Life History and Reproductive Biology of Clitoria Fragrans Relative to Fire History on the Avon Park Air Force Range

Home , Clitoria, Clitoria fragrans, Cnidoscolus stimulosus, Plant density, Tillandsia bartramii

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Electronic Theses and Dissertations, 2004-2019

2007

Life History And Reproductive Biology Of Clitoria Fragrans Relative To Fire History On The Avon Park Air Force Range

Michelle Nicole Lewis University of Central Florida

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STARS Citation Lewis, Michelle Nicole, "Life History And Reproductive Biology Of Clitoria Fragrans Relative To Fire History On The Avon Park Air Force Range" (2007). Electronic Theses and Dissertations, 2004-2019. 3240. https://stars.library.ucf.edu/etd/3240 LIFE HISTORY AND REPRODUCTIVE BIOLOGY OF CLITORIA FRAGRANS RELATIVE TO FIRE HISTORY ON THE AVON PARK AIR FORCE RANGE

MICHELLE N. LEWIS B.S. Drake University, 2000

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in the Department of Biology in the College of Sciences at the University of Central Florida Orlando, Florida

Fall Term 2007

ii ABSTRACT

The southeastern coastal plain of the United States is a center of endemism for plants in temperate North America and second only to California among the states. In the southeast,

Florida has the largest number of these endemic plants. The largest number of these Florida endemics can be found in the fire maintained scrub and sandhill communities located on sandy ridges in Central Florida. One such endemic is Clitoria fragrans, a rare perennial herb. C. fragrans reproduces via a mixed mating system. It produces both open, chasmogamous flowers and closed, selfed, cleistogamous flowers. Little else is known about its biology.

I monitored populations of C. fragrans from 2003-2005 on the Avon Park Air Force Range. I tracked plant density, finite rate of population increase, plant survivorship and reproduction relative to the time since fire and season of fire. I found that recently burned plots had a higher density of plants than those unburned for over 13 years. Unburned populations decreased in all years of the study. In all three years, the majority of flowers produced by Clitoria fragrans were cleistogamous. The production of chasmogamous flowers appears to be influenced by plant size and potentially fire. Unburned plots had less variation than recently burned plots for all independent variables.

iii

ACKNOWLEDGMENTS

I would like to thank my advisor, I. Jack Stout, for his help and encouragement

throughout the entire process. I would also like to thank Pedro F. Quintana-Ascencio for his

invaluable guidance on data analysis and interpretation for this manuscript. The rest of my

committee, Jan Nadeau, Betsy Von-Holle provided input on this manuscript. Steve Orzell, the

botanist at the Avon Park Air Force Range, provided his taxonomic expertise, knowledge of the

ecosystem and the funding opportunity for this project. The Department of Defense provided the

funding for my project. I would also like to thank the other Air Force personnel who aided in

data collection; Catherine Airey, Brent Bonner, Margaret Margosian and Brett Miley. The

Biology Graduate Student Association of the University of Central Florida and the graduate students in the Stout lab provided advice and moral support. Finally, I thank my friends and most importantly my family for their unwavering support.

iv TABLE OF CONTENTS

LIST OF FIGURES ...... vi

LIST OF TABLES...... vii

CHAPTER ONE: INTRODUCTION...... 1

CHAPTER TWO: METHODS...... 4

CHAPTER THREE: RESULTS...... 13

CHAPTER FOUR: DISCUSSION...... 26

APPENDIX A: SPECIES LIST FOR ALL TRANSECTS ...... 33

APPENDIX B: DESCRIPTIVE STATISTICS FOR DEMOGRAPHIC AND REPRODUCTIVE

VARIABLES ...... 37

LIST OF REFERENCES...... 40

v LIST OF FIGURES

Figure 1: Map of the distribution of Clitoria fragrans and location of transect study sites on the

Avon Park Air Force Range...... 6

Figure 2: Landscape-level response of Clitoria fragrans...... 16

Figure 3: Demographic traits for Clitoria fragrans on the transects. ………………………….. 17

Figure 4: NMS ordination based on habitat variables of the seven transects on which vital rates

and flowering of Clitoria fragrans were studied, APAFR, 2003-2005...... 18

Figure 5: Flowering responses of Clitoria fragrans in relation to time since fire and season of

fire. ………………………………………………………………………………………... 21

Figure 6: Average number of reproductive structures produced per plant of C. fragrans on the

transects and total rainfall per month...... 22

vi LIST OF TABLES

Table 1: Attributes of belt transects established to monitor growth, survival and reproduction of

C. fragrans on the Bombing Range Ridge, 2002-2005 ...... 8

Table 2: Flowers produced by C. fragrans on all transects in 2004 and 2005 ...... 23

Table 3: Flower production by C. fragrans on transects, 2004 ...... 23

Table 4: Flower production C. fragrans on transects, 2005 ...... 24

Table 5: Logistic regression results predicting the presence of chasmogamous flowers based on

the total number of cleistogamous flowers on an individual plant...... 25

vii CHAPTER ONE: INTRODUCTION

The southeastern coastal plain of the United States is a center of endemism for plants in

temperate North America and second only to California among the states (Gentry 1986). In the

southeast, Florida has the largest number of these endemic plants (Gentry 1986; Dobson et al.

1997; Estill and Cruzan 2001). The largest number of these Florida endemics can be found in the

fire maintained scrub and sandhill communities located on sandy ridges in Central Florida

(Christman and Judd 1990; Estill and Cruzan 2001). These ridges are derived from paleodunes

formed prior to and during the Pleistocene. The Lake Wales Ridge is the most prominent of these

features and one of the most endemic-rich areas of the state with a minimum of 23 endemic

plants (Dolan et al. 1999; Bridges and Orzell 2002). One example is Clitoria fragrans, a suffrutescent herb listed as threatened by federal and endangered by state agencies (McCoy and

Mushinsky 1992; Stout 2001). This plant is limited in its distribution to sandy ridges of

Highlands, Lake, Orange and Polk counties, including the Lake Wales and Bombing Range

Ridges (Fantz 1977).

