Influence of forest type on the diversity, abundance, and naïve occupancy of the mammal assemblage in the southeastern Brazilian Atlantic Forest

Abstract

The Brazilian Atlantic Forest has the highest rate of native vegetation destruction, which is one of the principal drivers of mammal extinctions. Therefore, reducing information gaps regarding diversity patterns, abundance, and habitat use is crucial to understand mammal persistence in fragmented landscapes. Our objective was to establish the γ diversity and to assess the extent to which the α, and β diversity, the relative abundance, and naïve occupation of medium and large-sized mammal communities differ between seasonal and ombrophilous forests. Between January 2019 and March 2020, we placed 22 camera traps in the Atlantic Forest of Minas Gerais. We calculate Hill's numbers using iNEXT.4steps package, the β-diversity with the Betapart package, as well as the relative abundance index (RAI), and naïve occupancy (PAO). We used Kruskal-Wallis and Mann-Whitney statistical tests to compare the RAIs between different species and forest types. Finally, we calculated the correlation between the RAIs and PAOs. We found 32 species, principally from the orders Carnivora and Artiodactyla. The alpha diversity and evenness profiles were not different between the two forest types (seasonal q0 = 0.91, q1 = 0.99, q2 = 1, J = 0.83; ombrophilous q0 = 0.96, q1 = 0.99, q2 = 1, J = 0.85). The beta diversity was low (βJAC = 0.37) which was mostly associated with species turnover (βJTU = 0.34), while nestedness was almost non-existent (βJNE = 0.02). The RAIs varied among mammalian species (H = 115.24, P = 0.000), with the highest values for Didelphis aurita (RAI = 4.55 ± 7.66) and Cuniculus paca (RAI = 2.35 ± 3.73) and the minor values for Speothos venaticus (RAI = 0.04 ± 0.24) and Galictis cuja (RAI = 0.06 ± 1.19). The RAIs of species was not significantly different between forests (U = 453.5; Z = 0.37; P = 0.70), and only Leopardus wiedii showed significant differences between forests (U = 84.5; P = 0.01). Most of the mammalian species had restricted occupancy to a few localities (< 50 %). The species Eira barbara and Didelphis aurita had the highest PAOs in both forests (> 50 %), and the species Tayassu pecari, Tamandua tetradactyla, and Speothos venaticus, the lowest values (5 %). We found a correlation of 75 % between the average RAI and naïve occupancy. The γ diversity was representative and consistent with the species found in the Atlantic Forest, and the relative abundance and naïve occupancy reflected the rarity of most species in the area. Additionally, the only difference between the two forests corresponds to species turnover. Therefore, we must conserve native remnants of both forests to ensure the existence of native mammals, mainly the most threatened species, to prevent more dramatic scenarios of local extinction in Minas Gerais.