The Next Generation of Adaptive Radiation Studies in Plants

Abstract

Adaptive radiation is an evolutionary process that has been promulgated in some clades as an explanation for species richness and disparity in morphological forms across ecological gradients. Studies designed to elucidate the mechanisms and causes of adaptive radiation have largely focused on animal systems, but plant clades have tremendous potential to answer elusive questions regarding adaptive radiations. The goals of this review are to (1) produce a synthetic understanding of adaptive radiations through studies that have investigated plants systems; (2) critically reflect upon contemporary studies to highlight how approaches have been successful as well as limiting; and (3) outline gaps in our understanding of adaptive radiations, while emphasizing that plant have ideal characteristics to answer future questions.Thirty-five adaptive radiation clades are highlighted, of which several are supported with multiple lines of evidence, such as the Hawaiian silverswords, Hawaiian lobeliads, and columbines. Plant adaptive radiation examples are commonly insular, diversified in the Miocene or Pliocene, are associated with dispersal mediated ecological opportunities, are polyploids, and have experienced hybridization. From those studies, a general model of plant insular adaptive radiation is proposed. The limitations of the current reliance of phylogenetic comparative approaches to detect adaptive radiations is considered, and an integrative approach that includes phylogenetics, genomics, and evolutionary ecology is advocated. The review concludes with a call for additional studies that are needed before we are to fully understand adaptive radiations, and they include: (1) How do biological interactions influence adaptive radiations, (2) what role does environmental change play in generating ecological opportunity, (3) how does genetic evolution drive adaptive radiation, (4) do models adequately

Exploring evolutionary adaptations of leaf heteroblasty in subspecific taxa of Hawaiian Chenopodium oahuense

“…Hawaiian Chenopodium has differentiated and adapted to different habitats across the archipelago, possibly aided by ecological release and evolutionary adaption to various xeric environments containing differential abiotic pressures. Our results are consistent with the suggestions of Schenk (2021) that this lineage is possibly in preliminary stages of adaptive radiation. Based on the results of this research, we have provided additional data clarifying the morphological boundaries between C. oahuense subsp.…”

“…Quantification of how specific morphological traits change in intermediate habitats will allow for important insights of how microevolutionary processes shape the form and function of these plants (Schenk, 2021). Specifically considering all populations of C. oahuense subsp.…”

“…These lineages represent one or few described taxa but warrant further investigation as populations appear to be diverging from each other morphologically, ecologically, or otherwise (Webster, 1951; Wagner et al, 1999; Cantley et al, 2020; Cole and Morden, 2021). Using the criteria outlined by Schenk (2021), we can detect early‐stage microevolutionary processes of an adaptive radiation for C. oahuense . Emerging adaptive radiations are particularly challenging to study because they may be in the initial stages of adaptive evolution and have not yet gone through extensive cladogenesis.…”

“…There are many reasons to hypothesize that Hawaiian C. oahuense is an emerging adaptive radiation across a variety of habitats (Cantley et al, 2020; Schenk, 2021). But a more accurate understanding of how such evolutionary processes such as introgression, hybridization, phenotypic plasticity, and heteroblasty play a role in the evolution of this taxon is impeded by a limited characterization of the remarkable heteroblastic change in leaf morphology for C. oahuense subsp.…”

Revised morphology and barcoding of Strobilanthes andersonii Bedd. a critically endangered plant

“…S. andersonii Bedd and its related species were descended from clade II and recently established in Western Ghats due to adaptive radiation. In evolutionary radiation, a fast escalation in the diversity of a group of organisms occurs by frequent speciation within a particular clade with fast evolutionary and ecological divergence in geographical location [19]. S. andersonii Bedd has close affinity with other Indian species.…”