Clitoria fragrans exhibits the classic features of a rare plant with its narrow geographic

distribution, restricted habitat and small local population sizes (McCoy and Mushinsky 1992;

Ward et al. 2003). Fantz (1977) prepared a taxonomic monograph on the genus Clitoria and

provided many details on the morphology and distribution of Clitoria fragrans. Aside from this

monograph, which was morphologic and taxonomic in scope, the species was reviewed in the

listing process (U.S. Fish and Wildlife Service 1999). Researchers have reported increased

1 flowering in C. fragrans following a fire; however, it should be noted that flowering has also

been observed in an area that had not been burned for 30 years (U.S. Fish and Wildlife Service

1999). More recently, Weekley and Menges (2003) classified C. fragrans as a re-sprouter in a study of species responses to prescribed fire in Lake Wales Ridge scrub. Little is known about the biology and life history of the species beyond these preliminary observations (Stout 2001;

Weekley and Menges 2003).

The life history of fire adapted plants has been reviewed for Australia (Williams et al. 1994; Ooi et al. 2006), California (Keeley 1991), southeastern U.S. (Platt et al. 1988; Waldrop et al. 1992;

Glitsenstein et al. 2003), and Florida (Hawkes and Menges 1995; Menges and Kohfeldt 1995;

Menges and Hawkes 1998). Above ground portions of herbaceous plants are destroyed by fire

(Robbins and Meyers 1992). Recovery of individuals may occur by resprouting from underground storage structures, e.g, roots, tubers, or xylopodia, or by recruiting from an existing soil seed bank (Petru and Menges 2003; Weekley and Menges 2003). Plants in post-burn populations may flower more successfully than long-unburned individuals. Population density, size of plants, seed set, and seed germination may decline with time since fire (Menges and Root

2004; Menges et al. 2006). The response of Clitoria fragrans to fire is poorly documented.

The purpose of my study was to asses certain aspects of the life history of Clitoria fragrans in relation to fire return interval. I focused on vital rates and attributes of closely monitored populations, specifically population density, finite growth rate and survivorship. In addition, I studied the flowering behavior and reproductive success of plants with and without a recent history of recovery from prescribed and wild fires.

2 I hypothesized that C. fragrans, a suffretescent herb, re-sprouts immediately after a fire event with no important recruitment from a soil seed bank. Therefore, I predict densities of marked populations will remain essentially unchanged following fire that consumes the ground cover vegetation. Likewise, I predict that in the absence of significant recruitment following fire events, the finite growth of C. fragrans will be approximately 1.0. Lastly, I predict survivorship will not be a function of time since the last fire event.

I hypothesized C. fragrans responds to fire events with both re-growth of stems and the production of insect pollinated chasmogamous flowers. I predict that plants will respond to top kill by fire with rapid regrowth and flowering in which chasmogamous flowers set seed from which genets are derived. I predict the production of cleistogamous flowers (self pollinated) will not be increased after fire events.

3 CHAPTER TWO: METHODS

Study organism

Clitoria fragrans is a perennial herb characterized by one to several erect stems sprouting annually from an underground xylopodium. The leaves are 3-foliate. Inflorescences are axillary

with one to two flowers (Fantz 1977). Clitoria fragrans has two types of flowers; showy, insect-

pollinated chasmogamous (CH) flowers and small, closed, self-pollinated cleistogamous (CL)

flowers (Fantz 1977). A single plant can have both flower types. Chasmogamous flowers

generally have a longer calyx tube (7-10mm) than cleistogamous flowers (3-4mm). According to

Fantz (1977), both flower types are borne from May to June, but cleistogamous flowers may be found until September. Fruits are borne July through September. The seeds are 4-6mm in diameter and have a viscous coat (Fantz 1977).

Clitoria mariana is the only other native species in this genus found in Florida. Clitoria ternatea is an exotic that escaped from cultivation, but is only found in Miami-Dade and Monroe counties and does not coexist with C. fragrans (Wunderlin and Hansen 2003). C. fragrans can be distinguished from C. mariana, and other legumes, by its non-twining habit and prominent

stipules (Fantz 1977). Clitoria fragrans can also be distinguished from other legumes by its 3- foliate leaves, compared to the 5, 7 or even 9-foliate leaves of Galactia elliottii (Wunderlin and

Hansen 2003).

4 Study Site

My study was conducted on the Avon Park Air Force Range (APAFR), a 106,000 acre (42,898.2

hectares) area at 27.38°N 81.22°W, to the east of the Lake Wales Ridge (National Weather

Service 1993, Figure 1). APAFR is located on a complex upland known as the Bombing Range

Ridge, which is between the Kissimmee River to the east and Arbuckle Creek to the west (White

1970). There are 29 state and federally-listed species plants and animals inhabiting the area.

Land uses of the range include cattle grazing, pine plantations, military activities, hunting and

camping. The Air Force manages this land through prescribed burning of approximately 25,000

acres per year (Orzell pers. comm.). Avon Park typically receives 124.7 centimeters of rain per year (The Weather Channel 2006). The area also has a 90% probability of having 258 or more frost-free (above 36F) days per year (Koss et al. 1988).

Distribution and Abundance of Clitoria fragrans on APAFR

Clitoria fragrans is found in sandhill and scrub communities on xeric soils (Menges et al. 2007).

From 2002-2005, I surveyed four soil types (Daytona sand, Duette sand, Narcoossee sand and

Zolfo sand) on the Avon Park Air Force Range for populations of Clitoria fragrans. These four soil types were determined to be the most likely to support C. fragrans. I mapped each population using a Trimble GPS unit with sub-meter accuracy. A population was arbitrarily defined as clusters of individuals with a minimum of 20 meters between individuals of adjacent

clusters. I counted and uniquely tagged each individual. I determined the boundaries of a

population by walking a minimum polygon with the GPS unit. A minimum of 2,954 individual

plants have been censused in 67 populations on APAFR (Lewis and Stout, unpublished data)

(Figure 1).

