Publicação
Population ecology of long-finned pilot whale (Globicephala melas) off the Western coast of the Iberian Peninsula
| Resumo: | This study focused mainly on providing information about the ecological and genetic characteristics of Iong-finned pilot whales (Globicephala meias) from the Western coast of the Iberian Peninsula, as weli as the determining the habitat preferences of this species, in that region. Additionally, the inclusion of samples from other regions ied to the investigation ofthe occurrence of population structure within the North Atiantic. Firstly, stomach contents and fatty acid analyses were used, to assess the dietary preferences and understand the influence of geographical and biological factors in the dietary ecoiogy of G. meias. Stomach contents results confirmed pilot whaies as mainly teuthophagous species and showed that Iberian whales had a more diverse diet, dominated by Octopodidae species, in comparison to the predominance of Ommastrephids in Scotland. The analysis of prey fatty acids, in the presnt study, also indicated that, although not conclusive, there is some evidence that iberian whales are feeding on octopods. Both stomach contents and fatty acid analyses reveaied the occurrence of significant geographical differences between animais from different regions of the North Atlantic (iberia, Scotland and USA). These results may be a consequence of the ingestion of different types of prey based on prey preference/availability or due to the exploitation of different feeding niches/habitats in the study areas, which suggest the possibiiity of the occurrence of different ecological groups with specific foraging habits in the North Atiantic. There were also biological influences on the dietary ecology of G. meias, particularly evident in the stomach contents analysis, where significant differences in the main prey consumed were associated with the Iength and sex of the animal. However, no significant differences occurred in the fatty acid profiles offemale/maie or mature/immature piiot whales. Secondly, the genetic population diversity and divergence of G. meias from six regions in the North Atlantic and adjacent waters were investigated, based on mitochondrial DNA (mtDNA) and MHC DRA and DOB loci. Both mtDNA and MHC diversities were comparabie to other abundant widespread cetaceans. Pairwise estimates of genetic differentiation (FST) indicated the occurrence of genetic structure at both regional and oceanic scaies at mtDNA, while MHC suggested that Iberian whaies represent a genetically differentiated group. Population structuring reveaied by mtDNA couid be reiated to the social structure presented by this species, associated with high leveis of female phylopatry. For the MHC loci, aithough the occurrence of historical balancing selection appeared to have an important role in shaping population diversity, the spatiai patterns of extnt diversity across the North Atlantic could be attributable to local selection pressures for specific pathogens/parasites or patterns of gene fiow and/or drift. Therefore, the combination of the results from ecological tracers (i.e. fatty acids, stomach contents) and genetic markers into a multi-tracer approach reveaied the occurrence of segregation oflong-finned piiot whaies from the different regions ofthe North Atlantic anaiysed. Furthermore, the resuits obtained in this thesis consistently show G. meias from the Western Iberian Peninsula as a potential different group within the North Atlantic, based on genetic (mtDNA and MHC) and trophi((stomach contents and fatty acids) analyses. Finally, since the identification of habitat preferences and suitable habitats within a species range has been defined as a priority for effective conservation and management, habitat modeling techniques (presence-only modeis, .i.e. PCA and Maxent) were used to determine piiot whales habitat preferences and suitabiiity in Atlantic Iberia, based on six ecogeographic variabies. Both methodologies identified depth and SST gradient as the most important variables for the ecological niche of pilot whales. SST was aiso an important variabie defined by PCA, aithough Maxent modei inciuded it as a variabie of minor importance. Higher habitat suitabiiity occurred in locations with shailower waters, higher values of SST gradient (aithough PCA, based on a shorter temporal scale, showed the opposite result for SST gradient) and SST values between 15 and 17°C. These resuits may indicate that pilot whales undertake incursions into coastal waters which may be related with a high concentration of Octopodidae spawners in these areas, in the upwelling season. However, it also highlights the importance of thinking carefully about the meaning of findings at different temporal scales, as weli as demonstrating the importance of using a fine temporal scale, in marine environments. The main results of this study contribute to the basic knowledge of this cetacean species, necessary for the determination of its conservation status and the identification of potential conservation concerns. In this context one ofthe key findings is the good evidence for existence of a separate Iberian population, which might be considered as a management unit for conservation purposes. |
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| Autores principais: | Monteiro, Silvia Raquel da Silva |
