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2003 Distribution, Spread, Activity Patterns, and Foraging Behaviors of the Introduced Pheidole Obscurithorax in the Southeastern United States Shonna R. Storz

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THE FLORIDA STATE UNIVERSITY

COLLEGE OF ARTS AND SCIENCES

DISTRIBUTION, SPREAD, ACTIVITY PATTERNS, AND FORAGING BEHAVIORS

OF THE INTRODUCED ANT PHEIDOLE OBSCURITHORAX IN THE

SOUTHEASTERN UNITED STATES

By

SHONNA R. STORZ

A Thesis submitted to the Department of Biological Science in partial fulfillment of the requirements for the degree of Masters of Science

Degree Awarded: Summer Semester, 2003

The members of the Committee approve the thesis of Shonna R. Storz defended on June 13,

2003

Walter R. Tschinkel Professor Directing Thesis

Thomas E. Miller Committee Member

Laura R. Keller Committee Member

Approved:

Thomas M. Roberts, Chairperson, Department of Biological Science

Donald Foss, Dean, College of Arts and Science

The Office of Graduate Studies has verified and approved the above named committee members.

ii

I’d like to dedicate this work to my husband, Brian L. Storz, for his never-ending belief in me and for his ability to always make me laugh.

iii

ACKNOWLEDGMENTS

This study would not have been possible without the support and field assistance of B. L.

Storz who spent an immeasurable amount of time with me driving across the southeast and collecting data. I’d like to thank my advisor, W. R. Tschinkel, for his not-so-gentle prodding and demand for progress, countless hours of help on Statistica, comments and suggestions on manuscripts and grants, and for his brilliant insights into what it all means. Thanks to my committee members, T. E. Miller and L. R. Keller for gentle prodding and valuable discussion.

Thanks also to T. E. Miller for lending me numerous items from his lab. Thanks to my lab mates, K. L. Haight, A. S. Mikheyev, J. N. Seal, and C. R. Smith, for helpful discussions and assistance, and for making my time spent in the lab enjoyable; they are a great bunch of guys.

Thanks to N. Plowes for getting me started with ant identifications and making it seem less daunting. Special thanks to M. Deyrup for assistance with ant identifications while at the

Ant Course; without his help I would likely have taken two more years to complete this research.

I am thankful for spending my tenure in graduate school at FSU; my fellow graduate students and the faculty have made my experience very rewarding and enjoyable. FSU undergraduates T.

Ballinger, N. Dix, M. Fisher, R. Moore, and T. Rhoades helped with specimen sorting and counting. I appreciate the hard work of two dedicated high school students, M. Ponce and S.

Mendenhall, in the FSU Young Scholars Program who helped monitor activity at nests. I thank the more than 86,000 who passed from this world in the name of science. This project was

iv partially funded by the Theodore Roosevelt Memorial Fund through the American Museum of

Natural History and by the Department of Biological Science at Florida State University.

v

TABLE OF CONTENTS

List of Tables ………………………………………………………………………… vii List of Figures ………………………………………………………………………... viii Abstract ………………………………………………………………………... x

INTRODUCTION ..……………………………………………………………………… 1

1. DISTRIBUTION, SPREAD, AND ECOLOGICAL ASSOCIATIONS OF THE INTRODUCED ANT PHEIDOLE OBSCURITHORAX NAVES IN THE SOUTHEASTERN UNITED STATES ….………………………………………….... 3

2. ACTIVITY RHYTHMS AND FORAGING TACTICS OF THE INTRODUCED ANT PHEIDOLE OBSCURITHORAX NAVES ………………….………………….. 24

CONCLUSION …………………………………………..……………………………… 46

APPENDICES …….…………………………………………………………….……..… 48

REFERENCES …………………………………………………………………………… 53

BIOGRAPHICAL SKETCH ……………………………………………………………… 59

vi

LIST OF TABLES

Table 1.1 Site characteristics at sites with P. obscurithorax present and absent ……… 11

Table 1.2 Mann-Whitney U tests of the abundances of the six most common ant species at sites with P. obscurithorax present and absent …………………………..… 13

Table 1.3 Spearman rank order correlations of the abundances of the six most common ant species and P. obscurithorax nest density ……………………………… 13

Table 2.1 Means and 95% confidence intervals for the activities represented in figure 2.6. ……………………………………………………………………………… 34

Table 2.2 Repeated measures ANOVA table for foraging activity vs. bait type ..……. 38

vii

LIST OF FIGURES

Figure 1.1 Pheidole obscurithorax nest densities at each site plotted on a map of the southeastern United States …………………………………………………………….. 10

Figure 1.2 Collection frequencies of 19 bait-collected ant species …………………… 12

Figure 1.3 Rarefaction curve for southeast survey …………………………………… 14

Figure 1.4 Frequency of 26 ant species collected in pitfall traps …………………….. 15

Figure 1.5 Rarefaction curves for pitfall-trap study ………………………………….. 16

Figure 1.6 Relationship between Pheidole obscurithorax nest densities measured at 21 sites in Tallahassee in two years ………………………………………………… 17

Figure 1.7 Pheidole obscurithorax presence at each of 21 sites in Tallahassee, Florida, in two years …………………………………………………………………… 18

Figure 1.8 Pheidole obscurithorax nest densities at 21 sites in Tallahassee, Florida, in June 2002 …………………………………………………...………………….….. 19

Figure 2.1 Relationship between numbers of outbound and inbound foragers counted for two minutes ……………………………………………………………….. 28

Figure 2.2 Relationship between numbers of outbound and inbound nest-surface tenders counted for two minutes …………………………………………………….… 29

Figure 2.3 Relationship between total nest-surface tenders (outbound plus inbound nest-surface tenders) and total foragers (outbound plus inbound foragers) counted for two minutes ……………………………………………………………………..… 29

Figure 2.4 Relationships between time of day and ground temperature, total numbers of scouts, total numbers of foragers, and total numbers of nest-surface tenders …….. 31

Figure 2.5 Relationships between temperature and total numbers of scouts, total numbers of foragers, and total numbers of nest-surface tenders ……………………... 32

viii Figure 2.6 Relationship between time and ground temperature for each of three non-consecutive days of observation ……………………………………………..…… 33

Figure 2.7 Activity levels during three time periods plotted for each of three days …. 34

Figure 2.8 Proportions of workers that are minors performing three tasks ……..……. 35

Figure 2.9 Relationships between nest size and total numbers of scouts, total numbers of foragers, and total numbers of nest-surface tenders ………………..…….. 36

Figure 2.10 Typical relationship between time and the numbers of minors recruited to a bait counted during 10-second intervals ……………………………………..…… 37

Figure 2.11 Relationships between bait type (sm = small, lg = large, and lgst = large staked) and (a) time to remove bait (small and large only), (b) numbers of minors at the bait, and (c) numbers of majors at the bait ……………………..……. 40

ix

ABSTRACT

A field survey of the southeastern United States showed that Pheidole obscurithorax

Naves, an ant introduced from South America, inhabits a 50-mile-wide band along the coast between Mobile, Alabama, and Tallahassee, Florida, and is continuing to increase its range.

Evidence suggests that P. obscurithorax has spread mostly by diffusion by natural means. It coexists with the fire ant Solenopsis invicta Buren, appears to be part of a largely exotic community of ants that are tolerant of highly disturbed habitats, and seems to have little negative effect on the ant communities that it invades. In Tallahassee P. obscurithorax is rapidly spreading, and its nest density increased by a factor of 6.4 over a two-year period. P. obscurithorax summer activity patterns appear to be regulated by time of day rather than by temperature, but they do not appear to be active above ground at temperatures over 36˚C.

Evidence suggests that foragers and nest-surface tenders are two separate populations and their activity is shifted in time relative to each other. The group prey retrieval tactics of P. obscurithorax related to prey size and mobility do not conform to predictions of central place foraging theory.

x

INTRODUCTION

Natural ecosystems are disappearing at increasing rates, largely as a result of human

disturbance. Along with the decline in natural habitats comes an increase in the amount of

disturbed habitat such as open fields, urban areas, and roadsides. Documenting the communities

that inhabit these ever increasing disturbed areas is an important step for conservation efforts.

Human activity is also increasing the transfer rate of exotic species across the globe. Introduced

species are often associated with disturbed habitat (Elton, 1958; Case, 1996), and many

introduced species are thought to have negative effects on the communities that they invade.

Invasion biology has historically focused on identifying common characteristics of highly

invadable habitats as well as of successful invasive species in order to predict the outcome of

invasions (Mooney and Drake, 1986; Vinson, 1986; Drake et al., 1989; Williams, 1994; Kareiva,

1996; Simberloff et al., 1997). While there has been progress in these areas, most research has

focused on a small subset of introduced species. In order to better understand what

characteristics make an invader successful, it is important to study a multitude of introduced

species for comparisons.

The ant, Pheidole obscurithorax, was introduced to the southeastern United States over

50 years ago (Naves 1985). To date, no studies have been conducted on this introduced ant, but its presence in the southeastern United States is recognized (Naves, 1985; McGlynn, 1999;

Deyrup et al., 2000; Wilson, 2002). It coexists with a well-studied introduced fire ant,

Solenopsis invicta, in disturbed habitat, but its effects on S. invicta or other ants are unknown.

1 The current study will document P. obscurithorax’s distribution in the United States, the ant communities and habitat characteristics associated with its presence, and its density and population increase in Tallahassee, Florida. Additionally, selected natural history characteristics, namely its activity rhythms and foraging behavior, will be documented.

