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At least 19 recordsLinked to original sources
USGS2005

Host diversity begets parasite diversity: Bird final hosts and trematodes in snail intermediate hosts

An unappreciated facet of biodiversity is that rich communities and high abundance may foster parasitism. For parasites that sequentially use different host species throughout complex life cycles, parasite diversity and abundance in ‘downstream’ hosts should logically increase with the diversity and abundance of ‘upstream’ hosts (which carry the preceding stages of parasites). Surprisingly, this logical assumption has little empirical support, especially regarding metazoan parasites. Few studies have attempted direct tests of this idea and most have lacked the appropriate scale of investigation. In two different studies, we used time-lapse videography to quantify birds at fine spatial scales, and then related bird communities to larval trematode communities in snail populations sampled at the same small spatial scales. Species richness, species heterogeneity and abundance of final host birds were positively correlated with species richness, species heterogeneity and abundance of trematodes in host snails. Such community-level interactions have rarely been demonstrated and have implications for community theory, epidemiological theory and ecosystem management.

Proceedings of the Royal Society B: Biological Sci↗
USGS2004

Long-term effects of flipper bands on penguins

Changes in seabird populations, and particularly of penguins, offer a unique opportunity for investigating the impact of fisheries and climatic variations on marine resources. Such investigations often require large-scale banding to identify individual birds, but the significance of the data relies on the assumption that no bias is introduced in this type of long-term monitoring. After 5 years of using an automated system of identification of king penguins implanted with electronic tags (100 adult king penguins were implanted with a transponder tag, 50 of which were also flipper banded), we can report that banding results in later arrival at the colony for courtship in some years, lower breeding probability and lower chick production. We also found that the survival rate of unbanded, electronically tagged king penguin chicks after 2-3 years is approximately twice as large as that reported in the literature for banded chicks. ?? 2004 The Royal Society.

Proceedings of the Royal Society B: Biological Sci↗
USGS2000

Nest predation increases with parental activity: Separating nest site and parental activity effects

Alexander Skutch hypothesized that increased parental activity can increase the risk of nest predation. We tested this hypothesis using ten open-nesting bird species in Arizona, USA. Parental activity was greater during the nestling than incubation stage because parents visited the nest frequently to feed their young during the nestling stage. However, nest predation did not generally increase with parental activity between nesting stages across the ten study species. Previous investigators have found similar results. We tested whether nest site effects might yield higher predation during incubation because the most obvious sites are depredated most rapidly. We conducted experiments using nest sites from the previous year to remove parental activity. Our results showed that nest sites have highly repeatable effects on nest predation risk; poor nest sites incurred rapid predation and caused predation rates to be greater during the incubation than nestling stage. This pattern also was exhibited in a bird species with similar (i.e. controlled) parental activity between nesting stages. Once nest site effects are taken into account, nest predation shows a strong proximate increase with parental activity during the nestling stage within and across species. Parental activity and nest sites exert antagonistic influences on current estimates of nest predation between nesting stages and both must be considered in order to understand current patterns of nest predation, which is an important source of natural selection.

Arizona↗
USGS2000

Cryptic genetic variation and paraphyly in ravens

Widespread species that are morphologically uniform may be likely to harbour cryptic genetic variation. Common ravens ( Corvus corax ) have an extensive range covering nearly the entire Northern Hemisphere, but show little discrete phenotypic variation. We obtained tissue samples from throughout much of this range and collected mitochondrial sequence and nuclear microsatellite data. Our study revealed a deep genetic break between ravens from the western United States and ravens from throughout the rest of the world. These two groups, the ‘California clade’ and the ‘Holarctic clade’ are well supported and over 4% divergent in mitochondrial coding sequence. Microsatellites also reveal significant differentiation between these two groups. Ravens from Minnesota, Maine and Alaska are more similar to ravens from Asia and Europe than they are to ravens from California. The two clades come in contact over a huge area of the western United States, with mixtures of the two mitochondrial groups present in Washington, Idaho and California. In addition, the restricted range Chihuahuan raven ( Corvus cryptoleucus ) of the south–west United States and Mexico is genetically nested within the paraphyletic common raven. Our findings suggest that the common raven may have formerly consisted of two allopatric groups that may be in the process of remerging.