Figure 1: Map of the distribution of Clitoria fragrans and location of transect study sites on the

Avon Park Air Force Range

6 Transects and Study Population

In 2002 and 2003, seven permanent belt transects were established to monitor the life history and

demographic performance of C. fragrans (Table 1). Due to the patchy nature of C. fragrans on

APAFR, these transects were arbitrarily placed in populations of the plant (Figure 1). Transects varied in length and fire history among the sites, but every one was two meters wide. The fire histories for each transect dates back to 1978. All but one of the transects are in Narcoossee sand

(Table 1). Narcoossee soils are described as sandy, siliceous, hyperthermic Entic Haplohumods

(Ford et al. 1990). I compiled a plant species list for each transect (Appendix A). I also measured the basal area of any tree with a dbh greater than one centimeter within an eight meter radius from the center of each transect. I used the presence/absence of all woody species found on the transects, total basal area, basal area of all pines and the basal area of all oaks in a non-metric multi-dimensional scaling (NMS) analysis using PCOrd to order the transects based on these habitat features (Grandin 2006).

7 Table 1: Attributes of belt transects established to monitor growth, survival and reproduction of

C. fragrans on the Bombing Range Ridge, 2002-2005

Date Date of Length Area Species

Transect Soil Type Established last fire* (m) (m2) Richness

Apr-04, AH1 Narcoossee 2002 8 16 22 Jul-02

AH2 Narcoossee 2002 1990 6 12 14

Feb-03, AH3 Narcoossee 2002 8 16 28 Feb-99

AH4 Narcoossee 2002 1990 6 12 15

OB1 Jul 03, Narcoossee 2003 5 10 14 166-167 Jul-01

OB1 Jul 03, Narcoossee 2003 6 12 20 170-171 Jul-01

Apr-04, SH3 Daytona 2003 8 16 29 Jun-95

Influence of time since fire and season of fire on density, population growth and survival

I examined the relationship between population size and plant density at the scale of the

population of C. fragrans (Figure 1). Using fire history data provided by the Air Force, I

performed a linear regression with the number of individuals in each population dependant on

the number of years since each population last experienced a fire event. I also performed a linear

regression on the density of individuals in each population dependant on the time since fire.

Next, I collected information on Clitoria fragrans’ vital rates from permanent transects in areas

burned and unburned in different seasons and years. Iindividual C. fragrans on the transects were mapped and marked with a numbered tag on a wire that was placed as close as possible to the plant without damaging its underground structure (Table 1). I repeated this survey every year at the end of the growing season (October – November, 2003-2005) by counting all plants, marking presence and absence of previously tagged plants and tagging and mapping any new ones. The change in numbers between years is based on plants with above ground growth. The presence of potentially dormant plants could not be determined without extensive digging to locate the xylopodium, thus compromising portions of the transect with unknown effects on the overall study. Therefore, I did not monitor dormant plants.

I calculated population density (plants per m2), survivorship and growth. The population growth

of C. fragrans was treated as a discrete growth event. The number of individuals present in a

given year compared with the number present in the next year yielded the proportional change in population size. The ratio is dimensionless and calculated as Nt+1 / Nt (Krebs 2001). I

9 calculated population survivorship each year by dividing the number of plants found in both Nt+1 and Nt with the number of plants found only in Nt. Low sample size (N = 7 sites, 84 plants) and limited replication of fire treatments (time and season) contributed to low statistical power and limited my options for analysis. I am presenting my results in graphs and including the raw data to allow their use in a future meta-analysis that could further clarify the patterns of response with fire for C. fragrans. Two of the sites have not burned for 15 years. According to Stout and

Marion (1993), sandhill typically has a fire return interval of one to five years, so these sites

unburned for 15 were classified as ‘unburned.’

Influence of time since fire, season of fire, rainfall and plant size on reproduction

I studied flower production and seed set by Clitoria fragrans throughout the growing season in

burned and unburned areas. On each transect, 12 plants (84 total) were randomly chosen to

monitor more thoroughly. I will refer to these as the transect plants for the rest of this paper.

Beginning in 2003, I visited each transect weekly from April through November, while the plants

were above ground. During these visits, I recorded the number and type of reproductive

structures on each of the transect plants. I marked reproductive meristems using colored thread,

color-coded by the date of census.

At each census, I classified reproductive parts as cleistogamous flowers, chasmogamous buds,

chasmogamous flowers (open), cleistogamous pods or chasmogamous pods. Early

chasmogamous buds and cleistogamous flowers often appeared similar; however chasmogamous

buds generally had a longer pedicel and larger calyx. Generally chasmogamous buds developed a

corolla in the second or third week, distinguishing them from cleistogamous flowers. They

10 continued to be classified as buds until the corolla opened. As chasmogamous and cleistogamous

pods matured, they darkened and dried. I also recorded the number of seeds in each pod. Mature

pods explosively dehisced, twisting and often leaving the open, dried pod still attached to the

pedicel. In the absence of the pod remnants, mature pods that were absent the following week

leaving only a pedicel were counted as having dehisced. I was able to track the development of

individual buds and assess the fate of cleistogamous and chasmogamous buds. Due to

inconsistencies in recording the fate of buds in 2003, I only considered bud fate in 2004 and

2005. One plant was never found again following 2003. It was assumed to have died; therefore,

the sample size is 83 for 2004 and 2005. In 2005, using digital Vernier calipers, I measured the

stem diameter of each transect plant in June and again at the end of the season (October-

November). At the end of the season (October-November), I also measured the height of every

transect plant. I used the natural log (ln) of these three measurements as independent variables in

a linear regression to examine the allometric relationship between plant size on the natural log

(ln) of the total number of flowers produced per plant in 2005. Two plants were not above

ground for either the June or October-November measurements, therefore these plants were

excluded and the sample size for this regression is 81. I obtained monthly rainfall data for the

Range for 2003-2005 from Air Force personnel. These data were used to seek patterns in rainfall

and reproductive responses of C. fragrans among transects and years. I used rainfall per month as the independent variable and the total number of reproductive structures produced over all 7 transects as the dependent variables in a linear regression. I performed this regression for each of the three years of the study.

