RESUMEN
BACKGROUND: The three-spined stickleback (Gasterosteus aculeatus) is a remarkable system to study the genetic mechanisms underlying parallel evolution during the transition from marine to freshwater habitats. Although the majority of previous studies on the parallel evolution of sticklebacks have mainly focused on postglacial freshwater populations in the Pacific Northwest of North America and northern Europe, we recently use Japanese stickleback populations for investigating shared and unique features of adaptation and speciation between geographically distant populations. However, we currently lack a comprehensive phylogeny of the Japanese three-spined sticklebacks, despite the fact that a good phylogeny is essential for any evolutionary and ecological studies. Here, we conducted a phylogenomic analysis of the three-spined stickleback in the Japanese Archipelago. RESULTS: We found that freshwater colonization occurred in multiple waves, each of which may reflect different interglacial isolations. Some of the oldest freshwater populations from the central regions of the mainland of Japan (hariyo populations) were estimated to colonize freshwater approximately 170,000 years ago. The next wave of colonization likely occurred approximately 100,000 years ago. The inferred origins of several human-introduced populations showed that introduction occurred mainly from nearby habitats. We also found a new habitat of the three-spined stickleback sympatric with the Japan Sea stickleback (Gasterosteus nipponicus). CONCLUSIONS: These Japanese stickleback systems differ from those in the Pacific Northwest of North America and northern Europe in terms of divergence time and history. Stickleback populations in the Japanese Archipelago offer valuable opportunities to study diverse evolutionary processes in historical and contemporary timescales.
Asunto(s)
Evolución Biológica , Smegmamorpha , Animales , Agua Dulce , Japón , Smegmamorpha/genéticaRESUMEN
The high genetic diversity of rear-edge refugia populations is predicted to have resulted from species repeatedly migrating to low latitudes during glacial periods over the course of Quaternary climate change. However, several recent empirical studies of cold-tolerant plants revealed the opposite pattern. We investigated whether current habitats of the cold-adapted and range-restricted Bupleurum euphorbioides in the Baekdudaegan, South Korea, and North Korea could be interglacial refugia, and documented how their rear-edge populations differ genetically from those of typical temperate species. Phylogeographic analysis and ecological niche modeling (ENM) were used. The genetic structure was analyzed using microsatellite markers and chloroplast DNA sequences. The congener B. longiradiatum was included as a typical temperate plant species. Despite having almost identical life history traits, these congeneric species exhibited contrasting patterns of genetic diversity. ENM revealed an apparent maximum range contraction during the last interglacial. In contrast, its range expanded northward to the Russian Far East (Primorsky) during the Last Glacial Maximum. Thus, we hypothesize that B. euphorbioides retreated to its current refugia during interglacial periods. Unlike populations in the central region, the rear-edge populations were genetically impoverished and uniform, both within populations and in pooled regional populations. The rear-edge B. euphorbioides survived at least one past interglacial, contributing to the species' genetic diversity. We believe that such genetic variation in the cold-adapted B. euphorbioides gives the species the necessary adaptations to survive an upcoming favorable environment (the next glacial), unless there is artificial environmental change.
RESUMEN
The effects of Quaternary climatic oscillations on the distributions of organisms in different parts of the world are not equally well understood, limiting the ability to understand the determinants of biodiversity. Compared with the mountain regions in southern Europe and southwestern North America, such effects on high-elevation species in the East Asian subtropical mountain systems located in southern and southeastern China have seldom been addressed. In this study, using Leptobrachium liui (Megophryidae), we made one of the earliest attempts to examine the interglacial high-elevation refugia scenario in these Asian mountains. Based on our current understanding of the study system, we formulated a hypothesis that these frogs of western origin were distributed more widely and continuously during glacial phases, allowing eastward dispersal, and that they are currently isolated in interglacial refugia at higher elevations. Microsatellite data and mitochondrial and nuclear sequence data were obtained with extensive sampling followed by the synthesis of phylogeographic and population genetic analyses and modeling of the species distribution. The analyses revealed a sequential eastward divergence of microsatellite clusters and gene lineages accompanied by a decline in genetic diversity. Molecular dating estimates revealed divergence events in the Pleistocene, and a reduction in local populations was inferred to have occurred at a time comparable to the end of the last glacial. Strong genetic isolation by distance reflecting a more continuous historical distribution was detected. Furthermore, environmental niche models inferred a wide planar distribution during the last glacial maximum, providing further support for the hypothesis.
RESUMEN
This paper reports the first discovery of the weevil genus Catapionus in Southwest China. Eighteen specimens of C. mopsus sp.n. were collected in two high altitude localities some 360 km apart: Mt. Haba in Yunnan (the type locality) at 4,158-4,195 m and Mt. Gongga in Sichuan at 3,533-4,143 m. Habitus and genitalia of a male and a female from each locality are extensively illustrated. Six specimens from each locality were DNA barcoded (dx.doi.org/10.5883/DS-CATAPCH). Taxonomic validation of the new species name was made by referring to high quality illustrations of the holotype and to its DNA barcode, and without providing a customary verbal description. This novel approach was chosen partly due to the redundancy of description in the presence of high quality images, and partly due to the lack of adequate and unambiguously identified comparative material. Analysis of mtDNA sequences dated the separation of both geographical populations at about 3.65 Ma. The disjunct distribution of Catapionus in Asia is discussed and mapped for the first time. Monophyly and internal relationships of the genus are discussed and remain untested, together with the generic assignment to the phylogenetically vague Cneorhinini and/or Dermatodini. Discovery of the southernmost members of Catapionus high in the mountains of Southwest China evokes a hypothesis on interglacial refugia. A new term "clogging taxonomy" is introduced for situations as encountered in Catapionus when an abundance of obscure historical species-group names impedes further research.