Global Patterns of Freshwater Fish Communities in Mediterrannean Biomes

GLOBAL PATTERNS OF FRESHWATER FISH COMMUNITIES IN MEDITERRANNEAN BIOMES

Elif Esther Fehm-Sullivan B.S., California State University, Sacramento, 2003

THESIS

Submitted in partial satisfaction of the requirements for the degree of

MASTER OF SCIENE

BIOLOGICAL SCIENCES

CALIFORNIA STATE UNIVERSITY, SACRAMENTO

FALL 2010

GLOBAL PATTERNS OF FESHWATER FISH COMMUNITIES IN MEDITERRANNEAN BIOMES

A Thesis

Elif Esther Fehm-Sullivan

Approved by:

______, Committee Chair Jamie Kneitel, Ph.D.

______, Second Reader Brett Holland, Ph.D.

______, Third Reader Patrick Foley, Ph.D.

______Date

Student: Elif Esther Fehm-Sullivan

I certify that this student has met the requirements for format contained in the University format manual, and that this thesis is suitable for shelving in the Library and credit is to be awarded for the thesis.

______, Graduate Coordinator ______Susanne Lindgren, Ph.D. Date

Department of Biological Sciences

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Abstract

GLOBAL PATTERNS OF FRESHWATER FISH COMMUNITIES IN MEDITERRANNEAN BIOMES

Elif Esther Fehm-Sullivan

Explaining patterns of species richness is a central theme in community ecology.

Ecologists have focused on local (within a site), regional (among sites in a given region), or geographical (among regions) explanations of diversity patterns. In the case of freshwater fish, studies illustrate that biological factors (competition and predation), along with physical factors (habitat diversity, water chemistry, flow regime, temperature and channel morphology), interact to influence species richness within and among communities and that both operate within a range of spatial scales.

This study identified global patterns of species richness and trophic diversity in twelve Mediterranean biome freshwater fish communities located on six continents.

Differences were found in both species richness and trophic diversity between continental river basins. This study also examined energetic, ecological, and historical factors that may explain freshwater fish species richness and trophic diversity among Mediterranean biome river basins. The energetic factor, average annual discharge, was found to explain species richness; and that none of the seven factors measured explained trophic diversity.

This result is contrary to studies that have shown net primary productivity as explaining species richness in global freshwater fish communities. The difference presented in this iv

study states that all basin studies were in one habitat type, the Mediterranean biome, whereas other studies examined several varying habitat types. The resulting specific knowledge can help conserve species richness and manage river basins altered by human activity.

______, Committee Chair Jamie Kneitel, Ph.D.

______Date

DEDICATION

In loving memory of Sherwood Anthony Fehm Jr. and Saba Phyllis Fehm-Sullivan.

ACKNOWLEDGMENTS

Completing a Masters is truly a marathon event, and I would not have been able to complete this journey without the aid and support of countless people over the past seven and a half years. I would like to express my gratitude to my supervisor, Dr. Jamie Kneitel, whose expertise, understanding, and patience added considerably to my graduate experience. I appreciate his vast knowledge and skill in many areas (e.g., statistical analysis, community ecology, and dry humor), and his assistance in writing. I also want to thank him for his calm reserve during times of stress. I would like to thank the other members of my committee, Dr.

Bret Holland, and Dr. Patrick Foley for the assistance they provided at all levels of my thesis project. Finally, I would like to thank Dr. Susanne Lindgren, the

Graduate Student Advisor, for giving me the opportunity to finish my thesis.

I would like to give my eternal gratitude to my father James E. Sullivan for the guidance and wisdom that he has given me throughout my life. I have been able to develop and grow as an individual as a result. He provided me with moral, emotional, and writing support during this entire process. I doubt I will ever be able to convey my appreciation fully. I must also acknowledge the quiet, constant, intense and enduring support of my mother Sadie Çançar Sullivan. A very special thank you goes to Dr. Barbara Cordonii, who years ago diagnosed my learning disabilities, and with whose tutelage enabled me to reach this level of

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education. Without her motivation and encouragement, I would not have considered a graduate career.

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TABLE OF CONTENTS Page

Dedication ...... vi

Acknowledgments...... vii

List of Tables ...... x

List of Figures ...... xi

Introduction ...... 1

Methods...... 9

Results ...... 11

Discussion ...... 24

Conclusion ...... 29

Appendix A. Trophic level richness per drainage basin...... 32

Appendix B. Data sources ...... 33

Appendix C. Species lists and trophic level ...... 34

Appendix D. Table of environmental factor values per drainage basin ...... 42

Appendix E. Calculation table for NPP ...... 43

Literature Cited ...... 44

LIST OF TABLES Page

Table 1. Trophic Level ANOVA ...... 14

Table 2. Species Richness ANOVA ...... 16

Table 3. Continental Trophic Richness ANOVA...... 18

Table 4. Multiple Regression on Species Richness and Trophic Diversity...... 21

LIST OF FIGURES Page

Figure 1. Global map of Mediterranean Biome Locations ...... 8

Figure 2. Trophic Level Histogram...... 15

Figure 3. Species Richness Histogram...... 17

Figure 4. Continental Trophic Species Richness Histogram...... 19

Figure 5. Continental Community Composition Chart...... 20

Figure 6. Species Richness Regression with the San Joaquin River...... 22

Figure 7. Species Richness Regression without the San Joaquin River...... 23

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INTRODUCTION

A central issue in both biogeography and community ecology is to understand the factors that shape species richness patterns across different spatial scales (Cody and

Mooney, 1978; Griffiths, 2006). Among vertebrates, fish have been one of the most intensely studied groups for local (within river), regional (among rivers), and geographical (among regions) community structure. Numerous common patterns in fish community organization have been identified among distinct river basins at several different spatial scales. For example, at a local scale, physical factors appear to determine species richness in variable environments (Capone and Kushlan, 1991). On larger spatial scales (regional and geographical), physical factors such as area, total discharge, and primary productivity, along with historical factors such as speciation rates and dispersal are the major determinant of species richness and regulate the importance of local-scale factors (Lamoureux et al., 2002).

