The fate of the missing spores

It is well-known that many species with small diaspores can disperse far during extended temporal scales (many years). However, studies on short temporal scales usually only cover short distances (in, e.g., bryophytes up to 15 m). By using a novel experimental design, studying the realized dispersal, we extend this range by almost two orders of magnitude. We recorded establishment of the fast-growing moss Discelium nudum on introduced suitable substrates, placed around a translocated, sporulating mother colony. Around 2,000 pots with acidic clay were placed at different distances between 5 m and 600 m, in four directions, on a raised bog, with increased pot numbers with distance. The experiment was set up in April-May and the realized dispersal (number of colonized pots) was recorded in September. Close to the mother colony (up to 10 m), the mean colonization rates (ratio of colonized pots) exceeded 50%. At distances between 10 and 50 m colonization dropped sharply, but beyond 50 m the mean colonization rates stabilized and hardly changed (1-3%). The estimated density of spores causing establishments at the further distances (2-6 spores/m2) was realistic when compared to the estimated spore output from the central colonies. Our study supports calculations from earlier studies, limited to short distances, that a majority of the spores disperse beyond the nearest vicinity of a source. The even colonization pattern at further distances raises interesting questions about under what conditions spores are transported and deposited. However, it is clear that regular establishment is likely at the km-scale for this and many other species with similar spore output and dispersal mechanism

Tillstånd och trender för arter och deras livsmiljöer

2015 års upplaga av den svenska rödlistan är den fjärde i ordningen. Den är baserad på IUCN:s rödlistningskriterier och revideras vart femte år. I rödlistan bedöms risken som enskilda arter av djur, växter och svampar löper att försvinna från Sverige. Bedömningen utförs av ArtDatabankens medarbetare i samverkan med över 100 externa experter, indelade i 14 expertkommittéer för olika organismgrupper. Under arbetet med 2015 års rödlista har tillstånd och trender bedömts för 21 600 arter och 1 318 lägre taxa (apomiktiska arter, underarter och varieteter), sammanlagt ca 22 900 taxa. Av de bedömda arterna klassificerades 2 029 som hotade (kategorierna CR, EN och VU) och 4 273 som rödlistade (inkluderar även kategorierna NT, RE och DD). Förhållandet mellan antalet rödlistade och antalet bedömda arter ar 19,8 %, vilket är ungefär samma värde som 2010 och 2005. I denna rapport jämförs antalet och andelen rödlistade arter mellan olika organismgrupper, biotoper, substrat och påverkansfaktorer. Texten ar indelad i en allmän del och åtta kapitel inriktade på olika landskapstyper. Landskapstyperna utgör en grov indelning av landets miljöer enligt följande kategorier: Skog, Jordbrukslandskap, Urbana miljöer, Fjäll, Våtmarker, Sötvatten, Havsstränder och Havsmiljöer. Skogen och jordbrukslandskapet är de artrikaste landskapstyperna med 1 800 respektive 1 400 arter som har en stark anknytning dit, och ytterligare flera hundra arter som förekommer där mer sporadiskt. De faktorer som påverkar flest rödlistade arter i Sverige är skogsavverkning och igenväxning, som båda utgör ett hot mot vardera ca 30 % av de rödlistade arterna. Avverkning minskar arealen av skog där naturliga strukturer och naturlig dynamik upprätthålls, och den orsakar därmed förlust av livsmiljöer. Igenväxning orsakas av ett antal faktorer, bland annat upphörande hävd (bete och slåtter), gödsling, trädplantering och brist på naturliga störningsregimer som t.ex. regelbundna översvämningar kring vattendrag och sjöar. Andra viktiga påverkansfaktorer är fiske, torrläggning av våtmarker, tillbakagång hos värdarter (främst alm och ask som drabbats av invasiva svampsjukdomar), klimatförändringar och konkurrens från invasiva arter. IUCN:s rödlisteindex beräknas för ett urval av de bedömda organismgrupperna. Rödlisteindex visar att skillnaderna mellan rödlistorna från 2000, 2005, 2010 och 2015 är små. Ett par undantag finns dock. Groddjur och stora däggdjur har fått en något förbättrad situation sedan 2000. Totalt förefaller det ändå som att trycket mot Sveriges artstock har förblivit relativt konstant under de senaste 15 åren