11 I did not have enough statistical power to test for significant differences among the transects based on fire effects. Therefore, I graphed percentage of transect plants that were reproductive with time since fire and season of fire. I graphed the average number of flowers produced per plant per site with time since fire and season of fire. Chasmogamous flower production is very small; therefore I used presence or absence of chasmogamous flowers as my dependent variable rather than raw numbers so that a more robust test may be used. Cleistogamous flowers are frequently produced, so I used the number of cleistogamous flowers produced per plant as an independent variable as well as site. I explored the relationship between the independent variables (number of cleistogamous flowers produced and site) and dependent variable

(presence/absence of chasmogamous flowers) using a binary logistic regression. I collected 57 cleistogamous and 10 chasmogamous seeds to measure the length (mm), height (mm) and weight

(g) of the seeds and performed an independent samples t-test assuming equal variances on mean differences in seed size.

12 CHAPTER THREE: RESULTS

Population-level response of Clitoria fragrans to time since the last fire

I found 67 populations of Clitoria fragrans ranging from 1 to 600 individuals on Avon Park Air

Force Range. Six of these populations were within 20 meters of another population. All others were isolated from neighboring populations. Population size was a decreasing function of time since fire at this spatial scale (Figure 2a; linear regression: F= 4.106, p = 0.047). However, there was no relationship between population density and time since fire at this spatial scale (Figure

2b; linear regression: F = 0.0232, p = 0.8794; quadratic: F = 0.4457, p = 0.7212).

Influence of time since fire and season of fire on density, population growth and survival

Recently burned transects had the potential to have a higher density of plants (Figure 3a,d) and increased population growth than those not burned (Figure 3b,e). However, long unburned transects had, similarly to the pattern seen at the larger scale, densities in the lower range of values and narrower variation than transects recently burned (Figure 3 a,d; 0.688-2.938plants/m2 and 0.917-1.333 plants/m2 respectively for recently burned and long unburned transects). The greatest population growth was recorded on a transect burned in winter. Annual survival was equal to or greater than 80% on six of seven transects in 2004 and five of seven transects in 2005

(Figure 3 c). Population survivorship appears to be more variable between years than among different fire regimes (Figure 3c,f; Appendix B). The transects with poorest survival in 2003-

2004 and 2004-2005 were burned in winter, spring, and summer (Figure 3 f).

13 Season of fire may have influenced density (Figure 3d). In 2003, sites unburned for 15 years (n

= 2) had a lower average population density (1.21 plants/m2) than the site burned in winter (2.00

plants/m2) or the four sites burned in the summer (1.71 plants/m2). These unburned sites also had

a lower variance in population density (0.03) than those burned in summer (0.84) (Appendix B).

In 2004 and 2005, the unburned sites had a lower average population density (1.12 plants/m2,

1.00 plants/m2) than the two sites burned in spring (2.94 plants/m2, 2.56 plants/m2) two sites burned in summer (1.52 plants/m2, 1.76 plants/m2) and one site burned in winter (2.94 plants/m2,

2.56 plants/m2 )(Figure 3 a, d). Again, the unburned sites also had a lower variance in population density for both 2004 and 2005 (0.03, 0.01) than site burned in both spring (0.86, 0.38) and summer (0.07, 0.23) (Appendix B).

Population growth exceeded 1.0 (r > 0.0) on two of seven transects in 2004 and 2005 (Figure

3b). Transects that remained unburned for 15 years did not exhibit population growth in either year (Figure 3b). Stable or negative growth characterized the remaining transects in 2004 and

2005. In both years, the average population growth varied between sites burned in winter (1.47,

0.87), spring (1.07, 0.89), summer (0.74, 1.15) and those not burned for 15 years (0.93, 0.89)

(Figure 3 e). Long unburned sites had a smaller variance in population growth (1.0x10-4, 1.3x10-

3) than those burned in spring (0.01, 0.02) and summer (0.05, 0.01) (Appendix B).

The variability in density, population growth and survivorship of C. fragrans among the sites

may be caused by differences intrinsic to the sites as well as the fire regimes of the sites. I

performed an ordination using the presence/absence of woody species found on each transect,

total basal area and basal area of oaks and pines. The ordination was two dimensional (Figure 4).

14 The sites in the lower left hand corner of the graph contained more woody species and had a higher basal area of trees than the other sites. One site, AH1, had no woody species at all.

700 a) 600 r ²=0.059 n = 67 500

400

N 300

200

100

0 -100 0 5 10 15 20 25 30 Time Since Fire (years) b) 3.5

3.0 n = 67

2.5

2.0

1.5

1.0

Density (plants/m^2) 0.5

0.0

0 5 10 15 20 25 30 TIme since fire (years)

Figure 2: Landscape-level response of Clitoria fragrans. a) Population size (N) of all populations of Clitoria fragrans found on APAFR relative to time since fire and b) Plant density of all populations of Clitoria fragrans found on APAFR relative to time since fire (Lewis and Stout, unpublished data). Fire history dates back to 1972.

16 a) d)

3.5 3.5

2003 3.0 2004 3.0 2005

2.5 2.5 2 2 m m

r r e

2.0 p 2.0 s pe ts n a Plant Pl 1.5 1.5

1.0 1.0

0.5 0.5 0246810121416 Unburned Winter Spring Summer Time since fire (years) Season of Fire 2003 2004 2005 b) e)

1.6 1.6 2003-2004 2004-2005 2003-2004 1.4 1.4 2004-2005 r= 0.00 r = 0.00 1.2 1.2 crease n i

increase

of 1.0 1.0 of te e a r e rat t e

t 0.8 ni 0.8 i ni F i F

0.6 0.6

0.4 0.4 Unburned Winter Spring Summer 024681012141618 Season of Fire Time Since Fire (years) c) f)

1.1 1.1 2003-2004 2004-2005 2003-2004 1.0 1.0 2004-2005 p 0.9

0.9 ivorshi v r vorship 0.8

0.8 on Su i t on suvi ti 0.7 la pula u 0.7 Po Pop 0.6 0.6

0.5 0.5 Unburned Winter Spring Summer 0246810121416 Season of Fire Time Since Fire (years)

Figure 3 :Demographic traits for Clitoria fragrans on the transects. a) population density b) population growth c) population survivorship relative to time since fire d) population density e) population growth and f) population survivorship relative to the season of the last fire. n = 7 for 2003, 2004 and 2005. 17 AH1

OB1 166-

OB1 170- 2 s i Ax

SH3

AH3 AH4

AH2

Axis 1

Figure 4: NMS ordination based on habitat variables of the seven transects on which vital rates and flowering of Clitoria fragrans were studied, APAFR, 2003-2005.