To better understand freshwater fish communities, ecologists have studied several aspects of community structure. These include biogeographic histories and their relation to the distribution of freshwater fishes (Novacek, 1976; Bernatchez and Wilson, 1998;

McDowall, 2002; Landini and Sorbini, 2005; Goren and Ortal, 1998), diversity of trophic categories (feeding patterns) (Tonn, 1990; Winemiller, 1991; Behrens and

Lafferty, 2007; Daufresne and Boёt, 2007; Erös, 2007; Mittelbach et al., 2007; Lévêque et al., 2008), and species richness (Hawkins et al., 2003; Oberdorff et al., 1995; Guégan et al., 1998; Oberdorff et al., 2001; Griffiths, 2006; Reyjol et al., 2007).

The inland water fishes of the Mediterranean have been studied since the first description of Tilapia galieae by Peter Artedi, considered the father of Ichthyology, more than 200 years ago (Goren and Ortal, 1998). Some biogeographers have recognized the importance of the isolation of fishes, and distinct drainages in shaping species richness and diversity. For example, Lyons and Willig (2002) noted that isolation preserved the products of speciation events which occurred either within single bodies of water, or when waters became fragmented and rejoined. Each isolated lake or river system tends to have its own characteristics and a substantial number of endemic species. In some cases, the present distribution of freshwater fishes has been shaped by millions of years of change in global water cycles (Lèvêque et al., 2008). Due to these constantly changing global water cycles (i.e. glaciation, water availability and temperature variation due to climate change), the nature and dynamics of freshwater systems have evolved continuously, at various spatial and temporal scales (Lèvêque et al., 2008). Although clearly there can be important differences among the fish species present in tributaries within any basin, species are typically more similar in any location within a river basin than they are among locations in neighboring basins (Griffiths, 2006). These basins and waterways can provide natural laboratories for the study of community structure and the processes that influence them. The similarities among some of the fishes in these historically isolated systems suggest broad-scale parallelism or convergence (Dyer, 2000;

Cussac et al., 2004; Landini and Sorbini, 2005).

Most studies of assemblage organization in stream fish address the effects of inter-specific interactions and environmental variation on assemblage structure and

3 resource use (Moyle and Light, 1996). Some effort has been devoted to quantifying large-scale variation and the multi-scale determinants of assemblage patterns and processes (Bernatchez and Wilson, 1998). As a result, it is uncertain whether determinants of local structure and function can be extrapolated to explain assemblage patterns over broad regional scales (Bernatchez and Wilson, 1998). Moreover, knowledge of the influence of regional constraints and historical processes on species distribution, abundance, and assemblage composition remain general, although this knowledge has been considered critical for advancement in stream fish ecology and conservation (Poff, 1997). Because as a general rule fish only move by swimming, no other single factor is more important in regional biogeography of freshwater fishes and drainage basin limits and affinities (Koleff et al., 2003).

Spatial variability in species diversity patterns are primarily explained by three hypotheses. These include the (1) species-area theory (Preston, 1962), which predicts that species richness increases as a power function of surface area; (2) species-energy theory (Wright, 1983), which predicts that species variation is correlated with energy availability in the system; and (3) historical theory (Whittaker, 1977), which explains richness gradients, on a global scale, by patterns of recolonization and maturation of ecosystems after glaciation (Guégan et al., 1998). This study undertakes an exploration to determine if any of these hypotheses for freshwater vertebrates (fishes) in similar climates holds true. Much research on the community ecology of temperate freshwater streams has been conducted in North America, and some researchers have assumed that the patterns observed in North America should be applicable elsewhere (Reyjol et al.,

2007; Rühland et al., 2008). Notably, this assumption has recently been called into question (Hendry and Stearns, 2004). In the circum-Mediterranean region, there is a dearth of information about factors causing the large-scale spatial structuring of fish assemblages. It is also doubtful whether the frameworks developed for temperate streams can be directly translated to such semiarid systems (Reyjol et al., 2007).

Mediterranean ecosystems largely occur along the western edges of continents between the 30° and 40° parallels in both northern and southern hemispheres. The world’s five Mediterranean-climate ecosystems are limited to: the region bordering the

Mediterranean Sea; central Chile; the Cape region of South Africa; southwestern and southern Australia; and all of California south to upper Baja California (Illes, 1978;

Moyle, 2002; Morgan, 2003; Figure 1). Moderated by cold ocean currents offshore, the

Mediterranean climate is characterized by mild, rainy winters and warm, dry summers

(Underwood et al., 2009). ). This favorable climate has made the Mediterranean Biome densely populated by humans (Clavero et al., 2004).

Consequently, these regions suffer from multiple threats, including deforestation and desertification that result from urbanization, agriculture, recreation and other human activities. Invasive plants and animals are also drastically altering the ecosystem and its biodiversity in all of the five Mediterranean regions of the world. As a result, the

Mediterranean biome, occurring on three percent of the earth’s total land area, is one of the most highly altered and imperiled ecosystems on the planet, with the most disturbed area of any biome (Underwood et al., 2009). In concert with high biodiversity and

5 endemism, this has resulted in all Mediterranean biome locations considered biodiversity hotspots (Myers et al., 2000).

Several studies have focused on comparisons of physical characteristics of species, species richness, and composition of Mediterranean biome communities within one continental location, or between two different continental locations. These studies have focused on the status of the high level of species richness and endemism in plant communities (Mooney and Dunn, 1970; Cody and Mooney, 1978; Arroyo and Cavieres,

1991; Heywood, 1993; Cowling et al., 199; and Underwood et al., 2009). They have also included avian communities (Kark and Sol, 2005) and freshwater fish communities

(Bernardo et al., 2003; Clavero at al., 2004; Darwall and Smith, 2006; Pascual et al.,

2007). Very few studies have focused on the communities or organisms found within the

Mediterranean biome and compared them across continents. These studies include those done by Mooney and Dunn (1970) on Mediterranean plant species, which focused on the physical similarities of plants illustrating instances of convergent evolution due to similarities in climate, despite separate distinct evolutionary histories. Additionally,

Cody and Mooney (1978) found similar occurrences of convergent evolution due to similar climates in their review of Mediterranean plant communities, in addition to other similar studies that focused on bird and lizard communities (Kark and Sol, 2005;

Ioannidis, 2008).

