Table of Contents

27 January 2015, Volume 53 Issue 1
Cover illustration: Selected eastern Asian–North American fern disjunct taxa. Left: Osmundastrum cinnamomeum (L.) Presl, photo by Jordan Metzgar, Pennsylvania, USA. Right (top): Adiantum pedatum L., photo by Jun Wen, J. Wen 10784 (US), Virginia, USA. Right (middle): Onoclea sensibilis L., photo by Jianying Xiang, Washington, DC, USA. Right (bottom): Adiantum aleuticum (Rupr.) C.A.Paris, photo by Jun Wen, J. Wen 10452 (US), Quebec, Canada. Art plate was designed by Alice Tang [Detail] ...
  • Reviews
  • Jian-Ying XIANG, Jun WEN, Hua PENG
    J Syst Evol. 2015, 53(1): 2-32.
    This paper reviews 31 groups in ferns and lycophytes hypothesized to show eastern Asian–North American disjunctions. Fourteen lineages have been supported by recent phylogenetic evidence: Lycopodium nikoense and Lycopodium sitchense; Isoëtes asiatica and the clade of the North American species complex closely allied to I. maritima; Osmundastrum cinnamomeum; Osmunda claytoniana; the Adiantum pedatum complex; the Cryptogramma acrostichoides complex; Diplaziopsidaceae; Cystopteris chinensis and the Cystopteris bulbifera clade; Asplenium rhizophyllum and Asplenium ruprechtii; diploid Phegopteris; Onoclea sensibilis; the Polypodium appalachianum clade; and the Polypodium glycyrrhiza clade. Phylogenetic and/or cytological evidence did not support the biogeographic disjunctions in six cases: (1) Isoëtes asiatica and I. truncata; (2) Botrychium ternatum; (3) Thelypteris beddomei and T. nipponicaThelypteris noveboracensis and T. nevadensis; (4) Thelypteris glanduligera and Thelypteris. japonicaT. simulata; (5) Woodwardia japonica and W. virginica; and (6) Woodwardia orientalis andWoodwardia fimbriata. Both vicariance and dispersal have been suggested to be the mechanisms for the formation of the disjunct pattern; and the Beringian region has been an active pathway for the migration of ferns and lycophytes between Asia and North America. Disjunctions of ferns and lycophytes reviewed here have been dated in the Tertiary, and are similar to the ages of eastern Asian–North American disjunctions in seed plants, supporting the close biogeographic co-diversification of ferns and seed plants. Future studies are needed to estimate divergence times and reconstruct biogeographic events in a broad phylogenetic framework, and to test the morphological stasis hypothesis in disjunct ferns and lycophytes.
  • Hong-Hu MENG, Xiao-Yang GAO, Jian-Feng HUANG, Ming-Li ZHANG
    J Syst Evol. 2015, 53(1): 33-46.
    Despite the absence of major Quaternary glaciations in arid Northwest China, significant climatic oscillations definitely impacted the evolution of the biota in situ. Phylogeography has grown as a discipline because it has provided explicit tools for the study of geographical subdivision among populations. But phylogeographical application for arid Northwest China has begun to blossom, which has provided evidence that aridification played a significant role in the increase of genetic diversity and species diversification. The time frame corresponds with Pleistocene climatic oscillations, which caused extreme aridity and the expansion of sandy deserts. In the Asian desert flora subkingdom and Eurasian forest subkingdom of Northwest China, the recurrent phylogeographical scenarios, identified by different case studies, broadly agree with longstanding biogeographic, floristic, and topographic concepts: (i) aridification promoted diversification and speciation of desert plants; (ii) desert expansion caused habitat fragmentation; (iii) the Altay–Tianshan Mountains included glacial refugia for plants; (iv) population expansion and recolonization from glacial refugia occurred during the postglacial period; and (v) desert plants persistence and alpine plants retreat during climate oscillations. We discuss the main phylogeographical findings in light of molecular and paleo-environmental evidence, emphasizing notable gaps in our knowledge and outlining future research perspectives for disentangling the evolutionary history of this arid region's flora.
  • Research Articles
  • Yu-Chen YANG, Shu-Huan YANG, Lu FANG, Jian-Fang LI, Cai-Rong ZHONG, Ren-Chao ZHOU, Su-Hua SHI
    J Syst Evol. 2015, 53(1): 47-52.
