Bioclimatic assessment of the geographic and climatic limits to hybridisation in a sexually deceptive orchid system

Abstract

Australia is a major centre of diversity for pollination by sexual deception, a pollination syndrome unique to orchids and characterised by highly specific pollinator relationships. Chiloglottis pescottiana is a rare natural hybrid between sexually deceptive C. trapeziformis and C. valida. We utilised bioclimatic models to predict the potential range of the parental orchid species, the hybrid and their pollinators. The predicted ranges of the parental orchid species rarely overlapped (only 2% of the core range), with the geographic separation of the species reflecting the occupation of largely distinct climatic niches and limiting opportunities for hybridisation. Comparison of the predictions with independent distributions of the orchid taxa revealed a close match. Unexpectedly, our results revealed that several related and morphologically similar orchid species are, nevertheless, ecologically distinct from C. valida. Our study demonstrates that bioclimatic modelling provides an additional tool for exploring a range of ecological and evolutionary questions.