2

CHAPTER 1

DISTRIBUTION, SPREAD, AND ECOLOGICAL ASSOCIATIONS OF THE INTRODUCED ANT PHEIDOLE OBSCURITHORAX NAVES IN THE SOUTHEASTERN UNITED STATES

Introduction

Species introduced to new areas, whether naturally or by humans, can alter the receiving community. These invasive species are increasingly recognized for the economic and conservation problems they create through direct (competition, predation, herbivory, parasitism, hybridization, habitat alteration) and indirect effects on a community (Elton, 1958; Vitousek et al.; Pimm, 1991; Simberloff et al., 1997; Brown and Lomolino, 1998; Manchester and Bullock,

2000; Pimentel et al., 2001). Elton's (1958) early view that disturbed and less speciose habitats are most susceptible to invading species is now thought to be overly simplistic. The success of an invader in any habitat depends on the species present, their interactions within the community, their interactions with the invading species (Simberloff, 1986), and the historical path by which the community arose (Vermeij, 1991; Lodge, 1993). This complexity is often compounded by the presence and effects of nonindigenous species already present in the community (Simberloff,

1997), by the amount of disturbance to the habitat (Tschinkel, 1988), and by the location and size of the area being invaded (Brown and Lomolino, 1998; Holway et al., 2002). Of the many invading organisms, social are among the most destructive. They affect large geographic areas, damage agricultural systems, are expensive to control, and reduce biodiversity in the communities they invade (Vinson, 1986; McKnight, 1993; Williams, 1994; Simberloff, 1997).

3 Among these, the fire ant Solenopsis invicta Buren and the Argentine ant, Linepithema humile

Mayr, are well-known invaders of North America that disrupt ant and other

communities (Porter and Savignano, 1990; Holway, 1998; Gotelli and Arnett, 2000).

Given the publicity about destructive invasive organisms, introduced species that have

little effect on the communities they invade are often overlooked, and ants are no exception.

McGlynn (1999) reported that only 2% (147/9358) of all known ant species have become

established outside their native ranges and that only 6% (9/147) of these are considered invasive in that they outcompete native ants. Within Florida alone, a hot spot for introduced species, 25%

(52/207) of the ant fauna is exotic and only 3% (7/207) are “potential ecological villains”

(Deyrup et al., 2000). Many introduced species that do not have large obvious effects on communities often go unnoticed and are understudied, while a small number of invaders are studied in great detail (Vermeij, 1996; McGlynn 1999). Regardless of the apparent effects of invaders, documenting their distributions, habitat characteristics, and species associations as well as investigating any effects they have on the communities they invade, be they small or large, is important for future comparisons.

Pheidole obscurithorax Naves is an ant native to northern Argentina and southern Brazil and presumably occurs along the Paraguay River system, which is traveled by ocean-going vessels. Its occurrence in North America was first observed in the port city of Mobile, Alabama, in the early 1950s (Naves, 1985; under the name, P. fallax obscurithorax). Several other ant species with ranges along the Paraguay River system (Brachymyrmex patagonicus Mayr,

Linepithema humile, Solenopsis invicta, and Solenopsis richteri Forel) have been transported to the southeastern United States via the ports of New Orleans, Mobile, and Pensacola (Naves,

1985). Pheidole obscurithorax coexists in disturbed habitats with the fire ant Solenopsis invicta,

4 which was introduced at Mobile in the late 1930s (Buren et al., 1974), but has been much slower

to expand its range, the extent of which is unknown. It was first observed in Tallahassee, Florida

(250 miles east of Mobile), in 1998 (W. R. Tschinkel, pers. comm.). To date no documented

investigations of P. obscurithorax have been conducted, although its occurrence in the southeastern United States is well documented (Naves, 1985; McGlynn, 1999; Deyrup et al.,

2000; Wilson, 2002). The goals of the study reported here were to determine (1) its range and likely site of introduction in the southeastern United States, (2) whether any habitat characteristics are associated with its success, and (3) whether it is associated with differences in ant communities across its range and (4) to document its spread and population increase in

Tallahassee, Florida, over a two-year period.

Methods

Southeast survey

A field survey was conducted during the summer of 2001 across five states (Florida,

Georgia, Alabama, Mississippi, and Louisiana) in the southeastern United States. Approximate site locations were initially chosen such that they were located 50 to 60 miles apart along five east-west transects centered at Mobile (presumed site of entry) spanning and extending beyond the expected range of P. obscurithorax. The initial survey determined that P. obscurithorax occupied a much smaller range than expected. I therefore implemented a second, more intensive sampling regime, involving sites at 25-mile intervals within the smaller potential geographic range of P. obscurithorax, which resulted in a larger sample of sites with P. obscurithorax.

Fifty-five sites were surveyed; 41 of these were located within the second sampling area

described above. The map shows all 55 sites (Fig. 1.1), but to avoid any bias due to uneven

5 sampling or the inclusion of sites potentially not suitable for P. obscurithorax, I included only the data collected from the 41 sites within the second sampling area for all analyses.

All sites were located on rights of way along two-lane highways as in Porter et al. (1991).

Characteristics were recorded at every site (latitude, longitude, elevation, surrounding vegetation type, type and percent of ground cover, grass height, and soil and air temperature), soil samples were collected, and standard survey methods (Porter et al., 1991) were used to estimate the nest densities of three conspicuous and easily identifiable ant species (Dorymyrmex bureni Trager, P.

obscurithorax, and S. invicta). More specifically, ant nests were counted along four transects

parallel to the road, two on each side of the highway (one along the pavement and the other

along the tree/shrub line). Each transect was 54 m long by 2 m wide (108 m2) for a total of 432

m2 surveyed per site.

Bait traps were used at each site to collect ground-foraging ants. In order to attract and

collect a wide array of ant species, I used two bait types placed inside individual glass test

tubes—oil-rich carbohydrate (shortbread cookie crumbs) and protein (hot dog pieces)—and three

collection times (15, 30, and 45 min). The use of cookie crumbs may allow less-dominant

species to remain at baits with dominant species, and the use of time intervals may allow

collection of both quick recruiters and those that are slower to recruit but may eventually

dominate the bait (Bestelmeyer et al., 2000). At each site 60 baits were arranged linearly into

groups of six (three carbohydrate and three protein) such that each group was placed 10 m from

the next; baits within each group were arranged hexagonally with 1m spacing. Two previously

designated baits from each group (one carbohydrate and one protein) were collected at each of

the three collection times. Ants collected at baits were taken to the lab, counted, and identified to

6 species (species identifications were aided by M. Deyrup; see Appendix 1 and 2 for site localities and species presence data).

Ant species abundance was estimated as the total number of bait tubes at each site that trapped a particular species rather than the number of individual ants trapped (counts of individual ants are estimates of both recruitment effort and abundance). Because the number of individuals collected is correlated with increasing number of species, and because of controversy over the use of diversity indices (Hurlbert, 1971; Heck et al., 1975; James and Rathbun, 1981;

Gotelli and Colwell, 2001), I used EstimateS software (Colwell 2000) to generate rarefaction curves to estimate expected number of species (species richness) at sites with and without P. obscurithorax.

I used the hydrometer method to conduct soil-texture analyses on the collected soil samples in order to determine the proportions of sand, clay, and silt at each site (Bouyoucos,

1927, 1936, 1962).

Because of the unexpected distribution of P. obscurithorax (see results below), I tested the a posteriori hypothesis that wind direction after summer rains influences the flight paths of ants on mating flights or of newly mated queens. I collected precipitation and wind data for

Mobile Regional Airport for four years (1998-2001) from the NOAA database online. For a randomly selected subset (n = 25) of the 76 days on which 0.25-1 inch of rain fell during June-

July, wind speed and direction were collected. I used a Rayleigh test (Batschelet, 1965) to determine whether a particular wind direction predominates.

Pitfall-trap study

During the summer of 2002 a pitfall-trap study was conducted in Tallahassee, Florida.

This study was designed to complement my investigation of P. obscurithorax's associations with

7 ant communities over a large geographic area (southeast survey) but on a smaller scale. Eight

roadside sites were chosen in Tallahassee where P. obscurithorax occurred at varying nest

densities (40-600 nests per ha) and had an average of 275 nests per ha. Roadside sites had

similar habitat characteristics (ground cover, surrounding vegetation, % canopy, etc.). At each

site 10 pitfall traps were spaced 10 m apart along linear transects. Pitfall traps consisted of 50-ml

plastic centrifuge tubes partially filled with 15 ml of a soap/propylene-glycol solution buried

with their openings (32 mm diameter opening) flush with the ground surface. All 80 traps were

set up on the same day and were left in place, undisturbed, for seven days (560 trap days). On the seventh day all traps were collected and the holes filled. Trap contents were sorted manually or by salt extraction (Lattke, 2000) depending on the amount of debris collected in the trap. All ants were counted and identified to species. Pitfall traps are commonly used to estimate the abundances and species compositions of ground-foraging ants (Bestelmeyer et al., 2000).

Although they have been shown to sample species compositions adequately, they tend to be biased toward fast-moving species (Andersen, 1991).

For each ant species, abundance was calculated as the number of individuals captured per pitfall trap. To investigate the association between P. obscurithorax abundance and species

richness, I constructed rarefaction curves based on the number of species captured in each trap

for three categories of P. obscurithorax abundance: (1) low (0 to 8 P. obscurithorax captured),

(2) moderate (9 to 17 P. obscurithorax captured), and (3) high (>17 P. obscurithorax captured).

Tallahassee survey

Twenty-one roadside sites were surveyed in Tallahassee, Florida, during June 2000 and

again during June 2002. At each site I estimated P. obscurithorax nest densities by counting

visible nests along linear transects from 54 to 108 m long and 1 m wide (at least 54 m2 per site).

8 Results

General observations

Pheidole obscurithorax is a large, dark ant up to 6 mm in length, and its workers are

dimorphic; the majors are larger than the minors and have enlarged heads. It nests in soil in open areas, where it produces conspicuous nests, each generally with a single large (1- to 5-cm-wide)

opening often covered by a leaf or other collected material. During one successful excavation of

a colony in Tallahassee, a single queen was located 3m below the surface. Pheidole

obscurithorax is omnivorous and collects a variety of arthropod prey, including other ants, and

less frequently plant material such as flower petals. Its midden piles are often littered with

heterospecific ant body parts, especially those of S. invicta, an abundant ant often found nesting

near P. obscurithorax nests. Pheidole obscurithorax uses a combination of foraging tactics; if a prey item is small enough, scouts carry it unaided back to the nest. If the prey item is too large,

teams of workers carry the prey to the nest whole. The size of prey handled and the speed at

which it is carried to the nest are remarkable. The workers defend their prey items from other

ants, including S. invicta, and P. obscurithorax both wins battles and loses them. Although little is known about its reproductive biology, small mating flights before dawn after summer rains have been observed (S. R. Storz, pers. obs.).