Influence of time since fire, season of fire, rainfall and plant size on reproduction

There does not appear to be a relationship between the time since the last fire event or the season of the last fire event and the percentage of transect plants that reproduced at each site (Figure

5a,c). Both recently burned sites as well as those not burned for over 10 years overlap in the flowering performance of C. fragrans (Figure 5a,c, Appendix B). Closer inspection reveals the

sites most recently burned have a higher average number of flowers produced per plant than

plants not burned in 14-15 years (Figure 5b,d). This trend was not consistent because some

recently burned transects produced the same general number of flowers per plant as the long-

unburned transects (Figure 5 b).

The percentage of plants flowering increased in variability from transects burned in winter to

spring to summer with a complete overlap in variability relative to the unburned transects (Figure

5 d). These data repeat the trend seen in the demographic traits. Sites not burned for 15 years

have a lower variance (1.53, 4.75) than those burned in spring (32.79, 21.37) and summer (31.34,

49.17) for 2004 and 2005, respectively (Appendix B).

Plants produced flowers from April through October and fruit from April through November in

2003-2005 (Figure 6). Cleistogamous flowers and fruit were borne primarily from April through

September with a few fruit being produced into November (Figure 6 c). Chasmogamous flowers

and fruit were primarily produced May-July, with the occasional April or August flower. The

majority of flowers (93%) produced in both 2004 and 2005 were cleistogamous (Table 3). Out of

the few chasmogamous flowers produced (n = 46), only two flowers produced fruit that then set

19 seed over both years (Tables 3 and 4). Cleistogamous seed set was also variable between sites

(Tables 3 and 4). During 2004 and 2005, approximately the same percentage of cleistogamous

flowers set seed (Table 2). In 2004, anywhere between 5 and 67% of cleistogamous flowers

produced on any transect set seed (Table 3). In 2005, this ranged from 0 to 60% (Table 4). In

2005, I used the natural log of three measurements of plant size (stem diameter taken in June,

stem diameter measured Oct-Nov, and stem height measured Oct-Nov.) in a linear regression to

examine the effect of plant size on flowering (n=81). The natural log of summer stem diameter

(p = 0.001) and fall stem diameter (p = 0.004) influenced the natural log of the total number of

flowers per plant (linear regression: R2 = 0.473, F = 24.925, p = 0.000), while the natural log of

the fall stem height (p = 0.224) was not significantly related to the natural log of the total number

of flowers produced per plant. 2003 was the only year in which rainfall significantly influenced

both the production of all reproductive structures (linear regression: R2 = 0.774, p = 0.004).

Rainfall did not significantly influence the production of reproductive structures in 2004 (linear regression: R2 = 0.177, F = 1.297, p = 0.299) or 2005 (linear regression: R2 = 0.433, F = 4.582, p

= 0.0761).

The logistic regression showed that the presence of chasmogamous flowers is significantly affected by the number of cleistogamous flowers the plant produces (Table 5a). However, site did not significantly affect the presence of chasmogamous flowers (Table 5b; p = 0.959 for 2004, p = 0.998 for 2005). On average, cleistogamous seeds had a length of 3.98mm, height of 3.55mm and weight of 0.03g. Chasmogamous seeds had an average length of 3.87mm, height of 3.73mm and weight of 0.03g. There was no difference in the length (p=0.37), height (p=0.113) or weight

(p=0.585) of cleistogamous and chasmogamous seeds.

20 a) c)

100 100 s s 80 80 ant ant g pl ng pl n 60 60 oweri oweri l l f f f

40 40 ge of a age o t t

Percen 20 Percen 20

0 0 0246810121416 Unburned Winter Spring Summer Time since fire (years) Season of fire 2003 2003 2004 2004 2005 2005

b) d)

14 14

12 12 2004 2005

plant

/ 10 10 plant /

owers 8 l ers

8 f ow l 6 r f

6 ber of be 4 4 ge num

a 2 r 2 Average num Ave 0 0

Unburned Winter Spring Summer 0 2 4 6 8 10121416 Season of fire Time since fire (years) 2004 2005

Figure 5: Flowering responses of Clitoria fragrans in relation to time since fire and season of fire. The percentage of reproductive plants on a transect and average number of flowers produced per plant at each site relative to time since fire (a, b) and season of fire (c, d). n = 7 for 2004 and 2005

1.4 18

16 1.2 a) 14 1.0 12 0.8 10

0.6 8 6 0.4 4

es 0.2 2 ur t

c 0.0 0 t u n b r r y n ly g p ct v c Ja Fe Ma Ap Ma Ju Ju Au Se O No De r

t CL flower 1.4 18

s CL fruit

e CH flower

v * 16 CH fruit i 1.2 b)

t Rainfall ) 14 Average 1.0 Rainfall 12 1972-2003 oduc

0.8 nches pr 10 i e ( l r 0.6 8 l a f of 6 n 0.4 i er a

b 4 R 0.2 2

0.0 0 n b r r y n ly g pt ct v c Ja Fe Ma Ap Ma Ju Ju Au Se O No De 1.4 18 age num

er c) 16 v 1.2 A 14 1.0 12 0.8 10

8 0.6 * 6 0.4 4 0.2 2

0.0 0 n b ar pr ay n ly g pt ct ov ec Ja Fe M A M Ju Ju Au Se O N D Month

Figure 6: Average number of reproductive structures produced per plant of C. fragrans on the transects and total rainfall per month. a) 2003, b) 2004 and c) 2005. *Sudden increase in rainfall a result of the September hurricanes in

2004 and October hurricane in 2005. n = 84 plants for 2003; n = 83 plants for 2004, 2005.

