Re-assignment of the Affinities of the Fossil Pollen Type Tricolpites trioblatus Mildenhall and Pocknall to Wilsonia (Convolvulaceae) and a reassessment of the ecological interpretations

Abstract

Tricolpites trioblatus Mildenhall and Pocknall was described from Upper Miocene–Pliocene sediments of New Zealand and attributed to the Hebe complex (Scrophulariaceae), which is common in the New Zealand vegetation, especially in montane and subalpine habitats. Pollen in Miocene–Pliocene sediments in central Australia is identified with T. trioblatus, and the depositional situations included shallow lakes, with fresh or brackish waters, sometimes becoming saline. The affinities of T. trioblatus are re-examined in the light of these disparate environments in Australia and New Zealand. It has been found that all the fossil grains examined are more comparable to pollen of Wilsonia, and perhaps Cressa (Convolvulaceae), than to those of the Hebe complex. Wilsonia and Cressa are found in salt marshes, hence affinities with them are ecologically more credible for central Australia. T. trioblatus is found in late Eocene sediments deposited under episodic marine transgressions; an environment likely to stimulate the evolution of new species tolerant to saline conditions.