Summary: Dynesius & Jansson (2000)

Over the course of Earth's history, climates have varied widely. Some climate cycles are reported on the scale of 10-100 thousand years, such as Milankovitch oscillation. Milankovitch cycles have been demonstrated to influence the location and size of species geographical distributions. Dynesius & Jansson (2000) further suggest that Milankovitch cycles also drive geographical patterns of species diversity, polyploidy, degree of specializations and the dispersal ability of organisms. When species ranges  are influenced by these climate cycles, they can be termed ORDs, or "orbitally forced species' range dynamics". These ORDs may constrain short-term evolutionary processes. Although adaptations may accumulate between climatic shifts, they may be lost when the climate shifts, due to population extinction of variation in selection pressure. The size of ORDs varies on both temporal and spatial scales, and can function to decrease gradual speciation, increase species range size and proportion of polyploid species. ORDs favour dispersability and tend to favour generalizations. Dynesius & Jansson (2000) indicate that large ORDs can promote species persistence (neither extinction nor speciation) and that ORDs show a corresponding increase with latitude (although how these ORDs vary with longitude or altitude is not indicated). One of the latitudinal patterns observed by ORDs is Rapoport's rule - a gradient in species' range sizes and diversity. Dynesius & Jansson (2000) argue that ORDs of different strengths may explain several biological phenomena (i.e. one driving force as opposed to many). ORDs provide a new opportunity for developing conservation strategies on different environmental scales.