Differences in sculpture and size of pollen grains: new morphological evidence of diversification in Pelliciera rhizophorae, an ancient Neotropical mangrove species

Abstract

The present study shows new evidence of morphological traits that supports the hypothesis of diversification between two genetic variants of Pelliciera rhizophorae (Tetrameristaceae), the most ancient species in the Neotropical mangrove ecosystem. Previous studies using molecular markers identified two variants of this species. Our new study, using pollen grain morphology, revealed differences in pollen sculpture between the two variants; that is, in Variant A the exine is characterised as perforate–verrucose, while in Variant B, it is punctuate. Pollen size in Variant A is larger than in Variant B, whereas the exine is thicker in Variant B than in Variant A. The differences in pollen morphology between the two variants represent new evidence suggesting that a diversification process might be occurring within P. rhizophorae, possibly due to adaptive processes in response to environmental conditions or pollination vectors.

Keywords:

• pollen morphology
• diversification
• exine sculpture
• Pelliciera rhizophorae
• Neotropics
• mangroves

Acknowledgements

We are grateful to the institutions that supported the development of this research: the International Foundation for Science (IFS) for funding this study (grant D/3832-3); logistical support provided by the Universidad del Valle (UNIVALLE) in Colombia, and the Smithsonian Tropical Research Institute (STRI) in Panama. We would also like to thank the STRI scientists who collaborated on this study: biologist Jorge Ceballos (support in SEM and LSCM), and Enrique Moreno (scientific expert in palynology). We are grateful to biologists Alonso Santos and Daniel Buitrago (fieldwork), as well as to José Alejandro Ramirez, an undergraduate student (Universidad de Panamá), for his support in fieldwork and slide preparation.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

International Foundation for Science

Notes on contributors

María Fernanda Castillo-Cárdenas

MARÍA FERNANDA CASTILLO-CÁRDENAS has been a contractor at the STRI in Panama since 2011. She graduated from UNIVALLE (Columbia) with a degree in biology with a major in genetics in 1999, an MSc in 2003 and a PhD in 2009. Her career has been dedicated to conducting studies in plant population genetics using molecular tools. She is a member of the Study Group in Ecogenetics and Molecular Biology research team at UNIVALLE. She has been working with the mangrove species Pelliciera rhizophorae since she began her graduate studies. Her first work on this species was carried out on Colombian populations from the Pacific Coast. Afterwards, her doctoral dissertation was dedicated to evaluating the phylogeography and population genetics of P. rhizophorae in populations on Neotropical coasts in its distribution range. Currently, her research is focused on the morphology and cytology of this mangrove species.

Oris Sanjur

ORIS SANJUR is the Associate Director for Science Administration at the STRI. She graduated from the Universidad de Panama with a degree in biology in 1991 and a PhD in cellular biology and development from Rutgers University (New Jersey, USA) in 1998. She was president of the Panamanian Association for the Advancement of Science (APANAC) from 2006 to 2009. She has been a member of the Board of Directors of the Coiba National Park biological station, the International Center for Sustainable Development (CIDES) and the Phytogenetic National Committee for the Ministry of Agricultural and Livestock Development (MIDA) in Panama. Her research interests have focused on evolutionary, systematic and ecological issues in Neotropical plants and animal species.

Nelson Toro-Perea

NELSON TORO-PEREA is associate professor in the Department of Biology at UNIVALLE (Colombia). He graduated from UNIVALLE with a degree in biology in 1986, an MSc in 1991 and a PhD from Vrije Universiteit Brussel (Belgium) in 1996. He is Director of the Study Group in Ecogenetics and Molecular Biology research team at UNIVALLE. He was one of the leaders of the first project in population genetics of mangrove species from the Colombian Pacific in 1998. His research has focused on biotechnology applied to conservation biology, ecogenetics in tropical ecosystems and barcoding as a tool in biological pest control.