Demographic population structure of a leafy epixylic hepatic Anastrophyllum hellerianum (Nees ex Lindenb.) R.M.Schust

Pohjamo, Maria; Laaka‐Lindberg, Sanna

doi:10.1023/b:vege.0000026330.62021.0a

Cited by 24 publications

(22 citation statements)

References 30 publications

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“…In Anastrophyllum hellerianum (Nees ex Lindenb.) R.M.Schust., the only other liverwort species for which this information is available, a much lower proportion (34%) of shoots was reported as being gemmiferous (Pohjamo & Laaka-Lindberg, 2003, 2004. Shoot-level production of gemmae, on the other hand, falling mostly in the range 900-5000 per shoot, is broadly in keeping with previous reports of 1000-7000 for Lophozia silvicola, and a mean of 1181 for Anastrophyllum hellerianum (Laaka-Lindberg, 1999;Pohjamo & Laaka-Lindberg, 2003, 2004.…”

Section: Discussionsupporting

confidence: 85%

“…R.M.Schust., the only other liverwort species for which this information is available, a much lower proportion (34%) of shoots was reported as being gemmiferous (Pohjamo & Laaka-Lindberg, 2003, 2004. Shoot-level production of gemmae, on the other hand, falling mostly in the range 900-5000 per shoot, is broadly in keeping with previous reports of 1000-7000 for Lophozia silvicola, and a mean of 1181 for Anastrophyllum hellerianum (Laaka-Lindberg, 1999;Pohjamo & Laaka-Lindberg, 2003, 2004. Holá et al (2011) examined gemma production in three Lophozia species including L. ventricosa, but comparison with our study is difficult since they provide no summary statistics and furthermore included non-gemmiferous shoots in their reported output.…”

Section: Discussionmentioning

confidence: 99%

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Gemma output in the liverwortLophozia ventricosa(Dicks.) Dumort: spatial variation, density dependence, and relationships among production components

Algar-Hedderson

Söderström

Hedderson

2013

Journal of Bryology

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Although gemma production is common among liverworts, and thought to play a key role in their population dynamics, quantitative data on numbers produced at shoot and colony levels, or on spatial variation in these numbers, are very sparse. Here we investigate gemma output of a boreal and arctic liverwort species, Lophozia ventricosa, at populations in Trøndelag, a boreal region of central Norway, and in arctic tundra on Svalbard. Production parameters investigated include colony size, shoot density, number of gemmae per shoot, proportion of shoots gemmiferous, and gemmiferous shoot density. Colony-level output was calculated as the product of the number of gemmae per shoot, colony size, and gemmiferous shoot density. Nested analysis of variance, used to spatially partition variance in these gemma-production components, reveals that the vast majority of the variation lies at the measurement level, i.e. among shoots within colonies or among colonies within plots. The only significant difference between the two geographic areas is that in boreal sites shoots tend to produce slightly more gemmae, and form larger, denser, colonies. This translates to somewhat higher colony-level output in boreal, compared to arctic, sites. Evaluation of a structural equations model reveals intricate patterns of relationship among the production components and provides strong evidence of negative density dependence of shoot-level production. We argue that explicit evaluation of size-number tradeoffs, allometric scaling of production with shoot size, and detailed studies of genetic versus phenotypic effects on production levels, are necessary to understand how asexual propagule production is shaped by selection on life histories.

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Section: Discussionsupporting

confidence: 85%

Section: Discussionmentioning

confidence: 99%

Gemma output in the liverwortLophozia ventricosa(Dicks.) Dumort: spatial variation, density dependence, and relationships among production components

Algar-Hedderson

Söderström

Hedderson

2013

Journal of Bryology

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“…Wet conditions are likely to provide a favourable environment for propagule germination and establishment for both gemmae and spores. In A. hellerianum, gemmae germinate faster than spores (Pohjamo and Laaka-Lindberg 2004), which indicates better establishment efficiency among asexual propagules (see also Kimmerer 1991). Furthermore, the asexual gemmae are genetically identical to their parents and sibs (in some cases also true for the spores, see Mishler 1988), and thus presumably well adapted to the local conditions.…”

Section: Variablementioning

confidence: 95%

“…In our previous study, the longest and, therefore, the most exposed shoots in the colonies of A. hellerianum were gemmiparous (Pohjamo and Laaka-Lindberg 2004). While rainy conditions facilitated the numbers of gemmae released, environmental conditions seemed not affect the dispersal distance patterns of the gemmae.…”