Southeast survey

Pheidole obscurithorax inhabits a 50-mile-wide band along the coast between Mobile,

Alabama, and Tallahassee, Florida. Its highest nest density occurred north of Pensacola, Florida

(Fig. 1.1). Pheidole obscurithorax nest density declined with increasing distance from Mobile and Pensacola (Pearson r = –0.55 and r = –0.69 respectively, P < 0.05). Pheidole obscurithorax abundance (number of bait tubes) also declined with increasing distance from Mobile (Pearson r

9 = –0.50, P < 0.05) but not from Pensacola (Pearson r = 0.03, P > 0.20). Pheidole obscurithorax

presence was associated with shorter grass. Average grass height was greater at sites where P.

obscurithorax was absent than that at sites where they were present (15.77 cm ± 0.87 vs. 12.08 cm ± 1.14, average ± standard error; t = –2.63, d.f. = 39, P < 0.02). Pheidole obscurithorax was not associated with any other habitat characteristic (Table 1.1). Grass height was not correlated with distance from Mobile or Pensacola.

Figure 1.1. Pheidole obscurithorax nest densities at each site plotted on a map of the southeastern United States. Sites within the oval are those included in analyses. P. obscurithorax occurs within a narrow band along the coast, and its nest densities are highest near Pensacola, Florida.

10 Table 1.1. Site characteristics at sites with P. obscurithorax present and absent. Present Absent Variable Mean Std.dev. N Mean Std.dev. N t-value d.f. p-value Latitude 30.6 0.3 17 30.5 0.4 24 0.59 39 0.55 Longitude 80.8 6.1 17 81.3 13.5 24 0.16 39 0.87 Elevation 171.6 112.2 17 169.7 99.4 24 0.06 39 0.95 Soil Avg. % sand 80.7 6.1 17 81.5 13.5 24 -0.21 39 0.83 Avg. % clay 4.2 1.9 17 4.8 4.8 24 -0.48 39 0.63 Avg. % silt 15.0 5.4 17 13.7 9.5 24 0.52 39 0.61 Ground cover % plant 72.5 16.8 17 75.7 13.0 24 -0.67 39 0.50 % bare 16.9 12.0 17 12.2 7.0 24 1.5 39 0.81 % litter 10.7 12.2 17 11.6 11.6 24 -0.23 39 0.81

If P. obscurithorax was introduced in Mobile, it appeared to have spread more extensively to the east (Fig. 1.1). I therefore hypothesized that, if winds blow predominately to the east after summer rains, the wind forces alates to fly eastward during mating flights and explains the eastward spread of P. obscurithorax. For the 25 days of weather data collected, wind speed ranged from 0.7 to 9.2 mph. No predominant wind direction was detected (Rayleigh test, z = 1.8, P > 0.05) (Batschelet, 1965).

Over 86,600 ants were collected at 1733 baits. Nineteen species of ants were collected, and the frequencies with which they occurred at the 41 sites were highly skewed. Solenopsis invicta occurred at 100% of the sites, whereas all other species occurred at less than 40% (Fig 1.

2). My collections follow a typical pattern of a few common species and many rare species. The proportions of bait tubes occupied by each ant species and the respective proportions of total ants collected showed a similar pattern. Eighty-five percent of the bait tubes were occupied by S. invicta, whereas the second and third most abundant species were D. bureni and P. obscurithorax, which occurred in 5 and 2% of the tubes respectively. Solenopsis invicta

11 represented 92% of the individual ants collected. No other ant species represented more than 2%

of the total, but their relative rankings differed somewhat from those of the frequencies collected

at bait tubes (Fig. 1.2).

(a) 100 80 60 40

20

Percentage of sites 0

x a e i s ta a il is 100 nn tata sp. idana rens orr neu ussi a oe en (b) llescenslor s analis 80 ex bureni conci u le f a ondyl m eta n reli ema hum us brun ido o ith e m mex musculus Solenopsis sp.F otus floridanusheidole d ica schaufdioc 60 l he echi n Pheidole m ar ole obscurithorP P rm Solenopsis iinvicd ido Pheidole m atr C Dorymyr ymyr MonomoriumLinep viride tomachFo he he ar P 40P P Campo rach Aphaenogaster floridana B Odon 20

tubes collected

Percentagebait of 0

a s . 100 t eni us a p. p rax an iride o dana d is s nvic bur ri i v (c) s i lo or runneus muscul ius analis um e dentata 80mex nops l b r e rel idole morrisi condyla s ol o io my mex S hina concinnaF ithema humilehus d y le obscurith r ec Pheido Phe ar Solenopsior 60 dole metallescensPheidolemy f Pheidole moerens onotus floridanu nep C D p Monomori Li omac Formica schaufussi hei t PheidoP achy phaenogasterParatr fl Cam 40 Br A Odon

ants collected 20 Percentageall of 0

i i ta us p. s le si p. ic rax ns ris o ul e s nna alis idana or fus a s escens danu au is inv l loridana or conci ius an ori ch curith e f e moer fl ter fl el nops dole dentata ca s iocondyl e Solenopsis For ei chus brunneusd ol Pheidole m mi ar S heidolmyrmexheidol muscogas Ph nepithema humi dole obs P P n Monomorium viride C Dorymyrmex buren hy Li oma For hei aratrechina amponotus P Pheidole metal phae P C Brac A Odont Species

Figure 1.2. Collection frequencies of 19 bait-collected ant species. (a) Percentage of sites (n = 41) at which each species was collected. (b) Percentage of all bait tubes (n = 1733) that captured each species. (c) Percentage of all ants collected (n = 86,681). Each representation of collections shows a typical pattern of one or a few common and many rare species.

12 The abundances of the six most common ant species were not associated with either P.

obscurithorax presence (Table 1.2) or its nest density (Table 1.3). Expected species richness estimated from the rarefaction curves was higher where P. obscurithorax was absent than where they were present (t = 29.3, df = 98, P < 0.0005) (Fig 1.3). When approximately 800 ants are sampled, eight species are expected at sites with P. obscurithorax, but 16 species are expected at sites without P. obscurithorax. In fact, eight species of ants collected within the smaller sampling area (Camponotus floridanus Buckley, Forelius analis Andre, Formica schaufussi

Mayr, Linepithema humile, Monomorium viride Brown, Odontomachus brunneus Patton,

Pheidole dentata Mayr, and Pheidole morrisi Forel) were absent from sites occupied by P. obscurithorax, but many of these are common woodland species.

Table 1.2. Mann-Whitney U tests of the abundances of the six most common ant species at sites with P. obscurithorax present and absent. Present Absent Species Rank sum N Rank sum N U p-value Solenopsis invicta 443.5 17 417.5 24 143.5 0.11 Dorymyrmex bureni 516.0 17 345.0 24 192.0 0.75 Pheidole metallescens 533.5 17 327.5 24 174.5 0.43 Pheidole floridana 525.5 17 335.5 24 182.5 0.57 Brachymyrmex musculus 475.0 17 386.0 24 175.0 0.44 Pheidole moerens 477.0 17 384.0 24 177.0 0.47

Table 1.3. Spearman rank order correlations of the abundances of the six most common ant species and P. obscurithorax nest density. P-values are not corrected for multiple comparisons. Species r p-value Solenopsis invicta 0.27 >0.08 Dorymyrmex bureni -0.08 >0.1 Pheidole metallescens -0.13 >0.1 Pheidole floridana -0.17 >0.1 Brachymyrmex musculus 0.23 >0.1 Pheidole moerens 0.29 >0.07

13 20

16 absent

12

8 present Species 4

0

0 500 1000

Individuals

Figure 1.3. Rarefaction curve for southeast survey. Curves represent the expected number of species at sites with and without Pheidole obscurithorax determined by resampling of each data set 50 times without replacement for each category. “Individuals” are the numbers of baits that collected each species as a surrogate for abundance. Fewer species are expected at sites with P. obscurithorax than at sites without it.

Pitfall-trap study

In the 80 pitfall traps, 2493 ants were captured, and 26 species were represented. Similar to those in the bait study, the distributions of percent of pitfall traps capturing each species and of their relative abundances in the traps were highly skewed, but P. obscurithorax occurred in nearly as many pitfall traps as S. invicta and was ranked a close second in abundance behind S.

invicta (Fig. 1.4). Interestingly, six of the seven most common ant species are introduced.

Pheidole obscurithorax abundance is not negatively associated with any of the six most

common species’ abundances. Rather, P. obscurithorax is positively, but weakly, associated

with two of the commonest species (Brachymyrmex musculus Forel and Cyphomyrmex rimosus

Spinola) (Spearman rank correlation, r = 0.30 and 0.29 respectively, P < 0.05). Pheidole

obscurithorax abundance is also positively, but weakly, associated with total ant abundance

(Spearman rank correlation, r = 0.24, P < 0.05).

