README_file.txt This file explains the contents of the dataset. Microsatellite_data_for_Gekko_hokouensis_and_G._yakuensis.csv This file is in STRUCTURE format and contains the raw data of allele lengths collected from 330 individuals using microsatellite genotyping. The first line lists the names of 16 microsatellite loci. The first column lists sample IDs, and the second column lists the names of sampling sites. Two alleles for each sample are listed in two consecutive columns in the subsequent columns. Missing data is represented with -9. These data include genotypic data for 20 pure G. hokouensis and 20 pure G. yakuensis used in Okamoto et al. (2020).
Marine amniotes, a polyphyletic group, provide an excellent opportunity for studying convergent evolution. Their sense of smell tends to degenerate, but this process has not been explored by comparing fully aquatic species with their amphibious relatives in an evolutionary context. Here, we sequenced the genomes of fully aquatic and amphibious sea snakes and identified repertoires of chemosensory receptor genes involved in olfaction. Snakes possess large numbers of the olfactory receptor ( OR ) genes and the type-2 vomeronasal receptor ( V2R ) genes, and expression profiling in the olfactory tissues suggests that snakes use the ORs in the main olfactory system (MOS) and the V2Rs in the vomeronasal system (VNS). The number of OR genes has decreased in sea snakes, and fully aquatic species lost MOS which is responsible for detecting airborne odours. By contrast, sea snakes including fully aquatic species retain a number of V2R genes and a well-developed VNS for smelling underwater. This study suggests that the sense of smell also degenerated in sea snakes, particularly in fully aquatic species, but their residual olfactory capability is distinct from that of other fully aquatic amniotes. Amphibious species show an intermediate status between terrestrial and fully aquatic snakes, implying their importance in understanding the process of aquatic adaptation.
Field surveys were made for geographic distributions of two geckos, Gekko hokouensis and G. yakuensis, within Yakushima, a mountainous island located in southwest of Kyushu, mainland Japan. Gekko yakuensis was found from an almost entire lowland area encompassing various environments, whereas G. hokouensis was restricted to four villages and their vicinity. In many other villages G. hokouensis was not found at all, although G. yakuensis occurred. The four villages having G. hokouensis populations are characterized by ports that have or once had regular vessel sails from other islands of the northern Ryukyus or southern Kyushu where this species is common. Our results strongly suggest that the current Yakushima populations of G. hokouensis have originated from multiple accidental artificial introductions from outside and that G. yakuensis is the only native gekkonid of the island. In this study, we also found hybrids of G. hokouensis and G. yakuensis from a few localities on Yakushima Island. This suggests that genetic introgression may be in progress from the former to the latter species on this island.
Interspecific hybridization has been occasionally reported for various combinations of geoemydid turtles, but genetic consequences of such hybridization have rarely been investigated. We surveyed the hybrid status of 40 individuals from a seemingly hybridizing turtle assemblage in a natural pond in northcentral Honshu, Japan. Analysis of mtDNA sequences confirmed that the parental species of this assemblage were Mauremys reevesii (Chinese three-keeled pond turtle) and Mauremys mutica (Asian yellow pond turtle), neither of which is native to the main islands of Japan, although M. reevesii was naturalized in the area before the 19th century. Extensive examination of pure strain samples of the 2 species yielded 10 morphological and 10 genetic diagnostic characters (allozyme and short interspersed repetitive elements) that were used to determine the hybrid status of the turtles in the assemblage. Morphological examination showed that 19 out of 40 individuals were not different from pure M. reevesii individuals, but the remaining 21 individuals exhibited M. mutica states at 1 to 6 characters, indicating interspecific crosses at a moderate to large scale. In the genetic characters, however, only 2 of the 21 individuals possessed marker alleles of M. mutica at a few loci and all others possessed alleles of M. reevesii only; thus neither pure M. mutica nor F1 hybrids were included in the assemblage. These results suggest that iterative backcrosses with pure M. reevesii have occurred. In the analysis using the genetic hybrid index (GHI), which was defined as the number of M. mutica type alleles over the 10 examined loci, the 2 individuals scored 5 and 2, respectively, and all others scored 0. This discrete distribution of GHI scores negates an assumption of a random mating hybrid swarm but suggests that these two individuals emerged by a different hybridization event, independent from that leading to the many other putative hybrids detected by morphological characters only. Our results suggest that even though the hybrid genotypes rarely prevailed in the population, once introgressed genes were diluted by successive backcrosses, they could have been retained over many generations.
Some new results concerning robustness and asymptotic properties of error bounds of a linear quadratic feedback design are applied to an aircraft control problem. An autopilot for the flare control of the Augmentor Wing Jet STOL Research Aircraft (AWJSRA) is designed based on Linear Quadratic (LQ) theory and the results developed in this paper. The variation of the error bounds to changes in the weighting matrices in the LQ design is studied by computer simulations, and appropriate weighting matrices are chosen to obtain a reasonable error bound for variations in the system matrix and at the same time meet the practical constraints for the flare maneuver of the AWJSRA. Results from the computer simulation of a satisfactory autopilot design for the flare control of the AWJSRA are presented.
In the Ryukyu Archipelago, Japan, Goniurosaurus geckos are currently divided into six allopatric taxa among nearby islands. Recent studies suggested the occurrence of large genetic divergence within a single island and the possible non-monophyly of a few taxa, but their species delimitation is not well resolved. We investigated the taxonomic relationships between the possibly geographically overlapped, highly diverged entities as well as other island populations via dense sampling. Our mitochondrial and nuclear DNA analyses showed that the two genetic groups were distributed in parapatry within Okinawajima Island and that they were hybridizing in narrow area around the contact zone. Geohistorical evidence suggests that the restricted gene flow has been caused by some intrinsic isolation mechanisms. Thus, we conclude that the two lineages represent full species. Mitochondrial analysis also showed that the genetic differences among other island populations were comparable to those between these species, thereby suggesting the presence of seven full species, including one unnamed taxon. We also discuss the possible cause of this divergence and why it has occurred at such a fine geographic scale.
A solution procedure is reported for stochastic decision problems with decentralized information structure. The procedure is applied to obtain the optimal control of decentralized stochastic linear regulator problems with delayed information sharing structure where observations are centralized with one-step delay.
The performance of Kalman-type, linear, discrete-time filters in the presence of modeling errors is considered. The discussion is limited to stationary performance, and bounds are obtained for the performance index, the mean-squared error of estimates for suboptimal and optimal (Kalman) filters. The computation of these bounds requires information on only the model matrices and the range of errors for these matrices. Consequently, a designer can easily compare the performance of a suboptimal filter with that of the optimal filter, when only the range of errors in the elements of the model matrices are available.
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