No studies have looked specifically at freshwater fish trophic diversity within a similar but isolated biome and compared them across continents, including the

Mediterranean biomes. Most fish assemblage comparisons are done across varying

6 latitudinal gradients of differing biotic regions such as Arctic, Nearctic, Tropical, and

Temperate regions (Winemiller, 1991), or are used to identify ichthyological “provinces” of the world (Lèvêque et al., 2008). In addition, studies have been done to investigate the freshwater icthyofauna of several Mediterranean streams (Goren and Ortal, 1999;

Kleynhans, 1999; Dyer, 2000; Kadye and Marshall, 2007). Many of these have been conducted to establish a baseline of species present after urbanization and/or to monitor restoration measures (Corbacho and Sanchez, 2001; Bernardo et al., 2003; Clavero et al.,

2004; Clavero et al., 2005; Habit et al., 2006; Magalhães et al., 2007). There are however, no comparative studies of global freshwater fish community patterns within a similar biome or latitudinal location. What makes the study of patterns in the

Mediterranean biome so uniquely compelling is its location. Being equidistant to the

Equator, this location minimizes or even eliminates any latitudinal gradient effects on species richness and trophic diversity (Winemiller, 1991; Mittelbach et al., 2007).

The purpose of this study was to compare freshwater fish community richness and structure among Mediterranean biomes, which have similar climatic conditions and minimal latitudinal gradient effects. Differences of community trophic diversity and species richness were tested between the biome locations, and related to measurable physical parameters. These parameters were hydrology, geology, ecology, and climate.

The hydrological parameters included total drainage basin area in square kilometers and mean annual discharge at the river mouth in cubic meters per second. The geological parameters were total surface area of the continent and area of glaciation. The ecological

7 parameter was net primary productivity. Finally, the climactic parameters were mean annual temperature and mean annual rain fall in the basin area.

Figure 1. Figure 1. Global Map of Mediterranean Biome Locations. California Mediterranean Research Learning Center (2009).

METHODS

The twelve rivers studied were distributed as follows: two river basins from each of the continents of Europe, Asia, North and South America, Africa and Australia

(Appendix A). Species richness was obtained by recording presence data from published sources of fish assemblages (Appendix B), which were then counted and totaled

(Appendix A and C). Fish species found in drainages located within the six continents were categorized into feeding guilds: insectivores, piscivores, herbivores, omnivores, and planktivores using diet information from www.fishdatabase.org (Appendix C).

These five feeding guilds are commonly used for trophic level classification of fish in

North America (Karr, 1986) and Europe (Griffiths, 2006). Only adult forms were taken into consideration as feeding behavior changes during ontogeny (Brown and Matthews,

1995). The number of species found in each of the five feeding guilds were counted and totaled to determine species richness within trophic levels (Appendix A).

Values for fish species richness were subject to several sources of error. First, the number of fish species may be underestimated due to inadequate sampling effort or extinctions due to human activity occurring before collections were made (Oberdorff et al., 1995). Secondly, the number of fish species may be overestimated if some species have been recently introduced in rivers (Moyle 2002). To minimize these potential adverse effects upon the accuracy of the study, only the most recent references were selected, and only fish currently found within these basins were used. Extinct fishes were not included in this study.

For each drainage system the following variables were determined from the literature (Appendix D) : (1) total surface area of the drainage basin in square kilometer

(km2), (2) mean annual discharge at the river mouth in cubic meters per second (m3/s),

(3) total surface area of the continent (km2), (4) mean annual temperate (C˚), (5) mean annual rain fall in the area (mm), (6) glaciated area within the study basin (km2), and (7) net primary productivity (kg2/yr) as can be seen in Table 2.

The seventh variable of net primary productivity was calculated using Lieth’s

(1975) model as applied by Golubyatnikov and Denisenko (2001) (Appendix E). As net aquatic productivity data was difficult to obtain, mean annual air temperature and mean annual rainfall were used to estimate average mass of terrestrial primary productivity from Lieth’s (1975) model as demonstrated by Oberdorff et al. (1995). Terrestrial primary productivity and aquatic primary productivity co-vary (Livingstone et al., 1982;

Oberdorff et al., 1995; Hugueny, 1989) and were used as a surrogate in this study; as seen in previous studies (Livingstone et al., 1982; Oberdorff et al., 1995; Hugueny, 1989).

Statistical Analysis

One-way analysis of variance (ANOVA), the two-way ANOVA, the chi-squared test, and multiple regressions were all used to assess hypotheses. One-way ANOVAs were used to determine whether the number of trophic levels present and species richness differed among continents. A two-way ANOVA was used to determine whether the species richness within each trophic level differed among continents. A chi-square test was conducted to determine if there was an association between number of species per

11 trophic level and continent. Finally, two backward elimination multiple regressions were used to determine if there were any relationships between the independent variables total surface area, mean annual discharge, total surface area of the continent, mean annual temperature, mean annual rain fall in the area, and the dependent variables of species richness and number of trophic levels present. The variable, total basin area of historical glaciation was removed from the multiple regressions because none of these basins had any history of glaciation (Mercer, 1983; Moyle and Herbold, 1987). After running the multiple regressions, the San Joaquin River became an outlier. Upon further investigation, as this river is a highly disturbed system and in fact is intermittently dry for over 132 miles (Pereira et al., 1996), it was removed from the data set.

Species richness (total and within trophic levels) data was not normally distributed.

All attempts at transformation of these data sets were unsuccessful at obtaining normal distribution, including squaring, taking the square root, taking the natural log, and multiplying the data set. As a result, non-parametric tests were used and caution should be used when interpreting the results. Data was analyzed using SPSS 17.0 software.

RESULTS

Numbers of trophic levels (trophic diversity) were statistically different among continental locations (Table 1, Figure 2). The continents of Asia, Europe, North

America, Africa and South America had somewhat similar trophic diversity. Trophic levels from all continents were significantly different from Australia (Figure 2). Rivers in Africa, Asia, Europe, North America, and South America supported almost twice as

12 many trophic levels as Australia (Figure 2). Total species richness was also significantly different among continents (Table 2, Figure 3). North America, Australia, and South

America had greater species richness then that of Asia, Europe and Africa. Across trophic levels and continents, there were significant differences in species richness (Table 3,

Figure 4). The omnivore trophic level had the greatest number of species than any other group (Figure 4 and 5).

