Climate, soils and vicariance - their roles in shaping the diversity and distribution of Nepenthes in Southeast Asia

Abstract

The Palaeotropical pitcher plant genus Nepenthes (Nepenthaceae) is characterized by specialized nutrient sequestration strategies, narrow endemism, and a patchy distribution in which vicariance is believed to have played a fundamental role. Using recent studies of the effects of climate, soil type and vicariance, we review patterns of diversity and endemism in Nepenthes. First we consider how climate influences the geographical range of the genus and diversity of prey trapping mechanisms. Second, we examine edaphic influences, specifically the relationship between limestone and ultramafic soils and the obligate edaphic endemic Nepenthes that inhabit them. Third, we examine the role of vicariance, with regards to the patchy distribution of suitable habitats throughout Southeast Asia, and the passive dispersal mechanism of Nepenthes seeds. Climate is the principal determinant of variation in pitcher functional traits and in perhumid environments, may drive the evolution of alternative nutrient sequestration strategies. Although little is known about the ecophysiological relationships between soil type and obligate edaphic Nepenthes, ultramafic and limestone substrates may strongly influence vegetation physiognomy, creating a diversity of environmental niches that are exploited by specialized Nepenthes species. Finally, the complex geology and geography of the Malay Archipelago drives diversification through vicariance.