Life on Edge: Central/peripheral populations of Picea sitchensis Bong.(Carr).
Mimura, Makiko*,1, Aitken, Sally1, 1 Forest Sciences, and Centre for Forest Gene Conservation, Vancouver, BC, Canada
ABSTRACT- Peripheral populations are usually smaller and inhabit less optimal environments than core populations. Gene flow can accelerate local adaptation by providing genetic variation into peripheral populations, or it can inhibit local adaptation at range peripheries by introducing maladapted alleles. Disjunct peripheral populations may be 1) locally adapted due to selection and isolation or 2) severely maladapted due to small population size, low genetic diversity and inbreeding. Understanding how distributions of species' range affect its local adaptation will provide us a guideline for better ex situ conservation strategies. We examined gamete pools of pollen, a major determinant of gene flow in wind-pollinated conifers, and evaluated some fitness-related quantitative growth traits to understand the evolutionary dynamics and fitness of peripheral populations. Ritland's MTLR estimated that outcrossing rate significantly decreased at the peripheral populations compared to the central populations. The estimated number of effective pollen donors per family ranged from 2.1 to 18.9, being highest in the central continuous population and lowest in the disjunct peripheral population. Multiple common garden experiments indicated that the disjunct peripheral populations were not under inbreeding depression regardless of their high biparental inbreeding rates. Thus, these results suggest that wind-pollinated conifer species may, at least in the short term, show resilience to isolation and inbreeding because of their high fecundity and longevity, and isolation may even accelerate local selection. This implies that peripheral isolated populations of conifer species are potential sources of adaptive genes to extreme environments and of recovery for populations.
Key words: Picea sitchensis, local adaptation, population locations, phenotypic and genetic variation
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