14

100 90 (a) 80 70 60 50 40 30 20

Percent traps of pitfall 10 0 40

sp 1 (b) 30

Pheidole lamia Pheidole Pheidole carroli

20 Solenopsis Pheidole flavens Pheidole Pheidole dentata Pheidole Solenopsis invicta Solenopsis Pheidole moerens Pheidole Pheidole floridana Pheidole Dorymyrmex bureni Formica schaufussi trapped Camponotus socius Camponotus

nuda Cardiocondyla Cyphomyrmex rimosus Cyphomyrmex Pheidole metallescens Pheidole Strumigenys louisianae Strumigenys Camponotus floridanus Camponotus 10 opaciceps Hypoponera Pseudomyrmex pallidus Pseudomyrmex Parathrechina concinna Parathrechina Pheidole obascurithorax Pheidole Brachymyrmex musculus Brachymyrmex Aphaenogaster ashmedi Aphaenogaster Odontomachus brunneus Odontomachus Percent ants of total

minutissima Crematogaster

0 septentrionalis Trachymyrmex vinelandica bicarinata Pheidole Species sp 1

Pheidole lamia Pheidole Pheidole carroli Pheidole

Solenopsis Pheidole flavens Pheidole Pheidole dentata Pheidole Solenopsis invicta Solenopsis Pheidole moerens Pheidole Pheidole floridana Pheidole ♦ Dorymyrmex bureni Dorymyrmex Formica schaufussi Formica Camponotus socius Camponotus ♦ ♦ Cardiocondyla nuda Cardiocondyla ♦ Cyphomyrmex rimosus Cyphomyrmex

metallescens Pheidole Hypoponera opaciceps Hypoponera floridanus Camponotus Strumigenys louisianae Strumigenys Pseudomyrmex pallidus Pseudomyrmex Parathrechina concinna ♦ Pheidole obascurithorax Pheidole Brachymyrmex musculus Brachymyrmex Aphaenogaster ashmedi Aphaenogaster Odontomachus brunneus Odontomachus ♦ ♦ minutissima Crematogaster Trachymyrmex septentrionalis Trachymyrmex Pheidole bicarinata vinelandica bicarinata Pheidole Species

Figure 1.4. Frequency of 26 ant species collected in pitfall traps. (a) Percentage of pitfall traps (n = 80) in which each species was trapped. (b) Percentage of all ants trapped (n = 2,493). Species marked with diamonds are nonnative. Solenopsis invicta and Pheidole obscurithorax were the most common ants trapped, and six of the most common ants are introduced.

15 Expected species richness estimated from the rarefaction curves is highest in the low P. obscurithorax category and lowest in the high P. obscurithorax category, and the expected species richness of the moderate category falls in between (Fig. 1.5). The species-richness curve representing the high P. obscurithorax category is also shallower than the other two curves, suggesting a less even species distribution.

25

20 0-8 P. obscurithorax

9-17 P. obscurithorax 15

> 17 P. obscurithorax

Species 10

5

0 0 400 800 1200 Individuals

Figure 1.5. Rarefaction curves for pitfall-trap study. Curves represent the expected number of species per pitfall trap for three categories of Pheidole obscurithorax abundance and were determined by resampling of each data set 50 times without replacement for each category. Pitfall traps that capture the greatest number of P. obscurithorax are expected to capture the smallest number of species.

16 Tallahassee survey

Pheidole obscurithorax nest density at the 21 roadside sites was greater in 2002 than that

in 2000 (302.8 nests per ha ± 87.2 vs. 47.4 nests per ha ± 20.6, average ± standard error;

Wilcoxon matched pairs test, P < 0.001). On average, P. obscurithorax nest density in

Tallahassee increased by a factor of 6.4 in two years. Nest density in June 2000 and nest density in June 2002 were positively related (Spearman rank test, P < 0.05; Fig. 1.6). With one exception, all sites occupied by P. obscurithorax in 2000 increased in nest density over the two- year period. Of the 14 sites not occupied by P. obscurithorax in 2000, seven were invaded by P. obscurithorax during the two-year period, and seven remained uninvaded (Fig. 1.7). Figure 1.8 shows the distribution of nest densities in Tallahassee in June 2002; populations located centrally have greater nest densities than those located near the periphery of the city.

1600

1400

1200

1000 (2) 800

600

Nestsper 2002 ha 400

200 (2)

(7) 0 0 50 100 150 200 250 300 350 400

Nests per ha 2000

Figure 1.6. Relationship between Pheidole obscurithorax nest densities measured at 21 sites in Tallahassee in two years (Spearman rank correlation, r = 0.5, P < 0.05). Each number in parentheses is the number of sites represented by the point to its left. Dashed line signifies no change in density (isometric population growth); sites on the line did not change in density (n = 7), sites above the line increased in density (n = 13), and site below the line decreased in density (n = 1).

17

Pheidole obscurithorax absent both

present both ↑ N absent 2000, present

Figure 1.7. Pheidole obscurithorax presence at each of 21 sites in Tallahassee, Florida, in two years. Seven sites had new infestations but followed no apparent geographic pattern.

18

Nests per ha 2002 Absent 1–200

201–400 ↑ N >400

Figure 1.8. Pheidole obscurithorax nest densities at 21 sites in Tallahassee, Florida, in June 2002. Densities are greatest near the center of town.

19 Discussion

The distribution of P. obscurithorax and its density within its range (Fig. 1.1) suggest that

it was introduced near Mobile, Alabama, or Pensacola, Florida. Both cities have ports that have

presumably allowed the introduction of numerous exotics. If no geographic or weather-driven

barriers exist directly to the west of Mobile, then the data suggest that Pensacola was the more

likely site of arrival because P. obscurithorax has spread more or less equally to the east and

west of Pensacola. Lending credibility to this hypothesis is that no significant pattern of east-

blowing wind was found, at least during the three years for which data were collected, that would

explain an eastward spread. Alternatively, if such barriers do exist, then P. obscurithorax could

have been introduced in Mobile, and it has spread mostly eastward. If ant abundance indicates colony size/age in P. obscurithorax, then the negative association between distance from Mobile

and P. obscurithorax abundance suggests that the populations near Mobile are older than

populations further away. Lack of a similar relationship with distance from Pensacola lends

support to Mobile as the likely site of entry. If rates of spread to the east and west were

available, a more precise location of entry could be determined. Why P. obscurithorax has

spread little to the north is unknown.

The gradual change in P. obscurithorax nest densities and continuous occurrence

throughout its range suggest that it is dispersing mostly by diffusion. In addition, the decrease in

nest density with increasing distance from both Mobile and Pensacola also suggests dispersal by

diffusion. Alternatively, P. obscurithorax’s absence from many sites directly to the west of

Tallahassee suggests its occurrence there is due to jump dispersal, possibly by human transport.

Although P. obscurithorax and S. invicta were introduced at approximately the same

time, P. obscurithorax is clearly increasing its range more slowly, and, at least on the eastern

20 front, its expansion still continues. Pheidole obscurithorax’s low rate of spread compared to that

of S. invicta is probably due to differences in reproductive biology such as less frequent mating

flights, fewer alates, or lack of high altitude, long distance mating flights. Additionally, P.

obscurithorax probably does not choose nest sites in nursery material that is transported by humans, and small nests are probably deep and not easily scooped up and moved.

Pheidole obscurithorax was associated with highly disturbed habitat (roadsides with shorter grass) and, so far as I know, is not found in less disturbed habitat such as wooded areas along roadsides or forests within its range. Its abundance on the Florida State University campus and the frequent affinity of exotic species for disturbed habitats (Elton, 1958) reinforce this finding. McGlynn (1999) characterized P. obscurithorax as belonging to the “generalized myrmicine” functional group, members of which are generalists in food and nest-site choice and defend food resources near their nests, but P. obscurithorax's dependence on human activity

(habitat disturbance) for successful invasion of and persistence in new habitats suggests it also shares characteristics with “opportunists” and “tramp” species.

To the extent that baits and pitfall traps adequately sample ant communities, P. obscurithorax does not appear to be causing decreases in species abundances, but, rather, it was positively associated with total ant abundance and with the abundance of two species of ants in pitfall traps. Although P. obscurithorax was associated with lower species richness at baits and in pitfall traps, I do not believe that P. obscurithorax is causing a decrease in species richness.

The eight ant species collected within the range of P. obscurithorax that were not found to coexist with it were rare species collected at only one or two study sites, and at least six of these are common woodland species (D. Lubertazzi, thesis, Florida State University, 1999) probably collected at the edge of their habitat. Highway roadsides are not species-rich habitats and may

21 therefore provide little opportunity for nonnative ants to cause ecological effects. In addition, the

large numbers of rare species may make detecting any effects difficult. Only an experimental

study will be able to determine the cause of the smaller values of species richness associated with

P. obscurithorax.

Interestingly, nearly all of the commonest and most abundant ants captured in pitfall traps are introduced. Either these exotic species have outcompeted native species, or, more likely, native ants are not adapted to open, disturbed habitats and are, therefore, not likely to be found in abundance in these habitats. A similar pattern is found in birds where introduced species are commonly found in disturbed, open habitat and native species tend to occur in native habitats

(Case, 1996). Large expanses of open, disturbed habitat, mostly caused by human activities, may simply be native-species-poor habitats to begin with but are favored by introduced species already adapted to similar habitats. It is likely that P. obscurithorax belongs to a smaller subset

of ants that are tolerant of even more highly disturbed habitat within the generally disturbed

areas I surveyed. A comparison of urban sites (Tallahassee) with non-urban sites throughout the

Southeast shows that the most disturbance-tolerant species (Solenopsis invicta, Pheidole

obscurithorax, Brachymyrmex musculus, Cyphomyrmex rimosus, Pheidole moerens,

Dorymyrmex bureni, and Cardiocondyla nuda), all exotics except for D. bureni, rank higher (and

cluster) in the more highly disturbed urban sites than the more rural ones. Two of these species

do not occur in the rural samples, and those that do move down in rank. Altogether, the case for

a community of ants that covaries with degree of habitat disturbance seems strong.

In Tallahassee P. obscurithorax is clearly thriving. The marked increase of existing

populations during the study and the colonization of several new sites lend support to the idea

that this species thrives where disturbance is greatest. In addition, the central location of the

22 higher nest densities in Tallahassee suggests that P. obscurithorax was introduced to the city’s center, possibly by humans, and is currently spreading outward.

