RESUMO
To further test the hypothesis that the Isthmus of Panama is a major barrier to gene flow in pantropical seabirds, we applied phylogeographic methods to mitochondrial control sequence variation in masked booby (Sula dactylatra) populations on either side of the Isthmus of Panama and the southern tip of Africa. In accord with Steeves et al. (2003), we found that all Caribbean masked boobies with the 'secondary contact' cytochrome b haplotype (m-B) shared a control region haplotype (Sd_100), which grouped with Indian-Pacific haplotypes and not Caribbean-Atlantic haplotypes. In addition, Sd_100 was more closely related to control region haplotypes in the Indian Ocean than in the Pacific. We also found that the 'secondary contact' birds diverged more recently from extant populations in the Indian Ocean than in the Pacific. Thus, it appears that these masked boobies did not breach the Isthmus of Panama. Rather, birds likely dispersed around the southern tip of Africa during favourable oceanographic conditions in the Pleistocene.
Assuntos
Aves/genética , Demografia , Genética Populacional , Filogenia , Animais , Sequência de Bases , Aves/fisiologia , Análise por Conglomerados , Primers do DNA , DNA Mitocondrial/genética , Geografia , Haplótipos/genética , Dados de Sequência Molecular , Oceanos e Mares , Panamá , Dinâmica Populacional , Análise de Sequência de DNARESUMO
The evolutionary theory of aging predicts that pelagic seabirds, which have low extrinsic mortality, should show exceptional longevity. These taxa appear to show the lowest rates of actuarial senescence among birds yet display declining reproductive performance at advanced ages. We have studied survival and reproduction of Nazca boobies (Sula granti) in the remote Galápagos Islands since 1984. We found a slight but detectable increase in mortality rate in the oldest (> or =19 yrs) cohort, indicating minimal actuarial senescence. The probability of successful reproduction (eggs or fledglings) declined from mid-life to the age of the oldest cohort. We are currently investigating the causal relationship between physical (foraging) performance, components of reproductive success, and longevity at our pristine study site.
Assuntos
Envelhecimento/fisiologia , Aves/fisiologia , Reprodução/fisiologia , Animais , Equador , Longevidade , ProbabilidadeRESUMO
Nazca boobies (Sula granti) show unconditional obligate siblicide immediately after hatching, reducing the typical two-egg clutch size to one. We studied body mass changes and levels of testosterone (T), corticosterone (CORT), and progesterone (P) for A-chicks (dominant, first hatched), B-chicks (subordinate, second hatched), and singletons, during the first 7 days after hatching, when siblicide normally occurs. Mass increase with age was higher for A-chicks than for singletons and B-chicks. This exaggerated the existing developmental advantage of A- over B-chicks that is due to hatching asynchrony. In nests with two chicks, CORT titer was significantly higher in B-chicks than in A-chicks. During ontogenetic development, CORT decreased with age for A-chicks, but did not change for singletons. P showed qualitatively similar ontogenetic changes to CORT, remaining unchanged for A-chicks but increasing for singletons. Thus, both CORT and P levels were lower for A-chicks than for singletons, and both hormones varied inversely with body mass. Overall, T levels did not differ between different categories of chicks. However, one B-chick in the process of reversing the dominance relationship with its older, but weakened, sibling had significantly elevated T. We suggest that CORT and P are regulated to promote exaggerated mass gain in socially challenged A-chicks, facilitating siblicide. Whether T induces aggressiveness during short time intervals of intense sibling rivalry needs further attention.
Assuntos
Agressão/fisiologia , Comportamento Agonístico/fisiologia , Corticosterona/sangue , Dominação-Subordinação , Progesterona/sangue , Relações entre Irmãos , Testosterona/sangue , Animais , Peso Corporal/fisiologia , Equador , Feminino , MasculinoRESUMO
We estimated the rate of extra-pair fertilizations (EPFs) in waved albatrosses (Phoebastria irrorata) on Isla Española, Galápagos, Ecuador, using multilocus minisatellite DNA fingerprinting. Waved albatrosses are socially monogamous, long-lived seabirds whose main population is on Española. Aggressive extra-pair copulation (EPC) attempts have been observed in the breeding colony during the days preceding egg-laying. Our genetic analyses of 16 families (single chicks and their attending parents) revealed evidence of EPFs in four families. In all cases males were the excluded parent. These data suggest that waved albatrosses have an unusually high rate of EPF relative to taxa with similar life histories. Future behavioural observations will determine the extent to which forced vs. unforced EPCs contribute to this high EPF rate.
Assuntos
Aves/genética , Animais , Sequência de Bases , Aves/fisiologia , Primers do DNA/genética , Equador , Feminino , Fertilização/genética , Masculino , Paternidade , Comportamento Sexual AnimalRESUMO
Se revisan diferentes procedimientos de investigación en relación a una vacuna contra la fertilidad. Se necesita mayor investigación al respecto. Una vacuna para el control de la fertilidad debe ser sometida a diversos juicios, desde los puntos de vista moral, político y religioso. Siempre se valorá la sobrepoblación, falta de recursos económicos, y el futuro de los países en desarrollo con alto índice de natalidad