Monoicous Species Research Articles

Co-variation of life history characters in the family Lophoziaceae: a multivariate analysis

The particular combinations of life history traits that organisms display are a product of trade-offs between conflicting demands on finite energy budgets. Organisms are, therefore, expected to display combinations of co-evolved life history traits, sometimes referred to as tactics or strategies, that overall maximize fitness within the constraints imposed by environmental and/or genetic limitations. This study uses a combination of Principal Component and Cluster analyses to examine patterns of life history co-variation in the family Lophoziaceae, based on data obtained from literature. We also evaluate the relationship between sexuality, reproductive mode and sporophyte/gemma frequency among members of this family. The species studied are resolved into more or less coherent groups that have specific life history trait combinations. No evidence of either phylogenetic constraint or close relationship to habitat parameters could be demonstrated. The results suggest trade-offs between spore frequency and gemma frequency. Dioicous species dominate the family, with about 90% of the species being dioicous. The relationship between sexuality and sporophyte frequency is statistically significant: monoicous species produce sporophytes more frequently than dioicous species. Mode of reproduction and gemmae production were both independent of sexuality. For species that can reproduce both ways, sexuality was independent of diaspore frequency. The data are consistent with the idea of coevolved life history “strategies” as in most others organisms studied.

Diaspore bank of bryophytes in tropical rain forests: the importance of breeding system, phylum and microhabitat

Diaspore banks are crucial for the maintenance and resilience of plant communities, but diaspore banks of bryophytes remain poorly known, especially from tropical ecosystems. This is the first study to focus on the role of diaspore banks of bryophytes in tropical rain forests. Our aim was to test whether microhabitat (substrate type) and species traits (breeding system, phylum) are important in explaining the diaspore bank composition. Using samples cultivated in the laboratory, we assessed the number of species and shoots emerging from bark, decaying wood and soil from two sites of the Atlantic rain forest (montane and sea level) in Brazil by comparing the contribution of species by phylum (mosses, liverworts) and breeding system (monoicous, dioicous). More species emerged from bark (68) and decaying wood (55) than from soil (22). Similar numbers of species were found at both sites. Mosses were more numerous in terms of number of species and shoots, and monoicous species dominated over dioicous species. Substrate pH had only weak effects on shoot emergence. Species commonly producing sporophytes and gemmae had a high contribution to the diaspore banks. These superficial diaspore banks represented the extant vegetation rather well, but held more monoicous species (probably short-lived species) compared to dioicous ones. We propose that diaspore bank dynamics are driven by species traits and microhabitat characteristics, and that short-term diaspore banks of bryophytes in tropical rain forests contribute to fast (re)establishment of species after disturbances and during succession, particularly dioicous mosses investing in asexual reproduction and monoicous mosses investing in sexual reproduction.

Note on the occurrence of Metzgeria saxbyi Pearson in southern Africa

Metzgeria saxbyi was originally described by Pearson (1931), based on material collected by H.H. Saxby in Ghana in 1910. Sim (1926) regarded the monoicous South African plants of Metzgeria as M. conjugata Lindb., a species resembling M. saxbyi, but not known from Africa (So, 2004; Wigginton, 2004b, 2009). Metzgeria saxbyi was first reported as occurring in South Africa and Swaziland by S. Arnell (1963), based on material which was originally identified as M. furcata (L.) Dumort. The material was collected in Swaziland: Horo Forest, 2531CB, April 1932, V.A. Wager 108 (PRE) and in South Africa: Cape Town, Table Mountain, Skeleton Gorge, 3318CD, January 1916, J.W. Bews PRECH8489 (PRE). The species was subsequently included in a series of southern African checklists up to Perold (2003) and neatly illustrated by O. van Kerckhove (in Wigginton 2004b: 94, Figure 56). Perold (2006) excluded the species from her latest checklist of South African liverworts and cited So (2004) and Wigginton (2004a). However, So (2004) did not actually exclude M. saxbyi from South Africa and Swaziland but did not see specimens from this region. Wigginton (2004a, 2009) did not include southern Africa in the distribution of Metzgeria saxbyi and noted that its occurrence in these countries needs confirmation. Sterile material of Metzgeria can be easily misidentified as characters like costal cortical cells and hair placement and presence occur sporadically. Marginal and costal hairs are a difficult character to use when the material is very old as these get broken with age. However, M. saxbyi is the only monoicous species in Africa (So, 2004; Wigginton, 2004b). The southern African specimens listed above were examined and found to be monoicous, the most important character used in identifying M. saxbyi. The occurrence of this species in South Africa as well as Swaziland is therefore confirmed.

Self-fertilization in mosses: a comparison of heterozygote deficiency between species with combined versus separate sexes

Self-fertilization is a key difference of adaptive significance between species with combined versus separate sexes. In haploid-dominant species such as mosses and ferns, species with either combined or separate sexes (monoicous and dioicous, respectively) have the potential to self-fertilize (intergametophytic selfing), but being monoicous allows an additional mode of selfing (intragametophytic selfing). We used allozyme electrophoresis to estimate deviations from expected levels of heterozygosity under Hardy-Weinberg equilibrium to infer selfing rates in 10 moss species from 36 New Zealand populations. We found that while there were deficiencies of heterozygotes compared to expectation in both monoicous and dioicous mosses, monoicous species had significantly higher levels of heterozygote deficiency than dioicous species (F(IS)=0.89+/-0.12 and 0.41+/-0.11, respectively). Estimated selfing rates suggest that selfing occurs frequently in monoicous populations, and rarely in dioicous populations. However, in two dioicous species (Polytrichadelphus magellanicus and Breutelia pendula), we found significant indications of mixed mating or biparental inbreeding in a handful of populations. These data provide the first analysis of heterozygote deficiency and selfing among haploid-dominant species with breeding system variation, and we discuss our results with respect to the consequences of inbreeding depression and the evolution of breeding systems.