Table 2: Flowers produced by C. fragrans on all transects in 2004 and 2005

Total # Cleistogamous Cleistogamous Chasmogamous Chasmogamous Year flowers flowers set flowers flowers flowers set seed produced seed 2004 331 308 (93%) 23 (7%) 65 (21%) 2 (8.7%)

2005 269 251 (93.3%) 23 (6.7%) 55 (22%) 0 (0%)

Table 3: Flower production by C. fragrans on transects, 2004

Total no. Cleistogamous Cleistogamous Chasmogamous Chasmogamous Transect flowers flowers set flowers flowers flowers set seed produced seed AH1 105 87 (83%) 18 (17%) 19 (22%) 2 (11%)

AH2 25 24 (96%) 1 (4%) 11 (46%) 0 (0%)

AH3 21 21 (100%) 0 (0%) 1 (5%) NA

AH4 6 6 (100%) 0 (0%) 4 (67%) NA

OB1 166-167 109 108 (99%) 1 (1%) 20 (19%) 0 (0%)

OB1 170-171 23 23 (100%) 0 (0%) 4 (17%) NA

SH3 42 39 (93%) 3 (7%) 6 (15%) 0 (0%)

23 Table 4: Flower production C. fragrans on transects, 2005

Total no. Cleistogamous Cleistogamous Chasmogamous Chasmogamous Transect flowers flowers set flowers flowers flowers set seed produced seed AH1 57 54 (95%) 3 (5%) 10 (18.5%) 0 (0%)

AH2 30 30 (100%) 0 (0%) 18 (60%) NA

AH3 19 19 (100%) 0 (0%) 8 (42%) NA

AH4 3 2 (67%) 1 (33%) 0 (0%) 0 (0%)

OB1 166-167 131 117 (89%) 14 (11%) 14 (12%) 0 (0%)

OB1 170-171 19 19 (100%) 0 (0%) 3 (16%) NA

SH3 10 10 (100%) 0 (0%) 2 (20%) NA

24 Table 5: Logistic regression results predicting the presence of chasmogamous flowers based on the total number of cleistogamous flowers on an individual plant. a) 2004 (Wald = 7/031, p = 0.008) and b) 2005 (Wald = 7.101, p = 0.008) a)

Predicted Chasmogamous Percentage Observed absent present Correct absent 77 1 98.7 Chasmogamous present 2 3 60.0 Overall Percentage 96.4

Predicted Chasmogamous Percentage Observed absent present Correct absent 74 1 98.7 Chasmogamous present 4 4 50.0 Overall Percentage 94.0

25 CHAPTER FOUR: DISCUSSION

My study confirms that fire affects the vital rates of populations of Clitoria fragrans. The population survey of xeric soils on the Bombing Range Ridge revealed the general pattern that time since fire has a significant negative effect on the number of individuals in populations

(Figure 2a). However, plant density showed no relationship with time since fire (Figure 2b). This may be due to the somewhat arbitrary boundaries drawn around each population. The polygons were outlined on the basis of location of plants rather than including all possible habitat. This may have obscured the pattern seen with population size and time since fire. Demonstration of the mechanisms by which time since fire and the season of fire events influences vital rates of C. fragrans is more problematic at the scale of transects embedded in local populations. I found important variation across sites (transects) in the response of population density, growth and survivorship with time since fire and the season of fire.

Populations of C. fragrans on recently burned transects ranged in density between 0.5 and 3.0 plants per m2. Long unburned transects ranged in density between 0.5 and 2.0 plants per m2.

The densities of long unburned populations were much less variable that the recently burned populations. The very modest increases in density on the burned transects suggests some recruitment of genets derived from seeds of plants that flowered within weeks following fire events. Alternatively, the new stems could be ramets from previously dormant xylopodia.

Lastly, the recruits could be from a seed bank. Recruitment from seed banks typically gives rise to several fold increases in density or the appearance of individual plants in locations with few or

26 no plants. Because neither of these latter circumstances were observed, I dismiss the seed bank

as an explanation of changes in density following fire events.

Changes in densities of C. fragrans may be explained by the season of fire events. The pattern that emerges is winter and summer burns have the potential to be associated with higher densities than spring burns and unburned areas. The source of the important variation across sites and seasons cannot be identified with my study design. An extrinsic factor, rainfall, may explain the greater densities after winter and summer burns relative to spring burns, which may be associated with dry conditions prior to the onset of summer rains. The suffrutescent nature of C. fragrans suggests early winter fires will have no impact on the future growth of above ground parts.

My data on population growth of C. fragrans indicates the local populations are relatively static.

Based on finite rates of increase, two of seven populations exhibited growth between 2003 and

2004 and 2004 and 2005. These periods of growth occurred the year of a fire event (n = 1), the

year following (n = 1) or two years following (n = 2). Two of these growth events were related to

summer burns, one a spring burn, and one a winter burn.

Plant survivorship in long unburned sites is around 85%, while recently burned sites have both

higher and lower survivorship. Survivorship may depend on the season in which the fire occurs,

e.g., winter burns should have little or no affect on dormant plants. Plant survivorship appears equally variable among all seasons of fire. The three transects with the lowest annual survival rates were burned in different seasons.

In general, burned sites have an increased variability among the demographic variables of

population density, population growth and plant survivorship relative to those sites unburned for

15 years. Neither the time since the last fire or the season of fire provided a consistent signal to

explain the demographic responses. Clearly other intrinsic or extrinsic factors contributed to the

observed variability. Interactions between time since fire and season of fire can be too subtle to

be detected in a purely graphical analysis. Limits placed on the analysis by the low statistical

power intrinsic to the data set preclude an analysis of interactions.

Sandhill plant associations typically have a fire return interval of one to three years (Stout and

Marion 1993). However, natural fire regimes have been disrupted through years of fire

suppression in many xeric pinelands. In contrast, prescribed burning has a long history at

APAFR. Nevertheless, two of my study sites had not been burned for 14 or more years and

supported reasonable numbers of C. fragrans. The population with the lowest density of plants

was the only site where more than one fire occurred during the study. Neither historic nor contemporary information offers insights into the site specific variability in the behavior of C.

fragrans relative to fire.

