Species distribution modelling and climatic niche as tools to aid in the integrative taxonomy of a South American species complex in Chromolaena (Asteraceae, Eupatorieae)

Abstract

Context The Chromolaena congesta complex is an informal group of taxa native to grasslands from south-eastern South America with numerous identification problems, currently under study using an integrative approach. Recent studies with morphological data have aided in defining some taxa, but many questions remain to be assessed, and there is much to gain from combining morphological data with other lines of evidence. Aims We investigated whether the species of the C. congesta complex could be circumscribed and differentiated according to climatic and distributional data and how these results compare to published morphological data. Methods We used a SDM approach and climatic envelope estimates of 12 taxa belonging to the C. congesta complex. To achieve that, we compiled a distributional database from herbarium specimen information and produced distribution models for each taxon by using MaxEnt and 19 bioclimatic variables. Key results We found that many species of the complex share similar predicted suitable distribution and climatic preferences, while also uncovering particular geographic and climatic patterns for C. ascendens and C. caaguazuensis. Our results also contributed with the circumscription of C. squarrulosa and provided data for further recognition of two taxonomic novelties. Conclusions Climatic and distributional data yielded interesting results for the taxonomy of this species complex, particularly when confronted with morphological data. Implications This study provided support for an apparently undescribed Chromolaena that merits recognition at species rank and the treatment of Eupatorium caaguazuense var. nervosum as a separate species from C. squarrulosa, while also supplying further evidence that morphologically diverse populations of C. squarrulosa should be treated as a single taxon.