Does the silver moss Bryum argenteum exhibit sex-specific patterns in vegetative growth rate, asexual fitness or prezygotic reproductive investment?

Horsley, Kimberly; Stark, Lloyd R.; McLetchie, D. Nicholas

doi:10.1093/aob/mcr027

Cited by 53 publications

(44 citation statements)

References 66 publications

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“…In the same way that the infrequent presence of sporophytes may explain female bias in some bryophytes Rydgren et al, 2010;Horsley et al, 2011), the relative rareness of C. patrisiae females in our study may be a phenotypic response to the exceptionally high fertilization success in females which subsequently incur relatively higher per capita expenditures of resource allocation as a result of greater rates of sporophyte maturation (É hrlen et al, 2000;Stark et al, 2000;Rydgren & Økland, 2002a).…”

Section: Discussionsupporting

confidence: 52%

“…Female dominance in dioicous bryophytes is suggested to be a result of the infrequent production of sporophytes (McLetchie, 1992;Stark et al, 2000;Rydgren et al, 2010;Horsley et al, 2011) with associated higher pre-zygotic cost of reproduction for the male sex Horsley et al, 2011; but see Bisang et al, 2006 for an exception). Males are expected to allocate disproportionately more resources than females due to the fact that there is only investment in production of gametes, whereas the greatest investment in female gametangia occurs following fertilization: a relatively rare event for most dioicous bryophytes.…”

Section: Discussionmentioning

confidence: 99%

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Sex ratio, spatial segregation, and fertilization rates of the epiphyllous mossCrossomitrium patrisiae(Brid.) Müll.Hal. in the Brazilian Atlantic rainforest

Alvarenga

Pôrto

Zartman

2013

Journal of Bryology

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In order to investigate which mechanisms the epiphyllous moss Crossomitrium patrisiae employs to overcome the typical constraints of dioicy in light of its spatially isolated habitat, we tested the predictions that high fertilization rates are achieved due to (1) high rates of sexual expression, (2) balanced sex ratios, and (3) high co-occurrence of both sexes in the same colony (leaf). Seven hundred and ninety-seven ramets were studied for total length, presence, and number of gametoecia and number of fertilized perichaetia in the female according to spatial segregation at leaf-and shrub-scales. High rates of sexual expression (76%) were confirmed. The other two predictions, however, were not upheld as C. patrisae exhibited a strong male bias (0.43 R : 1 = at ramet level, n5604). Despite considerable spatial segregation (co-occurrence of sexes was seen in 36.7% of shrubs and 12.8% of colonies), this species revealed one of the highest fertilization rates ever reported for a dioicous bryophyte at three spatial scales: nearly 90% of the mixed colonies bore sporophytes, 40% of all female ramets, and 74% of female ramets occurring in mixed colonies bore sporophytes. Thus, the relative rareness of females may be a phenotypic response due to heavy investment in sporophyte maturation as demonstrated by the high fertilization success of females. High rates of sexual expression and the occurrence of fertilization in nearly all cases of coincidence of sexes in common colonies, with low levels of abortion, contribute to the sexual reproductive success and, subsequently, the long-term survival of this species. Journal of Bryology 2013 VOL. 35 NO. 2 Alvarenga et al. Crossomitrium patrisiae sex ratio, spatial segregation, and fertilization rates Journal of Bryology 2013 VOL. 35 NO. 2 Alvarenga et al. Crossomitrium patrisiae sex ratio, spatial segregation, and fertilization rates Journal of Bryology 2013 VOL. 35 NO. 2 Alvarenga et al. Crossomitrium patrisiae sex ratio, spatial segregation, and fertilization rates Journal of Bryology 2013 VOL. 35 NO. 2

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Section: Discussionsupporting

confidence: 52%

Section: Discussionmentioning

confidence: 99%

Sex ratio, spatial segregation, and fertilization rates of the epiphyllous mossCrossomitrium patrisiae(Brid.) Müll.Hal. in the Brazilian Atlantic rainforest

Alvarenga

Pôrto

Zartman

2013

Journal of Bryology

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“…The spatial segregation of males and females is reflected in their dramatically different biology. In particular, male and female gametophytes of unisexual species often exhibit strong sexual dimorphism, differences in size, growth rate, prezygotic reproductive investment (Stark & McLetchie, 2006;Benassi et al, 2011;Horsley et al, 2011;Brzyski et al, 2014) and, possibly, in their ecological niche (Stark & McLetchie, 2006;Brzyski et al, 2014; but see Bisang et al, 2015). The distinct distribution patterns and different life-history traits among sexes of unisexual species suggest that male and female plants basically behave as distinct species, which might represent a strong selective pressure for the maintenance of unisexuality.…”

