Abstract
The genetic impact of barriers and Pleistocene glaciations on high latitude resident species has not been widely investigated. The Clark’s nutcracker is an endemic North American corvid closely associated with Pinus-dominated forests. The nutcracker’s encompasses known barriers to dispersal for other species, and glaciated and unglaciated areas. Clark’s nutcrackers also irruptively disperse long distances in search of pine seed crops, creating the potential for gene flow among populations. Using the highly variable mitochondrial DNA control region, seven microsatellite loci, and species distribution modeling, we examined the effects of glaciations and dispersal barriers on population genetic patterns and population structure of nutcrackers. We sequenced 900 bp of mitochondrial control region for 169 individuals from 15 populations and analysed seven polymorphic microsatellite loci for 13 populations across the Clark’s nutcracker range. We used species distribution modeling and a range of phylogeographic analyses to examine evolutionary history. Clark’s nutcracker populations are not highly differentiated throughout their range, suggesting high levels of gene flow among populations, though we did find some evidence of isolation by distance and peripheral isolation. Our analyses suggested expansion from a single refugium after the last glacial maximum, but patterns of genetic diversity and paleodistribution modeling of suitable habitat were inconclusive as to the location of this refugium. Potential barriers to dispersal (e.g. mountain ranges) do not appear to restrict gene flow in Clark’s nutcracker, and postglacial expansion likely occurred quickly from a single refugium located south of the ice sheets.
Highlights
Phylogeography is the study of processes underlying spatial and temporal dimensions of genetic variation [1]
We investigated the potential impact of barriers on genetic variation by performing a spatial analysis of molecular variance (SAMOVA; K = 2-12; 100 iterations) [42]; the process cannot test for rangewide panmixia as K cannot be set to K = 1
In the case of microsatellite data, these results should be interpreted with caution as both STRUCTURE and BAPS may struggle with situations where differentiation is low (FST < 0.030) [56], though global values (FST = 0.070) suggest this is likely not the case
Summary
Phylogeography is the study of processes underlying spatial and temporal dimensions of genetic variation [1]. Patterns of genetic variation attained through phylogeographic methods can provide insights into population-level response to disturbance and the processes responsible for historical dispersal and colonization [2,3]. Contemporary genetic patterns are strongly influenced by postglacial expansion from refugia [5,6], historical and contemporary barriers to dispersal [7,8], and dispersal potential [9]. Multiple expansions and contractions of ice sheets created a dynamic landscape that repeatedly fragmented historical populations, alternately creating barriers to dispersal and creating new habitats for colonization [10,11]. During the Pleistocene glacial maxima in North America, many populations were confined to refugia (ice-free areas) [10]. Additional areas along the periphery of the ice sheets are contested to have been ice-free, such as an Atlantic shelf near present-day Newfoundland [5,10,13]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