Proceedings of the Royal Society B: Biological Sci↗
USGS2002

Spatio-temporal dynamics of species richness in coastal fish communities

Determining patterns of change in species richness and the processes underlying the dynamics of biodiversity are of key interest within the field of ecology, but few studies have investigated the dynamics of vertebrate communities at a decadal temporal scale. Here, we report findings on the spado-temporal variability in the richness and composition of fish communities along the Norwegian Skagerrak coast having been surveyed for more than half a century. Using statistical models incorporating non-detection and associated sampling variance, we estimate local species richness and changes in species composition allowing us to compute temporal variability in species richness. We tested whether temporal variation could be related to distance to the open sea and to local levels of pollution. Clear differences in mean species richness and temporal variability are observed between fjords that were and were not exposed to the effects of pollution. Altogether this indicates that the fjord is an appropriate scale for studying changes in coastal fish communities in space and time. The year-to-year rates of local extinction and turnover were found to be smaller than spatial differences in community composition. At the regional level, exposure to the open sea plays a homogenizing role, possibly due to coastal currents and advection.

Proceedings of the Royal Society B: Biological Sci↗
USGS2003

Timing of autumn bird migration under climate change: advances in long–distance migrants, delays in short–distance migrants

As a response to increasing spring temperature in temperate regions in recent years, populations of many plant and animal species, including migratory birds, have advanced the seasonal start of their reproduction or growth. However, the effects of climate changes on subsequent events of the annual cycle remain poorly understood. We investigated long–term changes in the timing of autumn migration in birds, a key event in the annual cycle limiting the reproductive period. Using data spanning a 42–year period, we analysed long–term changes in the passage of 65 species of migratory birds through Western Europe. The autumn passage of migrants wintering south of the Sahara has advanced in recent years, presumably as a result of selection pressure to cross the Sahel before its seasonal dry period. In contrast, migrants wintering north of the Sahara have delayed autumn passage. In addition, species with a variable rather than a fixed number of broods per year have delayed passage, possibly because they are free to attempt more broods. Recent climate changes seem to have a simple unidirectional effect on the seasonal onset of reproduction, but complex and opposing effects on the timing of subsequent events in the annual cycle, depending on the ecology and life history of a species. This complicates predictions of overall effects of global warming on avian communities.

Proceedings of the Royal Society B: Biological Sci↗
USGS2005

Life-history variation of a neotropical thrush challenges food limitation theory

Since David Lack first proposed that birds rear as many young as they can nourish, food limitation has been accepted as the primary explanation for variation in clutch size and other life-history traits in birds. The importance of food limitation in life-history variation, however, was recently questioned on theoretical grounds. Here, we show that clutch size differences between two populations of a neotropical thrush were contrary to expectations under Lack's food limitation hypothesis. Larger clutch sizes were found in a population with higher nestling starvation rate (i.e. greater food limitation). We experimentally equalized clutches between populations to verify this difference in food limitation. Our experiment confirmed greater food limitation in the population with larger mean clutch size. In addition, incubation bout length and nestling growth rate were also contrary to predictions of food limitation theory. Our results demonstrate the inability of food limitation to explain differences in several life-history traits: clutch size, incubation behaviour, parental feeding rate and nestling growth rate. These life-history traits were better explained by inter-population differences in nest predation rates. Food limitation may be less important to life history evolution in birds than suggested by traditional theory. ?? 2005 The Royal Society.

Proceedings of the Royal Society B: Biological Sci↗
USGS2005

A mechanistic link between chick diet and decline in seabirds?

A climatic regime shift during the mid-1970s in the North Pacific resulted in decreased availability of lipidrich fish to seabirds and was followed by a dramatic decline in number of kittiwakes breeding on the Pribilof Islands. Although production of chicks in the mid-1970s was adequate to sustain kittiwake populations in the early 1980s, the disappearance of birds from breeding colonies apparently exceeded recruitment. No mechanism has been proposed to explain why recruitment would differ among fledglings fed lipid-rich or lipid-poor fish during development. Here we show that diets low in lipids induce nutritional stress and impair cognitive abilities in young red-legged kittiwakes, Rissa brevirostris. Specifically, growth retardation, increased secretion of stress hormones and inferior ability to associate food distribution with visual cues were observed in individuals fed lipid-poor diets. We conclude that lipid-poor diets during development affect the quality of young seabirds, which is likely to result in their increased mortality and low recruitment. ?? 2005 The Royal Society.

