Interspecific phylogenetic analysis enhances intraspecific phylogeographical inference: a case study in Pinus lambertiana

Abstract

Pinus lambertiana (sugar pine) is an economically and ecologically important conifer with a 1600-km latitudinal range extending from Oregon, USA, to northern Baja California, Mexico. Like all North American white pines (subsect. Strobus), sugar pine is highly susceptible to white pine blister rust, a disease caused by the fungus Cronartium ribicola. We conducted a chloroplast DNA (cpDNA) survey of Pinus subsect. Strobus with comprehensive geographical sampling of P. lambertiana. Sequence analysis of 12 sugar pine individuals revealed strong geographical differentiation for two chloroplast haplotypes. A diagnostic restriction site survey of an additional 72 individuals demarcated a narrow 150-km contact zone in northeastern California. In the contact zone, maternal (megagametophtye) and paternal (embryo) haplotypes were identified in 31 single seeds, demonstrating bidirectional pollen flow extending beyond the range of maternal haplotypes. The frequencies of the Cr1 allele for white pine blister rust major gene resistance, previously determined for 41 seed zones, differ significantly among seed zones that are fixed for the alternate haplotypes, or contain a mixture of both haplotypes. Interspecific phylogenetic analysis reveals that the northern sugar pine haplotype belongs to a clade that includes Pinus albicaulis (whitebark pine) and all of the East Asian white pines. Furthermore, there is little cpDNA divergence between northern sugar pine and whitebark pine (dS = 0.00058). These results are consistent with a Pleistocene migration of whitebark pine into North America and subsequent chloroplast introgression from whitebark pine to sugar pine. This study demonstrates the importance of placing phylogeographical results in a broader phylogenetic context.

Genetic diversity and structure of western white pine (Pinus monticola) in North America: a baseline study for conservation, restoration, and addressing impacts of climate change

“…Similar to WWP, the discontinuities in cpDNA haplotypes typically occurred in southern or central Oregon and were attributed to influences resulting from Pleistocence glaciation (Soltis et al 1997). Moreover, a recent study of sugar pine (Pinus lambertiana) found an abrupt discontinuity in cpDNA haplotypes between the Cascade Range and Sierra Mountains in northern California (Liston et al 2007). …”

Genetic divergence, range expansion and possible homoploid hybrid speciation among pine species in Northeast China

“…mongolica and P. densiflora in the wild as reported to have occurred between some other pine species (Watano et al, 2004;Liston et al, 2007;Wachowiak and Prus-G"owacki, 2008). Such unidirectional hybridization might have two alternative causes.…”

“…This independent inheritance of two cytoplasmic genomes provides the opportunity for tracing paternal and maternal genetic changes within a single species because of different rates of gene flow and for discriminating female and male parents of hybrids (Ennos, 1994;Liston et al, 2007;Wachowiak and Prus-G"owacki, 2008). In addition, the analysis of multiple nuclear loci can be used to examine interspecific divergence and clarify parental origins of putative hybrid species (for example, Ma et al, 2006;Li et al, 2010).…”

Discordant mtDNA and cpDNA phylogenies indicate geographic speciation and reticulation as driving factors for the diversification of the genus Picea

“…Such a dispersal pattern has been inferred for Tsuga (LePage 2003) and Pinus (e.g. Liston et al 2007). This dispersal scenario, distinct and presumably earlier than that involving the rest of the North American taxa, is in agreement with the status of P. breweriana, considered as the most primitive and divergent taxon in North America (Weng and Jackson 2000), based on crossing experiments (Gordon 1986) and molecular evidence (Ledig et al 2004).…”