23

CHAPTER 2

DAILY RHYTHMS AND FORAGING TACTICS OF THE INTRODUCED ANT PHEIDOLE OBSCURITHORAX NAVES

Introduction

Because ants are poikilothermic, their activity is dependent on temperature, and each species has particular constraints related to its body size, color, and metabolism. Ant activity patterns are influenced by temperature, time of day, and season as well as competitive interactions, and resource availability (Whitford and Ettershank, 1975; Bernstein, 1979; Porter and Tschinkel, 1987; Crist and MacMahon, 1991; Cerda et al., 1998; Human et al., 1998;

Fourcassie and Oliveira, 2002). Studies of the activity patterns of communities of ants have provided evidence that resource partitioning is achieved at least in part by differences in activity rhythms (Whitford and Ettershank, 1975; de Biseau, 1997; Cerda et al., 1998) and differences in social foraging behaviors (Traniello, 1987; de Biseau et al., 1997). In at least one invasive species of ant, Linepithema humile, its overlap of diet and activity times with those of native species are thought to be related to its negative effects on native ant communities (Human et al.,

1998).

Ant foraging strategies vary greatly on a continuum from solitary foraging to recruitment- based systems and coordinated group hunting (Holldobler and Wilson, 1990). The strategy adopted by a species is correlated with colony size (Beckers et al., 1989). Species with small colonies generally forage solitarily whereas species with larger colonies can afford to have inactive foragers waiting in the nest to be recruited. Bonabeau et al. (1998) used a model to

24 show that an advantage of recruitment-based foraging is increased efficiency as demonstrated in

Formica schaufussi (Traniello and Beshers, 1991). An understudied subset of recruitment-based

foraging is group prey retrieval in which recruited foragers carry food items to the nest as a

group rather than as single foragers. Several species exhibit this strategy (Sudd, 1960; Itzkowitz

and Haley, 1983; Franks, 1986; Traniello, 1987; see table in Beckers et al., 1989), but its

“evolution, mechanics, and energetics are poorly understood” (Traniello, 1989). Group retrieval

of prey decreases the numbers of workers required to obtain the same amount of prey and

increases the size range of prey available to a species (Traniello, 1983; Franks 1986). In F.

schaufussi, Robson and Traniello (1998) investigated the mechanism of regulating group size and demonstrated that scouts do not relay information regarding prey size to recruits but, rather, that group size is adjusted in response to moving versus nonmoving prey.

According to optimal foraging theory, social insects that forage from a central place maximize energy gain (Taylor, 1978; Detrain et al., 1999). Factors thought to affect optimal foraging include patch and resource quality, distance from the nest, risk, and competition. These factors have been investigated in solitary foragers and recruitment-based foraging systems

(Taylor, 1977; Traniello et al., 1984; Bailey and Polis, 1987; Bonser et al., 1998; Detrain at al.,

1999; de Biseau and Pasteels, 2000; Detrain et al., 2000; Roulston and Silverman, 2002), but to my knowledge optimal foraging through group retrieval has not been investigated. Foraging intensity is expected to increase with increasing food quality, but two studies that investigated recruitment rates in response to resource quality found conflicting results (Taylor, 1977; de

Biseau and Pasteels, 2000).

Here, I investigate the mechanisms of group retrieval and test predictions of central-place foraging theory with respect to prey size and mobility in Pheidole obscurithorax. This ant is

25 native to South America and was introduced to the southeastern United States in the 1950’s, currently inhabiting a 50-mile-wide band along the southeastern coast (see chapter 1). I also

provide the first documentation of the activity rhythms and foraging biology of P. obscurithorax.

Methods

Nest activity

To investigate temporal activity patterns, five P. obscurithorax nests were chosen in a grassy area surrounding a parking lot on the Florida State University campus. On three non- consecutive days in late June 2002 each nest was observed for approximately five minutes every hour for 24 consecutive hours. During each observation air temperature, ground temperature, weather, time, inbound and outbound traffic, and numbers of ants in the field were recorded. Ant traffic was monitored by counting ants crossing two circles of wire centered on the nest opening, an inner one of 6 cm diameter that included only the midden/excavated-dirt pile, and an outer one of 14 cm diameter extended past the midden. Ants crossing the small circle but not the large one were assumed to be nest maintenance workers (removing trash, soil, etc.) I refer to these as nest-surface tenders. The ants crossing the large wire are presumably foragers—many of these ants carried insects or other prey into the nest. The numbers of majors and minors crossing the wire circles in both directions (in and out) were recorded for two minutes. A quadrat (45 cm X

25 cm) was placed 30 cm from the center of the nest (well beyond the midden) in a haphazard direction, and an instantaneous scan count of majors and minors located within the quadrat was recorded. These workers are assumed to be scouts. Nest size was calculated by multiplying the midden/excavated-dirt pile’s length by its width. During two nights of observations mating flights and alate activity were observed (described below); data collected during these times were not included in the analyses (27 observation points). One of the five colonies moved its nest

26 during one day of observation; data collected on this colony during abnormal activity was not included in analyses

Foraging experiment

To investigate the foraging tactics of P. obscurithorax during group prey retrieval, 18 nests located in grassy areas on the FSU campus were presented with each of three bait treatments in a random order between 0800 and 1200 hours during June of 2002, their peak foraging season (pers. obs.). In most instances all three trials on each nest were conducted within two hours of one another with at least 15 minutes between trials. The baits consisted of the trunks of frozen beetle larvae cut to 15 mm (0.36 ± 0.04 g) or 30 mm (0.62 ± 0.09 g) in length (small and large respectively) placed on the center of a circular, cardboard bait card (22 cm diameter) or a 30 mm piece staked to the center of the bait card with an pin (large staked). The bait card was centered 50 cm from the nest opening in a haphazardly chosen direction. The time it took for the first P. obscurithorax worker (scout) to find the bait was noted, and then the number of minor and major workers recruited from the nest and crossing a wire placed 15 cm from the nest entrance were counted for 10 seconds every 30 seconds as in

Itzkowitz and Haley (1983). Recruitment was monitored until the bait was moved across a 21- cm-diameter circle on the bait card (removal of non-staked bait) or until 10 minutes after recruitment began (staked bait). The elapsed time to first worker recruitment (10 workers at bait), first major worker to arrive, and bait removal were recorded, as were the numbers of minor and major workers required to remove the bait. At the end of the first and second trials the bait was removed to prevent changes in the colonies’ nutrition status. In order to eliminate competitive interactions at baits, I removed any heterospecific ants that approached the bait card during the trial with an aspirator, which was only necessary during two trials. Nest-disc area was

27 estimated from its length and width. The ground temperature (2 cm below surface) was recorded

at the start of each trial.

Time and count data were analyzed with repeated measures ANOVAs because each

treatment (bait type) was administered to each of 18 nests. All analyses were conducted using

Statistica 6.0.

Results

Nest activity

P. obscurithorax activity occurred at all hours of the day. The number of outbound

foragers was positively correlated with the number of inbound foragers (Figure 2.1, Spearman r

= 0.84, P < 0.05). Similarly, outbound nest-surface tenders were positively correlated with

inbound nest-surface tenders (Figure 2.2, Spearman r = 0.64, P <0.05). In contrast, total foragers

(outbound plus inbound foragers) were not correlated with total nest-surface tenders (outbound plus inbound nest-surface tenders) (Figure 2.3, Spearman r = 0.32, P > 0.05).

160

140

120

100

80

60 Inbound foragers

40

20

0 0 20406080100120140160 Outbound foragers

Figure 2.1. Relationship between numbers of outbound and inbound foragers counted for two minutes.

28

140

120

100

80

60

40 Inbound nest-surfaceInbound tenders

20

0 0 20406080100120140 Outbound nest-surface tenders

Figure 2.2. Relationship between numbers of outbound and inbound nest-surface tenders counted for two minutes.

350

300

250

200

150 Total foragers

100

50

0 0 50 100 150 200 250 300 350 Total nest-surface tenders

Figure 2.3. Relationship between total nest-surface tenders (outbound plus inbound nest-surface tenders) and total foragers (outbound plus inbound foragers) counted for two minutes.

29 Figure 2.4 shows the average number of workers involved in each of three behaviors and

temperature plotted over time. Scouts and foragers show a similar pattern of increasing activity

after sunrise, a decrease in activity mid-day (1200-1400 hours), and another increase in activity

from 1400 hours until after sunset. Both scouts and foragers have minimal activity from

midnight until sunrise (0630 hours). Interestingly, nest-surface tenders tend to have an opposite

schedule. They are most active from late night until sunrise (2200-0600 hours), and then become

less active until mid-day (1200-1400 hours). After mid-day, their activity increases slowly until

their peak activity hours. The ground temperature fluctuated from 24 to 40 centigrade degrees

with roughly equivalent numbers of high and low temperature periods.

Figure 2.5 shows the average numbers of workers involved in the same three activities

plotted against ground temperature. The total number of scouts did not vary significantly with temperature, but there is a trend towards fewer scouts between 24 and 28 centigrade degrees.

The total numbers of foragers tends to increase with temperature, peaks between 28 and 34

degrees, and decreases above 34 degrees. Numbers of nest-surface tenders peak between 26 and

28 degrees and then decrease with increasing temperatures. Interestingly, all three behaviors

cease above 36 degrees, suggesting a temperature threshold for P. obscurithorax.

Because time and temperature are confounded, in order to determine if temperature predicts activity independently of time of day, I compared activity during time periods that had different temperatures on different days. Temperatures before dawn were similar on all three days, at mid-day were distinctly different, and at early night were slightly different (Figure 2.6).

Using Figure 2.6, I chose three time periods (early morning 0700-0900, mid-day 1500-1700, and early night 2100-2300 hours) to investigate whether activity differed with respect to day. For each of these time periods I plotted the mean activity levels for scouts, foragers, and nest-surface

30 40

36 32 28

Temperature (C) 24 2 4 6 8 1012141618202224 3.0

2.5

2.0

1.5

Total scouts 1.0

0.5

0.0 2 4 6 8 1012141618202224 90 Time 80

70

60

50

40 Total foragers 30

20

10 0 2 4 6 8 10 12 14 16 18 20 22 24 100 Time 90

80

70

60 50 40

30 Total nest-surfacetenders 20

10

0 2 4 6 8 10 12 14 16 18 20 22 24 Time Figure 2.4. Relationships between time of day and ground temperature, total numbers of scouts, total numbers of foragers, and total numbers of nest-surface tenders. Bars are averages ± 95% confidence intervals. Dashed-vertical lines are sunrise (0630 hours) and sunset (2045 hours). Note the different scales on the Y-axes.

