Phylogeography of Podocarpus matudae (Podocarpaceae): pre‐Quaternary relicts in northern Mesoamerican cloud forests

Abstract

Aim Cloud forests of northern Mesoamerica represent the northern and southern limit of the contact zone between species otherwise characteristic of North or South America. Several phylogeographic studies featuring temperate conifer species have improved our understanding of species responses to environmental changes. In contrast, conifer species that presumably colonized northern Mesoamerica from South America are far less studied. A phylogeographic study of Podocarpus matudae (Podocarpaceae) was conducted to identify any major evolutionary divergences or disjunctions across its range and to determine if its current distribution is associated with pre-Quaternary climatic and/or longdistance dispersal events. Location Northern Mesoamerica (Mexico and Guatemala).Methods Sixteen populations (157 individuals) of P. matudae were screened for variation at two plastid DNA markers. The intra-specific phylogenetic relationships among haplotypes were reconstructed using Bayesian inference. Population genetic analyses were undertaken to gain insight into the evolutionary history of these populations. To test whether genetic divergence among populations occurred at different time-scales plastid DNA sequence data and fossil-and coalescent-based calibrations were integrated. ResultsThe combination of plastid markers yielded 11 haplotypes. Differentiation among populations based on DNA variation (G ST ) (0.707, SE 0.0807) indicated a clear population structure in P. matudae. Differentiation for ordered alleles (N ST ) (0.811, SE 0.0732) was higher than that for G ST , indicating phylogeographical structure in P. matudae. Most of the total variation (81.3%, P < 0.0001) was explained by differences among populations. The estimated divergence time between the unique haplotypes from a Guatemalan population and the two most common haplotypes from the Sierra Madre Oriental in Mexico was between 10 and 20 Ma, and further haplotype divergence in the poorly resolved clade of the Sierra Madre Oriental occurred between 3 and 0.5 Ma.Main conclusions Divergence estimations support the hypothesis that extant Podocarpus matudae populations are pre-Quaternary relicts. This finding is consistent with fossil and pollen data that support a Miocene age for temperate floristic elements in Mesoamerican cloud forests, whereas further haplotype divergence within the Sierra Madre Oriental, Chiapas and Guatemala occurred more recently, coinciding with Pleistocene cloud forest refugia.

Genetic diversity and structure of wild populations ofCarica papayain Northern Mesoamerica inferred by nuclear microsatellites and chloroplast markers

“…The Isthmus of Tehuantepec forms a narrow piece of lowland that separates the southcentral Mexican highlands (Sierra de Ju arez and Sierra Madre del Sur) from the highlands of Chiapas (Ornelas et al, 2010). It has been suggested that the isthmus was a seaway for much of the Pliocene (Morrone, 2006), and therefore a major barrier to gene flow during this period (Twyford et al, 2013).…”

Historical reconstruction of climatic and elevation preferences and the evolution of cloud forest-adapted tree ferns in Mesoamerica

“…In contrast, South American tropical tree genera extend into Mexico and Central America, usually in forests at lower altitudes (Williams-Linera, 1997). Several tree species in the region with temperate and tropical affinities are considered Tertiary relicts (Graham, 1999; Ornelas, Ruiz-Sanchez & Sosa, 2010; Ruiz-Sanchez & Ornelas, 2014). Paleoecological reconstruction in northern Mesoamerica indicates that the present disjunct distributions of temperate and montane cloud forest woody genera in Mexico and Central America have resulted from climate change during the late Tertiary and Pleistocene (Martin & Harrell, 1957; Graham, 1999), and that the colonization of tropical tree species and dynamics of cloud forests attributed solely to Pliocene processes has been obscured by Pleistocene climate changes (Figueroa-Rangel, Willis & Olvera-Vargas, 2010; Poelchau & Hamrick, 2013; Ramírez-Barahona & Eguiarte, 2014).…”

“…However, the shared phylogeographical breaks of cloud forest-adapted taxa occurred as multiple vicariant events at different times (Ornelas et al, 2013). In contrast, plant species that presumably colonized cloud forest in the region from South America are little studied (Ornelas, Ruiz-Sanchez & Sosa, 2010; Gutiérrez-Rodríguez, Ornelas & Rodríguez-Gómez, 2011; Ramírez-Barahona & Eguiarte, 2014; Ornelas & Rodríguez-Gómez, 2015; Ornelas et al, 2016). Population expansion due to Pleistocene climatic cycling has been uncovered in some of these cloud forest-adapted species that presumably originated in South America (Gutiérrez-Rodríguez, Ornelas & Rodríguez-Gómez, 2011; Ramírez-Barahona & Eguiarte, 2014; Ornelas & Rodríguez-Gómez, 2015; Ornelas et al, 2016) but the times of interspecific and intraspecific lineage divergence are temporally incongruent (Ornelas et al, 2013; Ramírez-Barahona & Eguiarte, 2014).…”

Comparative Phylogeographic Analyses Illustrate the Complex Evolutionary History of Threatened Cloud Forests of Northern Mesoamerica

“…Previous phylogeographic studies of the Mesoamerican cloud forest biodiversity have emphasized species that have migrated south from North America [10]–[13]. Few studies, however, have been conducted on representatives of the Mesoamerican biota hypothesized to have migrated from South America [14], [15]. The phylogeographic patterns of temperate tree species with North American origins have been mainly attributed to isolation and climate changes during Pleistocene glaciations that promoted the expansion, fragmentation, and divergence of populations [11], [16].…”