Rowan Schley
RESEARCH
I am interested in questions concerning the evolution of tropical diversity across multiple scales. I use a range of genomic methods to approach these questions, including population genomics, phylogenomics and repeat analysis. Below is a list of projects I have led which aimed to answer some of these questions.
Hybridisation in Amazonian trees
Hybridization is widely acknowledged as a powerful creative force in plant evolution, known to generate genetic and morphological novelty, and occurs in at least 25% of plant lineages within some temperate floras.
However, hybridization’s role in the evolution of the Amazon rainforest’s megadiverse tree flora has never been examined empirically and was assumed to be negligible. This is counter-intuitive, given the extreme degree to which closely related species co-occur within the Amazon, thereby providing ideal conditions for hybridization.
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To address this knowledge gap, we examine the dynamics of hybridization across phylogenetic, spatial and temporal scales in members of the legume family, which dominates Amazonian rainforest.
In particular, we aim to assess whether hybridisation catalyses rapid radiations. We hypothesise that hybridisation between tree species 'reshuffles' traits underlying chemical defences against insect herbivory, traits that underlie divergence and facilitate co-existence in many tropical tree species. This 'reshuffling' of adaptive variation may then facilitate rapid diversification. To address this, we use the genus Inga, a species-rich (>300 spp.), widespread and economically important group of trees found in neotropical rainforests.
The 'Ecology' of Repeats in Palm Genomes
Genome size is a critically important trait governing ecological niches, growth rates and evolutionary potential within land plants, which show a staggering 2400-fold variation in genome size. Repetitive element expansion explains much genome size diversity, and the processes structuring repeat ‘communities’ are analogous to those structuring ecological communities. However, which environmental stressors influence repeat community dynamics has not yet been examined from an ecological perspective.
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To study this, we use the palm family (Arecaceae), an iconic group of plants that are a key element of many tropical floras. Genome size varies more than 60-fold across palms, and species within the family are adapted to environments spanning extremes of water stress, from the aridity of the Sahara desert to the perma-wet forests of New Guinea.
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Amazonia:
Museum or Cradle?
The flora of the Neotropics is unmatched in its diversity, however the mechanisms by which diversity has accumulated are unclear. Two major hypotheses of how the biota of the tropics evolved are the ‘museum’ model and the 'cradle' model. The 'museum' model posits that the Neotropical biota evolved gradually over time due to climatic stability and low extinction rates, whereas the 'cradle' model suggests that recent, rapid radiations are the reason behind the hyperdiversity of the tropics.
The Brownea clade (Leguminosae) is a characteristic component of the Neotropical flora, containing species which are 'hyperdominant' in Neotropical forests. This project aimed to examine diversification rates and the spatio-temporal evolution of this group to assess whether the Brownea clade followed the ‘cradle’ or ‘museum’ model of diversification, to help explain how a portion of Neotropical plant diversity was assembled.
Spatio-temporal evolution of the Sun Orchids
The diversification of the Australian flora during the past 20 million years has been driven by numerous climatic, biogeographical and phylogenetic factors.
Thelymitra, the Sun orchids, are a characteristic component of the Australian terrestrial orchid flora, with a recent history of rapid diversification and hybridization; studies examining these phenomena using molecular phylogenetics are few.
This project aimed to infer infra-generic relationships within Thelymitra, to investigate the dates and biogeographical patterns of species divergence within the genus. This was undertaken using phylogenetics, divergence dating and biogeographical analysis and helped highlight how climatic and geographical flux during the Tertiary period drove the rapid evolution of major components of the unique Australasian biota.