Proceedings of the Royal Society B: Biological Sci↗
USGS2006

Kittiwakes strategically reduce investment in replacement clutches

Many life-history traits are expressed interactively in life, but to a varying extent on different occasions. Changes in trait expression can be accounted for by differences in the quality of the environment (‘environmental constraint’ hypothesis) or by strategic adjustments, if the relative contribution of the trait to fitness varies with time (‘strategic allocation’ hypothesis). In birds, egg production is lower in replacement clutches than in first clutches, but it is unknown whether this reduction results from an environmental constraint (e.g. food being less available at the time when the replacement clutch is produced) or from a strategic allocation of resources between the two breeding attempts. To distinguish between these two hypotheses, we performed an experiment with black-legged kittiwakes ( Rissa tridactyla ). Pairs were either food-supplemented or not before the first clutch was laid onwards and we induced them to produce a replacement clutch by removing eggs once when the first clutch was complete. As predicted by the ‘strategic allocation’ hypothesis, egg production of food-supplemented and non-food-supplemented birds decreased between first and replacement clutches. This suggests that kittiwakes strategically reduce investment in egg production for their replacement clutches compared to first clutches.

Proceedings of the Royal Society B: Biological Sci↗
USGS2007

Communication using eye roll reflective signalling

Body reflections in the ultraviolet (UV) are a common occurrence in nature. Despite the abundance of such signals and the presence of UV cones in the retinas of many vertebrates, the function of UV cones in the majority of taxa remains unclear. Here, we report on an unusual communication system in the razorback sucker, Xyrauchen texanus, that involves flash signals produced by quick eye rolls. Behavioural experiments and field observations indicate that this form of communication is used to signal territorial presence between males. The flash signal shows highest contrast in the UV region of fhe visual spectrum (??max???380 nm), corresponding to the maximum wavelength of absorption of the UV cone mechanism in suckers. Furthermore, these cones are restricted to the dorsal retina of the animal and the upwelling light background is such that their relative sensitivity would be enhanced by chromatic adaptation of the other cone mechanisms. Thus, the UV cones in the sucker have optimal characteristics (both in terms of absorbance and retinal topography) to constitute the main detectors of the flash signal. Our findings provide the first ecological evidence for restricted distribution of UV cones in the retina of a vertebrate. ?? 2007 The Royal Society.

Proceedings of the Royal Society B: Biological Sci↗
USGS2006

Global phylogeographic limits of Hawaii's avian malaria

The introduction of avian malaria (Plasmodium relictum) to Hawaii has provided a model system for studying the influence of exotic disease on naive host populations. Little is known, however, about the origin or the genetic variation of Hawaii's malaria and traditional classification methods have confounded attempts to place the parasite within a global ecological and evolutionary context. Using fragments of the parasite mitochondrial gene cytochrome b and the nuclear gene dihydrofolate reductase-thymidylate synthase obtained from a global survey of greater than 13 000 avian samples, we show that Hawaii's avian malaria, which can cause high mortality and is a major limiting factor for many species of native passerines, represents just one of the numerous lineages composing the morphological parasite species. The single parasite lineage detected in Hawaii exhibits a broad host distribution worldwide and is dominant on several other remote oceanic islands, including Bermuda and Moorea, French Polynesia. The rarity of this lineage in the continental New World and the restriction of closely related lineages to the Old World suggest limitations to the transmission of reproductively isolated parasite groups within the morphological species. ?? 2006 The Royal Society.

