Rainbow parrotfish on the Great Barrier Reef, Australia.
Reef fish evolved the ability to feed by biting prey from surfaces relatively recently, a UC Davis study shows. The innovation has driven an explosion of evolution in reef fish.
Reef fish evolved the ability to feed by biting prey from surfaces relatively recently, a UC Davis study shows. The innovation has driven an explosion of evolution in reef fish.
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In the case of fish, the ability to bite rather than suck is a relatively recently evolved ability that led to a radiation of new species of fish that graze on surfaces such as the feeding method seen in very many different species of fish living on coral reefs, within the last 60 million years.
There may have been some biting done by teleosts before the end-Cretaceous, but our reconstructions suggest that it was very uncommon.
Katherine Corn, lead author
Graduate student
Department of Evolution and Ecology and Center for Population Biology
University of California Davis Davis, CA, USA.
Graduate student
Department of Evolution and Ecology and Center for Population Biology
University of California Davis Davis, CA, USA.
As the article by in UCDavis News by Andy Fell explains:
Suction, ramming and biting
Modern reef fish feed in a variety of ways. Many suck floating food into their mouths by rapidly expanding their heads. This suction feeding is thought to be ancestral in teleosts. A smaller number are “ram biters,” which catch food by essentially swimming onto it with their mouths open.
Many reef fish, including iconic species such as parrotfish, butterflyfish and triggerfish, bite their food off hard surfaces. This gives them access to prey such as snails and shellfish, echinoderms, anemones, algae and other animals and plants that may be quite firmly stuck to the substrate.
Corn, working with Professor Peter Wainwright and other colleagues in the UC Davis Department of Evolution and Ecology, classified 1,530 living species of reef fish by feeding method, then mapped them onto an evolutionary tree of the teleosts. They also studied the rate of body shape evolution in all of these fish.These two changes together really opened up biting as an effective mode for fishes,” Corn said. Biting allowed reef fish to access diverse new prey, promoting the evolution of a wide variety of body shapes, so once biting evolved, it was really able to take off, and this may explain the high rates of body shape evolution and diversity of biters that we see.
Katherine Corn, lead author
They found that at the end of the Cretaceous, nearly all of the fish in these lineages were suction feeders. Today, four in 10 reef species are “benthic biters” that browse on the substrate. The biting species are evolving in body shape at almost twice the rate of suction feeders, they discovered.
What set off these changes? The end of the Cretaceous saw changes in coral reefs, with more complex and branching structures that made grazing more productive. At the same time, teleosts evolved shorter jaws that were better for biting.
The team also showed that, once biting as a way of feeding became established, the rate of evolution for the biting fish was significantly greater than that for suction-feeders, as the following diagram shows:
Results from model fitting for the rate of body shape evolution. The center plot shows the distribution of multivariate, state-dependent rates colored by feeding mode. Branch colors on the phylogeny indicate per branch state-dependent rates of evolution, with gray indicating a lower rate and teal indicating a higher rate. On the outer ring, bars are colored by feeding mode, and the length of bars represents lower jaw length. Selected fishes have been drawn and placed near their clade on the phylogeny (clockwise from Inset at bottom right): L. cyanopterus (Inset), C. multicinctus, E. stercorarius, Z. scopas, A. scopas, H. aculeatus, S. guacamaia, S. obreptus, H. hentz, S. jello, P. modestus, O. holotaenia, A. strigatus, R. quaesita, C. cruentata, and P. millepunctata.
Fish images drawn by K.A.C.
Significance
We demonstrate that the stunning trophic diversity of modern reef fishes is a relatively recent state driven by a dramatic transformation in representation of major feeding modes. Since the Early Cenozoic, when over 95% of teleost lineages were suction feeders, there has been a steady increase in direct biting feeding modes. A variety of novelties and jaw modifications permitted reef fishes to feed on substrate-bound prey using direct biting and grazing behaviors and opened this rich adaptive zone, which we show elevated rates of body shape evolution. Taken together, our results indicate that recent diversification of the feeding mechanism played a major role in ecologically and phenotypically shaping the modern fauna of reef fishes.
Abstract
Diversity of feeding mechanisms is a hallmark of reef fishes, but the history of this variation is not fully understood. Here, we explore the emergence and proliferation of a biting mode of feeding, which enables fishes to feed on attached benthic prey. We find that feeding modes other than suction, including biting, ram biting, and an intermediate group that uses both biting and suction, were nearly absent among the lineages of teleost fishes inhabiting reefs prior to the end-Cretaceous mass extinction, but benthic biting has rapidly increased in frequency since then, accounting for about 40% of reef species today. Further, we measured the impact of feeding mode on body shape diversification in reef fishes. We fit a model of multivariate character evolution to a dataset comprising three-dimensional body shape of 1,530 species of teleost reef fishes across 111 families. Dedicated biters have accumulated over half of the body shape variation that suction feeders have in just 18% of the evolutionary time by evolving body shape ∼1.7 times faster than suction feeders. As a possible response to the ecological and functional diversity of attached prey, biters have dynamically evolved both into shapes that resemble suction feeders as well as novel body forms characterized by lateral compression and small jaws. The ascendance of species that use biting mechanisms to feed on attached prey reshaped modern reef fish assemblages and has been a major contributor to their ecological and phenotypic diversification.
Corn, Katherine A.;Friedman, Sarah T.;Burress, Edward D.;Martinez, Christopher M.;Larouche, Olivier;Price, Samantha A.;Wainwright, Peter C.
The rise of biting during the Cenozoic fueled reef fish body shape diversification
Proceedings of the National Academy of Sciences (PNAS) 19(31); e2119828119; DOI: 10.1073/pnas.2119828119
Copyright: © 2022 The authors.
Published by PNAS, Open access
Reprinted under a Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).
Again, we see the Theory of Evolution forming the basis of understanding biodiversity and confirmation that evolution proceeds at different rates dependent on environmental factors. We also see an explosive radiation from a root species into new niches and so new species when a new capability has become established, just as we would expect from the theory. A superficial examination of the geological column would appear to show a long period of stasis followed by a short burst of creative evolution.
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