Section: Dispersal Potential Of Spores and Gemmaementioning

confidence: 96%

“…To estimate the numbers of gemmiparous shoots on the logs, the number of all shoots (gemmiparous or not) was counted for 1 cm 2 samples (n = 3 for each log), and the shoot density was multiplied by the total area of asexual shoots. We corrected the estimated number of all shoots to the number of gemmiparous shoots based on our previous study in the same area (Pohjamo and Laaka-Lindberg 2004), where the proportion of gemmiparous shoots in the colonies of A. hellerianum was found to equal 37% out of all shoots.…”

Section: Field Studymentioning

confidence: 99%

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Dispersal potential of spores and asexual propagules in the epixylic hepatic Anastrophyllum hellerianum

et al. 2006

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Dispersal ability is of great importance for plants, which commonly occupy spatially and temporally limited substrate patches. Mixed reproductive strategies with abundant diaspore production are favoured in a heterogeneous landscape to ensure successful colonisation at different distances. In bryophytes, long-distance dispersal has been thought to take place primarily by spores, while asexual propagules are important in local dispersal and in the maintenance of colonies. In the present study, we investigated the dispersal potential of two equally sized propagules, sexually formed spores and asexually produced gemmae in the dioecious, epixylic hepatic, Anastrophyllum hellerianum, which inhabits spatially and temporally limited substrate patches. We trapped propagules at different distances (0-10 m) and directions from the source colonies in two experiments: one in a natural habitat within a forest and another involving an artificial set-up in an open habitat. Spore dispersal showed only slight distance dependence both in the open and the forest habitats, presumably as a consequence of wind affecting the dispersal pattern. Gemma dispersal was more strongly distance-dependent in the open habitat than in the forest sites. Considerably more gemmae were deposited during rainy than dry periods, possibly because of the effect of rain drops on gemma release. However, weather conditions had no effect on the dispersal patterns of spores or gemmae. In A. hellerianum, the combination of occasional spore production and practically continuous, massive gemma production facilitates dispersal both on local scale and over long distances. Unlike previously assumed, not only spores but also the asexual propagules may contribute to longdistance dispersal, thus allowing considerable gene flow at the landscape level.

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Dispersal and life history strategies in epiphyte metacommunities: alternative solutions to survival in patchy, dynamic landscapes

Löbel

Rydin

2009

Oecologia

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Host trees for obligate epiphytes are dynamic patches that emerge, grow and fall, and metacommunity diversity critically depends on efficient dispersal. Even though species that disperse by large asexual diaspores are strongly dispersal limited, asexual dispersal is common. The stronger dispersal limitation of asexually reproducing species compared to species reproducing sexually via small spores may be compensated by higher growth rates, lower sensitivity to habitat conditions, higher competitive ability or younger reproductive age. We compared growth and reproduction of different groups of epiphytic bryophytes with contrasting dispersal (asexual vs. sexual) and life history strategies (colonists, short- and long-lived shuttle species, perennial stayers) in an old-growth forest stand in the boreo-nemoral region in eastern Sweden. No differences were seen in relative growth rates between asexual and sexual species. Long-lived shuttles had lower growth rates than colonists and perennial stayers. Most groups grew best at intermediate bark pH. Interactions with other epiphytes had a small, often positive effect on growth. Neither differences in sensitivity of growth to habitat conditions nor differences in competitive abilities among species groups were found. Habitat conditions, however, influenced the production of sporophytes, but not of asexual diaspores. Presence of sporophytes negatively affected growth, whereas presence of asexual diaspores did not. Sexual species had to reach a certain colony size before starting to reproduce, whereas no such threshold existed for asexual reproduction. The results indicate that the epiphyte metacommunity is structured by two main trade-offs: dispersal distance vs. reproductive age, and dispersal distance vs. sensitivity to habitat quality. There seems to be a trade-off between growth and sexual reproduction, but not asexual. Trade-offs in species traits may be shaped by conflicting selection pressures imposed by habitat turnover and connectivity rather than by species interactions.

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Demographic population structure of a leafy epixylic hepatic Anastrophyllum hellerianum (Nees ex Lindenb.) R.M.Schust

Cited by 24 publications

References 30 publications

Gemma output in the liverwortLophozia ventricosa(Dicks.) Dumort: spatial variation, density dependence, and relationships among production components

Gemma output in the liverwortLophozia ventricosa(Dicks.) Dumort: spatial variation, density dependence, and relationships among production components

Dispersal potential of spores and asexual propagules in the epixylic hepatic Anastrophyllum hellerianum

Dispersal and life history strategies in epiphyte metacommunities: alternative solutions to survival in patchy, dynamic landscapes

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