Chloroplast DNA variation in the Quercus affinis–Q. laurina complex in Mexico: geographical structure and associations with nuclear and morphological variation

Abstract

The geographical distribution of chloroplast DNA (cpDNA) variation in 39 populations of two hybridizing Mexican red oaks, Quercus affinis and Q. laurina, was investigated using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Six haplotypes were identified. Of these, two (H1 and H4), separated by four mutations, had high frequencies (58 and 23% of the individuals, respectively) and were present across the whole geographical range of both species, often co occurring in the same populations. The other four haplotypes were rare, geographically restricted, and are probably derived from the two frequent haplotypes. Latitudinal or other clinal patterns in diversity levels or haplotype composition of populations were not apparent. The pattern of haplotype distribution was characterized by some mosaicism, with contrasting populations often situated in proximity. Average within-population diversity (hS=0.299) and population differentiation (GST=0.499) were, respectively, higher and lower than values reported in previous studies of oak species. There was evidence for phylogeographical structure, as indicated by NST (0.566) being significantly higher than GST. Haplotypic variation was largely species-independent, although some very weak associations were detected between haplotypes H1 and H4 and morphological and nuclear molecular variation correspondingly characterizing Q. affinis and Q. laurina. These oaks probably did not experience a marked restriction to one or a few particular subregions of their present range during the last glacial cycle. It is more likely that substantial populations persisted throughout several episodes of climatic change, but experienced recurrent latitudinal and altitudinal migrations which may have caused the widespread distribution of haplotypes H1 and H4 and frequent intermixing of populations.

High Rates of Gene Flow by Pollen and Seed in Oak Populations across Europe

“…Three stands (The Netherlands 98, Great Britain and Denmark) exhibited a global percentage of hybrid acorns of ≥ 30%. Widespread evidence of hybridisation exists in oak species, highly variable in direction and intensities (for recent examples see [59], [5], [7], [10], [6], [60]). Nevertheless, local hybridisation rates are certainly affected by a variety of factors such as tree density, flowering time, micro-environmental selection, species assignment, sampling strategy and the relative spatial arrangement of the species.…”

Diversity of galls induced by wasps (Hymenoptera: Cynipidae, Cynipini) associated with oaks (Fagaceae: <em>Quercus</em>) in Mexico

“…These zones are also suggested by the Q. crassifolia × Q. crassipes complex (TovarSánchez & Oyama 2004) in which three gall morphotypes were exclusively associated with the hybrid individuals found there (Tovar-Sánchez & Oyama 2006). However, this pattern cannot be generalized, since in another hybrid complex formed by Q. affinis × Q. laurina (González-Rodríguez et al 2004, only one gall morphotype was found in each of the species in this study (see Table 1). …”

Niche Divergence versus Neutral Processes: Combined Environmental and Genetic Analyses Identify Contrasting Patterns of Differentiation in Recently Diverged Pine Species

“…However, there is a broad area of overlap between P. strobiformis and P. ayacahuite mainly in the TMVB, an area that has already been identified as a contact zone for other temperate species (Fig. 2b; [48]). However, is important not to forget that ENMs are a simplification of the potential niche of a species and therefore, an over-prediction.…”