Population Dynamics of the Moss Polytrichum Piliferum in North-East Scotland

Hobbs, V. J.; Pritchard, N.M.

doi:10.2307/2260543

Cited by 27 publications

(15 citation statements)

References 20 publications

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“…The latter is true if the mortality of ramets is not correlated too highly, i.e. if mortality causes are fine‐grained (Cook 1985), as in fact has been observed for a few other Polytrichum species (Collins 1976; Hobbs & Pritchard 1987). The spatial distribution of genets suggests a ‘phalanx’ type of clonal growth in P. formosum , which might facilitate a more favourable microclimate for individual gametophytes leading to a higher genet survival.…”

Section: Discussionmentioning

confidence: 89%

“…As sporophytes were abundant in this population (M. van der Velde, personal observation), recently produced spores might be the source from which the new genets were recruited. However, the high genotypic diversity, and thus the importance of sexual reproduction in P. formosum , seems to contradict the highly infrequent observation of recruitment from spores in bryophyte populations (Hobbs & Pritchard 1987; Miles & Longton 1987, 1990; Innes 1990), although the lack of observations of recruitment from spores might also be explained simply by the difficulties in demonstrating its occurrence in the field (Newton & Mishler 1994). However, recruitment from spores might indeed be rare, but due to the extreme longevity of individuals, caused by clonal growth of genets, high levels of genotypic diversity may be reached due to accumulation of genets in the population (Sebens & Thorne 1985; During & Van Tooren 1987; Eriksson & Fröborg 1996).…”

Section: Discussionmentioning

confidence: 99%

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The reproductive biology of Polytrichum formosum: clonal structure and paternity revealed by microsatellites

et al. 2001

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Using highly polymorphic microsatellite markers, we assessed clonal structure and paternity in a population of the bryophyte species Polytrichum formosum. Identical multilocus genotypes of individual shoots were almost never observed in spatially separated cushions, but were found to be highly clustered within moss cushions. Therefore, asexual reproduction through dispersal of gametophyte fragments is not very important in P. formosum. However, asexual reproduction on a very localized scale through vegetative growth of genets (branching of gametophytes via clonal growth of rhizomes) is very extensive. The patchy spatial distribution of genets and the absence of intermingling among genets suggest that this species follows a 'phalanx' clonal growth strategy. Vegetative proliferation of genets will increase their size, and, consequently, will have considerable fitness consequences for individuals in terms of increased genet longevity and reproductive output. Although paternity analysis of sporophytes confirmed male genet size, i.e. gamete production, to be an important determinant of male reproductive fitness, it also showed that the spatial distance to female genets is the predominant factor that governs male reproductive success. Moreover, we showed that male gamete dispersal distances in P. formosum are much further than generally assumed, and are in the order of metres rather than centimetres. Combining the findings, we conclude that the high genotypic diversity observed for this facultatively clonal species is most likely explained by a preponderance of sexual reproduction over clonal reproduction.

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Section: Discussionmentioning

confidence: 89%

Section: Discussionmentioning

confidence: 99%

The reproductive biology of Polytrichum formosum: clonal structure and paternity revealed by microsatellites

et al. 2001

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“…One hypothesis that has been proposed is that the phases can exploit different ecological niches (Stebbins and Hill 1980). This has been found in yeasts (Banuett andHerskowitz 1994, Sia et al 2000) and mosses (Hobbs and Pritchard 1987), and is also readily apparent in algae with heteromorphic life cycles (Lubchenco andCubit 1980, Slocum 1980). This hypothesis may also be important for algal species with isomorphic life cycles, as isomorphic haploids and diploids may differ in ways that are morphologically subtle, but ecologically significant (Destombe et al 1989, Engel et al 2001.…”