The chi-square test conducted to determine a possible association between species richness of trophic levels and continent revealed a significant difference between trophic richness levels in the southern hemisphere and the northern hemisphere (X2 = 34.59, df=4, P<0.001 (Figure 5).

Ecological and Historical Factors on Species Richness

Among all six factors (total surface area of the drainage basin, mean annual discharge at the river mouth, total surface area of the continent, mean annual temperate, mean annual rain fall, and glaciated area within the study basin) there were no statistically significant relationships with species richness except for a weak positive relationship with annual average discharge (Table 3, Figure 6). The San Joaquin River was found to be the only outlier. With this outlier removed, there was a very strong positive relationship between species richness and annual average discharge (Table 4) as seen in Figure 7.

Ecological and Historical Factors on Number of Tropic Levels Present

Among all six factors of total surface area of the drainage basin, mean annual discharge at the river mouth, total surface area of the continent, mean annual temperate, and mean annual rain fall, there were no statistically significant relationships within tropic levels (Table 4).

Trophic Level SS df MS F-value P-value

Between 5.417 5 1.083 4.333 0.051 Continents

Within 1.500 6 0.250 Continents

Total 6.917 11 229.9

Table 1. Trophic Level ANOVA. Statistical summary of a one-way ANOVA results for between continent effects for number of trophic levels present. This table illustrates that there is a statistically significant difference between the numbers of trophic levels between continental locations. All statistically significant P-values are italicized.

Figure 2. Trophic Level Histogram. Mean trophic level diversity of Mediterranean fresh water fish for each continent location. Asia, Europe, North America, South America and Africa have twice as many trophic levels occupied as Australia.

Species Richness SS Df MS F-value P-value

Between 4916.667 5 983.33 5.717 0.028 continents

Within 1032.000 6 172.00 Continents

Total 5948.667 11

Table 2. Species Richness ANOVA. Statistical summary of a one-way ANOVA results for between continent effects for species richness. This table illustrates that there is a statistically significant difference between the numbers of trophic levels between continental locations. All statistically significant P-values are italicized.

Figure 3. Species Richness Histogram. Mean species richness of Mediterranean fresh water fish for each continent location. North America has the greatest number of species. Australia and South America are the second most specious and have similar species richness. Asia, Europe, and Africa are similar and have the least amount of species richness.

Source SS Df MS F-value P-value

Trophic Level 4038.90 4 1009.725 49.335 P <0.001

Continent 983.33 5 196.667 9.609 P<0.001

Trophic Level*Continent 2511.50 20 125.575 6.136 P<0.001

Error 614.00 30 20.467

Total (Corr) 8147.73 59

Table 3. Continental Trophic Richness ANOVA. Statistical summary of a two-way ANOVA testing possible interactions between tropic level, species richness and continent. This table illustrates that there is a significant difference in species richness among both trophic levels and continents. Additionally, there is a significant interaction between trophic level and content on species richness. All significant P-values are italicized.

Figure 4. Continental Trophic Species Richness Histogram. This represents all of the species present within the trophic levels present at each continental location.

Figure 5. Continental Community Composition Chart. This chart breaks down each continent into its representative trophic levels and their contribution to total species richness.

Dependent Parameter R F-value P-value Df Model variable Species Annual Average 0.478 2.965 0.116 11 SR=0.035(AAD)+15.524 Richness Discharge with San (SR) Joaquin River (AAD) Species Annual Average 0.852 23.847 0.001 10 SR=0.058(AAD)+0.571 Richness Discharge without San (SR) Joaquin River (AAD) Trophic Drainage Area 0.45 2.533 0.143 11 TD=4.065-1.197e^- Diversity (AREA) 6(AREA) (TD)

Table 4. Multiple Regression on Species Richness and Trophic Diversity. This table consists of the most descriptive factors on species richness and trophic diversity found when conducting a backwards multiple regression on the hydrological, geological, ecological, and climactic factors. Included are annual average discharge both with and without the San Joaquin River on species richness, and drainages area on trophic diversity. These values had the lowest P-value of all 7 factors measured against. Significant P values are italicized.

Figure 6. Species Richness Regression with the San Joaquin River. Species Richness of Mediterranean freshwater fish for each river as a function of annual average discharge at river mouth. This regression is illustrated with the San Joaquin River included.

Figure 7. Species Richness Regression without the San Joaquin River. Species richness of Mediterranean freshwater fish for each river excluding the San Joaquin River, as a function of annual average discharge at river mouth.

DISCUSSION

Freshwater fish community structure (trophic level diversity, trophic level richness, and species richness) differed across each of the six Mediterranean biomes.

North America supported the highest levels of species richness followed by Australia and

South America; Asia, Europe, and Africa were similar and had lower species richness

(Figure 3). Australia had the least amount of species richness present (Figure 2).

Continental trophic richness differed significantly with omnivory consistently having the highest species richness (Figure 4). Further observation revealed significant differences between types of trophic levels present among the continental locations specifically regarding the richness of both insectivores and piscivores between the northern and southern hemispheres (Figure 5). The northern hemisphere had significantly fewer insectivores than the southern hemisphere. Conversely, the northern hemisphere had significantly more piscivores then the southern hemisphere.

The second investigation comprising this study examined differences of community trophic diversity and species richness between the biome locations, in addition to seeing if these differences could be explained by measurable physical parameters such as hydrology, geology, ecology, and climate. Among all seven factors measured, only the hydrological parameters of annual average discharge demonstrated a positive effect upon species richness (Figure 7). No significant effects of the seven factors on trophic diversity were found.

Historically, biogeography is the science of studying and observing patterns in ecosystems at different spatial and temporal scales (Lamouroux, 2002). Previous studies

25 have done so by using various community properties, such as species richness and proportional composition of trophic levels (Moyle and Herbold, 1987; Lamouroux,

2002). Such patterns expressed in community convergence are an aspect of the hypothesis that characteristics of communities are predictable from their environment

(Schluter, 1986), and that communities are structured rather than random entities.

Models predicting similarities in community traits from independent systems having similar environmental features suggest the existence of key repeated mechanisms underlying community organization (Lamouroux, 2002). Therefore, while predictive tools in ecology often site specific and poorly transferable across ecosystems (Peters and

Myers, 1991), convergence studies can provide general models for predicting fundamental community patterns in multiple sites (Mooney and Dunn, 1970; Cody and

Mooney, 1978). This study investigated community structure across the broadly separate geographic regions in the Mediterranean biome and then compared this structure in terms of trophic level diversity.