31 2.5

2.0

1.5

1.0 scouts Total

0.5

0.0 24 26 28 30 32 34 36 38 40 Temperature (C) 50

40

30

Total foragers Total 20

10

0 24 26 28 30 32 34 36 38 40 50 Temperature (C)

40

30

20

Total nest-surface tenders 10

0 24 26 28 30 32 34 36 38 40 Temperature (C) Figure 2.5. Relationships between temperature and total numbers of scouts, total numbers of foragers, and total numbers of nest-surface tenders. Bars are averages ± 95% confidence intervals. Dashed-vertical line represents possible high-temperature threshold for surface activity. Note the different scales on the Y-axes.

32 40

38

36 day 1 day 2 34 day 3

32

30 (C) Temperature 28

26

24 0 2 4 6 8 10 12 14 16 18 20 22 Time Figure 2.6. Relationship between time and ground temperature for each of three non- consecutive days of observation. Dashed-vertical lines are sunrise (0630 hours) and sunset (2045 hours).

tenders (figure 2.7, Table 2.1). If temperature predicts activity I would expect to see marked differences in activity during the afternoon, fewer differences at early night, and no differences at early morning.

Between 0700-0900 hours, most levels of activity did not differ between the different days, although scouting was lower on day 3 than on day 1 (Figure 2.7). Because temperatures did not vary between these days (Figure 2.6), the differences in scouting activity cannot be attributed to temperature. Between 2100 and 2300 hours, activity levels did not differ with respect to day (Figure 2.7) suggesting that differences in temperatures ranging between 26 and

30 degrees do not influence activity. Between 1500 and 1700 hours, when temperatures on day 1 were above 36 degrees, activity levels differed with respect to day; the least activity occurred on

the hottest day (day 1) but activity did not differ between day 2 and 3 even though day 3 was

cooler. This suggests that activity is only strongly dependent on temperature above 36 degrees.

33

0700-0900 1500-1700 2100-2300 3.5 3.5 3.5 3.0 3.0 3.0 2.5 2.5 2.5

2.0 2.0 2.0

1.5 1.5 1.5 Total scouts Total Total scouts Total Total scouts Total 1.0 1.0 1.0

0.5 0.5 0.5

0.0 0.0 123 0.0 123 123 140 140 140 120 120 120 100 100 100 80 80 80 60 60 60 Total foragers Total foragers Total foragers Total 40 40 40

20 20 20

0 0 0 123 123 123 60 60 60

50 50 50

40 40 40

30 30 30

20 20 20

Total nest-surface tenders nest-surface Total 10 tenders nest-surface Total 10 tenders nest-surface Total 10

0 0 0 123 123 123 Figure 2.7. Activity levels during three time periods plotted for each of three days. Bars represent means and 95% confidence intervals.

Table 2.1. Means and 95% confidence intervals for the activities represented in figure 2.6. 0700-0900 1500-1700 2100-2300 Day 1 2 3 1 2 3 1 2 3 Total 2.2±1.0 1.1±1.4 0.7±0.6 0.3±0.3 1.8±0.8 2.2±1.3 1.5±0.9 0.8±1.1 1.1±1.0 scouts Total 24.6±7.9 26.6±18.4 8.6±5.7 1.1±1.8 51.5±31.4 23.2±15.2 47.2±40.2 74±67.9 17.3±13.8 foragers Total 15.2±14.5 25.5±29.1 8.2±8.9 0.0±0.0 22.2±22.1 10.0±10.6 12.9±11.7 19.8±20.26 21.0±35.0 nest-surface tenders

34 In order to test the influence of nest size, I calculated average activity for each nest ranked by nest size (Figure 2.9). Total numbers of scouts were not different between nests.

Total foraging activity tended to increase with nest size, but the smallest nest had one of the

highest foraging levels. Total nest surface-tenders also tended to increase with nest size, but the largest nest had one of the lowest activity levels.

The proportions of minors compared to those of majors were different depending of

behavioral task (Figure 2.8, F2, 747 = 65.28, P < 0.001). Scouts had the highest proportion of

minors (98%), foragers were a close second (94%), and nest-surface tenders had the least (79%)

(Tukey HSD post-hoc test, P < 0.05 for all comparisons).

1.7

1.6 a

1.5 b 0.98 1.4 0.94 1.3

c 1.2 arcsin (prop minors)^0.5

1.1 0.79 1.0 scouts foragers nest-surface tenders

Figure 2.8. Proportions of workers that are minors performing three tasks. Data were arcsin- square-root transformed. Bars are averages ± 95% confidence intervals and numbers in each bar are the untransformed proportions of minors for each activity. Letters above the confidence intervals represent significantly different means based on Tukey post-hoc tests.

35 2.0

1.5

Total scouts 1.0

0.5 50 100 120 144 168 380 Nest size (cm2)

40

30

20 Total foragers

10

0 100 120 144 168 380 50 Nest size (cm2)

40

30

20

Total nest-surface tenders nest-surface Total 10

0 100 100 120 120 144 144 168 168 380 380 Nest size (cm2)

Figure 2.9. Relationships between nest size and total numbers of scouts, total numbers of foragers, and total numbers of nest-surface tenders. Bars are averages ± 95% confidence intervals. Each nest size represents a single nest.

36 Foraging experiment

Pheidole obscurithorax recruitment to large baits does not occur as a continuous stream

of workers to the bait, nor do scouts recruit adequate numbers of workers to move the bait on the

first attempt. Rather, ants are recruited in waves until the bait is successfully moved. During a

recruitment event a scout quickly returns to the nest and within seconds of its entry into the nest,

recruits come out and follow the same path as the scout to the bait. Figure 2.10 shows a typical pattern of recruitment to a bait. Recruitment began after about three minutes and continued for about 20 minutes. Note the large spikes in recruitment followed by periods of less or no recruitment. Most of the recruited ants reached the bait, although majors got lost more often than minors. After a period of time workers would begin returning to the nest even though the bait was not in transit and more ants were still being recruited.

22

20 18

16

14

12

10

8

6 Number of minors recruited 4 2

0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (min)

Figure 2.10. Typical relationship between time and the numbers of minors recruited to a bait counted during 10-second intervals. Notice the large spikes in activity followed by low levels of recruitment.

37 The average time for scouts to find the bait was 3.6 minutes, and, in all but nine of the 54

trials, ants found the bait within five minutes. The average time for scouts to find the bait was

not different among the three bait types (Table 2.2, P = 0.40). Nest area was significantly but

weakly correlated with the time for scouts to find the bait (R = 0.30, P = 0.03), but it was not

correlated with any other measure of foraging activity.

Table 2.2. Repeated measures ANOVA table for foraging activity vs. bait type. First ant, recruitment, first majors, and removal all refer to time elapsed until each response occurred. Number of minors and majors are numbers of ants required to move the bait (or at the bait after 10 minutes of recruitment for the large staked bait). Average recruitment rate is averaged over the entire time recruitment occurred.

Dependent variable Source SS df MS F p-value ln 1st ant bait 1.55 2 0.78 0.93 0.40 error 28.34 34 0.83 ln recruitment bait 1.95 2 0.98 2.41 0.11 error 13.79 34 0.41 ln 1st majors bait 13.81 2 6.90 1.56 0.22 error 150.08 34 4.41 ln removal (sm vs lg only) bait 2.12 1 2.12 8.85 0.01* error 4.08 17 0.24 ln no minors bait 1.90 2 0.95 13.87 0.0001* error 1.57 23 0.07 ln no majors bait 4.55 2 2.27 7.09 0.004* error 7.37 23 0.32 ln avg recruitment rate bait 0.24 2 0.12 0.69 0.50 (minors) error 5.85 34 0.17 ln avg recruitment rate bait 2.26 2 1.13 3.83 0.03* (majors) error 8.27 34 0.30

38 The average times to recruitment of 10 ants (5.2 ± 1.9 minutes, average ± 95% CI) and to recruitment of the first major worker (5.0 ± 1.8 minutes) were not different among the baits

(Table 2.2, P = 0.11 and 0.22 respectively). The average time for ants to remove the small bait

(5.9 ± 1.4 minutes) was significantly less than that to remove the large bait (9.5 ± 2.9 minutes)

(Figure 2.11a, Table 2.2, P = 0.01). Average recruitment rate of minor workers (5.0 ± 1.5 minors per 10 seconds) was not different among the baits, but the average recruitment rate of major workers was higher at small baits (0.5 ± 0.3 majors per 10 seconds) than at large and large- staked baits (0.25 ± 0.1 majors per 10 seconds) (Table 2.2; Tukey post-hoc tests: sm vs. lg, sm vs. lgst, and lg vs. lgst, P = 0.06, 0.05, and 0.99 respectively)

Bait type had a significant effect on the number of minor and major workers at the bait at time of removal (Table 2.2, P = 0.0001 and P = 0.004 respectively). The average numbers of minors required to move the small bait (24.1 ± 4.6) was significantly less than that required to move the large bait (33.0 ± 7.2) (Figure 2.11b, Tukey HSD post-hoc test, P = 0.01).

