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Phyla scaberrima (Verbenaceae) is a herbaceous perennial species that is distributed from Mexico (center of origin) to Colombia, growing in forest and swamp edges or grasslands from sea level up to an altitude of 1800 m. The chemical properties and uses in popular medicine have drastically affected the population size of this species. In this study, we investigated genetic variability in populations of P. scaberrima using AFLP markers. Three AFLP primer combinations rendered a total of 997 markers in a sample of 131 individuals from five populations, including two populations from Mexico and three from Colombia. The average percentage of polymorphic loci, gene diversity and Shannon-Wiener index were 46.62, 0.0695, and 0.119, respectively. Analysis of molecular variance showed that the distribution of the genetic variability within populations (85.41%) was higher than between groups (8.11%) and between populations (6.48%). Principal coordinate analysis and Bayesian analysis for the K number of clusters showed that the individuals were dispersed in five (K= 5) clusters. The low levels of genetic diversity observed in these populations demonstrated that the populations from Mexico and Colombia need urgent management to recover their genetic variability.

The natural regeneration process allows the mangrove forests remain over time. Both, biological and physical factors can affect the establishment and early stages along the development of trees. This study examined the response of natural regeneration of mangroves in the Turbo River delta and El Uno bay (Urabá Gulf, Colombia) to intra-annual environmental variability. We quantified mortality, survival and recruitment of seedlings of three mangrove species, seasonally during one year, in 72 semi-permanent sub-plots of 1 m2. In the sub-plots, the total height and the diameter at the base of the stem of all mangrove seedlings with basal diameter less than 2.5cm were measured. Damage by herbivores was also recorded to each seedling. While Laguncularia racemosa recorded the highest rates of mortality, Rhizophora mangle showed the highest survival rate during the study period, although Avicennia germinans dominated the natural regeneration. Through a Redundancy Analysis these processes were associated to environmental variables such as: Direct Site Factor-DSF (sunlight), sediments input rate, herbivory, distances from mangroves to the river, to inner lakes, and to the coastline. These variables explained 43% of the natural regeneration variation; sedimentation rate was the most important variable, while light was very representative for the R. mangle survival. Based on historical records of precipitation, Turbo River flow rate and associated sediment loads, it was established that during the highest precipitation peak, the survival of all species decreases and during the dry season, when the conditions of flooding and sediments input were lower, it was improved. The results indicated that the sediments input rates and sunlight play an important role in the survival of natural regeneration of evaluated mangrove species.