| Assunto: | Ciências Naturais::Ciências Biológicas |
| Ano: | 2014 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | This study focused mainly on providing information about the ecological and genetic characteristics of Iong-finned pilot whales (Globicephala meias) from the Western coast of the Iberian Peninsula, as weli as the determining the habitat preferences of this species, in that region. Additionally, the inclusion of samples from other regions ied to the investigation ofthe occurrence of population structure within the North Atiantic. Firstly, stomach contents and fatty acid analyses were used, to assess the dietary preferences and understand the influence of geographical and biological factors in the dietary ecoiogy of G. meias. Stomach contents results confirmed pilot whaies as mainly teuthophagous species and showed that Iberian whales had a more diverse diet, dominated by Octopodidae species, in comparison to the predominance of Ommastrephids in Scotland. The analysis of prey fatty acids, in the presnt study, also indicated that, although not conclusive, there is some evidence that iberian whales are feeding on octopods. Both stomach contents and fatty acid analyses reveaied the occurrence of significant geographical differences between animais from different regions of the North Atlantic (iberia, Scotland and USA). These results may be a consequence of the ingestion of different types of prey based on prey preference/availability or due to the exploitation of different feeding niches/habitats in the study areas, which suggest the possibiiity of the occurrence of different ecological groups with specific foraging habits in the North Atiantic. There were also biological influences on the dietary ecology of G. meias, particularly evident in the stomach contents analysis, where significant differences in the main prey consumed were associated with the Iength and sex of the animal. However, no significant differences occurred in the fatty acid profiles offemale/maie or mature/immature piiot whales. Secondly, the genetic population diversity and divergence of G. meias from six regions in the North Atlantic and adjacent waters were investigated, based on mitochondrial DNA (mtDNA) and MHC DRA and DOB loci. Both mtDNA and MHC diversities were comparabie to other abundant widespread cetaceans. Pairwise estimates of genetic differentiation (FST) indicated the occurrence of genetic structure at both regional and oceanic scaies at mtDNA, while MHC suggested that Iberian whaies represent a genetically differentiated group. Population structuring reveaied by mtDNA couid be reiated to the social structure presented by this species, associated with high leveis of female phylopatry. For the MHC loci, aithough the occurrence of historical balancing selection appeared to have an important role in shaping population diversity, the spatiai patterns of extnt diversity across the North Atlantic could be attributable to local selection pressures for specific pathogens/parasites or patterns of gene fiow and/or drift. Therefore, the combination of the results from ecological tracers (i.e. fatty acids, stomach contents) and genetic markers into a multi-tracer approach reveaied the occurrence of segregation oflong-finned piiot whaies from the different regions ofthe North Atlantic anaiysed. Furthermore, the resuits obtained in this thesis consistently show G. meias from the Western Iberian Peninsula as a potential different group within the North Atlantic, based on genetic (mtDNA and MHC) and trophi((stomach contents and fatty acids) analyses. Finally, since the identification of habitat preferences and suitable habitats within a species range has been defined as a priority for effective conservation and management, habitat modeling techniques (presence-only modeis, .i.e. PCA and Maxent) were used to determine piiot whales habitat preferences and suitabiiity in Atlantic Iberia, based on six ecogeographic variabies. Both methodologies identified depth and SST gradient as the most important variables for the ecological niche of pilot whales. SST was aiso an important variabie defined by PCA, aithough Maxent modei inciuded it as a variabie of minor importance. Higher habitat suitabiiity occurred in locations with shailower waters, higher values of SST gradient (aithough PCA, based on a shorter temporal scale, showed the opposite result for SST gradient) and SST values between 15 and 17°C. These resuits may indicate that pilot whales undertake incursions into coastal waters which may be related with a high concentration of Octopodidae spawners in these areas, in the upwelling season. However, it also highlights the importance of thinking carefully about the meaning of findings at different temporal scales, as weli as demonstrating the importance of using a fine temporal scale, in marine environments. The main results of this study contribute to the basic knowledge of this cetacean species, necessary for the determination of its conservation status and the identification of potential conservation concerns. In this context one ofthe key findings is the good evidence for existence of a separate Iberian population, which might be considered as a management unit for conservation purposes. |
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