Dispersal of bryophytes across landscapes Niklas Lönnell ©Niklas Lönnell, Stockholm University 2014 Front cover illustration: Niklas Lönnell Back cover photograph: Carita Lönnell Paper cover: 270g Scandia 2000 Paper insert: 100g Color copy naturalwhite ISBN 978-91-7447-778-8 Printed in Sweden by US-AB, Stockholm 2014 Distributor: Department of Ecology, Environment and Plant Sciences, Stockholm University Some things in life are bad They can really make you mad Other things just make you swear and curse. When you're chewing on life's gristle Don't grumble, give a whistle And this'll help things turn out for the best... (Eric Idle) Contents Glossary .......................................................................................................... 6 Abstract ........................................................................................................... 7 List of Papers .................................................................................................. 9 Introduction .................................................................................................. 10 Dispersal .................................................................................................................. 10 Bryophyte dispersal .............................................................................................. 13 Objectives of the thesis ................................................................................ 16 Methods ......................................................................................................... 17 Study areas ............................................................................................................. 18 Study system 1 – Dicelium nudum ................................................................... 18 Study species .................................................................................................... 18 Study system 2 – limed mires ........................................................................... 21 Results and discussion ................................................................................. 23 References .................................................................................................... 28 Svensk sammanfattning ............................................................................... 33 Tack ............................................................................................................... 36 Glossary Anemochory – Wind dispersal Antheridium – The male elliptical reproductive organ from where the spermatozoids have to swim to the archegonium. Archegonium – The female bottle-shaped reproductive organ with a long neck with a canal which lead down to the venter where the eggcell is situ- ated. Bryophytes – A generic term for the polyphyletic group consisting of mosses, liverworts and hornworts Deposition (syn. landing) – The final stage of dispersal where the diaspores come to rest Diaspore (syn. propagule) – A dispersal unit that could be a seed, spore, gemmae or even a fragment (as bryophytes can regenerate from any part of the gametophyte). Dispersal – Transportation of diaspores away from the plant of origin (See introduction) Impaction – A deposition process when a diaspore continues its path to- wards an object instead of following the air stream around it Interception – A deposition process when a diaspore travels so near an ob- ject that it touches it Lagrangian stochastic dispersion model – A model that simulates a large number of trajectories of a single diaspore taking into account the variation in wind components. Liming – A practice to spread calcium compounds (to increase the pH) Release (syn. abscission, take-off) – The process when the diaspores leave the place of origin, in the case of bryophyte spores the capsule. Sedimentation – A deposition process when a diaspore is deposited due to gravity Settling velocity/speed (syn. falling/fall velocity/speed, terminal veloc- ity/speed) – A measure of how fast a diaspore falls. It is defined as the dias- pore speed when the drag force (upwards) and the force by gravity (down- wards) are equal and the particle will not increase its speed. Vector (syn. agent) – A carrier of diaspores, e.g. wind, water and animals -chory – a suffix used to describe different types of dispersal, for example wind dispersal would be anemochory -phily – a suffix used to describe different types of pollen dispersal, but could also be used to describe spore dispersal, wind dispersal would be an- emophily 0:6 Doctoral dissertation Abstract Niklas Lönnell Department of Ecology, Envi- ronment and Plant Sciences Stockholm University Lilla Frescati SE-106 91 Stockholm Sweden Dispersal, especially long-distance dispersal, is an important compo- nent in many disciplines within biology. Many species are passively dispersed by wind, not least spore-dispersed organisms. In this thesis I investigated the dispersal capacity of bryophytes by studying the colonization patterns from local scales (100 m) to land- scape scales (20 km). The dispersal distances were measured from a known source (up to 600 m away) or inferred from a connectivity measure (1–20 km). I introduced acidic clay to measure the coloniza- tion rates over one season of a pioneer moss, Discelium nudum (I–III). I also investigated which vascular plants and bryophytes that had colonized limed mires approximately 20–30 years after the first dis- turbance (IV). Discelium effectively colonized new disturbed substrates over one season. Most spores were deposited up to 50 meters from a source but the relationship between local colonization rates and connectivity in- creased with distance up to 20 km (I–III). Also calcicolous wetland bryophyte species were good colonizers over similar distances, while vascular plants in the same environment colonized less frequently. Common bryophytes that produce spores frequently were more effec- tive colonizers, while no effect of spore size was detected (IV). A mechanistic model that take into account meteorological parameters to simulate the trajectories for spores of Discelium nudum fitted rather well to the observed colonization pattern, especially if spore release thresholds in wind variation and humidity were accounted for (III). This thesis conclude that bryophytes in open habitats can disperse effectively across landscapes given that the regional spore source is large enough (i.e. are common in the region and produce spores abun- dantly). For spore-dispersed organisms in open landscapes I suggest that it is often the colonization phase and not the transport that is the main bottle-neck for maintaining populations across landscapes. Keywords: anemochory, bryophytes, colonization, connectivity, diaspores, dispersal kernel, establish- ment, spore dispersal, long-distance dispersal, mechanistic model, mosses, realized dispersal, spore release, Lagrangian stochastic model, wind dispersal 0:7 0:8 List of Papers This thesis is based on the work contained in the following papers, referred to by Roman numerals in the text I. Lönnell, N., Hylander, K., Jonsson, B.G. & Sundberg, S. (2012) The fate of the missing spores — patterns of realized dispersal beyond the closest vicinity of a sporulating moss. PLoS ONE, 7, e41987. II. Lönnell, N., Jonsson, B.G. & Hylander, K. Production of diaspores at the landscape level regulates local colonization: an experiment with a spore-dispersed moss. Accepted for publication in Ecography. DOI: 10.1111/j.1600-0587.2013.00530.x III. Lönnell, N., Sundberg, S., Norros, V., Rannik, Ü., Johansson, V., Ovaskainen, O. & Hylander, K. Colonization patterns of a wind-dispersed moss in relation to modelled dispersal based on meteorological data. Manuscript IV. Lönnell, N. & Hylander, K. Calcicolous plants colonize limed mires after long-distance dispersal. Manuscript 0:9 Introduction Dispersal Dispersal in a biological context can be defined as "intergenerational movement" or "movement leading to gene flow" or "movement of individuals to new locations away from their parents" and as it is im- portant component in many different both theoretical and applied dis- ciplines it has rendered an increasing attention during the last decades (Bullock, Kenward & Hails 2002; Cousens, Dytham & Law 2008; Clobert et al. 2012). Dispersal can be active, where the individual animal itself can decide on the direction, length and final goal of the dispersal event, or pas- sive,where the individual or dispersal unit (diaspore) is transported by some other vector e.g. animals (zoochory), water (hydrochory) or wind (anemochory) (Pijl 1982). Many fields of ecology and conserva- tion biology are dominated by research concerning animals, which is reflected in the high number of studies that have been devoted to ac- tive dispersal and animal-mediated pollination and dispersal. A ten- dancy for such a bias towards viewing dispersal from an animal per- spective could be detected in the conceptual framework of movement of an individual, where four mechanistic components that influences a movement path are distinguished: internal state (why move?), motion capacity (how to move?), navigation capacity (when and where to move?) and external factors (Nathan et al. 2008a). Consequently, an attempt to apply it on a wind-dispersed fungi encountered some chal- lenges: for example to distinguish between navigation and motion capacity is not unambiguous and the internal state of both the mother plant and the diaspores could be affected independently by external factors (Norros