Message - 7th IAL Symposium

The 7 th International Association for Lichenology Symposium 2012
2I: Adaptation and morphological evolution
(2I-O1) Submission ID: IAL0020-00004
THALLUS ARCHITECTURE AND DOMINANCE IN CLADINA
Crittenden P. D. 1 , Sturrock C. 2 , Ellis C. J. 3
1 School of Biology, University of Nottingham, Nottingham, United Kingdom
2 School of Biosciences, University of Nottingham, Nottingham, United Kingdom
3 Cryptogamic Herbarium, Royal Botanic Garden Edinburgh, Edinburgh, United Kingdom
The capacity of mat-forming lichens, most notably those in the subgenus Cladina, to dominate the
ground cover over large tracts of subarctic terrain has been attributed to their specialized mode of growth. Matforming
lichens grow acropetally (at the apices vertically upwards) while older basal regions of the thallus senesce
to produce an understorey of intact and persistent litter or necromass. This basal senescence is believed
to facilitate internal recycling of nitrogen and phosphorus used to fund high growth rates in the apices resulting,
under steady state conditions, in deeper mats casting deeper shade. However, how thallus architecture in
mat-forming lichens is adapted to promote dominance (sensu Grime) has not previously been investigated. We
hypothesise that the three-dimensional multi-branched structure of Cladina species is an adaptation to maximise
interception of light and nutrients and to generate deep zones of depletion below the “photic zone”. We
have used X-Ray computed tomography to determine vertical changes in gap fraction (light interception) and
leaf area index (LAI) in mats of Cladonia portentosa in Scottish moorland. We compare these data with field
measurements made in intact lichen mats of vertical gradients in light (determined using a fibre-optic quantum
sensor) and 15N capture from labelled simulated rainfall, and with laboratory measurements of vertical changes
in total chlorophyll content. We discuss the results in terms of possible trade-offs between needs for maximising
interception of resources to promote dominance, light capture for photosynthesis and regenerative capacity. We
also compare these first measurements of LAI within Cladina mats with those of forest trees.
(2I-O2) Submission ID: IAL0185-00001
PHENOTYPIC PLASTICITY IN LICHENS: INSIGHTS ON THE BIOLOGY OF THE EXTREME
MODIFICATIONS IN CETRARIA ACULEATA (PARMELIACAE)
Perez-Ortega S. 1 , Fernandez-Mendoza F. 2 , Raggio J. 3 , Vivas M. 3 , Ascaso C. 1 , Sancho L. 3 ,
Printzen C. 2 , De Los Rios A. 1
1 Biologia Ambiental, MNCN, CSIC, Madrid, Spain
2 Botany,Senckenberg Research Insititute, Frankfurt Am Main, Germany
3 Biología Vegetal II, Universidad Complutense, Madrid, Spain
Phenotypic plasticity has been widely reported in lichens and its importance affects not only to the
field of lichen ecophysiology but also to taxonomy and speciation genetics. We studied extremely modified
vagrant morphs of the lichen Cetraria aculeata commonly found in steppe environments from Central Spain. CO 2
exchange behaviour, water relationships, anatomical and ultrastructural modifications and genetic differentiation
were studied for several populations of normal attached morphs of C. aculeata and modified vagrant morphs.
We found that normal and vagrant morphs differ in the time span they are photosynthetically active. Further,
the severe modifications found in vagrant morphs have an anatomical and ultrastructural basis, with intercalary
growth being the most likely responsible for the abnormal growth found in vagrant morphs. Finally, we also
observed certain degree of genetic differentiation between normal and vagrant morphs; however they do not
differ in photobiont use.
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