Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

The Theory of Island Biogeography

The influence of diet on the distribution of nitrogen isotopes in animals was investigated by analyzing animals grown in the laboratory on diets of constant nitrogen isotopic composition. 
The isotopic composition of the nitrogen in an animal reflects the nitrogen isotopic composition of its diet. The δ^(15)N values of the whole bodies of animals are usually more positive than those of their diets. Different individuals of a species raised on the same diet can have significantly different δ^(15)N values. The variability of the relationship between the δ^(15)N values of animals and their diets is greater for different species raised on the same diet than for the same species raised on different diets. Different tissues of mice are also enriched in ^(15)N relative to the diet, with the difference between the δ^(15)N values of a tissue and the diet depending on both the kind of tissue and the diet involved. The δ^(15)N values of collagen and chitin, biochemical components that are often preserved in fossil animal remains, are also related to the δ^(15)N value of the diet. 
The dependence of the δ^(15)N values of whole animals and their tissues and biochemical components on the δ^(15)N value of diet indicates that the isotopic composition of animal nitrogen can be used to obtain information about an animal's diet if its potential food sources had different δ^(15)N values. The nitrogen isotopic method of dietary analysis probably can be used to estimate the relative use of legumes vs non-legumes or of aquatic vs terrestrial organisms as food sources for extant and fossil animals. However, the method probably will not be applicable in those modern ecosystems in which the use of chemical fertilizers has influenced the distribution of nitrogen isotopes in food sources. 
The isotopic method of dietary analysis was used to reconstruct changes in the diet of the human population that occupied the Tehuacan Valley of Mexico over a 7000 yr span. Variations in the δ^(15)C and δ^(15)N values of bone collagen suggest that C_4 and/or CAM plants (presumably mostly corn) and legumes (presumably mostly beans) were introduced into the diet much earlier than suggested by conventional archaeological analysis.

Influence of Diet On the Distribtion of Nitrogen Isotopes in Animals

Dispersal costs can be classified into energetic, time, risk and opportunity costs and may be levied directly or deferred during departure, transfer and settlement. They may equally be incurred during life stages before the actual dispersal event through investments in special morphologies. Because costs will eventually determine the performance of dispersing individuals and the evolution of dispersal, we here provide an extensive review on the different cost types that occur during dispersal in a wide array of organisms, ranging from micro-organisms to plants, invertebrates and vertebrates. In general, costs of transfer have been more widely documented in actively dispersing organisms, in contrast to a greater focus on costs during departure and settlement in plants and animals with a passive transfer phase. Costs related to the development of specific dispersal attributes appear to be much more prominent than previously accepted. Because costs induce trade-offs, they give rise to covariation between dispersal and other life-history traits at different scales of organismal organisation. The consequences of (i) the presence and magnitude of different costs during different phases of the dispersal process, and (ii) their internal organisation through covariation with other life-history traits, are synthesised with respect to potential consequences for species conservation and the need for development of a new generation of spatial simulation models.

Costs of dispersal

There is growing recognition of the important roles played by predators in regulating ecosystems and sustaining biodiversity. Much attention has focused on the consequences of predator-regulation of herbivore populations, and associated trophic cascades. However apex predators may also control smaller 'mesopredators' through intraguild interactions. Removal of apex predators can result in changes to intraguild interactions and outbreaks of mesopredators ('mesopredator release'), leading in turn to increased predation on smaller prey. Here we provide a review and synthesis of studies of predator interactions, mesopredator release and their impacts on biodiversity. Mesopredator suppression by apex predators is widespread geographically and taxonomically. Apex predators suppress mesopredators both by killing them, or instilling fear, which motivates changes in behaviour and habitat use that limit mesopredator distribution and abundance. Changes in the abundance of apex predators may have disproportionate (up to fourfold) effects on mesopredator abundance. Outcomes of interactions between predators may however vary with resource availability, habitat complexity and the complexity of predator communities. There is potential for the restoration of apex predators to have benefits for biodiversity conservation through moderation of the impacts of mesopredators on their prey, but this requires a whole-ecosystem view to avoid unforeseen negative effects. 'Nothing has changed since I began. My eye has permitted no change. I am going to keep things like this.' From 'Hawk Roosting', by Ted Hughes.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1461-0248.2009.01347.x

