Browsing by Author "Silva, Mónica C."
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- Absence of haemosporidian parasite infections in the long-lived Cory’s shearwater: evidence from molecular analyses and review of the literaturePublication . Campioni, Letizia; Martínez-de la Puente, Josué; Figuerola, Jordi; Granadeiro, José P.; Silva, Mónica C.; Catry, PauloThe apparent scarcity or absence of blood parasites in some avian groups, such as seabirds, has been related to intrinsic and extrinsic factors including host immunological capacity, host-parasite assemblage, and ecological parameters, but also to reduced sensitivity of some methods to detect low parasite prevalence/intensities of infection. Here, we examined the haemosporidian parasite prevalence in a breeding population of Cory's shearwater Calonectris diomedea borealis, a long-distance migrant seabird, nesting in the Macaronesian region, in the Eastern Atlantic. Previous studies on Calonectris diomedea complex were based on small sample sizes providing weak evidence for a lack of infections by haemoparasites. Here, we investigated the presence of both parasite infections in C. d. borealis and larvae of potential mosquito vectors on the area. By employing a PCR-based assay, we extensively examined the prevalence of blood parasites belonging to the genera Plasmodium, Haemoproteus, and Leucocytozoon in 286 individuals from different life stages (i.e., chicks, immatures, sabbatical, and breeding adults), facing their specific energetic trade-offs (immunological functions vs. life history activities). We sampled immatures and adult shearwaters, of different sexes, ages, and migratory origins, from two sub-colonies. None of the sampled individuals were infected by these parasites, supporting the hypothesis that there was no in situ or ex situ transmission of vector-borne parasites in marine habitats irrespective of host's life stage and in spite of the presence of the potential Plasmodium vector Culiseta longiareolata breeding in the area. These results suggest that the lack of transmission of haemosporidian parasites on Selvagem Grande may be related to the lack of suitable dipteran vectors at the study sites, which may result from the geographic isolation of this area.
- Absence of haemosporidian parasite infections in the long-lived Cory’s shearwater: Evidence from molecular analyses and review of the literaturePublication . Campioni, Letizia; Martínez-de la Puente, Josué; Figuerola, Jordi; Granadeiro, José Pedro; Silva, Mónica C.; Catry, PauloThe apparent scarcity or absence of blood parasites in some avian groups, such as seabirds, has been related to intrinsic and extrinsic factors including host immunological capacity, host-parasite assemblage, and ecological parameters, but also to reduced sensitivity of some methods to detect low parasite prevalence/intensities of infection. Here, we examined the haemosporidian parasite prevalence in a breeding population of Cory's shearwater Calonectris diomedea borealis, a long-distance migrant seabird, nesting in the Macaronesian region, in the Eastern Atlantic. Previous studies on Calonectris diomedea complex were based on small sample sizes providing weak evidence for a lack of infections by haemoparasites. Here, we investigated the presence of both parasite infections in C. d. borealis and larvae of potential mosquito vectors on the area. By employing a PCR-based assay, we extensively examined the prevalence of blood parasites belonging to the genera Plasmodium, Haemoproteus, and Leucocytozoon in 286 individuals from different life stages (i.e., chicks, immatures, sabbatical, and breeding adults), facing their specific energetic trade-offs (immunological functions vs. life history activities). We sampled immatures and adult shearwaters, of different sexes, ages, and migratory origins, from two sub-colonies. None of the sampled individuals were infected by these parasites, supporting the hypothesis that there was no in situ or ex situ transmission of vector-borne parasites in marine habitats irrespective of host's life stage and in spite of the presence of the potential Plasmodium vector Culiseta longiareolata breeding in the area. These results suggest that the lack of transmission of haemosporidian parasites on Selvagem Grande may be related to the lack of suitable dipteran vectors at the study sites, which may result from the geographic isolation of this area.
- Can thin-billed prions Pachyptila belcheri breed successfully on an island with introduced rats, mice and cats? The case of New Island, Falkland IslandsPublication . Catry, Paulo; Silva, Mónica C.; MacKay, S.; Campos, Ana R.; Masello, Juan F.; Quillfeldt, Petra; Strange, Ian J.Small burrowing petrels nesting on islands rarely survive introductions of mammalian predators. On New Island, a population of around two million pairs of thin-billed prions nests despite the presence of introduced ship rats, house mice and feral cats. Understanding the mechanisms of such coexistence is important, as it is important to establish a baseline for future monitoring. To do this, prion breeding success was determined for 7 years and in several habitats. Breeding success was high, except for the small fraction of the population that nests in tussock Poa Xabellata stands, where several lines of evidence suggest significant predation by rats. Such high breeding success possibly resulted from predator swamping in this highly seasonal environment. This study suggests that introduced mammals do not currently depress thin-billed prion breeding success on New Island. However, cats and rodents might have future harmful eVects if external factors depressed the prion population or allow a signiWcant population growth of predators on New Island.
