Evaluation of abundance indexes in open population studies: a comparison in populations of small mammals in southern Brazil / Avaliação de índices de abundância em estudos de populações abertas: uma comparação em populações de pequenos mamíferos do sul do Brasil

Many manuscripts comparing populations and/or analysing the structure of animal communities use indexes of captures as synonymous of abundance. However, the basic methods more suitable to this assumption - probabilistic estimates based on equal capture probability - have not been considered. In this study, the deviations caused by different types of capture indexes are compared with a common probabilistic population estimator (Cormack-Jolly-Seber). The analyses showed that Minimum Number Known Alive (MNKA) and the number of individuals showed greater association with the population estimator than with non-probabilistic indexes based on recaptures. Therefore, none of the indexes presented the same performance to estimate population size estimation which can lead to ecological misinterpretation. Some recommendations were also described.

Muitos estudos comparam populações e/ou analisam a estrutura de comunidades animais usando índices de captura como se fossem sinônimos de abundância. No entanto, os métodos mais adequados considerando o pressuposto - estimativas probabilísticas baseadas na igualdade da probabilidade de capturas - não têm sido considerados. Neste estudo, os desvios causados por diferentes tipos de índices de captura são comparados com um dos mais comuns estimadores populacionais probabilísticos (Cormack-Jolly-Seber). As análises mostraram que o número mínimo de animais conhecidos vivos (MNKA) e o número de indivíduos apresentaram maior associação com o estimador populacional do que com os índices não probabilísticos baseados em recapturas. Entretanto, nenhum dos índices apresentou o mesmo desempenho do estimador populacional o que pode levar a interpretações equivocadas. Algumas recomendações foram também descritas.

Simulation of population size and genome saturation level for genetic mapping of recombinant inbred lines (RILs)

Various population sizes and number of markers have been used to obtain genetic maps. However, the precise number of individuals and markers needed for obtaining reliable maps is not known. We used data simulation to determine the influence of population size, the effect of the degree of marker saturation of the genome, and the number of individuals required for mapping of recombinant inbred lines (RILs). Three genomes with 11 linkage groups were generated with saturation levels of 5, 10 and 20 cM. For each saturation level populations were generated with 50, 100, 154, 200, 300, 500 and 800 individuals with 100 replications for each population size. A total of 2100 populations was generated and mapped. Small marker numbers and small population sizes produced maps with more than 11 linkage groups. As population size and marker saturation increased, marker inversion and non-linked markers decreased, moreover, between-marker distance estimates were improved. In this study, a minimum size of 200, 300 and 500 individuals were necessary for obtaining reliable maps when they were evaluated over the saturation levels of 5, 10 and 20 cM, respectively.