    Compared with single gene analysis, multi-locus sequence data usually perform better in resolving phylogenetic relationships of closely related species. Sonneratia(Lythraceae s.l.), a genus of mangroves, is widely distributed in the Indo-West Pacific region. Sonneratia griffithii Kurz is one of the rarest species of this genus and morphological analyses have produced conflicting results regarding its affinity to other species of Sonneratia. In this study, we aimed to resolve the phylogenetic position of S. griffithii by using sequence data of the nuclear ribosomal internal transcribed spacer (nrITS) and 13 nuclear genes. We first reconstructed the phylogeny of five Sonneratia species using nrITS and the nuclear gene rpl9, which showed that S. caseolaris (L.) Engl. diverged first from the other species and that S. griffithiiwas closer to S. apetala Buch.-Ham. and S. ovata Backer; however, the relationships among S. griffithii, S. apetala, and S. ovata could not be resolved. Further phylogenetic analysis based on sequences of nrITS and 13 nuclear genes and using S. caseolaris as an outgroup showed that S. griffithii and S. apetala were sister species with high bootstrap support. We conclude that S. griffithii and S. apetala have the closest relationships. Furthermore, our phylogenetic analyses do not support previous intrageneric classifications of Sonneratia.
    J Syst Evol. 2015, 53(1): 53-62.
    Hybridization has played an important role in Saxifraga evolution causing reticulation and a high number of described hybrids, but little is known about how hybrid speciation had occurred in the genus. We focus on a group of closely related Saxifraga species of the subsection Triplinervium from Pyrenees, the phylogenetic relationships of which remain unsolved. Trying to unmask cryptic (or ancient) hybridization processes, we analyze one nuclear (ITS) and three plastid regions (rpl32-trnL, trnS-trnG-trnG, and 3′trnV-ndhC), as well as nuclear DNA content. Pollen and seed morphology and viability studies were carried out to evaluate the status of spontaneous hybrids. DNA ploidy levels were also inferred for the two Madeiran taxa (of the same Saxifraga subsection), where recent hybridization processes are not expected. Molecular markers revealed multiple reticulation events, which, as suggested by DNA content and chromosome numbers, have occurred in homoploidy (without genome doubling after hybridization). In addition, autopolyploidy has occurred in some species or populations, especially in the Madeiran archipelago colonization. Chromosome number variation appears to be related to centric fission events, which also could lead to the formation of the B chromosomes inferred in some taxa. Spontaneous hybrids do not produce viable seeds and this could be due to differences in parental chromosome numbers. Hybrid speciation has probably been successful by chromosomal arrangements, which also generated new, more or less intermediate, chromosomal numbers in this group of taxa.
  • Yong-Peng MA, Zhi-Kun WU, Kun DONG, Wei-Bang SUN, Tobias MARCZEWSKI
    J Syst Evol. 2015, 53(1): 63-71.
    The pollination biology of Rhododendron cyanocarpum (Franch.) W. W. Smith, an alpine species endemic to NW Yunnan, China, was investigated between 2007 and 2008. Floral traits including flowering time, floral morphology, petal color, and floral scents were assessed, and the associated pollinator assemblage and their foraging behavior were recorded. The flowering period of R. cyanocarpum ranges from late March to middle May and a single flower can last 8–10 days in its natural habitat. Flowers generally show marked herkogamy and the protruding style encourages pollinator foraging behavior that counteracts self-pollination. Floral scents comprise mostly aliphatics (64.37%) and terpenoids (29.88%), which make the flowers attractive for several insect groups, but a peak at 430 nm in the reflectance spectrum of petals suggest selection for the attraction of bumblebees. The two Bombus species, B. festivus and B. richardsiellus, representing 90% of total recorded visits, were the only insect species that can be considered to effectively pollinate R. cyanocarpum. Pollination treatments indicated the general self-compatibility of R. cyanocarpum; however, outcrossing seemed to be the dominant strategy, with low rates of self-fertilization providing a certain level of reproductive assurance in its alpine habitat.
  • Fa-Guo WANG, Hong-Mei LIU, Chun-Mei HE, Dong-Mei YANG, Fu-Wu XING
    J Syst Evol. 2015, 53(1): 72-81.
    Davalliaceae is a small family of derived ferns that grow epiphytic or occasionally epilithic in the tropics and subtropics of the Old World. Despite recent taxonomic and phylogenetic achievements, some aspects of its classification remain controversial. In this study, we provided new spore observations on Davalliaceae by using scanning electron microscopy. The newly generated data were integrated together with previously reported spore evidence of this group. The evolution of spore ornamentation and taxonomic implications of spore characters was optimized onto a phylogenetic tree based on plastid sequences. Verrucate colliculate spore ornamentation was identified as plesiomorphic character state within Davalliaceae. The Humata clade was characterized by the transition from verrucate colliculate to fused verrucate ornamentation. Several species complexes subject to taxonomic controversy were found to show informative variation in the spore ornamentation. In conclusion, our observations support the utility of spores as a morphological taxonomic trait in ferns, as long as the evolution of spore morphology is considered.