The concept of trophic levels is one of the oldest ideas in ecology and helps us to understand assemblage composition and energy flow within communities (Thompson et al., 2007). The results of the trophic diversity analysis of this study illustrate a prevalence of omnivory within all of the continental locations. This is not the only case where omnivory dominates communities, a fact that has been documented in several aquatic systems (e.g., marine, reservoirs, and estuarine) and is thought to stabilize food webs (Emmerson and Yearsley, 2004). The importance and prevalence of omnivory for the structure and dynamics of food webs is a long-standing controversy (Cousins, 1987;

Burns, 1989; Polis, 1991; Holt and Polis, 1997; Vandermeer, 2006; Thompson et al.,

2007). Omnivory is key to the fundamental understanding of food web dynamics, and as a result much debate has occurred over this subject (Polis and Strong, 1996; Hairston and Hairston, 1997; Thompson et al., 2007). Current theoretical models suggest that omnivory may in fact stabilize food webs (Emmerson and Yearsley, 2004; Thompson et al., 2007), and that larger food webs support higher levels of omnivory (Woodward and

Hildrew, 2002; Thompson et al., 2007). This theory was evident in this study, as there were greater numbers of species within continental locations that had higher levels of omnivory (Figure 4 and 5). Further analysis would be required to confirm this possibility.

The inverse proportion of piscivorous and insectivorous species richness between the northern and southern hemisphere is not surprising as both of these families evolved separately approximately 160 to 150 million years ago; salmonids evolved in Laurasia while the galaxiid family evolved in Gondwanaland (Waters et al., 2000; McDowall,

2002; Clavero et al., 2005; Lévêque et al., 2008). This finding supports both the well- documented biogeographical colonization histories of the southern and northern hemispheres (McDowall, 2002) and the positive relationship between body size and trophic level in fishes (see Data collected in Appendix C). Body size determines the range of prey species a predator can consume, allowing larger individuals with larger anatomy to feed at higher trophic levels (Winemiller, 1991; Jennings et al., 2001). The salmonid family dominates northern hemisphere freshwater fish communities in temperate locations, which tend to be large piscivorous fish (Jennings et al., 2001).

Meanwhile, in the southern hemisphere the galaxiid family dominates these same communities, which tend to be small insectivorous fish (Reyjol et al., 2007).

While these two historical explanations of trophic level composition contribute to understating the observed patterns, other ecological processes such as extinction, invasion, competition, and disturbance, may also play a role in shaping these communities.

As previously discussed, the difference in the predictive ability of varying factors is based on the size scale of the community patterns. On the local scale, physical factors appear to determine species richness in variable environments (Capone and Kushlan,

1991). On larger spatial scales (regional and geographical), physical factors such as area, total discharge, and primary productivity, along with historical factors such as speciation rates and dispersal are the major determinant of species richness, and regulate the importance of local-scale factors (Lamoureux et al., 2002). These differences in spatial variability in species diversity patterns are primarily explained by the three previously introduced theories: the species-area theory (Preston, 1962), the species-energy theory

(Wright, 1983), and the historical theory (Whittaker, 1977). This study sought to try and branch these two differing spatial scales by comparing similar a similar type of environment across a broad geographical area, in addition to trying to determine if any of the three aforementioned hypotheses held true for freshwater vertebrates (fishes) in similar climates.

The results of this study indicated that annual average discharge is the most important factor influencing freshwater fish species richness patterns globally across the

28 entire Mediterranean biome, illustrating for the Mediterranean biome that the species- area theory and historical theory do not explain species richness patterns. This finding is consistent with those of Poff and Allan (1995), Oberdorff et al. (2001) and Cattanéo

(2005). These studies show that changes in annual average discharge influence the functional organization of fish assemblages and/or demonstrated effects on species richness. While the species-energy theory does help explain species richness across the

Mediterranean biome, additional consideration is in order since several previous studies looking at freshwater species richness patterns have found that area, average annual discharge, and primary productivity explained species richness (Oberdorff et al., 1995;

Guégan, 1998; Hawkins et al., 2003; Clavero et al., 2004). Nevertheless, a general understanding of the degree of similarity of fish communities across geographical distinct basins is lacking. This is primarily because quantitative descriptors can sometimes become intercorreleated across basins, making it difficult to identify which factors are responsible for community structure (Lamaroux, 2002). Using these species richness theories as general predicative tools of community characteristics seem to initially require precise measurements of the factors defining the community’s habitat (Lamaroux, 2002).

A better understanding of Mediterranean biome communities could be achieved by further studies into the hydraulic nature of these basins, the effect of high disturbance of flow regime on primary productivity, and the effect of invasive species on the native community.

In this study, primary productivity not being a predictor of species richness could be due to the highly disturbed nature of the riparian habitat of the Mediterranean biome.

As previously stated, the Mediterranean biome is one of the most altered systems in the world. Several studies have illustrated that changes in natural stream regime affect primary productivity (Mallin et al., 1993). All rivers in this study, as with most

Mediterranean biome rivers, have been dammed and have several water diversions. The primary reasons for these dams are flood control, to regulate the fluctuation of water flow throughout the year, and agricultural purposes. As in all Mediterranean biome locations, agriculture has been a dominant feature of the terrestrial environment. This has led to the degradation of riparian habitats and diversion of water from the rivers themselves to irrigate vast croplands (Underwood et al., 2009). Due to the installation of these dams, the natural hydrology of these rivers has also been altered to reflect more of a constant flow regime rather than the cyclical flood regime that defines the Mediterranean biome

(Junk et al., 1989). The damming of a river has been called a cataclysmic event in the life of a riverine ecosystem (Ligon et al., 1995). By changing the flow of water, sediment, nutrients, energy, and biota, dams interrupt and alter most of a river’s important ecological processes (Ligon et al., 1995). This could be the reason that primary productivity in the basins studied does not reflect species richness.

