Concordance between DNA-based species boundaries and reproductive isolating barriers in the<i>Scytosiphon lomentaria</i>species complex (Ectocarpales, Phaeophyceae)

Hoshino, Masakazu; Ishikawa, Shikao; Kogame, Kazuhiro

doi:10.2216/17-77.1

Cited by 13 publications

(33 citation statements)

References 47 publications

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“…The brown alga Scytosiphon lomentaria species Ia (Hoshino et al. ) includes populations in which gamete fusion cannot be observed and these populations have been referred to as asexual populations (Kogame et al. ).…”

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confidence: 99%

Parthenogenetic female populations in the brown alga Scytosiphon lomentaria (Scytosiphonaceae, Ectocarpales): decay of a sexual trait and acquisition of asexual traits

Hoshino

Okino

Kogame

2018

Journal of Phycology

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In isogamous brown algae, the sexuality of populations needs to be tested by laboratory crossing experiments, as the sexes of gametophytes are morphologically indistinguishable. In some cases, gamete fusion is not observed and the precise reproductive mode of the populations is unknown. In the isogamous brown alga Scytosiphon lomentaria in Japan, both asexual (gamete fusion is unobservable) and sexual populations (gamete fusion is observable) have been reported. In order to elucidate the reproductive mode of asexual populations in this species, we used PCR-based sex markers to investigate the sex ratio of three asexual and two sexual field populations. The markers indicated that the asexual populations consisted only of female individuals, whereas sexual populations are composed of both males and females. In culture, female gametes of most strains from asexual populations were able to fuse with male gametes; however, they had little to no detectable sexual pheromones, significantly larger cell sizes, and more rapid parthenogenetic development compared to female/male gametes from sexual populations. Investigations of sporophytic stages in the field indicated that alternation of gametophytic and parthenosporophytic stages occur in an asexual population. These results indicate that the S. lomentaria asexual populations are female populations that lack sexual reproduction and reproduce parthenogenetically. It is likely that females in the asexual populations have reduced a sexual trait (pheromone production) and have acquired asexual traits (larger gamete sizes and rapid parthenogenetic development).

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Parthenogenetic female populations in the brown alga Scytosiphon lomentaria (Scytosiphonaceae, Ectocarpales): decay of a sexual trait and acquisition of asexual traits

Hoshino

Okino

Kogame

2018

Journal of Phycology

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“…Each individual served to make a herbarium specimen and total genomic DNA was extracted from a fragment for molecular experiments as described in Hoshino et al. (2018a). The sex of each gametophyte was determined using PCR‐based sex markers.…”

Section: Methodsmentioning

confidence: 99%

“…To examine the sexuality of the population, gametophytes of Scytosiphon lomentaria species IIa were collected in Oshoro Bay, Otaru, Hokkaido, Japan (43°21 0 N, 140°85 0 E) on March 21, 2018 (Table S1 in the Supporting Information). Each individual served to make a herbarium specimen and total genomic DNA was extracted from a fragment for molecular experiments as described in Hoshino et al (2018a). The sex of each gametophyte was determined using PCR-based sex markers.…”

Section: Methodsmentioning

confidence: 99%

“…Populations of S. lomentaria in Japan include at least five cryptic species (species Ia–Va; Hoshino et al. 2018a). Species Ia includes parthenogenetic female‐dominant populations in addition to populations consisting of both female and male gametophytes (sexual populations; Kogame et al.…”

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confidence: 99%

“…In laboratory cultures, both female and male gametes undergo parthenogenesis and develop into either parthenosporophytes (discoid or filamentous thalli) or gametophytes depending on temperature and daylength (Nakamura andTatewaki 1975, tom Dieck 1987). Populations of S. lomentaria in Japan include at least five cryptic species (species Ia-Va; Hoshino et al 2018a). Species Ia includes parthenogenetic female-dominant populations in addition to populations consisting of both female and male gametophytes (sexual populations; Kogame et al 2015, Hoshino et al 2018b).…”

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confidence: 99%

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Parthenogenesis is rare in the reproduction of a sexual field population of the isogamous brown alga Scytosiphon (Scytosiphonaceae, Ectocarpales)

Hoshino

Kogame

2019

Journal of Phycology

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Parthenogenetic development of unfused gametes is commonly observed in laboratory cultures among various brown algal taxa. There is, however, little information on the contribution of parthenogenesis to the reproduction of field populations. In this study, we investigated whether parthenogenesis is present in a sexual population of the isogamous brown alga Scytosiphon with a 1:1 sex ratio. In culture, both female and male gametes showed higher mortality and slower development compared to zygotes. More than 90% of surviving partheno‐germlings formed parthenosporophytes irrespective of the culture conditions tested. Therefore, if parthenogenesis occurs in the field, most unfused gametes are expected to form parthenosporophytes. Contrary to this expectation, parthenosporophytes were rare in the field population. We collected 126 sporophytic thalli and isolated and cultured a unilocular sporangium from each of them. We confirmed that cultures of 120 unilocular sporangia produced both female and male gametophytes by the observation of zygotes or amplification of PCR‐based sex markers indicating that these sporangia originated from zygotic sporophytes. Only females were detected in cultures from two sporangia and only males from four sporangia suggesting that these sporangia originated from parthenosporophytes. In the Scytosiphon population, although parthenogenesis is observable in culture, our results demonstrate that the contribution of parthenogenesis to reproduction is small (≤4.8%) compared to sexual reproduction. Unfused gametes may not survive to form mature parthenosporophytes in significant numbers in the field partly due to their higher mortality and slower development compared from zygotes.

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Species delimitation of Planosiphon gracilis morphospecies (Scytosiphonaceae, Phaeophyceae) from Japan and the description of Pl. nakamurae sp. nov.

et al. 2020

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Concordance between DNA-based species boundaries and reproductive isolating barriers in theScytosiphon lomentariaspecies complex (Ectocarpales, Phaeophyceae)

Cited by 13 publications

References 47 publications

Parthenogenetic female populations in the brown alga Scytosiphon lomentaria (Scytosiphonaceae, Ectocarpales): decay of a sexual trait and acquisition of asexual traits

Parthenogenetic female populations in the brown alga Scytosiphon lomentaria (Scytosiphonaceae, Ectocarpales): decay of a sexual trait and acquisition of asexual traits

Parthenogenesis is rare in the reproduction of a sexual field population of the isogamous brown alga Scytosiphon (Scytosiphonaceae, Ectocarpales)

Species delimitation of Planosiphon gracilis morphospecies (Scytosiphonaceae, Phaeophyceae) from Japan and the description of Pl. nakamurae sp. nov.

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