Abstract
Parrotia subaequalis (Hamamelidaceae) is a Tertiary relic species endemic in eastern China. We used inter-simple sequence repeat (ISSR) markers to access genetic diversity and population genetic structure in natural five populations of P.subaequalis. The levels of genetic diversity were higher at species level (H=0.2031) but lower at population level (H=0.1096). The higher genetic diversity at species levels might be attributed to the accumulation of distinctive genotypes which adapted to the different habitats after Quaternary glaciations. Meanwhile, founder effects on the early stage, and subsequent bottleneck of population regeneration due to its biological characteristics, environmental features, and human activities, seemed to explain the low population levels of genetic diversity. The hierarchical AMOVA revealed high levels (42.60%) of among-population genetic differentiation, which was in congruence with the high levels of Nei's genetic differentiation index (G ST=0.4629) and limited gene flow (N m=0.5801) among the studied populations. Mantel test showed a significant isolation-by-distance, indicating that geographic isolation has a significant effect on genetic structure in this species. Unweighted pair-group method with arithmetic average clustering, PCoA, and Bayesian analyses uniformly recovered groups that matched the geographical distribution of this species. In particular, our results suggest that Yangtze River has served as a natural barrier to gene flow between populations occurred on both riversides. Concerning the management of P.subaequalis, the high genetic differentiation among populations indicates that preserving all five natural populations insitu and collecting enough individuals from these populations for ex situ conservation are necessary.
Highlights
Parrotia subaequalis (Li et al 1997, 1999; Hao and Wei 1998) has fascinated botanists for its unique systematic position within Hamamelidaceae and for its Critically Endangered status
Ecology and Evolution published by John Wiley & Sons Ltd
Across all 139 P. subaequalis individuals form the five populations, a total of 108 reproducible bands were presented from the ten inter-simple sequence repeat (ISSR) primer set
Summary
Parrotia subaequalis (Li et al 1997, 1999; Hao and Wei 1998) has fascinated botanists for its unique systematic position within Hamamelidaceae and for its Critically Endangered status (sensu IUCN). The species remained in obscurity until 1992 when flowering plants were discovered and a new morphological study revealed that they have a set of unique floral traits not found in other members of the Hamamelidaceae. Among these unusual morphological characters, the most distinctive one is the presence of apetalous bisexual flowers. Subsequent molecular data suggested that Shaniodendron is sister to the West Asian species Parrotia persica (Li et al 1997, 1999) This phylogenetic placement resulted in the transfer of S. subaequale to Parrotia as P. subaequalis (Hao et al 1996; Li et al 1997, 1999; Hao and Wei 1998).
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