Journal of Systematics and Evolution最新文献

The fern genus Didymoglossum (Hymenophyllaceae) is not so diverse in Africa with seven species at most. However, its local taxonomy is surprisingly still strongly debated, in particular within the Didymoglossum erosum complex interpreted either as a single polymorphic species or as a group of at least three distinct but morphologically very close taxa (D. erosum, Didymoglossum chamaedrys, and Didymoglossum benlii). Investigating these taxonomic issues and more generally the diversity of the genus in Africa and its origin, we conducted a complete anatomo–morphological analysis coupled with a molecular phylogenetic work based on rbcL. Our results support the recognition of all seven species, including Didymoglossum robinsonii that is likely distinct from the Neotropical Didymoglossum reptans to which the African populations were traditionally attributed. We here propose new characters and a novel key to distinguish the seven African species which also include Didymoglossum ballardianum, Didymoglossum lenormandii, and Didymoglossum liberiense. Once the taxonomy is clarified with respect to the distinct evolutionary lineages evidenced, the biogeographic history of the genus in Africa is discussed based on a divergence time estimation and the reconstruction of the ancestral geographic areas. These analyses reveal a Mesozoic (Cretaceous) vicariance event within Didymoglossum which is the second one hypothesized for the family Hymenophyllaceae.

Clear species boundaries are crucial for plans and actions on biodiversity conservation. However, morphological similarities among allied species can result in taxonomic difficulties, thus impeding conservation efforts. In China, Cinnamomum japonicum Siebold is a well-known endangered plant, yet suffers from longstanding taxonomic issues. Here, we explicitly evaluate whether C. japonicum, C. chenii, and C. chekiangense are the same phylogenetic species on the basis of a multi-individual sampling strategy. We identified three sets of low-copy orthologous genes from 19 Lauraceae taxa for phylogenetic inferences. Both the concatenation and coalescent-based phylogenies supported that C. chenii individuals were embedded in the C. japonicum clade, indicating these two taxa are conspecific. Meanwhile, C. chekiangense accessions formed a monophyly which was not sister to C. japonicum. This result, together with the morphological differences that the leaves of C. japonicum are glabrous with a faveolate pattern of venation while those of C. chekiangense have trichomes and inevident lateral veins, led us to consider both as two distinct species. Based on 17 728 neutral single nucleotide polymorphisms (SNPs), the ADMIXTURE analysis suggested that the Chinese C. japonicum populations in Zhoushan Archipelago (=C. chenii) were genetically differentiated from the Japanese and Korean ones. Furthermore, ecological niche modeling predicted that the present distribution area of Chinese C. japonicum is likely to be unsuitable under global warming scenarios. Together with its limited distribution and genetic uniqueness, we recommend that Chinese C. japonicum deserves conservation priorities.

Southeast Asia (SEA) has seen strong climatic oscillations and fluctuations in sea levels during the Quaternary. The impact of past climate changes on the evolution and distribution of local flora in SEA is still poorly understood. Here we aim to infer how the Quaternary climate change affects the evolutionary process and range shifts in two pine species. We investigated the population genetic structure and diversity using cytoplasmic DNA markers, and performed ecological niche modeling to reconstruct the species past distribution and to project range shift under future climates. We found substantial gene flow across the continuous distribution of the subtropical Pinus yunnanensis. In contrast, the tropical Pinus kesiya showed a strong population structure in accordance with its disjunct distribution across montane islands in Indochina and the Philippines. A broad hybrid zone of the two species occurs in southern Yunnan. Asymmetric introgression from the two species was detected in this zone with dominant mitochondrial gene flow from P. yunnanensis and chloroplast gene flow from P. kesiya. The observed population structure suggests a typical postglaciation expansion in P. yunnanensis, and a glacial expansion and interglacial contraction in P. kesiya. Ecological niche modeling supports the inferred demographic history and predicts a decrease in range size for P. kesiya under future climates. Our results suggest that tropical pine species in SEA have undergone evolutionary trajectories different from high latitude species related to their Quaternary climate histories. We also illustrate the need for urgent conservation actions in this fragmented landscape.

Polyploids are common in Camellia sect. Paracamellia, which contain many important oil crop species. However, their complex evolutionary history is largely unclear. In this study, 22 transcriptomes and 19 plastomes of related species of Camellia were sequenced and assembled, providing the most completed taxa sampling of Camellia sect. Oleifera and C. sect. Paracamellia. Phylogenetic trees were reconstructed with predicted single-copy nuclear genes and plastomes. Phylogenetic trees with nuclear genes demonstrated that C. sect. Oleifera should be merged into C. sect. Paracamellia. Cytonuclear discordance and network analyses suggested hybridizations among polyploid species and relatives. The divergence of major clades in C. sect. Paracamellia was dated to be during the middle to late Miocene from the ancestral Lingnan region, and a rapid diversification during the Quaternary was found, probably through hybridization and polyploidization. The tetraploid Camellia meiocarpa Hu may have originated from hybridization between closely related diploid species. The hexaploid Camellia oleifera C. Abel probably originated from hybridization between closely related diploid and tetraploid (e.g., C. meiocarpa) species. The octoploid Camellia vietnamensis T. C. Huang ex Hu could have originated from hybridization between hexaploid C. oleifera and the closely related diploid species. Hybridization and polyploidization played an important role in generating the rich variation of important fruit traits, especially increased fruit size in polyploid species.