Dispersal of bryophytes across landscapes

Dispersal, especially long-distance dispersal, is an important component 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 landscape 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 colonization 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 disturbance (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 increased 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 effective 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 abundantly). 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.At the time of the doctoral defence the following papesr were unpublished and had  a status as follows: Paper 2: Epubl ahead of print; Paper 3: Manuscript; Paper 4: Manuscript</p

Genetic variation and reproductive patterns in wetland mosses suggest efficient initial colonization of disturbed sites

To understand colonization processes, it is critical to fully assess the role of dispersal in shaping biogeographical patterns at the gene, individual, population, and community levels. We test two alternative hypotheses (H I and H II) for the colonization of disturbed sites by clonal plants, by analyzing intraspecific genetic variation in one and reproductive traits in two typical fen mosses with separate sexes and intermittent spore dispersal, comparing disturbed, early-succession (limed) fens and late-successional rich fens. H I suggests initial colonization of disturbed sites by diverse genotypes of which fewer remain in late-successional fens and an initially balanced sex ratio that develops into a possibly skewed population sex ratio. H II suggests initial colonization by few genotypes and gradual accumulation of additional genotypes and an initially skewed sex ratio that alters into the species-specific sex ratio, during succession. Under both scenarios, we expect enhanced sexual reproduction in late-successional fens due to resource gains and decreased intermate distances when clones expand. We show that the intraspecific genetic diversity, assessed by two molecular markers, in Scorpidium cossonii was higher and the genetic variation among sites was smaller in disturbed than late-successional rich fens. Sex ratio was balanced in S. cossonii and Campylium stellatum in disturbed fens and skewed in C. stellatum in late-successional fens, thus supporting H I. In line with our prediction, sex expression incidence was higher in, and sporophytes were confined to, late-succession compared to disturbed rich fens. Late-successional S. cossonii sites had more within-site patches with two or more genotypes, and both species displayed higher sex expression levels in late-successional than in disturbed sites. We conclude that diverse genotypes and both sexes disperse efficiently to, and successfully colonize new sites, while patterns of genetic variation and sexual reproduction in late-successional rich fens are gradually shaped by local conditions and interactions over extended time periods

Pyramidula tetragona (Brid.) Brid. rediscovered in Fennoscandia and new to Norway

publishedVersio

Lonnell_Hylander_Envdata_JBiogeography2018

Environmental data and a species-by-site matrix. The excel-file also has meta-data in separate sheets

Determinants of bryophyte species composition and diversity on the Great Alvar of Öland, Sweden

Factors driving the species richness and distribution of bryophytes are poorly studied and not well understood, particularly in grasslands. We analysed the occurrence of bryophyte species and variation in species richness across 674 plots (0.5 m× 0.5 m) in alvar vegetation (grassland on limestone pavement with thin or no soil) on Öland (Sweden) in relation to substrate characteristics and chemistry, inundationfrequency, grazing pressure and geographical variables. We found 148 taxa, including 11 nationally redlisted ones. Species richness per plot was significantly associated with substrate type, positively associated with pH and grazing intensity, but negatively associated with soil depth. However, richness of species typical of, or restricted to, alvar habitats responded differently to richness of species more common in other habitats. Typical alvar species were favoured by high pH, shallow soil and lowphosphate availability, while generalists preferred relatively low pH, higher phosphate availability and organic or mull soil types. Distance from the alvar margin had only weak effects. Concerning the effects on individual species and community composition, inundation frequency and pH were found to have the largest effects, although other factors (substrate type, soil depth, bare soil, bare stone, phosphateavailability and grazing pressure) were more important for some individual species, stressing the importance of microsite variability and variability in management for regional species richness. From a conservation perspective, it is concluded that grazing is generally positive whilst factors increasing phosphate availability may disadvantage the typical alvar species, and proximity to the alvar margin is nota major problem

Map of the field site and study design at Jordbärsmuren.

<p>The mother colony was situated in the centre: pots were placed at 1, 5, 10, 30, 50, 80, 150, 300 and 600 m in each direction at in total 36 sampling stations. Note: The area with the sampling stations from 50 m and inwards are represented by a large white circle. Background aerial photographs: © Lantmäteriet Gävle 2011 (Permit I 2011/0094).</p

Mean colonization rate and spore density per distance.

<p>For each distance the number of sampling stations, the total number of pots put out, those who remained colonizable, colonized pots, mean colonization rates (ratio of colonized pots) and calculated density of spores, based on the number of colonised pots per distance from the mother colony.</p

RH_thresholds

RH thresholds and spore releas