Alternatively, the numbers of major workers were not different at the small vs. large bait (3.1 ±

1.1 and 2.5 ± 1.0 respectively) (Figure 2.11c, Tukey HSD post-hoc test, P = 0.9). The amount of time for the large bait to be removed (9.5 ± 2.9 minutes) was not different from the amount of time the large-staked bait was left out (13.2 ± 1.5 minutes), therefore the numbers of ants required to remove the large bait can be directly compared with the numbers of ants at the large- staked bait; the numbers of minors at the large and large-staked baits were not significantly different (Figure 2.11b, Tukey HSD post-hoc test, P = 0.29). However, the number of majors at the large bait (2.5 ± 1.0) was significantly less than that at the large-staked bait (5.4 ± 1.3)

(Figure 2.11c, Tukey HSD post-hoc test, P = 0.008). The numbers of minors and majors at the baits were not correlated (r2 = 0.12, P = 0.08). Minors constituted 91% of the workers at baits.

39 6.6 b (a)

6.4

6.2

6.0 a

ln (removal) 5.8

5.6

5.4 sm lg

Bait (b) b 3.8

b 3.6

3.4 a

minors) ln (no 3.2

3.0

2.8 sm lg lgst

2.0 Bait b (c)

1.8

1.6 a 1.4 a 1.2

1.0 majors) (no ln

0.8

0.6

0.4 sm lg lgst Bait Figure 2.11. Relationships between bait type (sm = small, lg = large, and lgst = large staked) and (a) time to remove bait (small and large only; time is in seconds), (b) numbers of minors at the bait, and (c) numbers of majors at the bait. Bars are averages ± 95% confidence intervals, and letters above the confidence intervals represent significantly different means based on Tukey post-hoc tests.

40 During this study temperature ranged from 26 to 29 centigrade degrees, and did not differ

between treatments (F2, 51 = 0.7, P = 0.5). Temperature was not correlated with time to find bait suggesting that temperature does not determine the number of scouts in the field, at least for the temperatures during this study. Temperature was also not correlated with any measures of recruitment behavior or numbers of ants at baits.

Discussion

The current study sought to investigate the relationships between time of day, temperature, and nest size with the activity patterns of P. obscurithorax. Of these three factors, time of day appears to be the best predictor of activity in the summer months, their peak foraging season. Additionally, the mechanisms of the foraging tactic of group prey retrieval was investigated to determine if prey size or mobility effects levels of recruitment or other foraging behaviors.

Time of day was a strong predictor of activity. Scouts and foragers shared a similar pattern of activity whereby most activity occurred during the day with a lull at mid-day.

Considering that scouts recruit other workers to food sources, this is not surprising. The nest- surface tenders, however, had an opposite pattern whereby most activity occurred at night.

Similarly, alate activity and mating flights occurred late at night. During one late night/early morning (0200-0500 hours) after it had rained the previous afternoon, mating flights occurred at four of the five nests, and on another night alates were seen around the entrances. During the flights roughly 200 hundred workers swarmed out of the nest, milled about, and followed any alates (predominantly female) walking around near the nest entrances. Up to 20 alates were seen outside of the nests and some took flight.

41 Within the temperature range of this study (24-40˚C), nest activity occurred 24 hours a day, and temperature had little effect on the activity rhythms of P. obscurithorax, with the

exception of an apparent high temperature threshold of 36˚C. Similarly, temperature did not

significantly affect any measures of scout or recruitment activity at baits. Many studies have

shown ant activity patterns to be related to temperature (Whitford and Ettershank, 1975;

Bernstein, 1979; Porter and Tschinkel, 1987; Crist and MacMahon, 1991; Cerda et al., 1998;

Human et al., 1998; Fourcassie and Oliveira, 2002) but included a wider range of temperatures.

If the current study had included cooler temperatures, it is likely that activity would have been

more closely tied with temperature.

In the 24-hour observations, colony size (nest-disc area) does not appear to influence

activity outside of the nest. Similarly, in the 18 colonies observed at baits, colony size was not

related to any measure of recruitment. However, size was weakly correlated with scouting,

suggesting that larger nests have more scouts, but nest size only explained 30% of the variation

in scout activity. If nest-disc size is related to colony size, as has been found in other species, it

is surprising that it would not be related to foraging or other nest activity, but the relationship

between nest-disc size and colony size in P. obscurithorax is not known.

Outbound and inbound foraging activity was correlated, as was the inbound and

outbound nest-surface tending activity, but foraging and nest-surface tending were not correlated

with one another. This suggests that these represent separate work forces. If a single population

of workers were accomplishing both tasks, but shifted in time, there would be a negative

relationship between foragers and nest-surface tenders, and the peak of foraging would

correspond to the lowest nest-surface tending activity. This was not the case here. Gordon

(1989) found that Pogonomyrmex barbatus workers consist of four distinct groups of above-

42 ground workers (foraging, patrolling, midden work, and nest maintenance) during normal

activity. It would be interesting to mark foragers and nest-surface tenders in P. obscurithorax to

determine if they are indeed two separate populations.

Minor workers comprise most of the above ground workforce, but the proportion of minors differs according to task; scouts and forgers have the highest proportion of minors (>

90%) while nest-surface tenders have fewer (79%) (Figure 2.8). Similarly, the proportion of minors retrieving baits was also greater than 90%. If these tasks are related to worker age, it is possible that the difference in proportions between the nest-surface tenders and scouts/foragers is due to differences in life span between majors and minors. Alternatively, these differences could correspond to genetic differences between the two castes in their tendencies or response thresholds to perform certain tasks as has been proposed by other authors (reviews by Gordon,

1996; Page and Erber, 2002). It would be interesting to know the make-up of the colony as a whole in order to determine if majors preferentially remain in the nest or if they simply make-up only 20% of the colony.

Bait size and mobility had no effect on scouting effort (time to find bait), time to recruit to bait, time to recruit first major, or recruitment rate of minors. Bait size did, however, affect the numbers of minors (but not majors) required to remove the baits and the time involved to do so. Removal of the large bait (2 times the mass of the small bait) required approximately 1.4 times as many minors and took 1.6 times as long than that for the small bait. Because P. obscurithorax recruitment builds over time, rather than all at once, it simply took longer for adequate numbers of workers to be recruited to move the larger bait.

Bait mobility had no effect on the numbers of minors at the baits. Alternatively, staked baits had twice as many majors at the end of the trial than the non-staked baits of the same mass,

43 but this difference cannot be accounted for by differences in recruitment rates of majors. It is possible that mobility did not influence the number of minors at the bait because the available bait surface area was limited; there simply was no additional surface for workers to join in the removal effort above and beyond that available for the numbers required to move the large bait.

Why this would not similarly limit the numbers of majors at the bait is unclear. Although

numbers of workers returning to the nest were not counted, many individuals were observed

leaving the baits. It is possible that majors are less likely than minors to leave a bait when

removal efforts fail, which could explain the greater numbers of majors at the staked baits. It

would be interesting to see if this same pattern occurs at baits where competition is occurring

with other ants.

It is clear that more workers were required to move the large bait, and, yet, recruitment

rates were not adjusted in response to bait size or mobility as expected from foraging theory; in

fact, recruitment rates of majors were slightly higher for small baits than for larger baits, contrary

to expectations. Robson and Traniello (1998) observed a similar lack of a modulated-

recruitment response to baits of various masses in Formica schaufussi, an ant with similar prey-

retrieval behavior as P. obscurithorax. They postulated that prey size was assessed not by

scouts, but by recruits who matched retrieval group size to prey mass. If the prey was in

transport, other recruits would not join the group. It is possible that this is also the case for P.

obscurithorax, but with some modification. F. schaufussi scouts appear to recruit adequate

numbers of workers during the initial recruitment event, as do scouts of Pheidole crassinoda

(Sudd, 1960). In F. schaufussi, many recruits never make it to the prey and others simply do not

join if the prey is in transit. P. obscurithorax, on the other hand, goes through several bouts of

recruitment until enough workers are recruited to move the prey. The multiple recruitment

44 events are probably in response to scouts’ and/or other workers’ perceptions of prey mobility; if the prey is not in transit, a scout/worker will return to the nest for more recruits. It is unclear whether a single scout is responsible for returning to the nest multiple times to recruit workers or if recruits at the prey decide to return to the nest and recruit more workers. It would be interesting to mark scouts and other workers returning to the nest during prey retrieval to investigate the mechanisms and dynamics of recruitment and prey retrieval in P. obscurithorax.

45

CONCLUSION

Pheidole obscurithorax inhabits a narrow range along the coastal southeastern United

States between Mobile, Alabama, and Tallahassee, Florida. It is associated with open, disturbed habitat and with shorter grass, which is interpreted as highly disturbed habitat. The available data suggests that P. obscurithorax is one of the many introduced species that has been successful at establishment in a new land but does not have negative effects on the communities that it inhabits. Possibly one reason for its lack of negative effect is that it occurs in highly disturbed habitat, which is species poor already. The ant communities associated with P. obscurithorax are largely exotic. A similar pattern has been found in birds; native species remain in what is left of their natural, undisturbed habitat, while the exotic species inhabit the open, disturbed areas (Case, 1996). I believe this will be an ever-increasing phenomenon as humans convert more and more natural habitat into disturbed habitat. It is probably a more prevalent phenomenon than we are aware, but the communities in the disturbed areas have not yet been characterized.

Pheidole obscurithorax has a remarkable ability to retrieve large prey items quickly. It is likely a direct competitor of the red imported fire ant, Solenopsis invicta, as they are both omnivorous, forage within the same time, seasonal, and temperature ranges. However, evidence does not suggest that P. obscurithorax is causing a decrease in S. invicta populations, probably because resources are not limiting. The foraging behaviors of P. obscurithorax during group prey retrieval did not conform to the predictions of central place foraging theory; recruitment

46 rates were not increased in response to more profitable prey items. However, baits with twice

the mass did not require twice the number of ants to remove which suggests group retrieval is

efficient.

While this study has illuminated many interesting findings about P. obscurithorax, it has,

like many observational studies, uncovered many more questions than it has answered. P.

obscurithorax is an interesting species of ant that is little studied. I hope that my research motivates current and future researchers to continue investigations on this understudied exotic species.

