The phrase "a decrease in diversification" is correct and usable in written English.
It can be used when discussing topics related to finance, ecology, or any field where diversification is relevant and you want to indicate a reduction in variety or options.
Example: "The recent market trends have led to a decrease in diversification among investment portfolios, which raises concerns about risk management."
Alternatives: "a reduction in diversification" or "a decline in diversification".
The γ statistic has been used as an objective way to infer a decrease in diversification rate.
Here, I examine whether detection of a decrease in diversification rates using γ necessarily requires that a high rate of diversification occurred near the base of a tree.
Despite these limitations, values ≤0.05 quantile of tree deviation captured lineages with lineages through time plots that are consistent with the expectation of early, rapid diversification followed by a decrease in diversification rate (Figure 1).
A popular method for inferring a decrease in speciation rate, which might suggest an early burst of diversification followed by a decrease in diversification rate is the γ statistic.
A priori it would be expected that a decrease in diversification through time would reduce statistical bias and increase statistical power and an acceleration in lineage diversification through time would likely increase bias and reduce statistical power.
Incomplete lineage sampling can also affect the value of the γ statistic, here in a direction that favors the hypothesis of a decrease in diversification rate, interpreted as equivalent to an early burst.
Two nodes showed a decrease in net diversification: the base of Thomasomyini clade and the most recent common ancestor of Reithrodon-Irenomys (nodes 91 and 84 respectively, see also Additional file 5: Table S5).
Rather, an examination of the mean lineages through time shows a sigmoid shape, indicating a recent decrease in diversification rate without an early burst.
In addition to a net increase, analyses also provide evidence for a net decrease in diversification rate from 0.96 to 0.11 speciation events per million years around 440,000 years ago.
We did not see a significant decrease in diversification rate through time in the MCCR test, but a model of diversification with two shift points to lower diversification rates fit the harpaline lineage accumulation through time the best.