The NMS ordination showed a clear pattern in differences among the seven transects based on woody species and basal area (Figure 4). The site AH1 can be separated out from the other sites based on its complete lack of woody species. However, AH1 did not perform differently from the other sites for all measures of reproduction and vital rates except population density.

Therefore, its exclusion from the analysis would not make any difference in my interpretations.

28 Thus, it is likely that there are other environmental differences among the sites that are more

influential on vital rates and reproduction than the presence and basal area of woody species.

The percent of plants reproducing at any given site is equally variable for both recently burned

(0.03-0.17) and long unburned sites (0.01-0.15) regardless of fire season. Some sites are

consistent for both years (AH1, OB1 166-167), while others (AH4, SH3) are highly variable in flowering behavior (Appendix B). AH4 is the only one of these sites to remain unburned. The variable reproductive responses may be a result of interaction between time since fire, season of fire and site habitat variables that were not measured. A sample of two years and seven sites was not large enough to discern any statistical significance through a linear regression.

For the three years of this study, individuals of Clitoria fragrans monitored on the transects produced more cleistogamous flowers and fruit than chasmogamous structures. In general, reproduction in Clitoria fragrans was fairly modest. In 2 years, only two chasmogamous flowers

matured to set seed on the 83 plants observed. Only one chasmogamous fruit dehisced,

contributing four potentially outcrossed seeds. Just over 20% of cleistogamous flowers matured

to set seed in each of the two years. In other species, the production of cleistogamous flowers

ensures reproductive output in environs that do not favor chasmogamous flowers (Le Corff 1993,

Berg and Redbo-Torstensson 1998). However, a binary logistic regression revealed that site did

not significantly affect the presence of chasmogamous flowers (p = 0.959 for 2004, p = 0.998 for

2005). Therefore, fire does not appear to play a role. However, in 2006, I observed large number

of chasmogamous flowers following a fire event at a site other than those described in this study.

29 Previously, no chasmogamous flowers had been observed. Therefore, I believe a fire response

may exist that could not be detected on the transects under the prevailing conditons.

Chasmogamous flowers may attract more floral predators because they are showy. Nearly every

chasmogamous flower, regardless of whether or not it matured into a legume, had some evidence

of floral herbivory (personal observation). Steets and Ashman (2004) found that herbivory

increased production of cleistogamous flowers relative to chasmogamous flowers.

I did not study the morphology of the chasmogamous flowers produced by Clitoria fragrans. It is

possible that individual chasmogamous flowers are unisexual. This could explain the lower percent of flowers maturing to set seed in chasmogamous flowers compared to the perfect, selfing cleistogamous flowers. Another sandhill ridge endemic, Ziziphus celata, exhibits self- incompatibility (Weekley et al. 2002). This mechanism, which has not been explored in Clitoria fragrans, prevents inbreeding (Barrett et al. 1996; Goodwillie et al. 2005). Given the dominance of cleistogamous flowers and seeds, chasmogamous flowers may be self-incompatible to prevent additional selfing.

Seeds are dispersed ballistically, so most new recruits likely come from plants currently in the population. These plants are producing mostly selfed seeds, therefore there is likely not much genetic diversity added in each generation. It has been suggested than self-fertilized seeds have higher fitness in the maternal environment than outcrossed progeny (Waller 1984; Schmitt et al

1985). Schmitt et al (1985) reported differential dispersal distances between chasmogamous and cleistogamous seeds in Impatiens capensis, which also has a ballistic dispersal mechanism. They

30 found that chasmogamous seeds were dispersed farther away from the maternal plant than

cleistogamous seeds, despite no discernable physical differences between the seed types. I found

no morphological difference between the cleistogamous and chasmogamous seeds in Clitoria

fragrans. It is possible that Clitoria fragrans also exhibits this differential dispersal pattern; however, I did not measure dispersal distances. When cleistogamous seeds are larger than chasmogamous, there is a clear fitness advantage for the cleistogamous seeds; however, when seeds are morphologically identical, chasmogamous flowers have a more variable response to

environmental variation in some species (Le Corff 1993).

The total number of cleistogamous flowers affected the presence of chasmogamous flowers

(Table 5). The more cleistogamous flowers a plant produced, the higher the probability that the

plant would also produce at least one chasmogamous flower (Table 5). I found an allometric

relationship between plant size (stem diameter measured in June and November) and the number

of flowers produced that year. In some species, chasmogamous flowers are more costly to

produce than cleistogamous flowers (Schemske 1978, Waller 1984). If energetic costs were the

sole limitation on the production of CH structures in C. fragrans, then one might expect larger plants to produce proportionally more CH structure than smaller plants. However, Le Corff

(1993) found that increased plant size led to increased overall flowering in Calathea micans, but

did not significantly alter the ratio of chasmogamous to cleistogamous flowers. My data also

suggest that larger plants produce more of both flower types. This suggests that there may not be

an energetic cost difference in the production of cleistogamous and chasmogamous flowers in

Clitoria fragrans. Further research should include investigations into the energetic costs of producing both flower types in Clitoria fragrans.

Rainfall significantly influenced the production of cleistogamous and chasmogamous structures

in 2003, but not in 2004 or 2005. There was increased hurricane activity in both 2004 and 2005

that caused spikes in rainfall, which diverged from the average rainfall of the last 30 years

(Figure 6). It is possible that other external conditions accompanying the hurricanes also affected

the production of flowers in C. fragrans such that rainfall did not have a significant influence in

these years.

Overall, there appears to be a trend of fire increasing both flowering and population density of

plants. Future studies should increase the sample size and increase the power of statistical

analyses. Also, further studies should include more fire intervals. I only had access to sites

recently burned (within two years) and long unburned (up to fifteen years). Adding sites that

have been burned some time between this interval will increase the understanding of Clitoria fragrans’ response to fire.

