The speciation view: Disentangling multiple causes of adaptive and non‐adaptive radiation in terms of speciation

Abstract

Biological diversification often includes burst of lineage splitting. Such “radiation” has been known to act as evolutionary arenas with the potential to generate unique phylogenetic clusters and further novel groups. Although these radiations when accompanied by ecological diversification, so‐called “adaptive radiation” have persisted as a central premise in evolutionary biology, the ecological and genetic mechanism of such rapid diversification has remained unclear. There are several critical definitions for the pattern of adaptive radiation, and those provide delimitation of adaptive and non‐adaptive radiation. That being said, only a few studies have provided any clear demarcations in our understanding of the adaptive and non‐adaptive causes of radiation from the mechanism of speciation. Here, we review the current consensus for the causes of adaptive radiation, especially along with the recent theoretical synthesis of “ecological speciation.” Further, we suggest the signature of adaptive and non‐adaptive radiation in the earliest stages of diversification from the viewpoint of speciation. These criteria from the speciation view are useful to find the cases with the signatures of adaptive/non‐adaptive radiation.

The biogeographic and evolutionary processes shaping population divergence in Laupala

“…Rather, it shows that neither a specific geographical context (with or without gene flow) nor ecological opportunity is an exclusive predictor of rapid divergence at the population or species level. This is in line with recent work on evolutionary radiations beyond those characterised by ecological opportunity and gene flow (Kagawa, 2022; Martin & Richards, 2019; Matsubayashi & Yamaguchi, 2022; Simões et al., 2016).…”

“…We found that the nine populations that we sampled showed striking population genetic structure at small spatio-temporal scales (Figure 1), with populations placed across a highly supported population-level phylogeny (Figure 2). The rapid and extensive differentiation among populations (this study) and species (Mendelson & Shaw, 2005) of (Kagawa, 2022;Martin & Richards, 2019;Matsubayashi & Yamaguchi, 2022;Simões et al, 2016).…”

The biogeographic and evolutionary processes shaping population divergence in Laupala

“…Rather, it shows that neither a specific geographical context (with or without gene flow) nor ecological opportunity is an exclusive predictor of rapid divergence at the population or species level. This is in line with recent work on evolutionary radiations beyond those characterised by ecological opportunity and gene flow (Kagawa, 2022; Martin & Richards, 2019; Matsubayashi & Yamaguchi, 2022; Simões et al., 2016).…”

“…We found that the nine populations that we sampled showed striking population genetic structure at small spatio-temporal scales (Figure 1), with populations placed across a highly supported population-level phylogeny (Figure 2). The rapid and extensive differentiation among populations (this study) and species (Mendelson & Shaw, 2005) of (Kagawa, 2022;Martin & Richards, 2019;Matsubayashi & Yamaguchi, 2022;Simões et al, 2016).…”

The potential role of spatial sorting in speciation and adaptive radiations

“…In Table 1, we provide a summary of studies highlighting a role for spatial sorting in generating phenotypic change associated with dispersal, which suggests this may be a more general mechanism of evolution change. Herein, we connect spatial sorting to the rich and complex evolutionary mechanisms reviewed by Matsubayashi and Yamaguchi (2022), which must be considered as we try to understand the processes that promote and impede speciation and adaptive radiations.…”

Reply to Kagawa's comment: Quantifying mixture modes of evolutionary radiations

“…In this reply and Matsubayashi and Yamaguchi (2022), we intend to bring a new perspective to adaptive and non‐adaptive radiations from the mechanical aspect of the evolution of reproductive isolation. Considering that ecological speciation itself is fragile (Gow et al, 2006), ecological and phenotypic patterns in the same evolutionary radiation change over time from the pattern of non‐adaptive radiation to that of adaptive radiation, and vice versa.…”

The biogeographic and evolutionary processes shaping population divergence in Laupala

“…Rather, it shows that neither a specific geographical context (with or without gene flow) nor ecological opportunity is an exclusive predictor of rapid divergence at the population or species level. This is in line with recent work on evolutionary radiations beyond those characterised by ecological opportunity and gene flow (Kagawa, 2022; Martin & Richards, 2019; Matsubayashi & Yamaguchi, 2022; Simões et al., 2016).…”

“…We found that the nine populations that we sampled showed striking population genetic structure at small spatio-temporal scales (Figure 1), with populations placed across a highly supported population-level phylogeny (Figure 2). The rapid and extensive differentiation among populations (this study) and species (Mendelson & Shaw, 2005) of (Kagawa, 2022;Martin & Richards, 2019;Matsubayashi & Yamaguchi, 2022;Simões et al, 2016).…”

The potential role of spatial sorting in speciation and adaptive radiations

“…In Table 1, we provide a summary of studies highlighting a role for spatial sorting in generating phenotypic change associated with dispersal, which suggests this may be a more general mechanism of evolution change. Herein, we connect spatial sorting to the rich and complex evolutionary mechanisms reviewed by Matsubayashi and Yamaguchi (2022), which must be considered as we try to understand the processes that promote and impede speciation and adaptive radiations.…”

Reply to Kagawa's comment: Quantifying mixture modes of evolutionary radiations

“…In this reply and Matsubayashi and Yamaguchi (2022), we intend to bring a new perspective to adaptive and non‐adaptive radiations from the mechanical aspect of the evolution of reproductive isolation. Considering that ecological speciation itself is fragile (Gow et al, 2006), ecological and phenotypic patterns in the same evolutionary radiation change over time from the pattern of non‐adaptive radiation to that of adaptive radiation, and vice versa.…”

The biogeographic and evolutionary processes shaping population divergence in Laupala

“…Rather, it shows that neither a specific geographical context (with or without gene flow) nor ecological opportunity is an exclusive predictor of rapid divergence at the population or species level. This is in line with recent work on evolutionary radiations beyond those characterised by ecological opportunity and gene flow (Kagawa, 2022; Martin & Richards, 2019; Matsubayashi & Yamaguchi, 2022; Simões et al., 2016).…”

“…We found that the nine populations that we sampled showed striking population genetic structure at small spatio-temporal scales (Figure 1), with populations placed across a highly supported population-level phylogeny (Figure 2). The rapid and extensive differentiation among populations (this study) and species (Mendelson & Shaw, 2005) of (Kagawa, 2022;Martin & Richards, 2019;Matsubayashi & Yamaguchi, 2022;Simões et al, 2016).…”

The potential role of spatial sorting in speciation and adaptive radiations

“…In Table 1, we provide a summary of studies highlighting a role for spatial sorting in generating phenotypic change associated with dispersal, which suggests this may be a more general mechanism of evolution change. Herein, we connect spatial sorting to the rich and complex evolutionary mechanisms reviewed by Matsubayashi and Yamaguchi (2022), which must be considered as we try to understand the processes that promote and impede speciation and adaptive radiations.…”

Reply to Kagawa's comment: Quantifying mixture modes of evolutionary radiations

“…In this reply and Matsubayashi and Yamaguchi (2022), we intend to bring a new perspective to adaptive and non‐adaptive radiations from the mechanical aspect of the evolution of reproductive isolation. Considering that ecological speciation itself is fragile (Gow et al, 2006), ecological and phenotypic patterns in the same evolutionary radiation change over time from the pattern of non‐adaptive radiation to that of adaptive radiation, and vice versa.…”