Section: Discussionmentioning

confidence: 99%

Population Demographics in Species With Biphasic Life Cycles

Thornber

Gaines

2004

Ecology

112

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Abstract. We develop and test models for the population dynamics of species that undergo regular alternations of generations between independent, free-living, haploid and diploid phases. The models are patterned after the dioecious, haploid-diploid lifecycle of many marine algae. If the two phases have equal demographic rates, all models (with or without density dependence) predict a stable distribution with a ratio of :1 (ϳ60% ͙2 haploids and 40% diploids). We find that observable deviations from this distribution can occur when the demographic rates (mortality, fecundity) between phases vary widely. Field surveys of three macroalgal species with independent, free-living haploids and diploids, Mazzaella flaccida, M. laminarioides, and M. splendens, reveal a consistent pattern of haploid dominance that significantly exceeds this null model expectation (72%, 76%, and 66%, respectively). These species also exhibit significant variation in haploid frequency among sites. We estimated the per capita fecundity and mortality rates for each phase of both M. flaccida and M. laminarioides and used this information to address two basic questions: (1) Which parameter better explains the overall high relative haploid abundance for each species? and (2) Which parameter better explains the variation in relative haploid abundance among sites?Differences in haploid and diploid mortality rates did not explain the high relative abundance of haploids for either M. flaccida or M. laminarioides. However, differences in fecundity rates between phases were consistent with the high relative abundance of haploids for M. flaccida; diploids usually had significantly higher per capita fecundity rates than haploids. For M. laminarioides, there were no significant differences in fecundity rates between phases.For M. flaccida, among-site variation in relative abundance of haploids can be explained by differences in mortality rates. The relative abundance of haploids was positively correlated with the ratio of diploid:haploid mortality rates; the sites with the highest ratio of diploid:haploid mortality had the highest percentage of haploids. Differences in mortality rates for M. laminarioides, and fecundity rates for M. flaccida and M. laminarioides, could not explain the observed variation in haploid abundance among sites.

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“…Typically, sperm dispersal is quite short, averaging 10 cm, in natural populations (Anderson and Lemmon, 1974;Kitagawa, 1985;Wyatt, 1985). Although there is an exception of Funaria hygrometrica that is a typical fugitive species (Miles and Longton, 1990), most population studies (i.e., Atrichum undulatum [Miles andLongton, 1987, 1990], Bryum argenteum [Miles and Longton, 1990], Polytrichum alpestre [Miles and Longton, 1990], and P. pili/erum [Hobbs and Pritchard, 1987]) indicate that natural regeneration from spores is usually rare. Derda and Wyatt (1990), however, pointed out that regardless of their potential dispersibility, recruitment ofindividuals into natural populations from spores and asexual propagules may be limited.…”

Section: Discussionmentioning

confidence: 99%

Allozyme variability within and among populations of the epiphytic mossLeucodon (Leucodontaceae: Musci)

Akiyama

1994

American J of Botany

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Enzyme electrophoresis was used to estimate genetic variability within and among populations of five species of the genus Leucodon (L. atrovirens, L. luteus, L. nipponicus, L. sapporensis, and L. temperatus). All of these perennial, dioecious plants are epiphytic on tree trunks and produce numerous spores that are released in winter. Gene diversity within populations (HS) was low (0.070) in L. nipponicus, which grows in disturbed habitats, and high (0.169–0.202) in the other four species, which inhabit stable environments. Gene diversity between populations relative to total diversity (GST) was low in L. temperatus (0.042) and L. luteus (0.043), suggesting that extensive gene flow occurs among populations. GST was moderate in L. sapporensis (0.104) and L. atrovirens (0.114); these values are still less than those previously reported for terrestrial mosses. Since epiphytes could disperse their spores effectively by the wind, low genetic divergence among populations may be related to the epiphytic habit of the species. On the other hand, high GST value (0.208) was found in L. nipponicus. It is probably explained by the genetic differentiation of populations by genetic drift, for the species forms geographically and ecologically isolated populations with small number of individuals. We also observed incongruity between morphological and genetic similarity among species.

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Population Dynamics of the Moss Polytrichum Piliferum in North-East Scotland

Cited by 27 publications

References 20 publications

The reproductive biology of Polytrichum formosum: clonal structure and paternity revealed by microsatellites

The reproductive biology of Polytrichum formosum: clonal structure and paternity revealed by microsatellites

Population Demographics in Species With Biphasic Life Cycles

Allozyme variability within and among populations of the epiphytic mossLeucodon (Leucodontaceae: Musci)

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