Abstract
Aim: Pleistocene (2.58 Ma–11.7 ka) climatic fluctuations have shaped intraspecific genetic patterns worldwide; however, their impact on species in many regions remains unknown. In order to determine the impact of Pleistocene climatic fluctuations on the tropical rain forests of western Ecuador, we explored the evolutionary history of the endemic palm Phytelephas aequatorialis. Location: Western Ecuador, north-western South America. Taxon: Phytelephas aequatorialis (Arecaceae). Methods: One hundred and seventy-six nuclear genes were sequenced in 91 individuals for phylogenomic and population structure analyses. The time of divergence between identified genetic lineages was estimated using a coalescent phylogenomic analysis. Palaeoecological niche modelling analyses were performed to determine areas of historical climatic suitability since the Last Glacial Maximum (LGM; 22 ka) that potentially acted as forest refugia during the Pleistocene. A Wilcoxon test and Pearson correlations were used to explore how current levels of genetic diversity, in terms of expected heterozygosity (Hs), have been shaped by several palaeoclimatic and geographic factors. Results: Phylogenomic and population structure analyses revealed two main genetic lineages with a north–south distribution, which diverged 1.14 Ma during the Pleistocene. Two potential Pleistocene refugia were identified, one along the Pacific coast of Ecuador and one in the Andean foothills of south-western Ecuador. The location of these refugia agrees with the spatial location of the two genetic lineages. Within the Andean foothills, Hs was lower for the southern lineage than for the northern lineage. Hs significantly increased with decreasing latitude across the species as a whole. Main conclusions: Pleistocene climatic fluctuations promoted intraspecific divergence in P. aequatorialis within the rain forests of western Ecuador. The Andean foothills of south-western Ecuador could be an important area for rain forest evolution because they potentially remained climatically suitable throughout the Pleistocene. Lower genetic diversity in the southern lineage, which apparently remained isolated in the Andean foothills during glacial cycles, adds evidence to the presence of a forest refugium in south-western Ecuador. The geographic pattern in genetic diversity suggests that P. aequatorialis colonized western Ecuador from the north. This study supports the role of Pleistocene climatic fluctuations in promoting intraspecific divergence, and for the first time, we show their impact west of the Andes.
| Original language | English |
|---|---|
| Pages (from-to) | 1023-1037 |
| Number of pages | 15 |
| Journal | Journal of Biogeography |
| Volume | 48 |
| Issue number | 5 |
| DOIs | |
| State | Published - 17 Jan 2021 |
Bibliographical note
Publisher Copyright:© 2021 The Authors. Journal of Biogeography published by John Wiley & Sons Ltd.
Funding
We thank Ecuador's Ministerio del Ambiente for providing the sampling permit to undertake this research (MAE-DNB-CM-2018-0082). We also thank Rodrigo Bernal for providing leaf material. This research was financially supported by the SENESCYT (PhD scholarship to S.E.), the Independent Research Fund Denmark (9040-00136B to H.B.), the Agence Nationale de la Recherche (ANR-15- CE02-0002-01 to T.L.P.C.) and the International Mixed Laboratory (LMI) BIO_INCA. We are also very grateful to the generous financial support provided by the International Palm Society (IPS) for funding a field trip to western Ecuador without which part of the sampling would not have been possible (field grant to S.E.). We dedicate this article to Dr. Calaway H. Dodson (1928-2020), botanist and orchidologist, who worked for many years on the flora of Ecuador and authored the five volumes of 'Orchids of Ecuador'. He was also the first Honorary Director of the Herbario Nacional del Ecuador (QCNE), now part of the Museo Ecuatoriano de Ciencias Naturales in Quito, Ecuador. We thank Ecuador's Ministerio del Ambiente for providing the sampling permit to undertake this research (MAE‐DNB‐CM‐2018‐0082). We also thank Rodrigo Bernal for providing leaf material. This research was financially supported by the SENESCYT (PhD scholarship to S.E.), the Independent Research Fund Denmark (9040‐00136B to H.B.), the Agence Nationale de la Recherche (ANR‐15‐ CE02‐0002‐01 to T.L.P.C.) and the International Mixed Laboratory (LMI) BIO_INCA. We are also very grateful to the generous financial support provided by the International Palm Society (IPS) for funding a field trip to western Ecuador without which part of the sampling would not have been possible (field grant to S.E.). We dedicate this article to Dr. Calaway H. Dodson (1928‐2020), botanist and orchidologist, who worked for many years on the flora of Ecuador and authored the five volumes of 'Orchids of Ecuador'. He was also the first Honorary Director of the Herbario Nacional del Ecuador (QCNE), now part of the Museo Ecuatoriano de Ciencias Naturales in Quito, Ecuador.
| Funders | Funder number |
|---|---|
| International Mixed Laboratory | |
| International Palm Society | |
| LMI | |
| Ministerio del Ambiente | MAE-DNB-CM-2018-0082 |
| Museo Ecuatoriano de Ciencias Naturales in Quito | |
| Agence Nationale de la Recherche | ANR‐15‐ CE02‐0002‐01 |
| Secretaría de Educación Superior, Ciencia, Tecnología e Innovación | |
| Danmarks Frie Forskningsfond | 9040‐00136B |
Keywords
- Arecaceae
- ecological niche modelling
- genetic diversity
- last glacial maximum
- north–south genetic discontinuity
- phylogenomics
- phylogeography
- population structure
- rain forest