Evidence for ecological causation of sexual dimorphism in a hummingbird.
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Unambiguous examples of ecological causes of animal sexual dimorphism are rare. Here we present evidence for ecological causation of sexual dimorphism in the bill morphology of a hummingbird, the purple-throated carib. This hummingbird is the sole pollinator of two Heliconia species whose flowers correspond to the bills of either males or females. Each sex feeds most quickly at the flower species approximating its bill dimensions, which supports the hypothesis that floral specialization has driven the evolution of bill dimorphism. Further evidence for ecological causation of sexual dimorphism was provided by a geographic replacement of one Heliconia species by the other and the subsequent development of a floral dimorphism, with one floral morph matching the bills of males and the other of females. (+info)
Effects of marine reserves on adjacent fisheries.
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Marine reserves have been widely promoted as conservation and fishery management tools. There are robust demonstrations of conservation benefits, but fishery benefits remain controversial. We show that marine reserves in Florida (United States) and St. Lucia have enhanced adjacent fisheries. Within 5 years of creation, a network of five small reserves in St. Lucia increased adjacent catches of artisanal fishers by between 46 and 90%, depending on the type of gear the fishers used. In Florida, reserve zones in the Merritt Island National Wildlife Refuge have supplied increasing numbers of world record-sized fish to adjacent recreational fisheries since the 1970s. Our study confirms theoretical predictions that marine reserves can play a key role in supporting fisheries. (+info)
Evolutionary history and phylogeography of the schistosome-vector freshwater snail Biomphalaria glabrata based on nuclear and mitochondrial DNA sequences.
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The phylogeography of the freshwater snail Biomphalaria glabrata remains poorly known, although this species is the major vector of schistosomiasis in the New World. It was here investigated in South America and the Lesser Antilles, based on partial mitochondrial large ribosomal subunit (16S rDNA) and nuclear internal transcribed spacer-2 (ITS-2) gene sequences. Sampling included 17 populations from a large part of the current geographic range of the species (Brazil, Venezuela and Lesser Antilles). Substantial variability was detected, as well as a high amount of phylogenetically informative signal. The molecular phylogeny inferred splits B. glabrata into Northern and Southern clades separated by the Amazon river, and may even suggest a supra-specific status for B. glabrata. Brazilian populations were the most diverse and appeared basal to the other populations. Venezuelan haplotypes formed a single clade, albeit not strongly supported. Two Venezuelan haplotypes appear rather similar to Brazilian haplotypes. Similarly, Lesser Antilles haplotypes clustered in the same monophyletic clade, which suggests that the recent colonisation of the Antilles has a northern South American origin. However, the estimated divergence time between Antilles and Venezuelan sequences is extremely large (conservatively higher than 10(5) years). These results are discussed in the light of (i) phylogeographic patterns at South American scale, and (ii) recurrent introduction of molluscs, especially in the Antilles, as a consequence of human activities. (+info)
Adaptation in a plant-hummingbird association.
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Sexual dimorphism in bill morphology and body size of the Caribbean purple-throated carib hummingbird is associated with a reversal in floral dimorphism of its Heliconia food plants. This hummingbird is the sole pollinator of H. caribaea and H. bihai, with flowers of the former corresponding to the short, straight bills of males, the larger sex, and flowers of the latter corresponding to the long, curved bills of females. On St. Lucia, H. bihai compensates for the rarity of H. caribaea by evolving a second color morph with flowers that match the bills of males, whereas on Dominica, H. caribaea evolves a second color morph with flowers that match the bills of females. The nectar rewards of all Heliconia morphs are consistent with each sex's choice of the morph that corresponds to its bill morphology and energy requirements, supporting the hypothesis that feeding preferences have driven their coadaptation. (+info)
Temporal stability of insular avian malarial parasite communities.
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Avian malaria is caused by a diverse community of genetically differentiated parasites of the genera Plasmodium and Haemoproteus. Rapid seasonal and annual antigenic allele turnover resulting from selection by host immune systems, as observed in some parasite populations infecting humans, may extend analogously to dynamic species compositions within communities of avian malarial parasites. To address this issue, we examined the stability of avian malarial parasite lineages across multiple time-scales within two insular host communities. Parasite communities in Puerto Rico and St Lucia included 20 and 14 genetically distinct parasite lineages, respectively. Lineage composition of the parasite community in Puerto Rico did not vary seasonally or over a 1 year interval. However, over intervals approaching a decade, the avian communities of both islands experienced an apparent loss or gain of one malarial parasite lineage, indicating the potential for relatively frequent lineage turnover. Patterns of temporal variation of parasite lineages in this study suggest periodic colonization and extinction events driven by a combination of host-specific immune responses, competition between lineages and drift. However, the occasional and ecologically dynamic lineage turnover exhibited by insular avian parasite communities is not as rapid as antigenic allele turnover within populations of human malaria. (+info)
Epidemiology and control of Schistosomiasis and other intestinal parasitic infections among school children in three rural villages of south Saint Lucia.
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OBJECTIVE: The purpose of this study was to determine the epidemiology of parasitic infections and the efficacy of treatment among school children in rural villages of south Saint Lucia. METHOD: A total of 554 school children participated in this study. Parasitic infections were confirmed by using Kato- Katz method. RESULTS & CONCLUSION: Overall, 61.6% of the school children were infected by any parasitic infection. The helminths identified were Ascaris lumbricoides (15.7%), Hookworm (11.9%), Strongyloides (9.7%), Trichuris trichiura (4.7%), Schistosoma mansoni (0.6%), Taenia solium (0.8%) and Enterobius vermicularis (2.1%), Entamoeba coli (9.7%), Iodameba butschlii (5%), Entamoeba histolytica (1.1%), Giardia lamblia (1.8%) and Endolimax nana (2.1%). The control intervention included treatment with albendazole 400 mg and praziquantel 40 mg/kg as well as awareness campaigns. Post-interventional assessment showed the total prevalence of intestinal parasitic infection reduced from 61.6 to 3.6% with a cure rate of 94.2%, following the control methods. (+info)