Mesabolivar: high endemism in Brazil's Atlantic Forest
(published in Zootaxa 3942: 1-60; request PDF)

Many pholcid species in the Atlantic Forest (AF) of Brazil appear restricted to small geographic ranges. Of the 132 species collected between 2003 and 2015 at 48 sites between Rio Grande do Sul and Rio Grande do Norte, 76 species (58%) were found at only one locality. The present paper focuses on such species in the genus Mesabolivar, and compares diversity and distribution patterns of this genus within and outside the AF. The percentage of species known from single localities is higher in the AF (34 of 52 species; 65%) than outside the AF (10 of 25; 40%). Distribution rages of species in the AF are significantly smaller than of species outside the AF (mean maximum distances between localities: 184 versus 541 km).

Mesabolivar, a highly diverse genus in South America, and in particular in Brazil's Atlantic Forest.

A comparison of distribution ranges between 52 Atlantic Forest species and 25 species from all other regions revealed significantly smaller ranges in Atlantic Forest species (mean 184 km, SD 382 km versus 541 km, SD 841 km; Independent Samples t-test, P=0.000). This is probably correlated with the large number of litter-dwelling species in the Atlantic Forest.

The high number of distribution-limited litter-dwelling species in the Atlantic Forest also explains the high number of species currently known from a single locality. In the Atlantic Forest, this value is at 65% (34 of 52 species). Outside the Atlantic Forest, only 40% (10 of 25 species) are known from a single locality. The true difference may be even bigger, considering the apparently denser sampling in the Atlantic Forest as compared to the rest of South America.