The distribution, diversity, and conservation status of Cycas in China

Abstract

As ancient gymnosperm and woody plants, cycads have survived through dramatic tectonic activities, climate fluctuation, and environmental variations making them of great significance in studying the origin and evolution of flora biodiversity. However, they are among the most threatened plant groups in the world. The principal aim of this review is to outline the distribution, diversity, and conservation status of Cycas in China and provide suggestions for conservation practices. In this review, we describe the taxonomy, distribution, and conservation status of Cycas in China. By comparing Chinese Cycas species with its relatives worldwide, we then discuss the current genetic diversity, genetic differentiation of Cycas, and try to disentangle the potential effects of Quaternary climate changes and topographical events on Cycas. We review conservation practices from both researchers and practitioners for these rare and endangered species. High genetic diversity at the species level and strong genetic differentiation within Cycas have been observed. Most Cycas species in southwest China have experienced population retreats in contrast to the coastal Cycas's expansion during the Quaternary glaciation. Additionally, human activities and habitat fragmentation have pushed these endangered taxa to the brink of extinction. Although numerous efforts have been made to mitigate threats to Cycas survival, implementation and compliance monitoring in protection zones are currently inadequate. We outline six proposals to strengthen conservation measures for Cycas in China and anticipate that these measures will provide guidelines for further research on population genetics as well as conservation biology of not only cycads but also other endangered species worldwide.

Population Differentiation and Demographic History of the Cycas taiwaniana Complex (Cycadaceae) Endemic to South China as Indicated by DNA Sequences and Microsatellite Markers

“…Most Asian Cycas are narrowly distributed and have similar life history traits, such as dioecy, long life spans, anemophilous, or entomophilous (Feng et al, 2014). At the species level, C. fairylakea had lower genetic diversity based on cpDNA and SSR than other Asian Cycas species (Zheng et al, 2017). C. changjiangensis had high genetic diversity based on cpDNA and SCNGs, which is consistent with previous results based on allozyme analysis by Jian et al (2005c).…”

“…Cycads are the oldest and the most primitive group of gymnosperm. They share evolutionary history and morphological characteristics with ferns (spermatophytes with flagella) and gymnosperms (naked seeds) (Zheng et al, 2017). Therefore, cycads are an ideal objective to study the evolutionary history of seed plants.…”

“…However, molecular phylogenetic analyses indicated that the extant cycads underwent a synchronous global re-diversification and are not much more than 12 million years old (Nagalingum et al, 2011). In recent years, researchers have studied cycad phylogeny Wei et al, 2015), conservation (Feng et al, 2014;Feng et al, 2016;Feng et al, 2017;Gregory and Lopez-Gallego, 2018;Tang et al, 2018a;Zheng et al, 2017), biogeography (Gutiérrez-Ortega et al, 2017Meerow et al, 2018;Cabrera-Toledo et al, 2019), pollination biology (Tang et al, 2018b;Santiago-Jimnez et al, 2019), and physiology (Vovides and Galicia, 2016). Cycads comprise two families (Cycadaceae and Zamiaceae), with 10 genera and 355 accepted species (Calonje et al, 2019).…”

The Cycad Genus Cycas May Have Diversified From Indochina and Occupied Its Current Ranges Through Vicariance and Dispersal Events

“…These multiple frequent rises and falls of sea level would likely promoted long-distance dispersal of Cycas seeds across the Pacific Islands through to Australia, Madagascar and East Africa. For example, species in the subsection Rumphiae developed seeds with spongy layer inside the sclerotesta (de Laubenfels and Adema, 1998); the "spongy" characteristic of the seeds facilitates the floatation of the seeds, potentially promoting a long trans-oceanic dispersal across the Pacific Islands (de Laubenfels and Adema, 1998;Xiao and Möller, 2015;Zheng et al, 2017).…”

Transcriptome analysis of two radiated Cycas species and the subsequent species delimitation of the Cycas taiwaniana complex

“…Cycads belong to the cycad–ginkgo clade and are a sister group to other gymnosperms, meaning their study is informative for our understanding of seed plant evolution. In addition, the cycads are of great ornamental and economic value (Zheng et al., ; Liu et al., ). Although they survived three global extinction events in the past, cycads are now particularly vulnerable to anthropological activities, such as habitat loss and overexploitation.…”