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Tasmanian Eucalyptus

Tasmania, Australia hosts 29 native species of Eucalyptus from two major subgenera: Eucalyptus and Symphyomyrtus. A few notable species include Eucalyptus globulus (timber), Eucalyptus regnans (tallest tree), and Eucalyptus radiata (essential oil).

Publications

An evolutionary case for plant rarity: Eucalyptus as a model system

Ecology & Evolution

Rarity as an evolved syndrome of traits.

Rare species have lower biomass and allocate more resources aboveground than common species
Plant biomass is under evolutionary selection: diverging selection between rare and common species, but convergent selection across the phylogeny
Plant biomass, under selection, is highly correlated with species' range size and habitat specificity

Functional traits under evolutionary selection drive geographic patterns in plant occurrence and therefore rarity.

Evolution of rarity and phylogeny determine above-and belowground biomass in plant-plant interactions

PLOS ONE

Rare species may use facilitative interactions with species based on rarity and phylogenetic relatedness to persist in complex communities, but in low frequency.

Rare species demonstrate progressively positive non-additive responses in biomass when interacting with phylogenetically intermediate, less rare species.
Rare species benefit from interactions with specific species, such as Eucalyptus globulus.

Eucalyptus Research

Tasmanian Eucalyptus as a model system to study the evolution of plant rarity and the role of rarity in species-species interactions.

Challenging long-standing assumptions to advance rarity theory

Rarity is often considered a stochastic, ecological response to environmental factors. Ecological perspectives suggest that rarity progresses on a continuum from commonness to rarity and ultimately to extinction, under Anthropogenic change. However, it is difficult to conserve rare biodiversity when we don't know if, how, or which species will become rare, nor if they will continue to persist in community.

Rabinowitz rarity (proposed in 1981) offers a geographic exploration of rarity that is based on the range size, habitat specificity, and local population size of a species. This framework can be used to create an ordinal rank system to characterize and compare variation in rarity. Applications of this system rethink geographic rarity to incorporate functional traits as a key mediator of rarity and rarity as a key mediator of species-species interaction outcomes.

What does this mean?

Rarity is an evolved condition characterized by unique functional traits, such as low biomass and increased allocation to aboveground structures. This syndrome is under convergent evolutionary selection across the phylogeny of Tasmanian Eucalyptus. Although rare species maintain low biomass and low abundance within communities, they demonstrate non-additive positive interactions with less rare species of similar and intermediate phylogenetic relatedness. In short... climate has likely driven rare species to repeatedly become smaller, but rare species perform well and persist with closely related common species.

This suggests that rare species may continue to persist in community due to their own rarity. However, as species become progressively more rare under climate change, the evolutionary and ecological processes that maintain rarity and the ecosystem functions supported by high biomass common species may be disrupted.