Similar, but Not the Same: Time and Mode of Climatic Niche Evolution in a Highly Endemic Lineage

Aim

Plant lineages are disproportionally diverse in areas characterised by specific climatic regimes. The campos rupestres habitats in the mountains of Eastern/Central Brazil, for instance, display huge plant endemism and high precipitation seasonality. The genus Vellozia is an emblematic group in there, with most species being endemic and few occurring disjunctively across mountain outcrops of the Neotropics. We aim to test the climate conservatism in the genus, as suggested by its high levels of endemism.

Location

Neotropic.

Taxon

Genus Vellozia (Velloziaceae, monocots).

Methods

We combined MAXENT ecological niche models (ENM) and phylogenetic comparative analyses. Niche overlap between species was estimated based on the environmental similarity and the spatial overlap projected by the ENM. We also traced the climatic niche in the environmental space to describe how its divergence accumulated through time.

Results

We found varying levels, from 16% to 100%, of species pairs displaying niche overlap across distinct lineages of the genus. When niches overlap, they are more similar than expected by chance and not due to habitat availability, suggesting habitat selection. Niche similarity estimates in both ecological and geographical space did not exhibit conserved phylogenetic signals. There was an expressive disparification in the climatic niches in the last 5 m.y., decoupled from the earlier peaks of lineages diversification.

Main Conclusions

Contrary to the expected, we found labile and fast evolution of climatic niches, implying that endemisms do not result from climate niche conservatism in Vellozia. The most diverse clade of Vellozia occupies cooler and wetter environments than the ancestral and other extant lineages of the genus. This pattern contrasts with the historical climatic turnover, for example, cooling-arid vs. warming-wet periods, established since the Pliocene glacial cycles. Moreover, it also poses additional challenges for this lineage and its associated habitats in the face of the current climate change.