ANDEAN SPECIATION AND VICARIANCE IN NEOTROPICAL MACROCARPAEA (GENTIANACEAE–HELIEAE)¹

Abstract

The genus Macrocarpaea (Griseb.) Gilg (Gentianaceae, Helieae) is among the largest woody genera of tropical gentians, with most of its species occurring in the wet mountainous forests of the Andes. Phylogenetic and dispersal-vicariance analyses (DIVA) of 57 of the 105 currently recognized species in the genus, using two data sets from nuclear DNA (ITS and 5S-NTS sequences) and morphology, show a single origin of the Andean species from an ancestral distribution that includes southeastern Brazil. Within the Andes, species divide into two major clades: (1) northern species from the cordilleras of northern Ecuador, Colombia, and Venezuela; and (2) southern species of the Andean Amotape-Huancabamba Zone in Ecuador and Peru, as well as the Andes of central and southern Peru and Bolivia. The Amotape-Huancabamba Zone is supported as the ancestral area for Macrocarpaea within the Andes. There are repeated speciation patterns within the Andes, and three Mesoamerican species derive from the northern clade, as is the single sampled species from the Guayana Shield. The position of the subclade of the three Caribbean species is less certain, but it currently nests among Andean species. An Atlantic coastal Brazilian clade is placed as sister group to all other Macrocarpaea, providing further support for an ancestral refuge in southeastern Brazil for the Helieae. The biogeographic analysis showed that local speciation is more common than long-distance dispersal, and allopatric speciation is more common than sympatric speciation. Using detailed, georeferenced herbarium collection data, patterns in environmental characteristics between clades and sister species were analyzed with Spatial Evolutionary and Ecological Vicariance Analysis (SEEVA), utilizing geographic information system (GIS) and statistical methods. Sister clades and taxa were evaluated for statistical significance in variables such as annual rainfall and temperature, elevation, temperature and rainfall seasonality, geological bedrock age, and soil type to evaluate ecological vicariance between sister groups. The results indicate that there are no general patterns for each variable, but that there are many significant divergences in ecological niches between both larger sister groups and sister species, and ecological niche conservation was also observed when subsequent nodes in the phylogeny were compared.

Phylogenetic insights into Andean plant diversification

“…The Amotape-Huancabamba zone might represent a dispersal barrier for high-elevation lineages under current climatic conditions. Support for this idea has been found in the distribution of groups such as Lithospermum (Boraginaceae; Weigend et al, 2010), Macrocarpea (Gentianaceae; Struwe et al, 2009), Nasa (Loasaceae; Weigend, 2002), Peperomia (Piperaceae; Symmank et al, 2011). The Central Andes are situated between the Amotape-Huancabamba zone and the southern limit of the dry Puna around 25-29 • S, where the precipitation regime changes from summer-rainfall to winter-rainfall (Luebert and Pliscoff, 2006), which is paralleled by floristic turnover (Villagrán et al, 1983;Martínez-Carretero, 1995;Arroyo et al, 1997Arroyo et al, , 1998.…”

“…Relationships between the northern and the Central Andes and the Brazilian highlands have been suggested for Tibouchina (Melastomataceae; Michelangeli et al, 2013), a connection also retrieved in phylogenetic studies on Elapghoglossum (Dryopteridaceae; Vasco et al, 2009), Sinningia (Gesneriaceae; Perret et al, 2006), Macrocarpaea (Gesneriaceae; Struwe et al, 2009), and Bromelioideae (Bromeliaceae; Givnish et al, 2014). The latter is the only dated dispersal scenario available (∼8 Ma; Givnish et al, 2011).…”

“…These radiations correspond to two well-supported subclades distributed to the South and to the North of the Amotape cross, within which allopatric speciation between adjacent zones of the same mountain range were hypothesized (Struwe et al, 2009). Migrations from the Southern Andes through the AmotapeHuancabamba zone into the Northern Andes suggest that the Amotape-Huancabamba zone was not a dispersal barrier for lineages of mid-elevations.…”

“…In a study of Macrocarpaea (Gentianaceae), a genus of montane forest species, an Andean origin around the AmotapeHuancabamba zone, with radiations in both north-and southwards directions was postulated (Struwe et al, 2009). These radiations correspond to two well-supported subclades distributed to the South and to the North of the Amotape cross, within which allopatric speciation between adjacent zones of the same mountain range were hypothesized (Struwe et al, 2009).…”

Landscape Genetics of Phaedranassa Herb. (Amaryllidaceae) in Ecuador

“…It appears that the mosaic of environments in the Northern Andes contributed to divergence in the genus. This biogeographical scenario is also reported for the genus Macrocarpaea (Gentianaceae-Helieae) from the Andes, in which local allopatric speciation was more common than sympatric speciation (Struwe et al 2009). …”