Hemispheric asymmetries in biodiversity--a serious matter for ecology

Abstract

Although the poles are less diverse than the tropics, this decline shows substantial asymmetries between the hemispheres, suggesting that responses to environmental change may differ substantially in the north and the south.

Figure 1. Temperature Variation with Latitude

(A) Mean and absolute minimum and maximum temperatures across the New World.(B) Mean and absolute range in sea surface temperatures across the Pacific at 165° W.

Figure 2. Latitudinal Variation in Cold Tolerance Strategies in Insects

The proportion of insects, as a function of latitude, that are moderately freeze tolerant down to relatively high sub-zero temperatures (moderate FT), that are freeze tolerant down to low sub-zero temperatures (strong FT), that are freeze tolerant but that cannot be classified (other FT), and that are freeze avoiding.

Figure 3. Variation in Upper Survival Temperatures of Macroalgae from across the Planet

Mean and standard error of upper survival temperatures of macroalgae (open symbols, macrothalli; closed symbols, microthalli) from cold areas across the planet. Ant., Antarctic; Arct., Arctic; CT, cool temperate; End., endemic; N, northern hemisphere only; S, southern hemisphere only; N+S, occurrence in both hemispheres. Redrawn from Wiencke et al. (1994).

Figure 4. Latitudinal Variation in the Energy–Water Correlates for Species Richness

Latitudinal distribution of energy–water correlates for species richness in which spatial variation in pure energy variables (closed bars), typically measured as temperature or potential evapotranspiration, or spatial variation in pure water availability variables (open bars), typically measured as rainfall or precipitation, best explains richness variation through space. Redrawn from Hawkins et al. (2003).

Figure 5. Number of Insect Species Pollinating Orchid Species in the Northern and Southern Hemispheres

Europe and North America, closed bars, n = 41; southern Africa, open bars, n = 73. Redrawn from Johnson and Steiner (2003).

Figure 6. Biological Diversity in the Northern and Southern Hemispheres

Regular differences between the northern and southern hemispheres in patterns of diversity show up in various groups such as the birds (A) (Adelie Penguin, Pygoscelis adeliae) and seed plant families (B) (King Protea, Protea cynaroides). North–south differences in life histories are also apparent in a diverse array of groups ranging from seaweeds (C) (Bull Kelp, Durvillaea antarctica) and insects (D) (the sub-Antarctic, flightless tineid moth Pringleophaga marioni) to birds (E) (Cape Sugarbird, Promerops cafer) and mammals (F) (Sloggett's Rat, Otomoys sloggetti, from the high Drakensberg in South Africa). (Photos: [A, C, and F] Brent J. Sinclair; [B and D] Steven L. Chown; [E] Mhairi L. McFarlane)