Proceedings of the Royal Society B: Biological Sci↗
USGS2007

Chromosome painting among Proboscidea, Hyracoidea and Sirenia: Support for Paenungulata (Afrotheria, Mammalia) but not Tethytheria

Despite marked improvements in the interpretation of systematic relationships within Eutheria, particular nodes, including Paenungulata (Hyracoidea, Sirenia and Proboscidea), remain ambiguous. The combination of a rapid radiation, a deep divergence and an extensive morphological diversification has resulted in a limited phylogenetic signal confounding resolution within this clade both at the morphological and nucleotide levels. Cross-species chromosome painting was used to delineate regions of homology between Loxodonta africana (2n = 56), Procavia capensis (2n=54), Trichechus manatus latirostris (2n = 48) and an outgroup taxon, the aardvark (Orycteropus afer, 2n = 20). Changes specific to each lineage were identified and although the presence of a minimum of 11 synapomorphies confirmed the monophyly of Paenungulata, no change characterizing intrapaenungulate relationships was evident. The reconstruction of an ancestral paenungulate karyotype and the estimation of rates of chromosomal evolution indicate a reduced rate of genomic repatterning following the paenungulate radiation. In comparison to data available for other mammalian taxa, the paenungulate rate of chromosomal evolution is slow to moderate. As a consequence, the absence of a chromosomal character uniting two paenungulates (at the level of resolution characterized in this study) may be due to a reduced rate of chromosomal change relative to the length of time separating successive divergence events. ?? 2007 The Royal Society.

Proceedings of the Royal Society B: Biological Sci↗
USGS2008

Diversity increases biomass production for trematode parasites in snails

Increasing species diversity typically increases biomass in experimental assemblages. But there is uncertainty concerning the mechanisms of diversity effects and whether experimental findings are relevant to ecological process in nature. Hosts for parasites provide natural, discrete replicates of parasite assemblages. We considered how diversity affects standing-stock biomass for a highly interactive parasite guild: trematode parasitic castrators in snails. In 185 naturally occurring habitat replicates (individual hosts), diverse parasite assemblages had greater biomass than single-species assemblages, including those of their most productive species. Additionally, positive diversity effects strengthened as species segregated along a secondary niche axis (space). The most subordinate species—also the most productive when alone—altered the general positive effect, and was associated with negative diversity effects on biomass. These findings, on a previously unstudied consumer class, extend previous research to illustrate that functional diversity and species identity may generally both explain how diversity influences biomass production in natural assemblages of competing species.

Proceedings of the Royal Society B: Biological Sci↗
USGS2008

Parasite manipulation of brain monoamines in California killifish (Fundulus parvipinnis) by the trematode Euhaplorchis californiensis

California killifish (Fundulus parvipinnis) infected with the brain-encysting trematode Euhaplorchis californiensis display conspicuous swimming behaviours rendering them more susceptible to predation by avian final hosts. Heavily infected killifish grow and reproduce normally, despite having thousands of cysts inside their braincases. This suggests that E. californiensis affects only specific locomotory behaviours. We hypothesised that changes in the serotonin and dopamine metabolism, essential for controlling locomotion and arousal may underlie this behaviour modification. We employed micropunch dissection and HPLC to analyse monoamine and monoamine metabolite concentrations in the brain regions of uninfected and experimentally infected fish. The parasites exerted density-dependent changes in monoaminergic activity distinct from those exhibited by fish subjected to stress. Specifically, E. californiensis inhibited a normally occurring, stress-induced elevation of serotonergic metabolism in the raphae nuclei. This effect was particularly evident in the experimentally infected fish, whose low-density infections were concentrated on the brainstem. Furthermore, high E. californiensis density was associated with increased dopaminergic activity in the hypothalamus and decreased serotonergic activity in the hippocampus. In conclusion, the altered monoaminergic metabolism may explain behavioural differences leading to increased predation of the infected killifish by their final host predators. ?? 2008 The Royal Society.

Proceedings of the Royal Society B: Biological Sci↗
USGS2009

Does influenza A affect body condition of wild mallard ducks, or vice versa?

Low pathogenic avian influenza (LPAI) viruses are well documented to circulate within wild waterfowl populations (Olsen et. al. 2006 ). It has been assumed that these infections are benign with no subsequent effects on life-history parameters. The study by Latorre-Margalef et al. (2009 ; hereafter L.-M. et al. ) represents an important step, as they attempt to test this assumption in wild birds. L.-M. et al. captured migrating mallards ( Anas platyrhynchos ) at a staging area and tested them for the presence of avian influenza A virus (IAV). They related IAV infection status to body mass and duration of time spent on the staging area. Overall, the study is well designed with impressive sample sizes and the analyses are carefully conducted and presented. However, in discussing these results, the authors assume causation based upon correlation and, although they acknowledge the possibility of immunosuppression during migration due to reduced energy stores, they do not discuss it as a possible explanation for their findings. Below, we consider several of the major findings by L.-M. et al. , providing alternative explanations for the results. Because the L.-M. et al. study design is correlational, it is not possible to use their data to distinguish between their interpretations and our alternative explanations.

