
Artificical Flower Trait Combination
MeanVisitation
Apis
Solitary Bees
Flies
Other
Figure 15. Apis was the most frequent visitor to all artificial flower trait combinations in
CAQU+AF plots. Bombus was not observed on artificial flowers throughout the experiment.
Functional Group Visitation in a CALE+AF Plot
0
0.5
1
1.5
2
2.5
3
SBN SBW SRN TBN SRW TBW TRN TRW
Artificial Flower Trait Combination
MeanVisitation
Apis
Solitary Bees
Flies
Other
Figure 16. Apis was the most frequent visitor to all artificial flower trait combinations in
CALE+AF plots. Bombus was not observed on any artificial flowers throughout the experiment.