Post-glacial expansion and population genetic divergence of mangrove species Avicennia germinans (L.) Stearn and Rhizophora mangle L. along the Mexican coast.
Mangrove forests in the Gulf of California, Mexico represent the northernmost populations along the Pacific coast and thus they are likely to be source populations for colonization at higher latitudes as climate becomes more favorable. Today, these populations are relatively small and fragmented and prior research has indicated that they are poor in genetic diversity. Here we set out to investigate whether the low diversity in this region was a result of recent colonization, or fragmentation and genetic drift of once more extensive mangroves due to climatic changes in the recent past. By sampling the two major mangrove species, Rhizophora mangle and Avicennia germinans, along the Pacific and Atlantic coasts of Mexico, we set out to test whether concordant genetic signals could elucidate recent evolution of the ecosystem. Genetic diversity of both mangrove species showed a decreasing trend toward northern latitudes along the Pacific coast. The lowest levels of genetic diversity were found at the range limits around the Gulf of California and the outer Baja California peninsula. Lack of a strong spatial genetic structure in this area and recent northern gene flow in A. germinans suggest recent colonization by this species. On the other hand, lack of a signal of recent northern dispersal in R. mangle, despite the higher dispersal capability of this species, indicates a longer presence of populations, at least in the southern Gulf of California. We suggest that the longer history, together with higher genetic diversity of R. mangle at the range limits, likely provides a gene pool better able to colonize northwards under climate change than A. germinans.
Escuela de Ciencias de la Salud, Universidad Autónoma de Baja California, Ensenada, Baja California, México; Facultad de Ciencias Marinas, Universidad Autónoma de Baja California, Ensenada, Baja California, México.
Eduardo
E
Sandoval-Castro
Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, California, United States of America.
Richard S
RS
Dodd
Departamento Académico de Biología Marina, Universidad Autónoma de Baja California Sur, La Paz, Baja California Sur, México.
Rafael
R
Riosmena-Rodríguez
Facultad de Ciencias Marinas, Universidad Autónoma de Baja California, Ensenada, Baja California, México.
Luis Manuel
LM
Enríquez-Paredes
El Colegio de la Frontera Sur, Tapachula, Chiapas, México.
Cristian
C
Tovilla-Hernández
Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, California, United States of America.
Juan Manuel
JM
López-Vivas
Instituto Tecnológico Superior de Villa La Venta, Huamanguillo, Tabasco, México.
Bily
B
Aguilar-May
Escuela de Ciencias de la Salud, Universidad Autónoma de Baja California, Ensenada, Baja California, México.
Raquel
R
Muñiz-Salazar
D032407:Avicennia / Q000235:genetics*; D002140:California; D002980:Climate; D057231:Climate Change; D017753:Ecosystem; D051456:Gene Flow / Q000235:genetics; D014644:Genetic Variation / Q000235:genetics*; D005828:Genetics, Population / Q000379:methods; D005843:Geography; D008800:Mexico; D018895:Microsatellite Repeats / Q000235:genetics; D018515:Plant Leaves / Q000235:genetics; D043982:Rhizophoraceae / Q000235:genetics*