CONCLUSION

The data and analysis presented here have led to the surprising conclusion that annual average discharge is the most important factor influencing fish species richness patterns globally across the entire Mediterranean biome. This illustrates that for the

Mediterranean biome the species-area theory and historical theory do not explain species

30 richness patterns. While the species-energy theory does help explain species richness in the Mediterranean biome, additional consideration is in order; since several previous studies looking at freshwater species richness patterns have found that area, average annual discharge and primary productivity explained species richness (Oberdorff et al.,

1995; Guégan, 1998; Hawkins et al., 2003).

The Mediterranean-climate regions of the world are renowned for high levels of richness and endemism in both flora and fauna. However, it is one of the most imperiled ecosystems in the world, and has the highest density of human population and agricultural practices. A fuller understanding of these freshwater Mediterranean communities, their composition, and the factors that contribute to their survival and enhancement will help formulate the required strategies to rehabilitate, conserve, and protect them in the future. Armed with the knowledge that annual average discharge of these highly endangered river basins directly influences species diversity, dam discharge regimes can be monitored and modified to result in the desired level of species richness.

APPENDICES

Appendix B. Data sources.

Average Drainage Average Annual Area of Average Average Annual Species Richness Area in Discharge in Continent in Annual Rain Area of Location Drainage Temperature in in Number of Square Cubic Meters Square Fall in Historical Degrees Species Kilometers per Second Kilometers millimeters Glaciation Celsius Illes, Global Runoff Encyclopedia Antunes, Magalhaes, Magalhaes, 1978; Bernardo et al., Mira Data Center, Britannica, 2008 2002 2002 Griffiths, 2003 2010 2008 2006 Europe Illes, Global Runoff Encyclopedia Corbacho and Clavero et Corbacho and 1978; Clavero et al., Guadiana Data Center, Britannica, Sanchez, al., 2004 Sanchez, 2001 Griffiths, 2005 2010 2008 2001 2006

World Illes, Global Runoff Encyclopedia World Weather Sari et al., Weather 1978; Bilga Data Center, Britannica, Information Sari et al., 2006 2006 Information Griffiths, 2010 2008 Service, 2000 Service,2000 2006 Asia Oren et al., World Encyclopedia Goren and Oren et al., 1973; Bar-Or, 1973; Global Weather Qishon Britannica, Bar-Or, 2000 Ortal, Goren and Ortal, 2000 Runoff Data Information 2008 1999 1999 Center, 2010 Service, 2000

World Global Runoff Encyclopedia World Weather May and Moyle, Weather May and Brown, Sacramento Data Center, Britannica, Information Brown, 2002 Information 2002 2010 2008 Service ,2000 2002 Service, 2000 North America World Global Runoff Encyclopedia World Weather San Moyle, Weather Moyle, Data Center, Britannica, Information Moyle, 2002 Joaquin 2002 Information 2002 2010 2008 Service, 2000 Service, 2000 Oyarzun, Gobierno Oyarzun, 1995; 1995; De Chile, Feige et al., Encyclopedia Gobierno De World Weather Cussac et Biobío Direccion 2009; Global Britannica, Chile, Information Dyer, 2000 al., 2004 General De Runoff Data 2008 Direccion Service, 2000 South Aguas, 2004 Center, 2010 General De America Aguas, 2004 Gobierno World Feige et al., De Chile, Encyclopedia Weather World Weather Dyer, 2000; 2009; Global Cussac et Itata Direccion Britannica, Information Information Figueroa et al., Runoff Data al., 2004 General De 2008 Service, Service, 2000 2010 Center, 2010 Aguas, 2004 2000 Flügel, 1995; Flügel, 1995; Kalejta and Global Runoff Encyclopedia World World Weather Cussac et Livingstone et al., Berg Hockey, Data Center, Britannica, Weather Information al., 2004 1982 1991 2010 2008 Information Service., 2000 Service, 2000 Africa Swanevelder, Flügel, 1995; Kleynhans, Global Runoff Encyclopedia 1981; World World Weather Cussac et Livingstone et al., Orange 1999 Data Center, Britannica, Weather Information al., 2004 1982 2010 2008 Information Service, 2000 Service, 2000 World Allen et al., 2002; Weather Unmack, Morgan, 2003; Global Runoff Encyclopedia World Weather Walker et Simpson et 2001; Morgan et al., Murray Data Center, Britannica, Information al., 1993 al., 1993; Cussac et 2005; Australian 2010 2008 Service, 2000 Information al., 2004 Department of Service, 2000 Fisheries, 2009 World Australia Allen et al., 2002; Weather Morgan, 2003; Information Unmack, Morgan, Global Runoff Encyclopedia World Weather Morgan,, 2004; Service, 2001; Swan 2004 Data Center, Britannica, Information Morgan et al., 2000; Viney Cussac et 2010 2008 Service, 2000 2005; Australia and al., 2004 Department of Sivapalan, Fisheries, 2009 2001

Appendix C. Species lists and trophic level.

Continent Asia

Location Turkey Israel

Drainage Bigla Qishon Trophic Trophic Species level Species Level Anguilla anguilla Piscivore Anguilla anguilla Piscivore

Salmo trutta macrostigma Omnivore Acantghobrama lissneri Omnivore

Oncorhynchus mykiss Omnivore Garra rufa Herbivore

Leuciscus cephalus Omnivore Hemigrammocapoeta nana Herbivore

Petroleuciscus borysthenicus Omnivore Clarias gariepinus Omnivore Rhodeus amarus Herbivore Aphanius mento Omnivore

Phoxinus phoxinus Omnivore Mugil cephalus Planktivore Vimba vimba Omnivore Liza ramada Planktivore

Chalcalburnus chalcoides Omnivore Orecochromis aureus Planktivore Barbus tauricus escherichi Planktivore Tilapia zillii Herbivore

Capoeta capoeta bergamae Planktivore Tristamella sacra Omnivore Gobio gobio Omnivore Mugil cephalus Omnivore