  • Zi-Yi CHEN, Zhu-Jun XIONG, Xiao-Yun PAN, Su-Qin SHEN, Yu-Peng GENG, Cheng-Yuan XU, Jia-Kuan CHEN, Wen-Ju ZHANG
    J Syst Evol. 2015, 53(1): 82-87.
    Alligator weed, Alternanthera philoxeroides (Mart.) Griseb., is one of the worst invasive weeds in the world. In the present study, the genome size of seven forms/biotypes of alligator weed from Argentina (native area), the USA (introduced area), and China (introduced area) was analyzed using flow cytometers; the ribosomal DNA internal transcribed spacer region (ITS) was cloned and sequenced. We found that the genome size of A. philoxeroides ranged from 5.72 to 8.50 pg/2C nucleus, consisting of four levels of genome and three kinds of ploidy. Among them, three levels and two kinds (tetraploid and hexaploid) were found in samples from Argentina, two levels and one kind (pentaploid) in US samples, and one level and one kind (hexaploid) in samples from China. Contrary to the significant variation in genome size, we found that the intraspecific differentiation of the ITS sequences in the seven forms/biotypes was extremely low, and that six of them shared ITS sequences with no or one single substitution. These results show that the change of genome size played a major role in the differentiation of A. philoxeroides, and that forms/biotypes with higher ploidy seem to have stronger invasive ability. Furthermore, the differences of A. philoxeroides in ploidy between samples from the USA and China showed that alligator weeds from these two invaded areas certainly have different native progenitors.
  • Nawal SHRESTHA, Xian-Chun ZHANG
    J Syst Evol. 2015, 53(1): 88-103.
    The Huperzia serrata (Thunb.) Trevis. complex in China includes taxonomically confusing taxa with unclear boundaries. The number of recognized taxa in this group has long been debated and with this, the group has undergone several taxonomic changes. The species circumscription of H. serrata complex in China is inadequate and unresolved and is in need of comprehensive systematic studies. To address these issues, we have attempted to infer diagnostic differences between the putative taxa and circumscribe species boundary of H. serrata complex in China using an integrative multivariate approach. Morphological characters were subjected to multivariate tests (principal component analysis, discriminant analysis, χ2-test, cluster analysis) followed by univariate analysis of variance and Tukey's post-hoc test. MaxEnt modeling was used to create distribution models of the species followed by niche equivalency and similarity tests. The morphometric analysis clearly separated the specimens into four distinct clusters representing H. crispata (Ching) Ching, H. nanlingensis Y. H. Yan & N. Shrestha, and two clusters of H. serrata comprising specimens from geographically isolated regions. The recognition of these four distinct taxa was supported by climatic data as well. Based on our analysis of morphological with climatic data and ecological niche modeling we recognized H. crispata, H. nanlingensis, the northern Chinese H. serrata, and the southern Chinese H. serrata as four different species. We identified the northern Chinese H. serrata as true H. serrata and the southern Chinese taxa as H. javanica. Our results, however, did not support the recognition of other infraspecific taxa previously recognized under H. serrata.
  • Xiang-Guang MA, Cai ZHAO, Chang-Bao WANG, Qian-Long LIANG, Xing-Jin HE
    J Syst Evol. 2015, 53(1): 104-116.
    Bupleurum commelynoideum H. Boissieu is a perennial herb occurring throughout the Hengduan Mountains region. This species was found to have more than one chromosome number in our previous chromosomal study. For a better understanding of its intraspecific genetic differentiation and interspecific relationships with other Bupleurum members, phylogenetic relationships among 15 populations of B. commelynoideum and 22 other Bupleurum members were investigated using the nuclear ribosomal DNA internal transcribed spacer (ITS) region and three chloroplast DNA (cpDNA) fragments (trnL-F, rps16, and rpl32-trnL). Both phylogenetic analyses of the ITS region and combined cpDNA data indicated that B. commelynoideum has more than one geographically delimited lineage. Among them, accessions from Shangri-La and other regions were considered as different cryptic species according to the unified species concept. Our analyses also revealed that a complex pattern of reticulate relationship exists in B. commelynoideum and its allied species. The chromosome numbers of four populations of B. commelynoideum and a closely related species B. rockii H. Wolff are reported. The results showed that the chromosome number of B. commelynoideum has abundant variations in both chromosome ploidy (2x; 4x; 6x) and basic chromosome number (x = 5; x = 6). Population DXS (x = 6), which has the different basic chromosome number, should represent a different kind of cryptic speciation in B. commelynoideum. The karyological evidence, together with the molecular data, indicated that the existence of at least three cryptic species in B. commelynoideum. This kind of genetic differentiation without morphological divergence might be caused by stabilizing selection imposed by the extreme environmental conditions of the alpine area.