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Title: Shifting migration patterns without genetic erosion: evidence from the Zamia pumila complex (Cycadales: Zamiaceae) at the northern of the Caribbean island biodiversity hotspot

Author
item SALAS-LEIVA, DAYANA - Mars, Inc
item Meerow, Alan
item CALONIE, MICHAEL - Montgomery Botanical Center
item FRANSISCO-ORTEGA, JAVIER - Florida International University
item GRIFFITH, PATRICK - Montgomery Botanical Center
item Nakamura, Kyoko
item Tondo, Cecile
item SANCHEZ, VANESSA - Mars, Inc
item KNOWLES, LINDY - Bahamas National Trust
item KNOWLES, DAVID - Bahamas National Trust

Submitted to: American Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/10/2017
Publication Date: 5/23/2017
Citation: Salas-Leiva, D., Meerow, A.W., Calonie, M., Fransisco-Ortega, J., Griffith, P., Nakamura, K., Tondo, C.L., Sanchez, V., Knowles, L., Knowles, D. 2017. Shifting migration patterns without genetic erosion: evidence from the Zamia pumila complex (Cycadales: Zamiaceae) at the northern of the Caribbean island biodiversity hotspot. American Journal of Botany. 104:757-771.

Interpretive Summary: The Bahamas archipelago is the northernmost land area of the Caribbean island biodiversity hotspot (CIBH). It consist of several geologically stable banks that provide direct evidence of global sea level changes that are valuable for understanding the relationship between climate and demographic changes inplant populations. We were interested to know if there are signatures of major changes on Quaternary gene flow patterns among population on the CIBH and reconstructed the history of the monophyletic Zamia pumila complex across the Bahamas. We tested several gene flow models, estimated the historical effective population sizes, and searched for signatures of possible demographic contractions/expansions of the populations. We detected gene flow and demographic/spatial expansion that supports colonization of the Little Bahamas paleo-province from the Grand Bahamas paleo-province. Populations maintained high migration rates that shifted to a restricted rate as sea levels rose. Two separate introductions of Zamia into the Bahamas were detected. Andros Island is implicated as the ancestral source for migration of Z. integrifolia towards islands of both paleo-provinces. We conclude that gene flow patterns on the Bahamas appear to be in synchrony with global climate change in the Quaternary and may act as buffer to contain genetic erosion. This has implications for managing biodiversity in the CIBH as seas levels continue to rise.

Technical Abstract: The Bahamas archipelago is the northernmost land area of the Caribbean island biodiversity hotspot (CIBH). It is defined by several banks composed of quaternary carbonates that are tectonically stable. Such stability has provided direct geological evidence of global ice-volume changes that is valuable for our understanding of the relationship between climate and demographic changes. We were interested to know if there are signatures of major changes on Quaternary gene flow patterns among population on the CIBH and reconstructed the phylogeographic history of the monophyletic Zamia pumila complex across the Bahamas. We tested several gene flow models, estimated the historical effective population sizes, and searched for signatures of possible demographic contractions/expansions of the populations. We detected gene flow and demographic/spatial expansion that supports colonization of the Little Bahamas paleo-province from the Grand Bahamas paleo-province around the Piancezian/Gelasian (Quaternary). Populations maintained a full migration model with high migration rates that shifted to a source-sink migration model with restricted rates. Two separate introductions of Zamia into the Bahamas were detected. Andros Island is implicated as the ancestral source for migration of Z. integrifolia towards islands of both paleo-provinces. Contemporaneous divergence among populations dates back to the beginning of Marine Isotope Stage 1 (MIS 1, current deglaciation), while lower genetic differentiation coincides with MIS 2 (last glacial period). We conclude that gene flow patterns on the Bahamas appear to be in synchrony with global climate change in the Quaternary and may act as buffer to contain genetic erosion.