Predator interactions, mesopredator release and biodiversity conservation

Interspecific killing among mammalian carnivores is common in nature and accounts for up to 68% of known mortalities in some species. Interactions may be symmetrical (both species kill each other) or asymmetrical (one species kills the other), and in some interactions adults of one species kill young but not adults of the other. There is a positive significant relationship between the body masses of solitary killer species and body masses of their victim species, and grouping species kill larger victims than solitary species. Interactions and consumption of the victim appear more common when food is scarce or disputed. In response to killers, victim species may alter their use of space, activity patterns, and form groups. Consequences of interspecific killing include population reduction or even extinction, and reduction and enhancement of prey populations, and may therefore have important implications for conservation and management of carnivores and their prey.

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Interspecific Killing among Mammalian Carnivores

We examined the relative roles of dominance in agonistic interactions and energetic constraints related to body size in determining local abundances of coyotes (Canis latrans, 8–20 kg), gray foxes (Urocyon cinereoargenteus, 3–5 kg) and bobcats (Felis rufus, 5–15 kg) at three study sites (hereafter referred to as NP, CP, and SP) in the Santa Monica Mountains of California. We hypothesized that the largest and behaviorally dominant species, the coyote, would exploit a wider range of resources (i.e., a higher number of habitat and/or food types) and, consequently, would occur in higher density than the other two carnivores. We evaluated our hypotheses by quantifying their diets, food overlap, habitat-specific abundances, as well as their overall relative abundance at the three study sites. We identified behavioral dominance of coyotes over foxes and bobcats in Santa Monica because 7 of 12 recorded gray fox deaths and 2 of 5 recorded bobcat deaths were due to coyote predation, and no coyotes died as a result of their interactions with bobcats or foxes. Coyotes and bobcats were present in a variety of habitats types (8 out of 9), including both open and brushy habitats, whereas gray foxes were chiefly restricted to brushy habitats. There was a negative relationship between the abundances of coyotes and gray foxes (P=0.020) across habitats, suggesting that foxes avoided habitats of high coyote predation risk. Coyote abundance was low in NP, high in CP, and intermediate in SP. Bobcat abundance changed little across study sites, and gray foxes were very abundant in NP, absent in CP, and scarce in SP; this suggests a negative relationship between coyote and fox abundances across study sites, as well. Bobcats were solely carnivorous, relying on small mammals (lagomorphs and rodents) throughout the year and at all three sites. Coyotes and gray foxes also relied on small mammals year-round at all sites, though they also ate significant amounts of fruit. Though there were strong overall interspecific differences in food habits of carnivores (P<0.0001), average seasonal food overlaps were high due to the importance of small mammals in all carnivore diets [bobcat-gray fox: 0.79±0.09 (SD), n=4; bobcat-coyote: 0.69±0.16, n=6; coyote-gray fox: 0.52±0.05, n=4]. As hypothesized, coyotes used more food types and more habitat types than did bobcats and gray foxes and, overall, coyotes were the most abundant of the three species and ranged more widely than did gray foxes. We propose that coyotes limit the number and distribution of gray foxes in Santa Monica Mountains, and that those two carnivores exemplified a case in which the relationship between their body size and local abundance is governed by competitive dominance of the largest species rather than by energetic equivalences. However, in the case of the intermediate-sized bobcat no such a pattern emerged, likely due to rarity or inconsistency of agonistic interactions and/or behavioral avoidance of encounters by subordinate species.

