ABSTRACT
The Miyako horse is a native Japanese horse breed. As with other native Japanese horses, the number of Miyako horses decreased due to mechanization and motorization, which reduced their roles, with just 14 in 1980. Although their population had increased to 55 horses by 2021, a further increase in their numbers is required to avoid extinction. Recently, their breeding has involved natural mating during group grazing; therefore, pedigree management has been difficult, and individual identification has been inconclusive. With the aim of formulating an effective breeding plan, this study used microsatellites to confirm parent-offspring relationships and evaluate the genetic diversity over time. First, the combination of microsatellite genotypes identified misunderstood parent-offspring relationships in 35.3% of the existing individuals, and a correct family tree was reconstructed. Next, the number of alleles and observed and expected values of heterozygosity were calculated separately for the populations during periods of 1998-2012 and 2013-2020. The values were 4.2, 0.705, and 0.653 and 3.9, 0.633, and 0.603, respectively, indicating that genetic diversity according to all indices decreased during period of 2013-2020. This was probably because of the bias of stallions in the 2013-2020 population. Errors in pedigree information in a small population such as Miyako horses could increase the risk of inbreeding, and confirmation of parent-offspring relationships using genotypes may be beneficial. Additionally, to maintain diversity in future breeding, it is important to avoid bias, particularly among stallions, and to ensure offspring of various individuals who are as distantly related to each other as possible.
ABSTRACT
Wild and cultured specimens of Prorocentrum lima (Ehrenb.) F. Stein from 26 widely different areas in 13 countries were examined in order to determine consistent characters for delimiting species boundaries in this taxon. The morphological characters valve shape, valve size, valve ornamentation, number and shape of valve pores, number and shape of marginal pores, and periflagellar platelets were observed using LM and SEM, and two molecular genetic regions were sequenced. We identified stable morphological characters that were consistent among wild specimens and all cultures, which were valve shape, valve ornamentation, and number and arrangement of periflagellar platelets. All cultures of P. lima identified by these characters formed a monophyletic group in phylogenetic analyses based on the two genes, which, however, included the species Prorocentrum arenarium. P. arenarium was determined to be within the range of morphological variation of P. lima, and therefore we synonymize the two taxa. Within this monophyletic group, P. lima was divided into several subclades in the all phylogenetic analyses. There were no morphological characters specifically related to any one subclade. The subclades appeared to correlate broadly to sample collection regions, suggesting that geographically separated populations may have become genetically distinct within this epi-benthic species. We have emended species boundaries in P. lima.
ABSTRACT
The dinoflagellate sub-class Prorocentrophycidae has a distinct morphology, lacking the typical dinoflagellate cell structure of a clear cingulum and sulcus. It includes species that produce the toxin okadaic acid. Despite its uniqueness, the group has been found polyphyletic in some previous molecular phylogenetic studies. We have re-investigated the phylogeny of this sub-class by culturing and sequencing new strains, comparing sequences from three genes, the mitochondrial cytochrome c oxidase subunit 1 (cox 1) and the nuclear large and small subunit rRNA (LSU and SSU) encoding genes. We analyzed sequences from twenty-five named and two still undescribed species of Prorocentrophycidae. We used newly recognized features of the secondary structure to align regions of the LSU rRNA. The phylogeny based on cox 1 provided the most well-supported tree and showed strong support for the monophyly of prorocentroid dinoflagellates, while the LSU phylogeny was inconclusive. As in previous studies, phylogeny based on SSU shows the group to appear paraphyletic, however, support values were low. Two strongly supported sub-clades were consistently identified. Benthic and planktonic modes appear to have evolved on multiple occasions within both clades of Prorocentriphycidae. The capability to synthesize toxins appears to have arisen early in prorocentroid evolution and, in particular, okadaic acid synthesis is present in some, but not all, members of Clade 2. The D2a region of the LSU rRNA appears to have developed a deletion in three definable steps during prorocentroid evolution. While the phylogenies inferred from the three genes were not congruent, our results give reserved support to the monophyly of the group.