- Contrasting patterns of population structure of Bulwer’s petrel (Bulweria bulwerii) between oceans revealed by statistical phylogeographyPublication . Silva, Mónica C.; Catry, Paulo; Bried, Joël; Kawakami, Kazuto; Flint, Elizabeth; Granadeiro, José P.The patterns of population divergence of mid-latitude marine birds are impacted by only a few biogeographic barriers to dispersal and the efect of intrinsic factors, such as fdelity to natal colonies or wintering grounds, may become more conspicuous. Here we describe, for the frst time, the phylogeographic patterns and historical demography of Bulwer’s petrel Bulweria bulwerii and provide new insights regarding the drivers of species diversifcation in the marine environment. We sampled Bulwer’s petrels from the main breeding colonies and used a statistical phylogeography approach based on surveying nuclear and mitochondrial loci (~9100 bp) to study its mechanisms of global diversifcation. We uncovered three highly diferentiated groups including the Western Pacifc, the Central Pacifc and the Atlantic. The older divergence occurred within the Pacifc Ocean, ca. 850,000 ya, and since then the W Pacifc group has been evolving in isolation. Conversely, divergence between the Central Pacifc and Atlantic populations occurred within the last 200,000 years. While the Isthmus of Panama is important in restricting gene fow between oceans in Bulwer’s petrels, the deepest phylogeographic break is within the Pacifc Ocean, where oceanographic barriers are key in driving and maintaining the remarkable structure found in this highly mobile seabird. This is in contrast with the Atlantic, where no structure was detected. Further data will provide insights regarding the extent of lineage divergence of Bulwer’s petrels in the Western Pacifc.
- Population census and nesting habitat selection of thin-billed prion Pachyptila belcheri on New Island, Falkland IslandsPublication . Catry, Paulo; Campos, Ana R.; Segurado, Pedro; Silva, Mónica C.; Strange, Ian J.Seabirds have the potential to be used as indicators for monitoring changes in the southern oceans. However, many species and populations are still poorly known. The thin-billed prion (Pachyptila belcheri) is the most abundant seabird species around the Falkland Islands, but this far, no detailed censuses of its populations had been carried out. In this study, we developed a methodology, based on standard field methods combined with a Geographical Information System, to census the biggest known colony (New Island) of this species. Data were also collected on nesting habitat preferences. Results indicate that there are 1,081,000 (95% confidence limits: 815,000–1,346,000) apparently active nest-burrow entrances on New Island South which, given the very high occupancy rates by known breeders, should correspond to a similar number of nesting couples. We present quantitative evidence that this result can be extrapolated for the entire island, giving an overall estimate of 2 million pairs. Prions have an almost ubiquitous distribution on New Island, but they are more frequent in areas with steeper slopes (excluding cliffs). Habitats dominated by introduced grass species generally hold higher densities of nests in comparison to most native formations.
- Searching for a breeding population of Swinhoe’s Storm-petrel at Selvagem Grande, NE Atlantic, with a molecular characterization of occurring birds and relationships within the HydrobatinaePublication . Silva, Mónica C.; Matias, Rafael; Ferreira, Vânia; Catry, Paulo; Granadeiro, José PedroLong-distance dispersal plays a critical role in population dynamics, particularly in species that occupy fragmented habitats, but it is seldom detected and investigated. The pelagic seabird Swinhoe's Storm-petrel, Oceanodroma monorhis, breeds exclusively in the NW Pacific. Individuals have been regularly observed in the Atlantic Ocean since the 1980s, but breeding has never been confirmed. In this study, we searched for evidence of breeding of Swinhoe's Storm-petrels on Selvagem Grande Island, NE Atlantic, between 2007 and 2013. During this period, six individuals were captured, sexed and characterized molecularly for two mitochondrial loci, cytochrome oxydase I and the control region, to confirm species identity, survey genetic diversity and estimate evolutionary relationships within the Hydrobatinae. These individuals were confirmed to be Swinhoe's Storm-petrels, and all except one are females. Phylogenetic analyses suggest sister relationship with Matsudaira's Storm-petrel and dismiss misidentifications with other dark rump species. Patterns of genetic variation suggest that dispersal occurred likely by more than a single female. Despite the record of a pair duetting in a burrow, breeding could not be confirmed. Swinhoe's Storm-petrels are regularly occurring at Selvagem Grande, but capture/recapture patterns suggest that a possible breeding population is small and likely not self-sustaining. In seabirds, long-distance dispersal events may facilitate colonization of new habitats created in the context of predicted climate change impacts on the marine ecosystems.
- Understanding the mechanisms of antitropical divergencein the seabird White-faced Storm-petrel (Procellariiformes:Pelagodroma marina) using a multilocus approachPublication . Silva, Mónica C.; Matias, Rafael; Wanless, Ross M.; Ryan, Peter G.; Stephenson, Brent M.; Bolton, Mark; Ferrand, Nuno; Coelho, Manuela M.Analytical methods that apply coalescent theory to multilocus data have improved infer-ences of demographic parameters that are critical to understanding population divergenceand speciation. In particular, at the early stages of speciation, it is important to implementmodels that accommodate conflicting gene trees, and benefit from the presence of sharedpolymorphisms. Here, we employ eleven nuclear loci and the mitochondrial control regionto investigate the phylogeography and historical demography of the pelagic seabirdWhite-faced Storm-petrel (Pelagodroma marina)bysamplingsubspeciesacrossitsanti-tropical distribution. Groups are all highly differentiated: global mitochondrial ΦST= 0.89(P < 0.01) and global nuclear ΦSTvaries between 0.22 and 0.83 (all P < 0.01). The completelineage sorting of the mitochondrial locus between hemispheres is corroborated by approx-imately half of the nuclear genealogies, suggesting a long-term antitropical divergence inisolation. Coalescent-based estimates of demographic parameters suggest that hemisphericdivergence of P. marina occurred approximately 840 000 ya (95% HPD 582 000–1 170 000),in the absence of gene flow, and divergence within the Southern Hemisphere occurred190000ya(95%HPD96000–600 000), both probably associated with the profound palaeo-oceanographic changes of the Pleistocene. A fledgling sampled in St Helena (tropicalSouth Atlantic) suggests recent colonization from the Northern Hemisphere. Despite thegreat potential for long-distance dispersal, P. marina antitropical groups have beenevolving as independent, allopatric lineages, and divergence is probably maintained byphilopatry coupled with asynchronous reproductive phenology and local adaptation.