A saga of survival for seedlings of the rare mangrove Pelliciera rhizophorae

Background/Question/Methods

Successful seedling establishment is vital for plant population growth and colonization of new populations. For species comprised of few populations, seedling establishment may present a barrier to colonization of new sites. Pelliciera rhizophorae (the tea mangrove) is a rare mangrove species that occurs in Central and South America. The distribution of P. rhizophorae is restricted to a handful of populations in the Caribbean, with larger, more contiguous populations on the Pacific coast. The goals of this study were to 1) determine if plants from the Caribbean coast differ in seedling survival rates than plants from the Pacific coast; and 2) quantify seedling establishment rates of P. rhizophorae from in multiple habitats. Seedlings from the Caribbean and Pacific coasts of Panama were planted in common gardens. These common gardens were located on the Caribbean coast of Panama in three different forest types: Pelliciera canopy, Rhizophora canopy and open canopy. Survival, height and internodal length were measured in each canopy type for one year after planting.

Results/Conclusions

Survival and growth varied among habitat types and between plant origin (Caribbean or Pacific). Although initial mortality differed between seedlings of Caribbean and Pacific origin, ultimately the Kaplan-Meier survival curves were not significantly different between origin (Χ² = 1.5, df = 1, p = 0.218) or among habitats (X²= 1.3, df= 2, p=0.523). However, Caribbean seedlings were taller than Pacific seedlings in the Rhizophora canopy (t-test, t = 3.37, df = 11.8, p-value = 0.005). Growth did not differ significantly in the other habitat types. Despite its small population sizes and relative rarity in the Caribbean, Pelliciera rhizophorae seedlings of Caribbean origin grow faster than seedlings of Pacific origin, perhaps resulting from local adaptation.