Proceedings of the Royal Society B: Biological Sci↗
USGS2010

Long-term isolation of a highly mobile seabird on the Galapagos

The Galapagos Islands are renowned for their high degree of endemism. Marine taxa inhabiting the archipelago might be expected to be an exception, because of their utilization of pelagic habitats—the dispersal barrier for terrestrial taxa—as foraging grounds. Magnificent frigatebirds ( Fregata magnificens ) have a highly vagile lifestyle and wide geographical distribution around the South and Central American coasts. Given the potentially high levels of gene flow among populations, the species provides a good test of the effectiveness of the Galapagos ecosystem in isolating populations of highly dispersive marine species. We studied patterns of genetic (mitochondrial DNA, microsatellites and nuclear introns) and morphological variation across the distribution of magnificent frigatebirds. Concordant with predictions from life-history traits, we found signatures of extensive gene flow over most of the range, even across the Isthmus of Panama, which is a major barrier to gene flow in other tropical seabirds. In contrast, individuals from the Galapagos were strongly differentiated from all conspecifics, and have probably been isolated for several hundred thousand years. Our finding is a powerful testimony to the evolutionary uniqueness of the taxa inhabiting the Galapagos archipelago and its associated marine ecosystems.

Galapagos Islands↗
USGS2011

Semiochemical compounds of preen secretion reflect genetic make-up in a seabird species

Several vertebrates choose their mate according to genetic heterozygosity and relatedness, and use odour cues to assess their conspecifics' genetic make-up. In birds, although several species (including the black-legged kittiwake) exhibit non-random mating according to genetic traits, the cues used to assess genetic characteristics remain unknown. The importance of olfaction in birds' social behaviour is gaining attention among researchers, and it has been suggested that, as in other vertebrates, bird body scent may convey information about genetic traits. Here, we combined gas chromatography data and genetic analyses at microsatellite loci to test whether semiochemical messages in preen secretion of kittiwakes carried information about genetic heterozygosity and relatedness. Semiochemical profile was correlated with heterozygosity in males and females, while semiochemical distance was correlated with genetic distance only in male–male dyads. Our study is the first to demonstrate a link between odour and genetics in birds, which sets the stage for the existence of sophisticated odour-based mechanisms of mate choice also in birds.

Proceedings of the Royal Society B: Biological Sci↗
USGS2012

Tissue loss (white syndrome) in the coral Montipora capitata is a dynamic disease with multiple host responses and potential causes

Tissue loss diseases or white syndromes (WS) are some of the most important coral diseases because they result in significant colony mortality and morbidity, threatening dominant Acroporidae in the Caribbean and Pacific. The causes of WS remain elusive in part because few have examined affected corals at the cellular level. We studied the cellular changes associated with WS over time in a dominant Hawaiian coral, Montipora capitata , and showed that: (i) WS has rapidly progressing (acute) phases mainly associated with ciliates or slowly progressing (chronic) phases mainly associated with helminths or chimeric parasites; (ii) these phases interchanged and waxed and waned; (iii) WS could be a systemic disease associated with chimeric parasitism or a localized disease associated with helminths or ciliates; (iv) corals responded to ciliates mainly with necrosis and to helminths or chimeric parasites with wound repair; (v) mixed infections were uncommon; and (vi) other than cyanobacteria, prokaryotes associated with cell death were not seen. Recognizing potential agents associated with disease at the cellular level and the host response to those agents offers a logical deductive rationale to further explore the role of such agents in the pathogenesis of WS in M. capitata and helps explain manifestation of gross lesions. This approach has broad applicability to the study of the pathogenesis of coral diseases in the field and under experimental settings.

Proceedings of the Royal Society B: Biological Sci↗