Systematics of Indian Taxaceae

Abstract

The thesis embodies the results of original investigations done on Systematics of Indian newlineTaxaceae . newlineChapter 1 deals with an introduction to gymnosperms and their evolutionary history, their newlineclassification and global diversity of extant gymnosperms followed by the evolutionary newlinehistory of the conifers, their current geographical distribution and taxonomic positions. The newlinechapter also provides an introduction to the family Taxaceae and all genera including their newlineevolutionary history, various current and previous systems of classification, extinct and newlineextant diversity and distribution of taxads of the world including Indian taxads and their newlinetaxonomic position. The chapter highlights the gap areas in the understanding of taxonomy newlineof Indian taxads, their distribution along with their uses and conservation threats. newlineGymnosperms are an ancient group of naked seeded plants which originated in the late newlineCarboniferous Period or perhaps Early Devonian reaching to its zenith in their species newlinediversity during Late Triassic and subsequently declined steadily from the Mid Cretaceous newline(Chamberlain, 1935; Pant, 1982; Anderson et al., 2007). Global diversity of extant newlinegymnosperms though relegated to secondary position with only four classes- the Pinopsida, newlineCycadopsida, Ginkgoopsida and Gnetopsida, four orders, thirteen families, 84 genera and newlineca 987 species due to dominant evolutionary and successful radiation of the flowering newlineplants which is the largest group of all with about 250,000 species in the Anthropocene newline(Anderson et al., 2007; Farjon, 2008; Eckenwalder, 2009). Out of the extant thirteen newlinefamilies, six families are monogeneric. Pinopsida with its accepted six families is the newlinelargest class among gymnosperms. Pinopsids which are commonly known as conifers, are newlinemonophyletic group of woody gymnosperms barring a few and are well represented in the newlinefossils records. They were abundant during their long evolutionary history dating back to newlineCarboniferous more than 300 million years ago until angiosperms appeared during the newlineEarly ...