paula.conde.ac@gmail.com

CENAP/ICMBio (11) 4416-6633

MODELOS TEÓRICOS DE DISTRIBUIÇÃO DE ABUNDÂNCIA DAS ESPÉCIES PARA CARACTERIZAÇÃO DA DIVERSIDADE BIOLÓGICA E A UTILIZAÇÃO DE DIFERENTES MEDIDAS DE ABUNDÂNCIA

(THEORETICAL MODELS OF SPECIES ABUNDANCE DISTRIBUTION TO CHARACTERIZE THE BIOLOGICAL DIVERSITY AND THE USE OF DIFFERENT MEASURES OF ABUNDANCE)

The species abundance distributions (SADs) are considered an informative way to describe the biological diversity revealling one of the most well-established patterns in ecology: the predominance of rare species in biological communities. The generality of such pattern made it relevant to analyze other biodiversity parameters and to induce the development of theoretical models of SAD. On the other hand, statistical models of SAD occupied a central role in biology as an empirical principle that underlies many ecological theories. Was suggested that SADs follow an approximately lognormal distribution, but that may appear truncated by the effect of sample size, being completely revealed only in large samples. This idea is associated with the statistical property of consistency, which implies that the accumulation of evidence - represented by the increase in sample size - leads the samples distribution to the true model, as well as the estimates of the parameters to their real values. Beyond the effect of sample size, the SADs may differ depending on the measure of abundance adopted. Studies suggest that biomass could be a more efficient measure of abundance to reveal the underlying distribution of biological communities in smaller samples or scales (differential veiling). In this context, our aim in this study was to investigate and discuss the advantage of considering biomass in theoretical models of SAD. Thus, we evaluated the effect of sample size on the quality of models fitness under two different measures of species abundance: biomass and number of individuals. We simulated samples of different sizes taken from an empirical database of Scarabaeinae beetles. Furthermore, we adjusted the simulated samples to different SAD models and evaluated the efficiency of each kind of abundance index to reveal the correct model, as well as the accuracy and precision of the parameters estimates. Our results show that the efficiency of biomass in revealing the underlying distribution is not as general as suggested by previous works. According to our analysis criteria, biomass was not far more efficient in revealing the correct model or in providing greater accuracy and precision in parameters estimates than the number of individuals was. Thus, the statement that the SAD biomass is not veiled on small scales or samples does not seems to be general. Moreover, our results also indicate that the effect of differential veiling on SADs using biomass and number of individuals depends on the choice of the evaluated model and data set. Considering the sampling effects studied here in biodiversity evaluation we highlight the lack of studies investigating the use of biomass in SADs and implications of different effects on this measure indicate the urgent call for further studies on this subject which enable to isolate the effect of scale from the sample size.

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