Cuticular hydrocarbons of Cerambycidae species can function as signals for sex recognition. Little is known about the copulatory signals of the juniper bark borer Semanotus bifasciatus, a major economic threat to Platycladus orientalis Franco in China. Here, we investigated the cuticular hydrocarbons of both sexes of S. bifasciatus to determine the chemically mediated mating signals using the solid-phase microextraction (SPME) technique with carbowax/divinylbenzene fibers (CAR/DVB) and then analyzed by coupled gas chromatography-mass spectrometry (GC-MS). A series of aliphatic saturated straight-chain n-alkanes (n-C₂₃ to n-C₂₈), internally branched monomethylalkanes at carbons 3, 11, or 13, and dimethylalkanes were identified, which showed no qualitative differences in either sex and were similar in the samples with SPME fiber extraction and those with hexane extraction. The bioassay showed that 11-methylpentacosane (11-MeC₂₅), 11-methylhexacosane (11-MeC₂₆), and 11-methylheptacosane (11-MeC₂₇) have sex-specific recognition functions that triggered more mating attempts at a female-specific ratio of 100:4:60 than at a male-specific ratio of 100:85:50. In addition, the female-specific ratio of 11-methylalkanes can elicit about 70% of male mating attempts within about 60 s, whereas live females elicit about 98% of male mating attempts within 25 s. The discrepancy in the initiation of mating attempts by synthetic mixtures and live females suggests that the methyl isomers 3-MeC₂₅, 3-MeC₂₇, and/or 11,15-diMeC₂₇ may also be involved in the mating behavior of S. bifasciatus. These results suggest that 11-MeC₂₅, 11-MeC₂₆, and 11-MeC₂₇ constitute the contact sex pheromone of S. bifasciatus, with the presence or absence of 11-MeC₂₆ in particular playing an important role in mate recognition by males.

Previous phylogenetic analyses indicated that Polygonoideae, the largest subfamily in the Polygonaceae, is monophyletic. Phylogenetic relationships within the Polygonoideae have been substantially controversial. We collected 160 samples representing all currently recognized tribes for a more comprehensive phylogenetic analysis of the subfamily. Here, we reconstructed phylogenetic relationships of the Polygonoideae, inferred ancestral character states, and estimated the divergence time with a dense taxon sampling. This study corroborated and expanded previous results regarding the phylogenetic relationships of the Polygonoideae clade, and resolved the phylogenetic status of some controversial taxa by integrating molecular and morphological evidence. Phylogenetic analyses based on the complete plastomes suggested strong support for six primary clades that correspond to the most recent circumscription of tribes: Polygoneae, Rumiceae, Calligoneae, Pteroxygoneae, Fagopyreae, and Persicarieae. In addition, we provided further morphological data and assessed characters that supported different clades. The 3-colpate pollen, 5-parted perianth, and 3 styles were inferred to be the ancestral states of Polygonoideae. Divergence time estimation revealed that Polygonoideae originated around the late Cretaceous, and diversification was concentrated in the Eocene and Miocene. Time estimation indicated that the rapid uplift of the Tibetan Plateau and the intensification of the Asian monsoons might be potential driving forces for the diversification of Polygonoideae. Overall, this study advances our understanding of the phylogeny and diversification of the Polygonoideae and highlights the adaptive evolution of the taxa.

Gomphomastacinae is a grasshopper subfamily in Eumastacidae, with a morphology and distribution distinct from other subfamilies. The alpine genera of Gomphomastacinae that inhabit the Qinghai–Tibet Plateau in China show unique characteristics adapted to high-altitude life. However, their phylogenetic position and biogeographic history remain controversial. Thus, to determine the diversification history of these alpine genera and the origin of the subfamily, we obtained mitochondrial genome sequences from all seven Gomphomastacinae genera distributed in China. The reconstructed phylogeny was well supported and confirmed the phylogenetic position of Gomphomastacinae within Eumastacidae. Time calibration revealed a deep-time origin of the subfamily dating back to the Cretaceous period, and the diversification among alpine genera was also an ancient pre-Miocene event (30–50 Ma). Based on phylogeny and time estimates, the most likely biogeographic scenario is that Gomphomastacinae originated from an ancestral lineage that lived in East Gondwana and dispersed to Central and Western Asia through India. Subsequently, the alpine genera likely diverged along with the uplift of the Qinghai–Tibet Plateau and survived drastic climate change by in situ adaptation to high-altitude dwellings.