Section: Researchmentioning

confidence: 99%

Increased diversification rates follow shifts to bisexuality in liverworts

et al. 2016

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SummaryShifts in sexual systems are one of the key drivers of species diversification. In contrast to angiosperms, unisexuality prevails in bryophytes. Here, we test the hypotheses that bisexuality evolved from an ancestral unisexual condition and is a key innovation in liverworts.We investigate whether shifts in sexual systems influence diversification using hidden state speciation and extinction analysis (HiSSE). This new method compares the effects of the variable of interest to the best-fitting latent variable, yielding robust and conservative tests.We find that the transitions in sexual systems are significantly biased toward unisexuality, even though bisexuality is coupled with increased diversification. Sexual systems are strongly conserved deep within the liverwort tree but become much more labile toward the present.Bisexuality appears to be a key innovation in liverworts. Its effects on diversification are presumably mediated by the interplay of high fertilization rates, massive spore production and long-distance dispersal, which may separately or together have facilitated liverwort speciation, suppressed their extinction, or both. Importantly, shifts in liverwort sexual systems have the opposite effect when compared to angiosperms, leading to contrasting diversification patterns between the two groups. The high prevalence of unisexuality among liverworts suggests, however, a strong selection for sexual dimorphism.

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“…This idea is somewhat weakened by theoretical models predicting that, if dispersal traits are plastic, an increase in dispersal rate, and hence, of spore production should be observed (Ronce et al 2005). Alternatively, recent evidence indicates that sex expression is under genetic control (Horsley, Stark & McLetchie 2011), raising the hypothesis that 'vegetative' ecotypes might be selected on islands.…”

Section: O I S L a N D B R Y O P H Y T E S L O S E D I S P E R S A mentioning

confidence: 99%

Baker's law and the island syndromes in bryophytes

et al. 2013

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Summary1. The evolution of island syndromes has long served as a model to understand the mechanisms accounting for phenotypic differentiation. Combining literature data with actual observations, we determine whether typical syndromes such as the loss of dispersal power and the bias towards selfcompatibility (Baker's law) apply to vagile organisms, using bryophytes as a model. 2. The life-history traits (LHTs) observed in oceanic island floras were statistically different from those observed on continents, evidencing the evolution of island syndromes. In contrast, LHTs of continental and continental island floras were similar, pointing to differences in migration intensity between continents, continental islands and oceanic islands. 3. The proportion of bisexual species was significantly higher on oceanic islands than on continents. A significant proportion of species that are unisexual or bisexual on continents shifted towards exclusive bisexuality on oceanic islands, suggesting that Baker's law applies to bryophytes. The underlying mechanisms, however, probably differ from in situ selection for selfing. 4. The proportion of species producing specialized asexual diaspores, which are assumed to play a role in short-distance dispersal (SDD), was higher on oceanic islands than on continents. The proportion of species producing spores, which are involved in long-distance dispersal (LDD), exhibited the reverse trend, suggesting a shift in the prevalent reproductive strategy to favour SDD on oceanic islands. Approximately 50% of the species, however, maintained the ability to produce sporophytes on oceanic islands, and the relative frequency of fertile shoots within collections of four model species was even higher on islands than on continents. 5. Synthesis. Bryophytes exhibit typical island syndromes, indicating that migration rates between oceanic islands and continents are not sufficient to prevent the effects of genetic drift and contradicting the view that the sea does not impede migration in the group. Significant shifts in life-history traits (LHTs) towards increased production of specialized asexual diaspores and decreased sporophyte production on oceanic islands indeed point to a global loss of long-distance dispersal (LDD) ability. The maintenance of traits characteristic for LDD in a large number of species has, however, substantial consequences for our understanding of island plant evolution, and in particular, for our vision of islands as evolutionary dead ends.

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Does the silver moss Bryum argenteum exhibit sex-specific patterns in vegetative growth rate, asexual fitness or prezygotic reproductive investment?

Cited by 53 publications

References 66 publications

Sex ratio, spatial segregation, and fertilization rates of the epiphyllous mossCrossomitrium patrisiae(Brid.) Müll.Hal. in the Brazilian Atlantic rainforest

Sex ratio, spatial segregation, and fertilization rates of the epiphyllous mossCrossomitrium patrisiae(Brid.) Müll.Hal. in the Brazilian Atlantic rainforest

Increased diversification rates follow shifts to bisexuality in liverworts

Baker's law and the island syndromes in bryophytes

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