Competition and intraguild predation among three sympatric carnivores

To evaluate whether the abundance of coyotes Canis latrans was influenced by the availability of anthropogenic foods in a humanized landscape, we compared three neighboring areas (hereafter referred to as NA, CA, and SA) under contrasting human pressures within the Santa Monica Mountains of California, USA. We quantified the use of anthropogenic foods by coyotes and assessed local densities within these three regions. Overall, 761 coyote feces were analyzed; identified food items were categorized into 11 food types (7 native and 4 anthropogenic). Though small mammals (lagomorphs and rodents) were the main prey of coyotes in all areas and seasons, log-linear modeling of multiway contingency tables indicates that consumption of anthropogenic foods by coyotes varied significantly throughout study areas. Thus, in the most humanized area (CA; 24% of this region is residential habitat), anthropogenic foods (trash, livestock, domestic fruit) comprised seasonally between 14 and 25% of total items in coyote diets, whereas in the least humanized area (NA; 2% residential) anthropogenic foods only comprised seasonally between 0 and 3% of items. Coyote density, estimated by foot-hold trapping surveys and by genotyping feces, was also highly variable between areas. The heavily human-impacted CA area had the highest coyote density (2.4–3.0 ind. km−2), whereas coyote density was significantly lower (0.3–0.4 ind. km−2) in the least humanized area (NA). In the third region (SA; 10% residential), with an intermediate level of human pressure, both importance of anthropogenic foods in coyote diet (4–6%) and coyote density (1.6–2.0 ind. km−2) were intermediate compared to the other regions. Our data suggest that subsidization by anthropogenic foods augments coyote densities and alters their diets in the Santa Monica Mountains, California. We include data from literature to show that anthropogenic foods are used by omnivorous mammals throughout the world. Surprisingly, however, the potential effects of allochthonous inputs on such species are not well-understood. Thus, further research on this phenomenon in humanized landscapes is needed.

Does availability of anthropogenic food enhance densities of omnivorous mammals? An example with coyotes in southern California

Previous studies carried out in the Donana National Park reported that red foxes (Vulpes vulpes) were killed by Iberian lynxes (Lynx pardinus), whereas similar-sized Eurasian badgers (Meles meles) were not. Therefore, we predicted that fox would avoid lynx predation risk by niche segregation whereas we did not expect such a segregation between badger and lynx. As an approach for evaluating our predictions, we compared their diet, activity patterns, and habitat use in an area of Donana where the three carnivores are sympatric. Lynxes preyed almost uniquely on European rabbits (Oryctolagus cuniculus), and though badgers and foxes were omnivorous, rabbits also were a major prey, resulting in high overlaps throughout the year. However, badgers preyed largely on small rabbits, whereas lynxes and foxes preyed mainly on medium-sized rabbits. There were also interspecific differences in activity patterns. Maximum levels of activity among lynxes were during sunrise and dusk (49–67%). Foxes were most active during dusk and night (34–67%), and badgers were mainly nocturnal (53–87%). Though there were seasonal differences in the amount of activity of each species, specific activity patterns changed little throughout the year. There was a strong difference in annual habitat use by the three species (P < 0.0001). Lynxes used mainly the Mediterranean scrubland during both the active (PMAX) and the resting (PMIN) periods. During PMIN, foxes used the Mediterranean scrubland intensively (40% of locations on average), but during PMAX, they used the pastureland much more intensively despite this habitat being poorer in their main prey (rabbits). As a consequence, foxes and lynxes exhibited segregation in their habitat use during the active period. Badgers also used the Mediterranean scrubland intensively, especially during PMIN. There were no seasonal differences in habitat use for lynx and fox, but there was for badgers (P < 0.015). Within the study area, the three species selected habitat suggesting they were sensitive to factors such as vegetation and prey abundance. However, in general, carnivore habitat use did not correlate with rabbit abundance. We propose that foxes avoided lynxes by using, during activity, habitats not frequented by lynxes, and that a low predation risk associated with the distinctive foraging mode of badgers may facilitate its coexistence with other carnivores.

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Niche relations among three sympatric Mediterranean carnivores

