The past quarter century has seen an unprecedented increase in the number of new and emerging infectious diseases throughout the world, with serious implications for human and wildlife populations. We examined host persistence in the face of introduced vector-borne diseases in Hawaii, where introduced avian malaria and introduced vectors have had a negative impact on most populations of Hawaiian forest birds for nearly a century. We studied birds, parasites, and vectors in nine study areas from 0 to 1,800 m on Mauna Loa Volcano, Hawaii from January to October, 2002. Contrary to predictions of prior work, we found that Hawaii amakihi (Hemignathus virens), a native species susceptible to malaria, comprised from 24.5% to 51.9% of the avian community at three low-elevation forests (55-270 m). Amakihi were more abundant at low elevations than at disease-free high elevations, and were resident and breeding there. Infection rates were 24 -40% by microscopy and 55-83% by serology, with most infected individuals experiencing low-intensity, chronic infections. Mosquito trapping and diagnostics provided strong evidence for yearround local transmission. Moreover, we present evidence that Hawaii amakihi have increased in low elevation habitats on southeastern Hawaii Island over the past decade. The recent emergent phenomenon of recovering amakihi populations at low elevations, despite extremely high prevalence of avian malaria, suggests that ecological or evolutionary processes acting on hosts or parasites have allowed this species to recolonize low-elevation habitats. A better understanding of the mechanisms allowing coexistence of hosts and parasites may ultimately lead to tools for mitigating disease impacts on wildlife and human populations.Hemignathus virens ͉ host-parasite coevolution ͉ Plasmodium relictum ͉ Culex quinquefasciatus T he past quarter century has seen an unprecedented increase in the number of new and emerging infectious diseases throughout the world, with serious implications for human and wildlife populations (1). This rise in the emergence of new infectious diseases is attributed to many factors, among them human alteration of habitats, transportation of vectors and pathogens, and climate and weather patterns, including anthropogenic climate change (2, 3). Vector-borne diseases in particular may undergo geographic range shifts and large changes in abundance with climate change because rising temperatures will affect vector distribution, parasite development, and transmission rates (4).Identifying the factors that allow for coexistence of hosts and parasites has been a topic of intensive study in the ecological literature for decades (5, 6). Modeling and empirical studies have identified host and vector abundance, vector competence and behavior, host community, spatial and metapopulation dynamics, host demography, seasonality, parasite virulence, and host resistance, among others, as being of importance (7,8). A better understanding of the mechanisms of host-parasite coexistence may ultimately lead to t...

Stable isotope analysis has become an increasingly valuable tool in investigating animal ecology. Here we document the turnover rates for carbon in the liver, muscle, and whole blood tissue, as well as the tissue-diet discrimination values for carbon and nitrogen isotopes in the liver, whole blood, muscle, and hair, of the white-footed mouse (Peromyscus leucopus (Rafinesque, 1818)). A 168-day diet-switching experiment was conducted with a laboratory population of whitefooted mice. The d 13 C values for all tissues deviated less than 1% from those of the diet except for whole blood, which had a slightly higher tissue-diet discrimination factor of 1.8%. All tissues were enriched in 15 N by approximately 3% relative to the diet except for liver tissue, which was 4.5% higher than the dietary d 15 N value. Turnover rates for tissues of white-footed mice were ranked liver > whole blood > muscle. The half-lives calculated for liver tissue differed significantly between the two diet switches performed in this experiment. We demonstrate that there is potential for variation in tissue-diet discrimination values and tissue turnover rates between even closely related species. These findings highlight the importance of determining species-specific estimates of these parameters prior to the use of stable isotope analysis in field investigations of animal ecology.Résumé : L'analyse des isotopes stables devient un outil de plus en plus précieux dans l'étude écologique des animaux. Nous déterminons ici les taux de remplacement du carbone dans les tissus du foie, du muscle et du sang entier, ainsi que les valeurs de discrimination tissu-régime des isotopes de carbone et d'azote dans le foie, le sang entier, le muscle et le poil chez la souris à pieds blancs (Peromyscus leucopus (Rafinesque, 1818)). Nous avons mené une expérience de changement de régime alimentaire de 168 jours avec une population de laboratoire de souris à pieds blancs. Les valeurs de d 13 C dans tous les tissus diffèrent de moins de 1 % de celles du régime, excepté dans le sang entier qui possède un facteur de discrimination tissu-régime légèrement plus élevé de 1,8 %. Tous les tissus sont enrichis en 15 N d'environ 3 % par rapport au régime, excepté le tissu hépatique qui l'est de 4,5 % au-dessus de la valeur d 15 N du régime. Les taux de remplacement des tissus de la souris à pieds blancs sont par ordre foie > sang entier > muscle. Les demi-vies calculées pour le tissu hépatique sont significativement différentes dans les deux changements de régime faits au cours de l'expérience. Nous démontrons la possibilité de variation dans les valeurs de discrimination entre les tissus et le régime et dans les taux de remplacement des tissus même entre des espèces fortement apparentées. Ces observations soulignent l'importance de déterminer des estimations spécifiques à l'espèce de ces variables avant d'utiliser l'analyse des isotopes stables dans des recherches en nature en écologie animale.[Traduit par la Rédaction]