Diversification rates indicate an early role of adaptive radiations at the origin of modern echinoid fauna

Abstract

Evolutionary radiations are fascinating phenomena corresponding to a dramatic diversification of taxa and a burst of cladogenesis over short periods of time. Most evolutionary radiations have long been regarded as adaptive but this has seldom been demonstrated with large-scale comparative datasets including fossil data. Originating in the Early Jurassic, irregular echinoids are emblematic of the spectacular diversification of mobile marine faunas during the Mesozoic Marine Revolution. They diversified as they colonized various habitats, and now constitute the main component of echinoid fauna in modern seas. The evolutionary radiation of irregular echinoids has long been considered as adaptive but this hypothesis has never been tested. In the present work we analyze the evolution of echinoid species richness and morphological disparity over 37 million years based on an extensive fossil dataset. Our results demonstrate that morphological and functional diversifications in certain clades of irregular echinoids were exceptionally high compared to other clades and that they were associated with the evolution of new modes of life and so can be defined as adaptive radiations. The role played by ecological opportunities in the diversification of these clades was critical, with the evolution of the infaunal mode of life promoting the adaptive radiation of irregular echinoids.

Deep-Time Demographic Inference Suggests Ecological Release as Driver of Neoavian Adaptive Radiation

“…However, there exists a strong difference in the level of subjective inference about the role of ecological opportunity in the radiation of major clades based on the fossil record and in more process-based studies of smaller 'insular' recent clades. Studies of large-scale adaptive radiations are necessarily inferential, based on the fossil record (e.g., marine invertebrates [69], ammonites [70], irregular echinoids [71], tracheophyte plants [72], Neotropical cichlids [73], tetanuran dinosaurs [74], or based on comparative phylogenetic birth/death or Lineage Through Time (LTT) analyses of species richness (e.g., various angiosperm clades [75], birds [76], or based on phenotypic diversity (e.g., suboscine ovenbirds and woodcreepers [77], Neotropical cichlids [73], or based on correlation with time-calibrated geophysical and climatic episodes (e.g., passerines [29,78], or some combination of the above.…”

A Total-Evidence Dated Phylogeny of Echinoids and the Evolution of Body Size across Adaptive Landscape

“…6 and S21 of SI File 4). An increase in morphological and ecological innovation among Jurassic echinoids was also previously recognized using both discrete characters and geometric morphometrics (Hopkins and Smith 2015; Boivin et al 2018), data types that can support contradictory macroevolutionary patterns (Mongiardino Koch et al 2017). These previous studies recognized evolutionary innovations mainly among irregular echinoids, whereas our results show that multiple clades of regular echinoids (echinothurioids, calycineans and camarodonts) also contributed to this expansion of ecospace.…”

“…Smith and Jeffery (1998) explored determinants of extinction selectivity across the Cretaceous-Paleogene mass extinction. Eble (2000) and Boivin et al (2018) analyzed the interplay of morphological disparity and diversity across different lineages. Hopkins and Smith (2015) showed echinoid evolution to be punctuated by bursts of change linked to ecological innovations.…”

Ricerca biologica e ibridazione metodologica con il design

“…Gli echinoidi, comunemente conosciu come ricci di mare e dollari della sabbia, sono invertebra bentonici appartenen al phylum Echinodermata e diffusi in tu gli habitat marini -dagli ambien inter dali alle profondità oceaniche, dall'equatore ai poli -dove svolgono un ruolo ecologico chiave grazie alla loro a vità di grazing (Boivin et al, 2018;.Lo scheletro degli echinoidi si configura come una stru ura complessa ad alto potenziale per il trasferimento biomime co. La stru ura è di origine mesodermica ed è composta da calcite CaCO3 frammista a piccole quan tà di MgCO3. Essa è contraddis nta da un arrangiamento poroso (stereoma) con spazi ripieni di cellule e fibre dermali (stroma), ed è differenziata in piastre scheletriche di varia pologia e funzione, unite assieme a formare una teca compa a (Brusca & Brusca, 1996).…”