The Fate of Clades in a World of Recurrent Climatic Change: Milankovitch Oscillations and Evolution

Abstract

▪ Abstract Variations in Earth's orbit with periods of 10–100 thousand years (kyr) (Milankovitch oscillations) have led to recurrent and rapid climatic shifts throughout Earth's history. These cause changes in the geographical distributions of clades, which we term orbitally forced range dynamics (ORD). The magnitude of ORD varies geographically, e.g., with latitude. Climatic shifts cause extinction, splitting, and merging of gene pools and clades. They select among individuals and clades for traits enhancing the ability to survive in situ and to establish new populations. There is also nonadaptive sorting caused by the large geographical variation in ORD, as only gene pools that are in the right place when climate shifts survive. ORD lead to sorting at many levels of genealogic inclusiveness. Clades that have survived climatic shifts during at least one entire period of the longest significant Milankovitch oscillations (100 kyr), we name β-clades. The products of more recent cladogenesis are α-clades, which are always nested within a β-clade. We conclude that ORD may promote α-clade formation but curb rates of β-clade formation. In areas with little ORD, where gene pools persist without going extinct or merging, clade splits and divergence may accumulate leading to high rates of β-clade formation and β-anagenesis (evolutionary change persisting >100 kyr). High ORD should lead to low numbers of β-clades, β-clades with low levels of spatial genetic divergence, little geographical subdivision and large ranges, organisms with high vagility and low specialization, high proportions of β-clades formed by polyploidization, and little β-anagenesis. We predict global and interregional geographic patterns in these variables caused by differential ORD. Thus, ORD potentially explains a wide array of patterns, suggesting ORD as a fundamental factor in evolution. The vulnerability of biotas to many human activities should vary with the magnitude of ORD.

The Relationship Between Global and Regional Distribution Diminishes Among Phylogenetically Basal Species

“…Due to their narrow global distributions, many derived species might be more receptive to global climatic oscillations than basal species (Bennett 1997;Jansson and Dynesius 2002). Imagine, for instance, a derived species that has originated and established a narrow global distribution at the northern edge of a climatically suitable part of the globe.…”

Diversity patterns and biogeography of Diaptomidae (Copepoda, Calanoida) in the Western Palearctic

“…This fact seems to contradict the glaciation hypothesis by Svenning et al (2011), i.e., that beta diversity patterns are a result of Hydrobiologia (2017) Quaternary climate change (Jansson & Dynesius, 2002). At the Western Palearctic scale, this hypothesis predicts strong turnover in Southern Europe, where the glacial impact was mild enough to allow refugia as well as local evolutionary diversification; however, a strong difference in beta-similarity decay is predicted as well (Baselga, 2010;Baselga et al, 2012a, b;Freijeiro & Baselga, 2016).…”

Are Iberian endemics Iberian? A case-study using water beetles of family Dytiscidae (Coleoptera)

“…The Pleistocene origin of the majority of the species is very robust with respect to uncertainties in the rate of the molecular clock, or with respect to the method used for estimating the ultrametric tree (direct enforcement in PAUP or the NPRS method of Sanderson, 1997). These results are against the view of the Pleistocene as a time of little evolutionary change at the species level (Coope, 1979;Elias, 1994;Bennet, 1997;Klicka & Zink, 1997, 1999Janson & Dynesius, 2002). On the contrary, at least for diving beetles the Pyrenees and the Ebro valley seem to have been almost insurmountable geographical barriers during most of the Pleistocene, isolating Iberian populations from those in the rest of Europe long enough for them to speciate in allopatry.…”