The development of Sri Lankan biogeography in the colonial period

Abstract

Studies of the patterns and processes of biogeography necessarily contingent on a robust taxonomic foundation which, in turn, depends on a thorough exploration of the biota of the concerned regions. The formal exploration of the flora and fauna of Sri Lanka commenced in the second half of the 17th century, during the Dutch colonial period. The earliest cabinet of Sri Lankan plants was acquired by Paul Hermann between 1672 and 1679. This resulted in three floras of Sri Lanka being published in a span of three decades: Hermann (1717), Johannes Burman (1737) and Carl Linnaeus (1747). The publication of near-complete ‘floras’ of India and Sri Lanka at the end of the 19th century paved the way for Henry Trimen to seek to explain the geographic affinities of the Sri Lankan angiosperms, noting the disjunct distributions of several plant groups between Sri Lanka and southern India on one hand, and Sri Lanka and Indomalaya on the other. This allowed John Christopher Willis to undertake further investigations of the distributions of the Sri Lankan flora, especially within the island. Willis was the first botanist to observe the high incidence of microendemism in the island, leading to his since-discredited theory of Age and Area, which argued that taxa with smaller distributions must be of more recent evolutionary origin. In contrast to the development of the floral inventory centred on the Herbarium in the Royal Botanic Garden, Peradeniya, the faunal inventory lacked an institutional foundation. Most species were described by foreign zoologists, often based on specimens that lacked precise locality data. Zoogeographical studies have thus lagged phytogeographic analyses, and also been bedevilled by taxonomic uncertainties. Nevertheless, in his pioneering global zoogeography, Alfred Russel Wallace (1877) considered Sri Lanka, together with South India, as a distinct sub-region of his Oriental Region, thereby recognizing the distinction of the biota of this sub-region from that of the rest of India. Wallace, however, invoked numerous land-bridges to explain faunal disjunctions. Meanwhile, D.N. Wadia’s work on the orogeny of the subcontinent helped explain historical biotic connectivity. His identification of the plains of erosion in Sri Lanka laid the ground for the future biogeographic characterization of the island. By the time of Independence in the mid-20th century, a stable picture of the external relationships of the island’s biota had emerged: close and evidently recent links to the southern Western Ghats of India; older links to Indomalaya, evidently severed by the Gangetic ‘Chatterjee Partition’ and the subsequent desiccation of much of the Indian peninsula; and a handful of possible ‘Gondwanan’ links to Madagascar. However, the large number of biotic disjunctions between Sri Lanka and regions further afield remained to be explained. Dispersal appears to be the most likely scenario for most of these. Despite the accumulation of vast amounts of geospatial data by the end of the colonial period, a quantitative characterization of the distribution of the flora yet remains a desideratum. For the distribution of animals within the island, only the most rudimentary information existed at the time of Independence, and accretion to this pool of data has been modest even in the 70 years since.