A comparative study on genetic effects of artificial and natural habitat fragmentation on Loropetalum chinense (Hamamelidaceae) in Southeast China

Abstract

Elucidating the demographic and landscape features that determine the genetic effects of habitat fragmentation has become fundamental to research in conservation and evolutionary biology. Land-bridge islands provide ideal study areas for investigating the genetic effects of habitat fragmentation at different temporal and spatial scales. In this context, we compared patterns of nuclear microsatellite variation between insular populations of a shrub of evergreen broad-leaved forest, Loropetalum chinense, from the artificially created Thousand-Island Lake (TIL) and the Holocene-dated Zhoushan Archipelago of Southeast China. Populations from the TIL region harboured higher levels of genetic diversity than those from the Zhoushan Archipelago, but these differences were not significant. There was no correlation between genetic diversity and most island features, excepting a negative effect of mainland-island distance on allelic richness and expected heterozygosity in the Zhoushan Archipelago. In general, levels of gene flow among island populations were moderate to high, and tests of alternative models of population history strongly favoured a gene flow-drift model over a pure drift model in each region. In sum, our results showed no obvious genetic effects of habitat fragmentation due to recent (artificial) or past (natural) island formation. Rather, they highlight the importance of gene flow (most likely via seed) in maintaining genetic variation and preventing inter-population differentiation in the face of habitat 'insularization' at different temporal and spatial scales.

Scale-dependent effects of habitat fragmentation on the genetic diversity of Actinidia chinensis populations in China

“…ZSA is an oceanic island that has undergone long-term isolation of ca. 7000-9000 years 27 . Long-term oceanic isolation decreased the genetic diversity and increased the genetic differentiation of insular populations, while there were small genetic effects on the TIL islands that experienced short-term isolation by water.…”

“…The Zhoushan Archipelago (ZSA), located in the East China Sea, was originally a part of mainland China and formed by rising sea levels ca. 7000-9000 years ago 27 (Fig. 1).…”

“…However, some studies did not find negative effects of habitat fragmentation on genetic diversity 21 , 22 . The differentiated effects of habitat fragmentation on genetic diversity may be associated with species characteristics (e.g., mating pattern), environmental features (e.g., landscape attributes) 23 – 25 , or the scale of habitat fragmentation 26 , 27 . Compared to monoecious plants, dioecious plants have higher potential for adaptation and higher genetic diversity because they have higher selection efficacy both against deleterious mutations and for beneficial mutations 28 .…”

Forest fragmentation in China and its effect on biodiversity

“…They have been the focus of long‐term biodiversity monitoring since 2002 for a wide range of taxa, including birds (Ding et al , ; Si et al , ), plants (Hu et al , ; Yu et al , ), spiders (Wu et al , ), reptiles (Wang et al , , ), amphibians (Wang, Lane, & Ding, ) and mammals (Wang et al , ; Xu et al , ). These studies explored the biodiversity distribution patterns, including alpha and beta diversity (Yu et al , ; Si et al , ), in these newly formed islands through a genetic‐, species‐, functional‐ and phylogenetic‐based approach (Yu et al , ; Ding et al , ; Yuan et al , ; Si et al , ), and by considering temporal changes in biodiversity (Hu et al , ; Song et al , ) aim to explore the mechanisms of biodiversity maintenance in these fragmented islands (Wilson et al , ). These studies have shown that biological communities are less diverse, more functionally similar and phylogenetically clustered on small and isolated islands (Ding et al , ; Si et al , ).…”

“…They have been the focus of long-term biodiversity monitoring since 2002 for a wide range of taxa, including birds Si et al, 2017), plants (Hu et al, 2011a;Yu et al, 2012), spiders , reptiles (Wang et al, 2010c, amphibians (Wang, Lane, & Ding, 2012) and mammals (Wang et al, 2010c;Xu et al, 2014). These studies explored the biodiversity distribution patterns, including alpha and beta diversity (Yu et al, 2012;Si et al, 2016), in these newly formed islands through a genetic-, species-, functional-and phylogenetic-based approach (Yu et al, 2012;Ding et al, 2013;Yuan et al, 2015;Si et al, 2017), and by considering temporal changes in biodiversity Song et al, 2018) aim to explore the mechanisms ; around Menglun town in Xishuangbanna ; areas suitable for gibbons in tropical Hainan (Zhang et al, 2010a); and the Taibai Mountain Nature Reserve in Shaanxi (Sun et al, 2009a). The proportion of patches in each size category is shown.…”