Cobitis fahirae Omnivore Neogobius fluviatilis Omnivore

Mugil cephalus Omnivore

Continent Europe Location Iberian Peninsula Drainage Guadiana Mira

Species Trophic level Species Trophic level Petromyzon marinus Piscivore Anguilla anguilla Piscivore Anguilla anguills Piscivore Chondrostoma lemmingii Omnivore Alosa alosa Omnivore Barbus sclateri Omnivore Anaecypris hispanica Planktivore Barbus bocagei Omnivore Barbus comiza Piscivore Chondrostoma polylepis Planktivore Luciobarbus microcephalus Omnivore Rutilus alburonides Omnivore Barbus sclateri Omnivore Mugil cephalus Omnivore Chondrostoma polylepis Omnivore Leuciscux pyrenaicus Omnivore Rutilus lemmingii Omnivore Tinca tinca Omnivore Tropidophoxinellus alurnoides Omnivore Coitis paludica Omnivore Gasterosteus aculeatus Omnivore Blennius fluviatilis Omnivore Oncorhynchus mykiss Omnivore Esox lucius Piscivore Carassius auratus Herbivore Cyprinus carpio Omnivore Gobio gobio Omnivore Lepomis gibbossus Omnivore Micropterus salmoides Piscivore Gambusia holbrooki Insectivore Mugil cephalus Omnivore

Continent North America Location California Drainage Sacramento San Joaquin Trophic Trophic Species level Species level Lampetra tridentata Piscivore Lampetra tridentata Piscivore

Lampetra fluviatilis Piscivore Lampetra fluviatilis Piscivore Lampetra pacifica Piscivore Entosphenus hubbsi Piscivore Acipenser transmontanus Omnivore Acipenser transmontanus Omnivore Acipenser medirostris Omnivore Acipenser medirostris Omnivore Alosa sapidissima Omnivore Alosa sapidissima Omnivore Dorosoma petenese Herbivore Dorosoma petenese Herbivore Cyprinus carpio Omnivore Cyprinus carpio Omnivore Carassius auratus Herbivore Carassius auratus Herbivore Notemigonus crysoleucas Omnivore Notemigonus crysoleucas Omnivore Orthodon microlepidotus Omnivore Orthodon microlepidotus Omnivore Mylopharodon conocephalus Omnivore Mylopharodon conocephalus Omnivore Lavinia exilicauda Omnivore Lavinia exilicauda Omnivore Ptychocheilus grandis Piscivore Ptychocheilus grandis Piscivore Gila bicolor Omnivore Pogonichthys macrolepidotus Omnivore Pogonichthys macrolepidotus Omnivore Hesperoleucus symmetricus Omnivore Hesperoleucus symmetricus Omnivore Hesperoleucus symmetricus Omnivore Rhinichthys osculus Omnivore Rhinichthys osculus Omnivore Richardsonius egregius Omnivore Notemigonus crysoleucas Omnivore Notemigonus crysoleucas Omnivore Pimephales promelas Herbivore Pimephales promelas Herbivore Catostomus occidentalis Herbivore Catostomus planyrhynchus Herbivore Ictalurus furcatus Omnivore Catostomus occidentalis Herbivore Ictalurus punctatus Omnivore Ictalurus furcatus Omnivore Ictalurus catus Piscivore Ictalurus punctatus Omnivore Ictalurus nebulosus Omnivore Ictalurus catus Piscivore Ictalurus melas Omnivore Ictalurus nebulosus Omnivore Hypomesus transpacificus Planktivore Ictalurus melas Omnivore Hypomesus nipponensis Omnivore Hypomesus transpacificus Planktivore Spirinchus thaleichthys Omnivore Hypomesus nipponensis Omnivore Oncorhynchus kisutch Planktivore Spirinchus thaleichthys Omnivore Oncorhynchus tshawytscha Omnivore Oncorhynchus kisutch Planktivore Oncorhynchus mykiss Omnivore Oncorhynchus tshawytscha Omnivore Oncorhynchus keta Omnivore Oncorhynchus mykiss Omnivore Oncorhynchus gorbuscha Omnivore Oncorhynchus keta Omnivore Oncorhynchus nerka Planktivore Oncorhynchus gorbuscha Omnivore Salmo trutta Omnivore Oncorhynchus nerka Planktivore Salvelinus fontinalis Omnivore Salmo trutta Omnivore Salvelinus namaycush Omnivore Continent North America con’t Location California Drainage Sacramento San Joaquin Salvelinus namaycush Omnivore Lucania parva Omnivore Salvelinus fontinalis Omnivore Salvelinus confluentus Omnivore Lucania parva Omnivore Menidia beryllina Planktivore Gambusia affinis Omnivore Gasterosteus aculeatus Omnivore

Menidia beryllina Planktivore Morone saxatilis Omnivore Gasterosteus aculeatus Omnivore Morone chrysops Piscivore Morone saxatilis Omnivore Archoplites interruptus Omnivore Morone chrysops Piscivore Pomoxis nigromaculatus Omnivore Archoplites interruptus Omnivore Pomoxis annularis Piscivore Pomoxis nigromaculatus Omnivore Lepomis gulosus Omnivore Pomoxis annularis Piscivore Lepomis cyanellus Omnivore Lepomis gulosus Omnivore Lepomis macrochirus Omnivore Lepomis cyanellus Omnivore Lepomis gibbosus Omnivore Lepomis macrochirus Omnivore Lepomis microlophus Omnivore Lepomis gibbosus Omnivore Micropterus salmoides Omnivore Lepomis microlophus Omnivore Micropterus punctulatus Omnivore Micropterus salmoides Omnivore Micropterus dolomieui Omnivore Micropterus punctulatus Omnivore Micropterus coosae Omnivore Micropterus dolomieui Omnivore Perca flavescens Omnivore Micropterus coosae Omnivore Percina macrolepida Omnivore Perca flavescens Omnivore Hysterocarpus traski Omnivore Percina macrolepida Omnivore Eucyclogobius newberryi Omnivore Hysterocarpus traski Omnivore Acanthogobius flavimanus Omnivore Eucyclogobius newberryi Omnivore Tridentiger bifasciatus Omnivore Acanthogobius flavimanus Omnivore Leptocottus armatus Omnivore Tridentiger bifasciatus Omnivore Cottus asperrimus Omnivore Leptocottus armatus Omnivore Cottus gulosus Omnivore Cottus asperrimus Omnivore Planktivoretichthys stellatus Omnivore Cottus gulosus Omnivore Mugil cephalus Omnivore Planktivoretichthys stellatus Omnivore Mugil cephalus Omnivore

