These comparisons further support the argument that the primary driver of biodiversity loss during the Late Devonian biodiversity crisis was a dramatic decline in speciation rate.
The analysis of speciation mode, however, does identify a mechanism for the observed decline in speciation rate: a dramatic lack of vicariant speciation during the study interval.
This is consistent with the Devonian analyses (e.g., Stigall 2012a, b) indicating decline in speciation rate and lack of vicariance during invasive regimes.
This corroborates results of previous generic and family level analyses [3], [5], but temporal changes in rates alone cannot identify the biological reason for the decline in speciation rate.
In this analysis, the hypothesis that speciation rate declined during the Late Devonian biodiversity crisis due to a reduction in speciation by vicariance is tested.
That is, a relatively high, early rate of diversification followed by a decrease in speciation rate.
Epigenetic variation in germ cells could play a role in speciation.
To explain these speciation bursts, they referred to an increase in speciation rate due to evolutionary and biogeographic events.
During the Late Devonian Biodiversity Crisis, the primary driver of biodiversity decline was the dramatic reduction in speciation rates, not elevated extinction rates; however, the causes of speciation decline have been previously unstudied.
In addition, Rabosky and Lovette's [ 8] SPVAR model was implemented to analyze the commonly observed pattern of "explosive-early" radiations, in which clades show an initial burst of diversification followed by a gradually declining speciation rate.
And given that this kind of bacteria infect up to a fifth of all insect species, it may play an even wider role in speciation of the insect world.
