Demetria Mondragón

SEED DISPERSAL AND GERMINATION OF THE EPIPHYTE TILLANDSIA BRACHYCAULOS (BROMELIACEAE) IN A TROPICAL DRY FOREST, MEXICO

Abstract A crucial need for population maintenance of epiphytic species is the location of suitable microsites on a host tree. Quantitative evaluation of epiphyte seed dispersal and germination is needed to more fully understand successful host colonization; this process is especially important in dry forests, where drought and oligotrophy diminish population growth rates. In a 3-year field experiment, we evaluated seed dispersal and germination of Tillandsia brachycaulos and explored some environmental factors affecting these life-cycle phases. There was significant variation in dispersal curves depending on year and height of seed release. Forty-one percent of seeds experimentally released were not dispersed and only ca. 0.5% of dispersed seeds were captured in seed traps. The number of trapped seeds decreased with distance; most seeds were captured within 1.5 m of the seed source. Seeds dispersed farther (15 m) when released from greater heights. Seed germination under controlled conditions (98%) was higher than in a field experiment (3%). Neither year nor tree height significantly affected germination of T. brachycaulos. Differences in seed dispersal and germination among years could result from variable precipitation. Establishment of new genets seems to be an important bottleneck for population growth in T. brachycaulos. Our results show that seed dispersal and germination are processes that determine such establishment.

A phylogeny of Bromeliaceae (Poales, Monocotyledoneae) derived from an evaluation of nine supertree methods

There are 26 phylogenetic studies for Bromeliaceae based on different sources of evidence. Despite this broad phylogenetic coverage of Bromeliaceae, however, the available phylogenetic data display a scattered sampling, with little overlap among different types of evidence. The aim of this study is to integrate the available phylogenetic information of the Bromeliaceae in one hypothesis using a supertree. To test which of them integrates best the information for Bromeliaceae, nine supertree methods were employed: Avcon, MSS, MinFlip, MMC, MRP, PhySIC_IST, Robinson–Foulds Supertree, Sfit, and SuperFine. Supertrees were compared with a reference tree, generated from the maximum likelihood (ML) analysis of a supermatrix integrated by 120 taxa of Bromeliaceae and seven cpDNA regions. In order to select which method best reconstructs the most robust phylogeny, two different sets of source trees were used: (i) those generated from the analysis of each individual DNA regions; and (ii) four selected phylogenies (from the 26 published works). We used the consensus fork index, normalized partition metric, patristic distance coefficient, and the Shimodaira–Hasegawa test to compare supertrees with the reference tree. The best performing methods were used to construct a supertree using all phylogenies of Bromeliaceae. The SuperFine method generated the best supertree. The lack of overlapping among phylogenies was the major limiting factor for the integration of the phylogenetic information of Bromeliaceae. Nonetheless, supertree methods helped in the identification of poorly sampled groups, as well as to explore levels of agreement among published phylogenetic studies for Bromeliaceae.

Presence of Vaejovis franckei in epiphytic bromeliads in three temperate forest types

Abstract Reports of scorpions on epiphytic bromeliads in temperate forests are scarce. Here we present some ecological aspects of this animal-plant interaction in three different types of temperate forests (pine, pine-oak and oak forest) in Oaxaca, Mexico. From 2005 to 2007, we collected 373 bromeliads belonging to 10 species, and each plant was defoliated in search of scorpions. We found 35 individuals of Vaejovis franckei Sissom 1989 in 19 bromeliads: 22 specimens in Tillandsia carlos-hankii with 21% occupancy and an average abundance of 2.1 ± 1.9 individuals/plant; 12 specimens in T. prodigiosa (10% occupancy, average abundance  =  1.6 ± 0.6) and one specimen in T. calothyrsus (3% occupancy, average abundance  =  1 ± 0.0). Pine-oak forest had 29 individuals; pine forest, 4 individuals; and oak forest, 2 individuals. Percentage of occupancy differed among localities, while average abundance remained the same. Vaejovis franckei preferred T. carlos-hankii and pine-oak forest, which was correlated with the percentage of occupancy but not with the average abundance.