Abstract
Mating system has important implications for the genetic structure and diversity of populations, especially threatened and endangered species. In this study, mating system of the endangered aquatic fern Ceratopteris pteridoides in China was investigated using AFLP markers and selfing test. The results of AFLP analyses showed that the estimate of multilocus outcrossing rate (tm) was high at species level (tm = 0.999), indicating that C. pteridoides is a predominant outcrossing species. The small differences between tm and ts (0.136 ± 0.003) at species level showed that there is a low tendency for mating between relatives. The selfing test showed that isolated gametophytes formed the rate of normal sporophytes in three populations (BLH, ZDH, WCH) ranging from 72.9% to 77.8% with a mean value of 75.2%, indicating that C. pteridoides has a high level of intragametophytic selfing potential. Our investigation found that some of the studied populations of C. pteridoides have a prolific capacity for vegetative reproduction (clonal growth). The results revealed that the diploid homosporous pteridophyte C. pteridoides predominantly favors gametophytic crossing with a certain level of inbreeding along with clonal growth. We suggest that mating system of C. pteridoides may be adjusted to promote selfing rate in response to factors including the characteristics of hermaphrodite, and colonization events and small extant populations. As a result of the high outcrossing rate of C. pteridoides, we recommend that ex situ plantings would be most suitable for enhancing possible intermingling of the different populations thus minimizing inbreeding.
Highlights
Ceratopteris (Parkerkiaceae) is a genus of ferns that occurs in the New World and Old World tropics and subtropics
These highthroughput marker technologies allow for the analysis of a large number of individuals with a large number of markers in a relatively short time, as only a few random amplified polymorphic DNA (RAPD) primers, inter simple sequence repeats (ISSRs) primers or a single amplified fragment length polymorphism (AFLP) primer pair allow the generation of sufficient markers to obtain a robust estimate of outcrossing rate (Gaiotto et al, 1997; Han et al, 2009; Sinha et al, 2015)
The present study indicates that AFLP markers which are dominant with lower information content than co-dominant markers, such as allozyme and SSR markers, are suitable for investigating mating system in C. pteridoides
Summary
Ceratopteris (Parkerkiaceae) is a genus of ferns that occurs in the New World and Old World tropics and subtropics. The genus contains six species (C. cornuta, C. pteridoides, C. richardii, C. thalictroides, C. froesii, and C. siliquosa), which exhibit one of three mating systems: automixis, autogamy, and xenogamy (Lloyd, 1974a; Hickok et al, 1995). Two species of Ceratopteris (C. thalictroides and C. pteridoides) occur in China (Diao, 1990). Self-fertilization of a single gametophytes is termed intragametophytic selfing or automixis; Random crosses between gametophytes (sib gametophytes) produced from spores of the same sporophyte has been termed intergametophytic selfing or autogamy and is equivalent to cross-selfing in higher plants; Crosses between gametophytes (non-sib gametophytes) produced from spores of different sporophytes has been termed intergametophytic crossing or xenogamy and is equivalent to crossing in higher plants. Ceratopteris exhibits a biphasic life cycle with independent autotrophic haploid and diploid generations
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