(1692–1693) Proposals to conserve the names Fossombronia caespitiformis and Jungermannia angulosa with conserved types (Marchantiophyta: Fossombroniaceae)

Fossombronia caespitiformis De Not. ex Rabenhorst was validly published as No. 123 of Rabenhorst's Hepat. Eur. (Die Leberm. Eur., Decas XIII u. XIV, 1860). Based upon a Cesati gathering from Locarno [Switzerland], the brief diagnosis reads 'Abunde fructificans! diff a F angu losa sporis echinulatis. The current and long-standing con cept of F caespitiformis is of a monoicous species with patent to erect, undulate to cr?spate leaves and spores with a verrucate to cristate distal surface, with the cristae often truncate, but never sharply pointed or truly echinate. These characters have been used to circumscribe this species since the revision of Fossombronia Raddi by Lindberg (in Not. S?llsk. Fauna Fl. Fenn. F?rh. 13: 380-390 + Tab. I, 1874) and are not contrary to the protologue. The diagnostic char acter ''sporis echinulatis could easily be applied incorrect ly to spores that are actually cristate, since both morpholo gies can appear somewhat similar when visualized with an optical microscope. Regardless, that character alone is in sharp contrast to the spore morphology of F angulosa referred to in De Notaris's diagnosis. The current and long standing concept o? Fossombronia angulosa (Dicks.) Raddi is of a more robust, dioicous plant with horizontal to patent leaves that are usually nearly plane and spores that have an areolate distal surface. This view of these two Old World

Cyathodium foetidissimum (Marchantiales), An Asiatic Species New to Tropical America

Abstract Cyathodium foetidissimum Schiffn., an Asiatic species is reported for the first time for the Neotropics. The species is distinguished by the presence of a central multistratose area of cells; oil cells with a single oil body; strongly dimorphic rhizoids; large ventral scales; monoicous condition with an apical, male receptacle flanked by archegonia in undulate laminar involucres; an operculum of 12 cells; upper cells of the capsule with bar-like thickenings; elaters with three bands; and verrucose spores. The closest relative in habit is Cyathodium spruceanum Prosk., but plants of this species lack a “midrib” and have oil bodies and chloroplasts in the thallus cells; it is dioicous and the spores are lamellate-reticulate. Mature male plants of Cyathodium foetidissimum have been found along with bisexual thalli. This is the first report of both types of gametophytes occurring simultaneously in monoicous species of neotropical Cyathodium.

Sporophyte Production and Sexuality of Mosses in Two Northern Michigan Habitats

The hypothesis that dioicous mosses produce sporophytes less fre- quently than monoicous mosses was tested by sampling populations in two con- trasting habitats. In a dry aspen forest the mean percentages of populations with sporophytes were 75.9 for monoicous and 19.3 for dioicous species, while in a wet coniferous forest the means were 84.1 for monoicous and 12.3 for dioicous species. Dioicous species with antheridia borne in splash cups showed significantly higher sporophyte production than those without splash cups. However, dioicous species with male plants dwarfed and epiphytic on female plants did not show significantly greater sporophyte production. Differences in sporophyte production between hab- itats were minimal. Since there is no evidence that apogamy is frequent in mosses, it is reasonable to assume that sporophyte production is dependent upon fertilization. Sperms are released from the antheridia in the presence of free water and must travel to an egg within an archegonium to effect fertilization. Although the sperms are biflagellate, it is doubtful that they rely much upon swimming for dispersal. Showalter (1926) showed that sperms of Riccardia pinguis placed at one side of a 1 x 0.5 cm drop of water swam vigorously but never dispersed themselves throughout the drop. Rather, because of lipids in the sperm mass, sperms are carried along passively as surface films on splashing drops of water or by water flowing over the plants (Muggoch & Walton 1942; Paolillo 1981). Insects and other minute invertebrates have also been recorded as vectors of sperm transfer (Harvey- Gibson & Miller-Brown 1927). Both self-fertile and self-sterile monoicous species have been reported (Lazarenko & Lesnyak 1972; Lazarenko 1974; Ashton & Cove 1976). While sperms need only travel a short distance to fertilize an archegonium in self-fertile species, in dioicous and self-sterile monoicous species sperms must travel from one plant to another. Sperms are short-lived and can disperse only limited distances. Sperm transfer distances have been measured for several dioicous species (Bedford 1938, 1940; Longton & Greene 1967, 1969; Newton 1971; Riemann 1972; Clayton-Greene et al. 1977; Wyatt 1977; Reyn- olds 1980) and one monoicous species (Anderson & Lemmon 1974). Most measurements were minimum estimates, determined by measuring the distance from plants bearing spo- rophytes to the nearest male, and most of the studies indicated that sperms rarely have an effective range of fertilization over 10 cm. Thus, separation of the sexes on different plants would seem to decrease the probability of fertilization; and in general, dioicous species would be expected to produce sporophytes less frequently than monoicous species. Using data on fruiting derived from Dixon's Handbook of British Mosses (1924), Gem- mell (1950) compiled a contingency table demonstrating the relationship of sexuality to frequency of sporophyte production. Of the 239 monoicous species, 232 fruited frequently. Of the 252 dioicous species, 148 fruited frequently, 47 rarely, and 57 very rarely. Lefebvre (1969) presented data based on 350 specimens showing that dioicous species of Belgian