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

■ Abstract Contributions from the field of population biology hold promise for understanding and managing invasiveness; invasive species also offer excellent opportunities to study basic processes in population biology. Life history studies and demographic models may be valuable for examining the introduction of invasive species and identifying life history stages where management will be most effective. Evolutionary processes may be key features in determining whether invasive species establish and spread. Studies of genetic diversity and evolutionary changes should be useful for

/pdf/the-population-biology-of-invasive-species-bdndjv53b3.pdf

The Population Biology of Invasive Species

To curb the future economic and environmental impacts of invasive exotic species, we need to understand the mechanisms behind exotic invasions. One commonly accepted mechanism for exotic plant invasions is the enemy release hypothesis (ERH), which states that plant species, on introduction to an exotic region, experience a decrease in regulation by herbivores and other natural enemies, resulting in a rapid increase in distribution and abundance. The success of classical biological control has been used as support for ERH, but this observational evidence does not directly test ERH, and the more experimental evidence is equivocal. Competitive release through greater generalist enemy impact on natives seems to be an important but understudied mechanism of enemy release, but there is a serious need for experiments involving exclusion of natural enemies in invaded plant communities. With a clearer understanding of the role of enemy release in exotic plant invasions, we can begin to build a comprehensive predictive model of exotic plant invasions.

https://www.cell.com/trends/ecology-evolution/pdf/S0169-5347(02)02499-0.pdf

Exotic plant invasions and the enemy release hypothesis

Community ecology theory can be used to understand biological invasions by applying recent niche concepts to alien species and the communities that they invade. These ideas lead to the concept of ‘niche opportunity', which defines conditions that promote invasions in terms of resources, natural enemies, the physical environment, interactions between these factors, and the manner in which they vary in time and space. Niche opportunities vary naturally between communities but might be greatly increased by disruption of communities, especially if the original community members are less well adapted to the new conditions. Recent niche theory clarifies the prediction that low niche opportunities (invasion resistance) result from high species diversity. Conflicting empirical patterns of invasion resistance are potentially explained by covarying external factors. These various ideas derived from community ecology provide a predictive framework for invasion ecology.

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Community ecology theory as a framework for biological invasions

A behavioral syndrome is a suite of correlated behaviors expressed either within a given behavioral context (e.g., correlations between foraging behaviors in different habitats) or across different contexts (e.g., correlations among feeding, antipredator, mating, aggressive, and dispersal behaviors). For example, some individuals (and genotypes) might be generally more aggressive, more active or bold, while others are generally less aggressive, active or bold. This phenomenon has been studied in detail in humans, some primates, laboratory rodents, and some domesticated animals, but has rarely been studied in other organisms, and rarely examined from an evolutionary or ecological perspective. Here, we present an integrative overview on the potential importance of behavioral syndromes in evolution and ecology. A central idea is that behavioral correlations generate tradeoffs; for example, an aggressive genotype might do well in situations where high aggression is favored, but might be inappropriate...

https://www.jstor.org/stable/10.1086/422893

Behavioral syndromes: An integrative overview

Biotic invaders are species that establish a new range in which they proliferate, spread, and persist to the detriment of the environment. They are the most important ecological outcomes from the unprecedented alterations in the distribution of the earth's biota brought about largely through human transport and commerce. In a world without borders, few if any areas remain sheltered from these im- migrations. The fate of immigrants is decidedly mixed. Few survive the hazards of chronic and stochastic forces, and only a small fraction become naturalized. In turn, some naturalized species do become invasive. There are several potential reasons why some immigrant species prosper: some escape from the constraints of their native predators or parasites; others are aided by human-caused disturbance that disrupts native communities. Ironically, many biotic invasions are apparently facilitated by cultivation and husbandry, unintentional actions that foster immigrant populations until they are self-perpetuating and uncontrollable. Whatever the cause, biotic invaders can in many cases inflict enormous environmental damage: (1) Animal invaders can cause extinctions of vulnerable native species through predation, grazing, competition, and habitat alteration. (2) Plant invaders can completely alter the fire regime, nutrient cycling, hydrology, and energy budgets in a native ecosystem and can greatly diminish the abundance or survival of native species. (3) In agriculture, the principal pests of temperate crops are nonindigenous, and the combined expenses of pest control and crop losses constitute an onerous "tax" on food, fiber, and forage production. (4) The global cost of virulent plant and animal diseases caused by parasites transported to new ranges and presented with susceptible new hosts is currently incalculable. Identifying future invaders and taking effective steps to prevent their dispersal and establishment con- stitutes an enormous challenge to both conservation and international commerce. Detection and management when exclusion fails have proved daunting for varied reasons: (1) Efforts to identify general attributes of future invaders have often been inconclusive. (2) Predicting susceptible locales for future invasions seems even more problematic, given the enormous differences in the rates of arrival among potential invaders. (3) Eradication of an established invader is rare, and control efforts vary enormously in their efficacy. Successful control, however, depends more on commitment and continuing diligence than on the efficacy of specific tools themselves. (4) Control of biotic invasions is most effective when it employs a long-term, ecosystem- wide strategy rather than a tactical approach focused on battling individual invaders. (5) Prevention of invasions is much less costly than post-entry control. Revamping national and international quarantine laws by adopting a "guilty until proven innocent" approach would be a productive first step. Failure to address the issue of biotic invasions could effectively result in severe global consequences, including wholesale loss of agricultural, forestry, and fishery resources in some regions, disruption of the ecological processes that supply natural services on which human enterprise depends, and the creation of homogeneous, impoverished ecosystems composed of cosmopolitan species. Given their current scale, biotic invasions have taken their place alongside human-driven atmospheric and oceanic alterations as major agents of global change. Left unchecked, they will influence these other forces in profound but still unpredictable ways.

