Introduction

In 1874, E. Morren and Andre described the genus Ronnbergia based on the discovery of Ronnbergia morreniana, a species with a unique appearance that did not resemble the other Bromeliaceae genera known at that time. In one of the first taxonomical treatments of Bromeliaceae, Mez (1956) proposed the combined presence of simple and lax inflorescences, asymmetrical sepals, and the absence of epipetal appendages as the diagnostic characters to differentiate the genus Ronnbergia from other genera within the subfamily Bromelioideae. Based on these simple criteria, 14 species have been described within this genus so far. The majority of species of Ronnbergia (10 spp.) are found in the rainforests of the northwestern regions of South America and Central America (Smith and Downs 1979, Manzanarez 2002). The remaining four species, recently described, are restricted to fragments of Atlantic rainforests in southeastern Bahia, Brazil (Leme 2003) (Figure 1). Due to the similarity between Ronnbergia and other groups in the subfamily Bromelioideae, such as Aechmea, it is likely that the geographic disjunction pattern of the Ronnbergia species is a result of erroneous taxonomic placement.

In Bromeliodeae circumscribing genera has long been a problem due to the lack of a defining set of morphological characteristics (Smith and Downs 1979, Faria et al. 2004, Schulte et al. 2005, 2009). Several authors have attempted solutions by focusing their research on the phylogenetic value of traditional morphological characters used to delimit genera within Bromelioideae (e.g., Brown and Gilmartin 1984, Brown and Terry 1992, Faria et al. 2004, Sajo et al. 2004). These studies often called for redefinition of generic limits and promoted new taxonomical changes (e.g., Read 1984, Smith and Kress 1989, Smith and Spencer 1992, Brown and Leme 2005). Species of Aechmea subgenus Pothuava, and the "Aechmea lingulata complex" show strongest taxonomic and phylogenetic affinities with Ronnbergia (Smith and Downs 1979, Leme 2003, Leme and Siqueira Filho 2007, Aguirre-Santoro 2009). This correspondence, however, has not been supported in formal taxonomical treatments because the absence of epipetal appendages in Ronnbergia has traditionally isolated it from Aechmea (Mez 1956, Smith and Downs 1979).

In the last five years, several phylogenetic approaches have advanced our understanding of how Ronnbergia evolved. A highly-supported molecular-based study by Givnish et al. (2004) hypothesized that Bromeliodeae emerged from the same ancestor as the largely Andean genus Puya. Faria et al. (2004) evaluated the unclear relationships and phylogeny of the conflictive genus Aechmea, based on morphological data. Their results showed the polyphyly of the genus and its close relationship with other genera like Acanthostachys, Billbergia, Hohenbergia, Lymania, Quesnelia, Neoregelia and Ronnbergia. Schulte et al. (2009) used molecular data to reconstruct the phylogeny of the subfamily. By showing that Bromeliodeae is a sister group of Puya and highlighting the basal position of Andean genera like Greigia, Bromelia, Ochagavia, Deinacanthon...