Revisiting the Asclepiadoideae (Apocynaceae) from the Espinhaço Range

Abstract

A survey of the Asclepiadoideae (Apocynaceae) from the Espinhaço Range is presented. Based on the determinations of 3,615 collections, 133 species and 24 genera were recorded for this region; the most diverse genera are Ditassa (30 species), Oxypetalum (24), Minaria (19), Hemipogon (9), and Matelea (8). Within the Espinhaço Range, 108 species occur in Minas Gerais and 66 species occur in Bahia; 41 (ca. 30%) of these species are found in both states. Fortytwo (ca. 30%) species are endemic to the Espinhaço Range, which are mostly found in the Serra do Cipó and Diamantina Plateau, in Minas Gerais, and Chapada Diamantina, in Bahia. The sampling effort in Bahia is nearly half of that in Minas Gerais. As seen with Minas Gerais, this suggests that collecting more in Bahia will lead to the discovery of new taxa and to a better understanding of the distribution ranges of known species. In comparison with a survey published almost 10 years ago, for the Minas Gerais section of the Espinhaço Range, the classification of nearly 20% of the species has changed; most of these changes were based on phylogenetic studies. As a consequence, these studies about the Asclepiadoideae are revealing lineages that evolved predominantly in the Espinhaço Range, such as Minaria and Hemipogon. They also indicate that cladogenesis events might have been more frequent in the Espinhaço Range of Minas Gerais compared to the section in Bahia or, alternatively, extinctions events have been rarer in the Minas Gerais section. This pattern suggests that environmental factors are directly involved in the diversification of these plants along the Espinhaço Range and that comparative studies between the two sections of this range may reveal the principal causes associated with the rise of microendemics.