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

Abstract

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

Do motile spermatozoids limit the effectiveness of sexual reproduction in bryophytes? Not in the liverwort Marchantia polymorpha

“…The internalized external water‐conducting system in Marchantia , comprising pegged rhizoids inside the ventral scales and carpocephala grooves, with flow rates of several cm/h (Duckett et al, ) is in fact far more effective at maintaining water balance than hydroids in polytrichalean mosses (Duckett & Ligrone, ). The virtually 100% fertilization rate recorded here in Marchantia surpasses the previous record of 90% for a dioicous Brazilian rainforest epiphyllous moss Crossomitrium petrisiae (Alvarenga et al, ). A further feature contributing to the likelihood of fertilization is the demonstration by Nakamura et al () that the ribbed umbrella form of the Marchantia archegoniophore, with its hydrophobic upper surface has the optimal construction for water capture and for retaining water droplets beneath the cap.…”

Distribution, ecology, and reproduction of bryophytes in a humid enclave in the semiarid region of northeastern Brazil

“…All of the individuals of that species were observed with sporophytes (eight occurrences). The short life spans of those substrates require specific strategies of the occupying species to effectively maintain their populations (Frahm 2003) -such as a prostrate growth habit and/or a short life cycle -with high fertility and high diaspore production levels (Zartman 2003;Alvarenga et al 2013).…”

How does reproductive strategy influence demography? A case study in the tropical, unisexual epiphyllous moss Crossomitrium patrisiae

“…1A, B ) than other epiphyllous bryophytes, which are mostly liverworts of the family Lejeuneaceae ( Gradstein, 1997 ). Gametophytes cover small portions of the available space, ~10% ( ± 0.05 SD) of leaf surface ( Alvarenga et al, 2013 ). Th e sporophyte setae reach 4-12 mm ( Fig.…”

“…Long-distance dispersion occurs mainly through spores that are abundantly produced during the rainy season. Moreover, on an individual basis, C. patrisiae presents one of the highest rates of sexual expression (76% of examined shoots) and fertilization (89% of cosexual populations, 40% of total female and 73% of female shoots occurring in cosexual colonies) ever recorded for a bryophyte with unisexual individuals ( Alvarenga et al, 2013 ). Th e earlier use of gemmae in the life cycle certainly contributes to mating success.…”

“…Müll.Hal. has one of the highest fertilization rates ever recorded for a unisexual bryophyte ( Alvarenga et al, 2013 ). Such an extraordinary divergence in life history calls for a thorough investigation of the demographic mechanisms that contribute to the success of this species in such an extreme habitat.…”