47

Appendix A Southeast survey site locality information

48

The first two letters of site ID represent the state. The date is the date of sampling. In range describes which sites were included in the analyses (Y = yes, N = no) as described in chapter 1. Site ID County Locality Date In range? FL 1 Okaloosa Hwy 90, 3.9 mi W of Hwy 85 4/14/2001 Y FL 2 Walton Hwy 90, 4.1 mi E of Hwy 131 6/9/2001 Y FL 3 Holmes Hwy 90, 26.3 mi E of Hwy 131 6/9/2001 Y FL 4 Bay Hwy 79, 13.4 mi N of Hwy 98 6/9/2001 Y FL 5 Jefferson Hwy 90, 7.8 mi W of Hwy 19 8/1/2001 Y FL 6 Madison Hwy 90, 5.2 mi E of Hwy 145 8/1/2001 Y FL 7 Gadsden Hwy 90, 9.9 mi W of Hwy 12 8/16/2001 Y FL 8 Jackson Hwy 90, 17.5 mi E of Hwy 231 8/16/2001 Y FL 9 Jefferson Hwy 98, 11.6 mi E of Hwy 363 8/20/2001 Y FL 10 Taylor Hwy 121, 9.5 mi N of Hwy 19/27/221 8/20/2001 Y FL 11 Leon Hwy 20, 1.6 mi W of Capital Circle 8/21/2001 Y FL 12 Wakulla Hwy 319, 12.2 mi S of Hwy 276 8/21/2001 Y FL 13 Calhoun Hwy 20, 4 mi W of Hwy 71 8/25/2001 Y FL 14 Gulf Hwy 71, 23 mi S of Hwy 20 8/25/2001 Y FL 15 Liberty Hwy 20, 0.3 mi W of Hwy 65 10/5/2001 Y FL 16 Liberty Hwy 65, 21 mi S of Hwy 20 10/5/2001 Y FL 17 Walton Hwy 331, 0.2 mi N of Hwy 98 10/21/2001 Y FL 18 Santa Rosa Hwy 87, 6.8 mi N of Hwy 98 10/21/2001 Y FL 19 Santa Rosa Hwy 87, 11.3 mi N of Int 10 10/21/2001 Y GA 1 Thomas Hwy 319, 4 mi N of Hwy 319/19 8/17/2001 Y GA 2 Decatur Hwy 12, 1 mi W of Hwy 27 8/18/2001 Y GA 3 Seminole Hwy 91, 1.3 mi S of Hwy 84 8/18/2001 Y AL 1 Baldwin Hwy 184/112, 6.5 mi W of Hwy 29 4/14/2001 Y AL 2 Mobile Hwy 98, 12.5 mi NW of Int 65 4/15/2001 Y AL 3 Greene Hwy 14, 1.5 mi S of Int 20 5/5/2001 N AL 4 Marengo Hwy 43, 22.1 mi S of Hwy 80 5/5/2001 N AL 5 Clarke Hwy 43, 56 mi N of Int 65 5/5/2001 Y AL 6 Baldwin Hwy 59, 2 mi S of Int 65 5/5/2001 Y AL 7 Escambia Hwy 21, 1.1 mi N of Int 65 5/6/2001 Y AL 8 Geneva Hwy 79/167, 22.3 mi N of Hwy 90 8/16/2001 Y AL 9 Geneva Hwy 59, 0.8 mi E of Hwy 54/52 9/15/2001 Y AL 10 Covington Hwy 55, 12.1 mi N of Hwy 331/54/85 9/15/2001 Y AL 11 Escambia Hwy 29, 20 mi SW of Hwy 55/84/29 9/15/2001 Y AL 12 Escambia Hwy 31, 2.8 mi W of Hwy 29 9/15/2001 Y AL 13 Baldwin Hwy 59, 17.6 mi N of Hwy 65 9/15/2001 Y AL 14 Mobile Hwy 45, 23.8 mi N of Hwy 65 9/16/2001 Y AL 15 Baldwin Hwy 59/90, ? mi S of Int 10 (near Loxley) 9/16/2001 Y MS 1 Greene Hwy 57, 13 mi SE of Hwy 49 4/15/2001 Y MS 2 Harrison Hwy 53, 6.2 mi W of Hwy 49 4/15/2001 Y MS 3 Wilkinson Hwy 61, 49 mi N of Hwy 190 5/3/2001 N MS 4 Pike Hwy 51, 8.4 mi N of Hwy 98 5/4/2001 N MS 5 Simpson Hwy 13, 2.1 mi S of Hwy 49 5/4/2001 N MS 6 Forrest Hwy 42, 0.3 mi W of Hwy 49 5/4/2001 Y MS 7 Clarke Hwy 18, at Int 59 intersection 4/5/2001 N MS 8 George Hwy 63, 2 mi S of Lucedale 9/16/2001 Y MS 9 Stone Hwy 26, 17.5 mi W of Hwy 57 9/16/2001 Y MS 10 Jackson Hwy 57, 2 mi N of Int 10 9/16/2001 Y LA 1 Baton Rouge Hwy 1, 1.4 mi N of Hwy 90 5/1/2001 N LA 2 Pointe Coupee Hwy 167, at Int 49 intersection 5/2/2001 N LA 3 Rapides Hwy 1, 1.7 mi SE of Int 49 5/2/2001 N LA 4 Lasalle Hwy 165, 0.2 mi S of Hwy 84 5/2/2001 N LA 5 Ouachita Hwy 15, 1.1 mi E of Hwy 165 5/2/2001 N LA 6 Madison Hwy 65, 1.4 mi S of Int 20 5/3/2001 N LA 7 Tensas Hwy 65, 47 mi S of Int 20 5/3/2001 N LA 8 Livingston Hwy 190, ? mi W of Int 55 (near Hammond) 5/3/2001 N

49

Appendix B Species presence/absence data at southeast survey site

50 An “X” signifies the species presence at each site, and a dash signifies its absence. Aphaenogaster Brachymyrmex Camponotus Cardiocondyla Dorymyrmex Forelius Formica Linepithema Monomorium Odontomachus Site ID floridana musculus floridanus sp bureni analis schaufussi humile viride brunneus FL 1 ------FL 2 ------FL 3 ------FL 4 - - - - X - - - - - FL 5 ------FL 6 X ------FL 7 X - - - X - - - - X FL 8 ------FL 9 - - - - X - - - - - FL 10 ------FL 11 - - - X X - - - - - FL 12 - - - - X - - - - - FL 13 ------FL 14 - - - - X - X - - - FL 15 X X X - X - - - - - FL 16 ------FL 17 ------FL 18 - - - - X - - - - - FL 19 - X - - X - - - - - GA 1 - X X - X - - - - - GA 2 ------GA 3 - - - - X - - - - - AL 1 ------AL 2 - - - - X - - - - - AL 3 - - - - - X - - X - AL 4 ------AL 5 - - - - - X - X - - AL 6 ------AL 7 ------AL 8 ------AL 9 - - - - X - - - - - AL 10 - - - - X X - - - - AL 11 - X - - X - - - - - AL 12 ------AL 13 - X ------AL 14 ------AL 15 ------MS 1 ------MS 2 ------MS 3 ------MS 4 - X ------X - MS 5 ------X - MS 6 ------X - MS 7 ------MS 8 - X ------MS 9 ------MS 10 ------LA 1 ------LA 2 ------LA 3 ------X - - LA 4 ------X - LA 5 ------X - LA 6 ------X - LA 7 ------LA 8 ------

51 Paratrechina Paratrechina Pheidole Pheidole Pheidole Pheidole Pheidole Pheidole Solenopsis Solenopsis Site ID concinna longicornus dentata floridana metallescens moerens morrisi obscurithorax diplorhopteran invicta FL 1 ------X - X FL 2 ------X - X FL 3 ------X - X FL 4 - - - X X - - - - X FL 5 ------X FL 6 - - - X X - - - X X FL 7 X - X - X - - - X X FL 8 ------X FL 9 ------X FL 10 ------X FL 11 - - - X - - - X - X FL 12 - - - X X - - - - X FL 13 - - - - X X - - - X FL 14 ------X FL 15 - - - X X - X - - X FL 16 ------X FL 17 ------X FL 18 ------X - X FL 19 - - - - X X - X - X GA 1 ------X GA 2 ------X GA 3 ------X AL 1 ------X - X AL 2 ------X - X AL 3 X ------X X AL 4 ------X AL 5 ------X AL 6 ------X - X AL 7 ------X AL 8 ------X AL 9 ------X - X AL 10 ------X AL 11 ------X - X AL 12 ------X - X AL 13 - - - X - - - X - X AL 14 ------X - X AL 15 X - - - - X - X - X MS 1 ------X MS 2 - - - X - - - - - X MS 3 ------X MS 4 - X ------X MS 5 - - X - - - - - X X MS 6 ------X MS 7 ------X X MS 8 ------X - X MS 9 ------X MS 10 - - - - X X - X - X LA 1 ------X LA 2 ------X LA 3 ------X LA 4 ------X LA 5 X ------X LA 6 X ------X LA 7 ------X LA 8 ------X

52

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BIOGRAPHICAL SKETCH

I was born December 3, 1974 in Denver, Colorado, but moved to northern California with my mom when I was two years old, so I consider myself a California girl. Neither of my parents received an education above high school, but somehow my brother, Scott McClure, and I both ended up with high-reaching goals and have completed Bachelors degrees. I have supported myself since I was 17 years old and have financed my own education, something I am very proud of. I received my Bachelors of Science from the University of California at Davis from the Section of Evolution and Ecology in June of 1999. Within two months time of my graduation I got married to Brian Storz, and we moved to Tallahasee, Florida, to begin graduate school. Graduate school was a huge adjustment for me, but I am proud to say I have been successful, and, by the time you are reading this, I will have earned my Masters Degree from the Department of Biological Science (June 2003) at Florida State University. I am, and always will be, fascinated with Biology, and, for the most part, I have enjoyed research; but I love teaching. My experiences in research have given me an entirely different perspective on education, and I will be a better teacher for it. I plan to pursue a career in education; now I just have to figure out at what age level I can have the greatest influence in students’ lives.

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