By understanding the lichen response to habitat dynamics we can identify management actions to reduce the vulnerability of biodiversity to global change, including climate change.

Our research is focussed on epiphytes in Scottish woodlands, at three distinct scales: the biology of the lichen symbiosis, the population and individual species response, and the whole community response.

The Lichen Symbiosis

The lichen symbiosis - fungal and photobiont partner (alga or cyanobacteria) - is a model system for understanding how close species interactions might influence the biodiversity response to climate change. Our work has supported the hypothesis that spore dispersed cyanolichens (with need for resynthesis with their photobiont during establishment) have a requirement for facilitation through the prior colonisation of asexual cyanolichens (which disperse both fungus and photobiont together); spores sequester the photobiont from asexual propagules. Since spores are smaller and disperse further than asexual propagules, this reverses expectations under climate change (Belinchón et al. 2015), suggesting that migration to track suitable climate space by spore-dispersed species might be rate-limited by the dispersal of asexual species with larger and heavier propagules.

• Belinchón, R., Yahr, R. & Ellis, C.J. (2015) Interactions among species with contrasting dispersal modes explain distributions for epiphytic lichens. Ecography, 38: 762-768.

Population and Species Response

Our research is increasingly focussed at the population scale, through the development of dynamic models that inform conservation practice. First, we have linked species distributions to growth rates (Eaton & Ellis 2012; Ellis et al. 2017), to confirm the functional sensitivity of lichens to large-scale climate. Climatically-sensitive growth is then coupled with the contrasting availability of suitable microhabitat under different climates. This cross-scale interaction explains the particular sensitivity of oceanic species to microhabitat at range edges (Lisewski & Ellis 2010), and their dependency on ancient 'old-growth' woodland in sub-optimal climates (Ellis et al. 2009). Applying this linkage in population models, we have quantified the degree to which microhabitat quality needs to increase to offset a growth-rate decline caused by climate change (Ellis 2018), and the additional severity of threat caused by climate change in combination with declining microhabitat suitability (e.g. tree disease).

• Eaton, S. & Ellis, C.J. (2012) Local experimental growth rates respond to macroclimate for the lichen epiphyte Lobaria pulmonaria. Plant Ecology and Diversity, 5: 365-372.
• Ellis, C.J. (2018) A mechanistic model of climate change risk: growth rates and microhabitat specificity for conservation priority woodland epiphytes. Perspectives in Plant Ecology, Evolution and Systematics, 32: 38-48.
• Ellis, C.J., Geddes, H., McCheyne, N. & Stansfield, A. (2017) Lichen epiphyte response to non-analogue seasonal climates: a critique of bioclimatic models. Perspectives in Plant Ecology, Evolution and Systematics, 25: 45-58.
• Ellis, C.J., Yahr, R. & Coppins, B.J. (2009) Local extent of old-growth woodland modifies epiphyte response to climate change. Journal of Biogeography, 36: 302-313.
• Lisewski, V. & Ellis, C.J. (2010) Epiphyte sensitivity to a cross-scale interaction between habitat quality and macroclimate – an opportunity for range-edge conservation. Biodiversity & Conservation, 19: 3935-3949.

Lichen growth experiments are used to characterise a functional climate change response.

Traits and Community Response

Research at the community-scale aims to understand how woodland structure affects the species composition and richness of epiphyte communities, but also how assembly rules (e.g. competetion/facilitation) might affect trait-based community succession (Ellis & Coppins 2007; Lewis & Ellis 2010; Ellis & Ellis 2012). A focus on the ecology of traits (Ellis et al. 2021) provides a key link to climate change and ecosystem function, since the changing composition and diversity of an epiphyte community as a tree ages - in terms of species and their traits - interacts with the climatic setting (Ellis & Coppins 2006). Work is now exploring how different phenotypic adaptations (Wan & Ellis 2020) affect the lichen niche, community structure and response to climate change.

• Ellis, C.J. & Coppins, B.J. (2006) Contrasting functional traits maintain lichen epiphyte diversity in response to climate and autogenic succession. Journal of Biogeography, 33: 1643-1656.
• Ellis, C.J. & Coppins, B.J. (2007) Reproductive strategy and the compositional dynamics of crustose lichen communities on aspen (Populus tremula L.) in Scotland. The Lichenologist, 39: 377-391.
• Ellis, C.J. & Ellis, S.C. (2013) Signatures of autogenic epiphyte succession for an aspen chronosequence. Journal of Vegetation Science, 24: 688-701.
• Ellis, C.J., Asplud, J., Benesperi, R., Branquinho, C, Di Nuzzo, L., Hurtado, P., Martinez, I., Matos, P., Nascimbene, J., Pinho, P., Prieto, M., Rocha, B., Rodriguez-Arribas, C., Thus, H. & Giordani, P. (2021) Functional traits in lichen ecology: a review. Microorganisms, 9: 766.
• Lewis, J.E.J. & Ellis, C.J. (2010) Taxon- compared to trait-based analysis of epiphytes, and the role of tree species and tree age in community composition. Plant Ecology and Diversity, 3: 203-210.
• Wan, S. & Ellis, C.J. (2019) Are lichen growth form categories supported by continuous functional traits: water-holding capacity and specific thallus mass? Edinurgh Journal of Botany, 77:65-76.