Different patterns of colonization of Oxalis alpina in the Sky Islands of the Sonoran desert via pollen and seed flow

Abstract

Historical factors such as climatic oscillations during the Pleistocene epoch have dramatically impacted species distributions. Studies of the patterns of genetic structure in angiosperm species using molecular markers with different modes of inheritance contribute to a better understanding of potential differences in colonization and patterns of gene flow via pollen and seeds. These markers may also provide insights into the evolution of reproductive systems in plants. Oxalis alpina is a tetraploid, herbaceous species inhabiting the Sky Island region of the southwestern United States and northern Mexico. Our main objective in this study was to analyze the influence of climatic oscillations on the genetic structure of O. alpina and the impact of these oscillations on the evolutionary transition from tristylous to distylous reproductive systems. We used microsatellite markers and compared our results to a previous study using chloroplast genetic markers. The phylogeographic structure inferred by both markers was different, suggesting that intrinsic characteristics including the pollination system and seed dispersal have influenced patterns of gene flow. Microsatellites exhibited low genetic structure, showed no significant association between geographic and genetic distances, and all individual genotypes were assigned to two main groups. In contrast, chloroplast markers exhibited a strong association between geographic and genetic distance, had higher levels of genetic differentiation, and were assigned to five groups. Both types of DNA markers showed evidence of a northward expansion as a consequence of climate warming occurring in the last 10,000 years. The data from both types of markers support the hypothesis for several independent transitions from tristyly to distyly.

Historical connections among river basins and climatic changes explain the biogeographic history of a water rat

“…The small number of microsatellite loci used and their capability of detecting the true population structure is another plausible explanation for the discrepancy between this marker and mtDNA. Other recent studies using a similar number of microsatellite markers in other organisms ( Pérez-Alquicira et al, in press ; Villamor, Costantini & Abbiati, in press ; Zheng et al, in press ) also found significant genetic structure in some cases. Another study using the same microsatellite loci ( Maroja, Almeida & Seuánez, 2003 ) found significant genetic differentiation in N. squamipes samples from a very small geographic area (maximum distance among sites = 6 km).…”

Peer Review #2 of "Historical connections among river basins and climatic changes explain the biogeographic history of a water rat (v0.1)"

“…The small number of microsatellite loci used and their capability of detecting the true population structure is another plausible explanation for the discrepancy between this marker and mtDNA. Other recent studies using a similar number of microsatellite markers in other organisms (Pérez-Alquicira et al, 2018;Villamor et al, 2018;Zheng et al, 2018) also found significant genetic structure in some cases. Another study using the same microsatellite loci found significant genetic differentiation in N. squamipes samples from a very small geographic area (maximum distance among sites = 6 km).…”

Evidence for spatial clines and mixed geographic modes of speciation for North American cherry‐infesting Rhagoletis (Diptera: Tephritidae) flies

“…But this is not always the case. With respect to the issue of clines, latitudinal variation has been detected within some SW and NoM species, which has been argued to have resulted from the movement of populations as glaciers advanced and retreated during the Pleistocene (e.g., Perez-Alquicira, Weller, Domínguez, Molina-Freaner, & Tsyusko, 2018;Potter, Hipkins, Mahalovich, & Means, 2015). In addition, a suture zone has been postulated to exist between southeastern Arizona and southwestern New Mexico in which hybrid zones between trees, birds, and mammals appear to be concentrated above background (Swenson & Howard, 2005).…”