Spatial ecology and diet of Iberian lynx (Lynx pardinus) and the abundance of its main prey, the European rabbit (Oryctolagus cuniculus), were studied in southwestern Spain from December 1992 to December 1996 when a decline in rabbit populations occurred. Our objectives were to relate spatial ecology of lynx to rabbit abundance, water availability, and protection from human disturbance. Rabbits were almost the sole prey of lynx; rabbit remains were present in 99.2% (n = 1,171) of feces analyzed. Rabbit abundance and density in 6 different habitats were estimated by line transect sampling. Rabbits were more abundant in Mediterranean scrubland, closely followed by ash stands. Pastureland and lentiscus in plantations had 4.5 times fewer rabbits, and pine plantations 15-20 times fewer rabbits, than the Mediterranean scrubland. Abundance of rabbits in the Mediterranean scrubland was not spatially uniform, as density for 1994 and 1995 varied from 42-55/ha in the area close to the edge of the marsh (locally called the Vera) to 2-7/ha far from the Vera. Rabbit density was 3.5 times higher during spring than during autumn. A decline in rabbit density occurred in 1996 when numbers were 72-91 % lower than the previous years. We mapped warren density in Mediterranean scrubland and pastureland to determine intra-habitat differences in spatial distribution of rabbits. Warren density, entrance density, and mean number of entrances per warren declined significantly with distance from the Vera in the Mediterranean scrubland, following a negative exponential function (adj. r 2 ranging between 83 and 97%). However, none of these variables showed any trend in relation to the Vera in the pastureland. The lynx population contained three stable pairs of adults plus young raised each year, some of which remained on the study area as subadults (older than one year). The seasonal number of different lynx in the study area ranged between 7 and 17. Average adult and young/subadult seasonal density was 0.77 (range = 0.72-0.88) and 0.46 individuals/km 2 (range = 0.07-1.12), respectively. We estimated home range and daily movements of lynx to determine changes that might be due to sex, season, or changing prey density. On average, total lynx home range size was 7.3 km 2 for young, 9.5 km 2 for adult females, and 18.2 km 2 for adult males. Mean core areas (60% isopleth using the kernel approximation) were on average 15%, 10%, and 34% of total home ranges of young, adult females, and adult males, respectively. Significant differences were found for home range and core area sizes among sex-age classes, but neither season nor year affected home range size or core area size. Daily movements averaged 8.0 km. Daily distance traveled was not affected by sex-age class or season, but was different among years, with lynx traveling shorter distances in 1993 and 1996. Daily home range size averaged 1.46 km 2 , and again only varied by year. Lynx daily movements were associated with permanent, artificial water sites. Habitat use by lynx was remarkably constant, with no differences detected among sex-age classes, active or inactive locations, seasons, or years. The habitat most frequently used was Mediterranean scrubland (53% of locations), and both it and ash stands were the only habitats preferred by lynx; pine and eucalyptus plantations were avoided, and marsh, pastureland and lentiscus in plantations were neither preferred or avoided.

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Spatial ecology of Iberian lynx and abundance of European rabbits in southwestern Spain

1. Spatial relationships between Iberian lynx and other carnivores were studied by radio-tracking and/or track censusing in two adjacent areas of Donana (south-western Spain). 2. Both radio-tracking and track censusing showed that lynx were restricted to an undisturbed area of Pistacia lentiscus shrubs called Matasgordas. Minimum and maximum lynx density in Matasgordas were estimated as 0.55 and 0.75 ind. km -2 . 3. Egyptian mongoose tracks were mainly detected outside Matasgordas (83% of tracks), European badger tracks were detected most often inside Matasgordas (76% of tracks), and red fox tracks were frequently detected both outside (54%) and inside (46%) Matasgordas. Surveys of tracks and faeces undertaken in other 14 areas where P. lentiscus shrubs also dominated corroborated the census data obtained inside and outside Matasgordas. 4. Trapping and radio-tracking of mongooses and common genets indicated that both species avoided use of Matasgordas. They were almost exclusively trapped (24 out of 25 mongooses and all of 11 genets) and mainly radio-located (94.5% and 95.4% of times, for mongooses and genets, respectively) in the areas of P. lentiscus shrubs situated outside Matasgordas. Their densities were estimated as 0.2 and 0.03 ind. km -2 inside, and as 2.0 and 0.7 ind. km -2 outside Matasgordas for mongooses and genets, respectively. 5. Lynx may kill mongooses, genets, and foxes ; thus, the avoidance of Matasgordas by smaller carnivores (mongooses and genets) could be related to the risk of lynx predation. It is suggested that the decline of the lynx in the Donana area may have caused the increase in the population size of smaller, previously rarer carnivores. 6. The true relationship between lynx and foxes remains unclear, and badgers were apparently indifferent to lynx presence or absence.

José M. Fedriani

Papers

Competition and intraguild predation among three sympatric carnivores

Does availability of anthropogenic food enhance densities of omnivorous mammals? An example with coyotes in southern California

Niche relations among three sympatric Mediterranean carnivores

Spatial ecology of Iberian lynx and abundance of European rabbits in southwestern Spain

Spatial Relationships Between Iberian Lynx and Other Carnivores in an Area of South-Western Spain