32 APPENDIX A: SPECIES LIST FOR ALL TRANSECTS

Transect OB1 OB1 Species AH1 AH2 AH3 AH4 166-167 170-171 SH3 Andropogon spp. x x x x Aristida stricta var. beyrichiana x x x x x Arnoglossum floridanum x Ascemnome ciscindula x Asimina reticulata x Bulbosytlis ciliatifolia x x Carphephorus corymbosus x Cenchrus incertus x Eremochloa ophiuroides x Centrosema virginianum x x Chamaecrista fasciculata x Chapmannia floridana x x x x x x Clitoria fragrans x x x x x x x Cnidoscolus stimulosus x x Crotolaria rotundifolia x Cyperus retrorsus x x x Dichanthelium spp. x x x x x x Cuscuta sp. x Elephantopus elata x x Eragrostis virginica x Euphorbia polyphylla x x Galactia elliottii x x x x Galactia regularis x x x x x x Garberia heterophylla x Gaylussacia dumosa x x Eleusine indica x Gratiola hispida x Hieracium megacephalon x Conyza canadensis x Indigofera caroliniana x x x Liatris chapmanii x x Liatris tenuifolia x x Licania michauxii x x Lyonia fruticosa x Opuntia humifusa x Paspalum setaceum x Piloplephis rigida x Pinus clausa x Pinus palustris x x Pityopsis graminifolia x x x Polygala grandiflora x 34 Polygonella gracilis x x Polypremum procumbens x x

Transect OB1 OB1 Species AH1 AH2 AH3 AH4 166-167 170-171 SH3 Pterocaulon pycnostachyum x x x x Quercus chapmanii x Quercus geminata x x x x Quercus hemispherica x x Quercus myrtifolia x x x x x Rhynchosia cinerea x x Rhynchospora megalocarpa x x Ryhnchosia michauxii x Sabal etonia x Scleria paucasiflora x Serenoa repens x x x x x x Smilax auriculata x x x x Sorghastrum secendum x x Stillingia sylvatica x x x x x x Stylisma patens x Tephrosia chrysophylla x Tillandsia bartramii x Tillandsia usneoides x Tragea urens x Ximenia americana x x Xyris carolineana x Zornia bracteata… x

36 APPENDIX B: DESCRIPTIVE STATISTICS FOR DEMOGRAPHIC AND REPRODUCTIVE VARIABLES

Season of fire Unburned Winter Spring Summer N 2.0 1.000 0.000 4.000 Mean 1.208 2.000 NA 1.709 2003 Median 1.208 NA NA 1.625 St dev 0.177 NA NA 0.914

y Var 0.031 NA NA 0.836 N 2.0 1.000 2.000 2.000 Mean 1.125 2.938 1.344 1.517 2004 Median 1.125 NA 1.344 1.517 St dev 0.177 NA 0.928 0.259 Var 0.031 NA 0.861 0.067

Population Densit N 2.0 1.000 2.000 2.000 Mean 1.000 2.563 1.125 1.758 2005 Median 1.000 NA 1.125 1.758 St dev 0.118 NA 0.619 0.483 Var 0.014 NA 0.383 0.233 N 2.0 1.000 2.000 2.000

e Mean 0.930 1.469 1.071 0.738 2003- Median 0.930 NA 1.071 0.738 eas

r 2004 St dev 0.010 NA 0.101 0.214 Var 0.000 NA 0.010 0.046 N 2.0 1.000 2.000 2.000 Mean 0.892 0.872 0.891 1.149 2004- 2005 Median 0.892 NA 0.891 1.149

Finite rate of inc St dev 0.035 NA 0.155 0.122 Var 0.001 NA 0.024 0.015 N 2.0 1.000 2.000 2.000 Mean 0.895 0.969 0.919 0.710

ship 2003- r Median 0.895 NA 0.919 0.710 o 2004 v St dev 0.040 NA 0.014 0.175 rvi u Var 0.002 NA 0.000 0.031 N 2.0 1.000 2.000 2.000 Mean 0.858 0.638 0.859 0.939 2004- 2005 Median 0.858 NA 0.859 0.939

Population S St dev 0.082 NA 0.199 0.003 Var 0.007 NA 0.040 0.000

Average number of flowers Percentage of reproductive plants per plant 2005 2004 2005 2004 2003

M M M M M St dev St dev St dev St dev St dev M M M M M e e e e e V V V V V e e e e e N N N N N d d d d d a a a a a

a a a a a i i i i i

r r r r r a a a a a n n n n n

n n n n n

U n 2 1 0 0 0 2 1 0 0 0 4 1 0 0 0 2.180 1.237 0.290 0.120 0.389 b 2 2 2 2 2 ...... 0 6 3 4 5 0 6 3 4 5 7 5 0 0 1 u . . . . . 0 0 0 0 0 4 2 7 1 2 4 2 7 1 2 5 3 8 1 5 rn

2 5 5 5 5 2 5 5 5 5 3 1 4 4 1 ed

W 0 0 0 2 2 1 1 1 1 1 Seaso . . . . . N N N N N . . . . . N N N N N NA NA NA NA NA i 4 4 8 7 3 0 0 0 0 0 n A A A A A A A A A A 2 2 3 5 3 0 0 0 0 0

t 39 e

0 0 0 0 3 0 0 0 0 0

n offire 2 3 S 0 0 0 4 9 0 0 0 4 9 2 2 2 0 2 0 0 0 0.177 0.177 0.000 4.623 5.726 1 2 p ...... 5 7 0 1 1 5 7 0 1 1 0 0 0 0 0 0 0 0 . . r 3 7 i 4 0 0 8 3 4 0 0 8 3 0 0 0 0 0 3 3 0 n 7 9 5 5 0 6 3 5 5 0 6 3 0 0 0 0 0 1 1 0 g 2 3

S 4 3 0 0 0 7 6 0 0 0 7 6 2 2 2 4 2 0.297 0.417 0.333 7.012 5.598 0 0 0 u 9 1 ...... m 7 6 4 7 2 7 6 4 7 2 0 0 0 0 0 0 1 1 . . 1 3 1 2 9 9 9 1 2 9 9 9 0 0 0 0 0 8 7 1 m 7 3 0 5 5 2 2 0 5 0 2 2 0 0 0 0 0 8 4 1 0 7 e

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