16th Annual Biology Research Symposium
“Hotspots: Cetacean Species Richness Patterns in the Oceanic Eastern Tropical Pacific” presented by Lisa T. Ballance, Southwest Fisheries Science Center, National Oceanic and Atmospheric Admin (NOAA)
Wednesday, May 15, 2013
Hershey Hall, Room 158
The question of what geographical regions to protect in order to maximize biological diversity is central to the design of effective conservation programs. It was with this goal in mind that the term biodiversity hotspot was first introduced for terrestrial ecosystems. Since that time, much research has focused on marine biodiversity hotspots. We describe species richness hotspots for 28 species of cetaceans (~1/3rd of the world’s cetacean diversity) in the eastern tropical Pacific (ca. 20 million km2) based on data collected using line transect methods aboard NOAA research vessels, August – November, in each of 10 years during a 21-year period (1986-2006). Our approach was to 1) calculate species-specific density for areas directly surveyed (using species- and area-specific published values of g(0) and f(0)), 2) interpolate species-specific density across the entire study area (using a 1° x 1° grid, two smoothing algorithms, and two resolutions), 3) calculate species richness based on all species-specific interpolated densities (by converting density to presence/absence on a species-specific basis), 4) identify richness hotspots (defined as any grid cell that contained greater than 40% of the total species pool, ≥11 species), and 5) assess the relationship between richness hotspots and species-specific density. Richness hotspots were clearly evident in three distinct regions: the Equatorial Front, the Costa Rica Dome, and waters to the southwest of Baja California, Mexico. Although these hotspots encompassed areas of highest density for a few species, the correlation between richness and density for any given species was low (mean 0.25, range 0.03 - 0.44), as was the proportion of cells where a particular species was present and encompassed by a hotspot (mean 20%, range 4 - 56%). These results were robust to smoothing algorithm and spatial resolution. Richness hotspots were clearly correlated with oceanographic variability, specifically with the edges of adjacent surface oceanographic features. We propose that temporal variation in the spatial distribution of oceanic habitat provides the mechanism that creates these richness hotspots and we show that in a climatological framework, these “oceanographic edges” do capture areas of highest density for the component species. Our results provide support for the concept of marine protected areas as effective tools to protect component species.
Sponsor(s): Department of Ecology and Evolutionary Biology