Abstract Detail

Systematics Section

Barba Montoya, Jose Antonio [1], Magallon Puebla, Susana [2], Trejo Salazar, Roberto  [1].

Understanding arid Neotropical biodiversity: the timing and diversification rate of tribe Pachycereeae (Cactaceae, Caryophyllales).

Arid Neotropical biomes encompass an exceptionally rich biological diversity. To provide insights about some of the diversification dynamics underlying their species richness, we consider tribe Pachycereeae (Cactoideae), corresponding to the North American columnar cacti, including emblematic forms such as the saguaro (Carnegiea gigantea) and the Old Man (Cephalocereus senilis). We conduced a Bayesian phylogenetic analysis on a sample of 86 species, representing all the genera in Pachycereeae, plus two outgroups, using sequences of the cp rpl16 intergenic spacer. The resulting phylogeny was used to estimate the age and phylogenetic diversification rate of the tribe and its main lineages. Age estimation was conducted with an uncorrelated lognormal relaxed molecular clock, implementing a secondary calibration derived from a Cactaceae-wide study. The onset of diversification of Pachycereeae was estimated at 8.52 Ma (late Miocene). Diversification rates were calculated on the basis of the age and standing diversity of clades, using an estimator that accounts for the possibility of extinction. The diversification rate of Pachycereeae as a whole ranged between 0.595 and 0.380 speciation events/Ma, which is very high, in comparison with a variety of angiosperm lineages. Nevertheless, diversification rate heterogeneity was detected within the group. The recent onset and high rate of Pachycereeae diversification suggest that the group probably represents a rapid radiation that took place recently, possibly as a consequence of global and regional aridification trends. The causal relationship of Pachycereeae diversification and its pollination syndrome will be explored.

Broader Impacts:

1 - Instituto de Ecologia, UNAM, Ecologia Evolutiva, Circuito exterior s/n anexo al Jardín Botánico Exterior Apartado Postal 70-275 Ciudad Universitaria, UNAM 04510 México, D.F. , Mexico City, Distrito Federal, 04510, Mexico
2 - Instituto de Biologia, UNAM, Botanica, Circuito Exterior s/n, Ciudad Universitaria, Copilco, Coyoacán A.P. 70-367 México, Distrito Federal. C.P. 04510 , Mexico City, Distrito Federal, 04510, Mexico

Keywords:
neotropics
diversification
Bayesian estimation
rpl16
arid biomes
Phylogeny
relaxed molecular clock 
diversification rate.

Presentation Type: Oral Paper:Papers for Sections
Session: 19
Location: Lindell B/Chase Park Plaza
Date: Monday, July 11th, 2011
Time: 2:15 PM
Number: 19004
Abstract ID:378