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Biotic invasions: causes, epidemiology, global consequences, and control

Data on eradication operations against alien mammals on New Zealand islands show that there was a substantial increase in the number of successful eradications in the 1980s and 1990s. The most significant change has been in the ability to eradicate rodents from increasingly large islands (to over 11,000ha), using aerial poisoning techniques. Based on the New Zealand experience, there are good prospects for further eradications of alien mammals from islands around the world, facilitating ecological restoration and the recovery of threatened species. However, instances of reinvasion of rats (Rattus spp.) and stoats (Mustela erminea) onto previously cleared islands illustrate the importance of prevention, effective monitoring and a fuller understanding of invasion risks.

/pdf/the-eradication-of-mammals-from-new-zealand-islands-2yogcrpg54.pdf

The eradication of mammals from New Zealand islands

Aim To investigate and establish the significance of various island biogeographic relationships (geographical, ecological and anthropological) with the species richness of introduced mammals on offshore islands.



Location  The 297 offshore islands of the New Zealand archipelago (latitude: 34–47°S; longitude: 166–179°E).



Methods  Data on New Zealand offshore islands and the introduced mammals on them were collated from published surveys and maps. The species richness of small and large introduced mammals were calculated for islands with complete censuses and regressed on island characteristics using a Poisson distributed error generalized linear model. To estimate the ‘z-value’ for introduced mammals on New Zealand islands, least-squares regression was used [log10 S vs. log10 A].



Results  High collinearity was found between the area, habitat diversity and elevation of islands. The island characteristics related to the species richness of introduced mammals differed predictably between large and small mammals. The species richness of introduced large mammals was mostly related to human activities on islands, whereas species richness of introduced small mammals was mostly related to island biogeographical parameters. The ‘z-value’ for total species richness is found to be expectedly low for introduced mammals.



Main conclusions  Distance appears to have become ecologically trivial as a filter for introduced mammal presence on New Zealand offshore islands. There is strong evidence of a ‘small island’ effect on New Zealand offshore islands. The species richness of both small and large introduced mammals on these islands appears to be most predominantly related to human use, although there is some evidence of natural dispersal for smaller species. The ecological complexity of some islands appears to make them less invasible to introduced mammals. Some human activities have an interactive effect on species richness. A small number of islands have outlying species richness values above what the models predict, suggesting that the presence of some species may be related to events not accounted for in the models.

/pdf/island-biogeography-and-the-species-richness-of-introduced-365wwsyn06.pdf

Island biogeography and the species richness of introduced mammals on New Zealand offshore islands

Determining the origin of individuals caught during a control/eradication programmeenables conservation managers to assess the reinvasion rates of their target species andevaluate the level of success of their control methods. We examine how genetic tech-niques can focus management by distinguishing between hypotheses of ‘reinvasion’and ‘survivor’, and deﬁning kin groups for invasive stoats (Mustela erminea) on Secre-tary Island, New Zealand. 205 stoats caught on the island were genotyped at 16 micro-satellite loci, along with 40 stoats from the opposing mainland coast, and the age andsex were determined for each individual. Using these data, we compare and combine avariety of genetic techniques including genetic clustering, population assignment andkinship-based techniques to assess the origin of each stoat. The population historyand individual movement could be described in ﬁne detail, with results indicating thatboth in-situ survival and breeding, and reinvasion are occurring. Immigration to theisland was found to be generally low, apart from in 1 year where around 8 stoats emi-grated from the mainland. This increased immigration was probably linked to a stoatpopulation spike on the mainland in that year, caused by a masting event of southernbeech forest (Nothofagus sp.) and the subsequent rodent irruption. Our study providesan example of some of the ways genetic analyses can feed directly into informing man-agement practices for invasive species.Keywords: assignment, connectivity, immigration, invasion, microsatellite, Mustela ermineaReceived 26 October 2012; revision received 8 July 2013; accepted 9 July 2013

Using genetic techniques to quantify reinvasion, survival and in situ breeding rates during control operations

Many studies in molecular ecology have focused on the use of repeat DNA markers to determine the nature of mating systems in a wide variety of animal species. Whilst these studies typically have focused on important issues such as the evolutionary consequences of fitness variation among males, genetic studies of mating systems are potentially also important because they can generate information of significance to wider issues in wildlife management. For example, genetically modified, sexually transmitted viral diseases have been suggested as potential agents for the control of vertebrate pest species. An understanding of the epidemiology of such agents requires an intimate knowledge of the sexual contact rates between individuals of the target species. Here, we report the use of minisatellite DNA profiling to reveal the mating system in two New Zealand populations of the introduced Australian brushtail possum. The brushtail possum is New Zealand’s most important mammalian pest and a species for which control by a sexually transmitted immunocontraceptive has been proposed. Encouragingly, we report considerable variation in the reproductive success of males at both study sites, with one male siring offspring from four females in one year (mean no. of offspring/reproductively successful male/ year at the two sites is 1.95‐2.15), while many sired none. This bias in the pattern of reproductive success among males will probably facilitate the spread of an immunocontraceptive agent and thereby increase the power of this approach to biological control.

M. N. Clout

Papers

Biotic invasions: causes, epidemiology, global consequences, and control

The eradication of mammals from New Zealand islands

Island biogeography and the species richness of introduced mammals on New Zealand offshore islands

Using genetic techniques to quantify reinvasion, survival and in situ breeding rates during control operations

Molecular ecology and biological control: the mating system of a marsupial pest.