Continent South America Location Central Chile Central Chile Drainage Biobio Itata Species Trophic level Species Trophic level Ameiurus melas Omnivore Ameiurus melas Omnivore Ameiurus nebulosus Omnivore Ameiurus nebulosus Omnivore Ancistrus erinaceus Herbivore Ancistrus erinaceus Herbivore Australoheros facetus Omnivore AustraloHerbivoreos facetus Omnivore Basilichthys australis Omnivore Basilichthys australis Omnivore

Basilichthys microlepidotus Omnivore Basilichthys microlepidotus Omnivore Brachygalaxias bullocki Omnivore Brachygalaxias bullocki Omnivore Brachygalaxias gothei Omnivore Brachygalaxias gothei Omnivore Bullockia maldonadoi Omnivore Bullockia maldonadoi Omnivore Carassius auratus auratus Omnivore Carassius auratus auratus Omnivore Carassius carassius Omnivore Carassius carassius Omnivore Cheirodon australe Herbivore Cheirodon australe Herbivore Cheirodon galusdai Herbivore Cheirodon galusdai Herbivore Cheirodon interruptus Planktivore Cheirodon interruptus Planktivore Cheirodon kiliani Omnivore Cheirodon kiliani Omnivore Cheirodon Piscivoreiculus Herbivore Cheirodon iculus Herbivore Cnesterodon decemmaculatus Omnivore Cnesterodn decemmaculatus Omnivore Cyprinus carpio carpio Omnivore Cyprinus carpio carpio Omnivore Diplomystes camposensis Omnivore Diplomystes camposensis Omnivore Diplomystes chilensis Omnivore Diplomystes chilensis Omnivore Diplomystes nahuelbutaensis Herbivore Diplomystes nahuelbutaensis Herbivore Galaxias globiceps Omnivore Galaxias globiceps Omnivore Gambusia affinis Omnivore Gambusia affinis Omnivore Lepomis gibbosus Omnivore Lepomis gibbosus Omnivore Nematogenys inermis Omnivore Nematogenys inermis Omnivore Odontesthes brevianalis Omnivore Odontesthes brevianalis Omnivore Odontesthes gracilis Omnivore Odontesthes gracilis Omnivore Odontesthes hatcHerbivorei Omnivore Odontesthes hatcHerbivorei Omnivore Odontesthes mauleanum Omnivore Odontesthes mauleanum Omnivore Odontesthes wiebrichi Omnivore Odontesthes wiebrichi Omnivore Orestias agassizii Herbivore Orestias agassizii Herbivore Orestias ascotanensis Omnivore Orestias ascotanensis Omnivore Orestias chungarensis Omnivore Orestias chungarensis Omnivore Orestias laucaensis Omnivore Orestias laucaensis Omnivore Orestias parinacotensis Omnivore Orestias parinacotensis Omnivore Orestias piacotensis Planktivore Orestias piacotensis Planktivore

Continent Africa Location South Africa South Africa Drainage Orange Berg Species Trophic level Species Trophic level Austroglanis sclateri Omnivore Pseudobarbus phlegethon Insectivore Barbus aeneus Omnivore Oncorhynchus mykiss Omnivore Barbus anoplus Omnivore Pseudobarbus burgi Omnivore Barbus hospes Omnivore Sandelia capensis Omnivore Barbus kimberleyensis Piscivore Calaxias zebratus Planktivore Barbus pallidus Omnivore Micropterus dolomieu Omnivore Barbus trimaculatus Omnivore Lepomis macrochirus Omnivore Clarias gariepinus Omnivore Labeo umbratus Herbivore Labeo capensis Herbivore Liza richardsonii Planktivore Labeo umbratus Herbivore Mugil cephalus Omnivore Liza richardsonii Planktivore Mesobola brevianalis Planktivore Mugil cephalus Omnivore Pseudobarbus quathlambae Insectivore Tilapia rendalli Herbivore Tilapia sparrmanii Herbivore Cyprinus carpio Omnivore Oreochromis mossambicus Herbivore Pseudobarbus quathlambae Insectivore

Continent Australia Location Southern Australia South Western Australia

Drainage Darling-Murray Swan-Avon Species Trophic level Species Trophic level Retropinna semoni Omnivore Lepidogalaxias salamandroides Omnivore Mugil cephalus Omnivore Galaxias occidentalis Omnivore Percichthys chilensis Omnivore Percichthys chilensis Omnivore Percichthys melanops Omnivore Percichthys melanops Omnivore Galaxias fuscus Insectivore Galaxiella munda Insectivore Nematalosa erebi Omnivore Galaxiella nigrostriata Insectivore Hypseleotris spp Omnivore Tandanus bostocki Omnivore Galaxias brevipinnis Omnivore Bostockia porosa Omnivore Galaxias maculatus Insectivore Nannatherina balstoni Omnivore Pseudaphritis urvillii Omnivore Nannatherina vittata Omnivore Craterocephalus amniculus Omnivore Mugil cephalus Omnivore Melanotaenia splendida tatei Omnivore Pseudogobius olorum Omnivore Philypnodon macrostomus Insectivore Macquaria colonorum Omnivore Galaxias rostratus Insectivore Philypnodon grandiceps Omnivore Tandanus tandanus Omnivore Macquaria ambigua ambigua Piscivore Neosilurus hyrtlii Omnivore Tasmanogobius lasti Omnivore Anguilla reinhardtii Omnivore Macquaria australasica Omnivore Galaxias olidus Omnivore Maccullochella peelii peelii Omnivore Melanotaenia fluviatilis Insectivore Craterocephalus fluviatilis Omnivore Gadopsis marmoratus Omnivore Anguilla australis Insectivore Afurcagobius tamarensis Omnivore Mordacia mordax Piscivore Bidyanus bidyanus Omnivore Herbivoreinosoma microstoma Omnivore Mogurnda adspersa Piscivore Nannoperca australis Omnivore Leiopotherapon unicolor Omnivore

Continent Australia con’t Location Southern Australia Drainage Darling-Murray Species Trophic level

Cyprinus carpio Omnivore Salvelinus confluentus Omnivore Carassius auratus Omnivore Misgurnus anguillicaudatus Omnivore Oncorhynchus mykiss Omnivore Perca fluviatilis Omnivore Rutilis rutilis Omnivore Tinca tinca Omnivore

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