An Ecological Perspective on the Biodiversity of Tropical Island Streams

Abstract

Articles Images of exotic tropical streams and waterfalls are commonly used to denote the beautiful and unique features associated with island landscapes. Yet the continued existence of such scenic habitats is being threatened in a variety of ways. The ecology and the potential for sustainability of insular tropical stream and river drainages are not well understood. Furthermore, it is not yet clear how the concepts derived from studies of continental stream ecosystems in the temperate zone can be effectively applied to understand and manage streams and rivers on islands in tropical areas. With ever-increasing development pressure in these areas, there is a growing need to establish more unified themes for research, management, and conservation of tropical stream ecosystems. This special section of BioScience presents recent research on different types of tropical streams and emerging themes in this area. The articles describe important aspects of how tropical stream ecosystems are structured and how these ecosystems function and change over time in response to natural processes and human activities. Several articles emphasize the magnitude of impacts resulting from human alteration of the physical and biological characteristics of these ecosystems. There is growing recognition, from studies of both temperate continental and tropical insular ecosystems, of the importance of conserving the biological resources of watersheds as well as the other "ecosystem services" they provide, such as a clean water supply, fishery resources, and recreation. In recent years, integration of watershed-scale considerations into management and conservation planning has gained momentum. As these articles illustrate, tropical stream ecologists are developing new approaches to understand, manage, and conserve these environments.These articles also clearly document that the main differences in biodiversity among tropical island streams reflect regional variations in geology, terrain, climate, and land use. However, across a wide range of latitudes, most tropical streams differ significantly from those found on continents by having relatively short, straight, and steep channels in comparatively small, narrow watersheds. Low-latitude island watersheds are often influenced by major fluctuations in precipitation and generally show the effects of exposure to tropical storms, hurricanes, and occasional major droughts (Covich et al. 2003, Oki andBrasher 2003). In contrast to the more seasonally driven temperate stream systems, tropical stream networks tend to be more event driven, and these events may be relatively unpredictable. Because tropical Gordon C. Smith (e-mail: gordon_smith@fws.gov

Chironomidae (Diptera: Insecta) in oceanic islands: New records for the Azores and biogeographic notes

“…Lotic systems are characterized by small (most less than 10 km 2 ), short and steep watersheds (Smith et al, 2003;Hughes, 2005;Hughes and Malmqvist, 2005) with short, steep, deeply incised streams. Permanent streams, fed by lakes or spring waters, exist only in Santa Maria, Sa˜o Miguel, Sa˜o Jorge, Faial and Flores islands (DROTRH/INAG, 2001).…”

High gene flow due to pelagic larval dispersal among South Pacific archipelagos in two amphidromous gastropods (Neritomorpha: Neritidae)

“…However, although a community ecologist would view them as freshwater animals (for example, Bandel and Riedel, 1998;Smith et al, 2003), their population ecology may be more similar to that of a marine species, because of their pelagically dispersing larvae. Relatively long pelagic larval durations (PLDs) have been estimated from laboratory cultures of amphidromous gastropod veligers (40-98 days, Holthuis, 1995;Kano, 2006) and the otoliths of amphidromous Galaxiid fishes and gobies (63-266 days, Radtke et al, 1988Radtke et al, , 2001Mcdowall et al, 1994;Hoareau et al, 2007b).…”

The effects of storm-induced events on the seasonal dynamics of epilithic algal biomass in subtropical mountain streams

“…Tropical and subtropical mountain streams are characterised by large-scale meteorological disturbances such as monsoons, rainstorms, and typhoons (Smith et al 2003). These influences can affect physical and biogeochemical processes, the food-web structure, and ecosystem metabolism (Webster et al 2005;Huang et al 2007;Yang et al 2009).…”