Fruit, nectar, bugs and blood: How bat teeth and jaws evolved for a diverse dinnertime | UW News
The pale-faced bat, Phylloderma stenops, is a noctilionoid bat with an omnivorous diet.
Credit: Sharlene Santana/University of Washington
A side-view image of the skull of a greater spear-nosed bat, Phyllostomus hastatus, a noctilionoid species with an omnivorous diet.
Credit: Sharlene Santana/University of Washington
What this can tell us about the evolution of bats and especially their dentition is the subject of a study of the noctilionoid bats published in Nature Communications last August.
Tell me all about the noctilionoid bats and their evolution. Noctilionoid bats, also known as New World leaf-nosed bats, are a diverse group of bats primarily found in the Americas. They are characterized by their distinctive leaf-like structures on their noses, which vary in shape and size among different species. These nose leaves play a role in echolocation and are thought to aid in the focusing of their ultrasonic calls. Here's an overview of Noctilionoid bats and their evolution:Bats are of course, a major source of embarrassment for creationists because their 'science textbook', the Bible, classifies them as a bird 'kind' and recognises only one 'kind'. Given that one of creationism's flexible definitions of a 'kind', in an attempt to equate it to the scientific definition of a species, is a group that can only breed with one another, this ignores the fact that there are hundreds of different species of bat that don't normally interbreed, yet according to the Bible they are all the same 'kind', a bird 'kind', according to a verse that is followed by one that implies there are birds that go about on 'all fours'. (Leviticus 11:14-20)In summary, Noctilionoid bats, or New World leaf-nosed bats, are a diverse group of bats found throughout the Americas. They are characterized by their distinctive nose leaves and advanced echolocation abilities. Their evolution is a subject of ongoing research, and they have adapted to a wide range of ecological niches in the New World. Conservation efforts are crucial to protect these unique and ecologically important creatures.
- Taxonomy and Diversity:
Noctilionoid bats are a superfamily within the suborder Microchiroptera, which includes the majority of the world's bat species. This superfamily is divided into several families, including the Phyllostomidae (leaf-nosed bats), Mormoopidae, and Noctilionidae. The Phyllostomidae is the most diverse family, with over 200 species found in a wide range of habitats throughout the Americas.- Morphology:
Noctilionoid bats exhibit a range of sizes, from small species with a wingspan of a few inches to larger species with wingspans of over a foot. They have well-developed wings and are known for their unique nose leaves, which vary in form from simple, lance-shaped structures to elaborate, complex structures that cover their entire face. These nose leaves are believed to play a role in directing echolocation calls and possibly in communication.- Behavior:
Noctilionoid bats are primarily insectivorous, but some species have adapted to different diets, such as fruit, nectar, or even small vertebrates. They are known for their advanced echolocation abilities, emitting high-frequency ultrasonic calls to navigate and locate prey. They often have a wide range of foraging strategies and are found in diverse ecosystems, including forests, deserts, and caves.- Evolution:
The evolution of Noctilionoid bats is a topic of ongoing research, but several key points are recognized:
- Noctilionoid bats are believed to have originated in South America. Fossil evidence suggests their presence in the region as far back as the Eocene epoch (about 50 million years ago).
- They likely evolved from primitive microchiropteran ancestors, with adaptations for echolocation and varied diets emerging over time.
- The development of the nose leaves is a distinctive feature of this group and has evolved multiple times within the superfamily. It is thought to be associated with their reliance on echolocation and may have played a role in speciation by enabling niche specialization.
- Noctilionoid bats have radiated into numerous ecological niches, leading to a wide diversity of species with various morphological and behavioral adaptations.
- Conservation: Many Noctilionoid bat species are threatened by habitat destruction, pollution, and other environmental factors. Conservation efforts are essential to protect these bats and the ecosystems they inhabit.
It's hopeless muddles like that that made scientists realise they needed to come up with a better classification system, because the primitive authors of the Bible clearly didn't understand taxonomy.
Now, according to research by a group of scientists which included researchers from the University of Washington:
A group of bats has a similar — and more expansive — evolutionary story to tell. There are more than 200 species of noctilionoid bats, mostly in the American tropics. And despite being close relatives, their jaws evolved in wildly divergent shapes and sizes to exploit different food sources. A paper published Aug. 22 in Nature Communications shows those adaptations include dramatic, but also consistent, modifications to tooth number, size, shape and position. For example, bats with short snouts lack certain teeth, presumably due to a lack of space. Species with longer jaws have room for more teeth — and, like humans, their total tooth complement is closer to what the ancestor of placental mammals had.
According to the research team behind this study, comparing noctilionoid species can reveal a lot about how mammalian faces evolved and developed, particularly jaws and teeth. And as a bonus, they can also answer some outstanding questions about how our own pearly whites form and grow.
“Bats have all four types of teeth — incisors, canines, premolars and molars — just like we do,” said co-author Sharlene Santana, a University of Washington professor of biology and curator of mammals at the Burke Museum of Natural History & Culture. “And noctilionoid bats evolved a huge diversity of diets in as little as 25 million years, which is a very short amount of time for these adaptations to occur.”
“There are noctilionoid species that have short faces like bulldogs with powerful jaws that can bite the tough exterior of the fruits that they eat. Other species have long snouts to help them drink nectar from flowers. How did this diversity evolve so quickly? What had to change in their jaws and teeth to make this possible?” said lead author Alexa Sadier, an incoming faculty member at the Institute of Evolutionary Science of Montpellier in France, who began this project as a postdoctoral researcher at the University California, Los Angeles.
Scientists don’t know what triggered this frenzy of dietary adaptation in noctilionoid bats. But today different noctilionoid species feast on insects, fruit, nectar, fish and even blood — since this group also includes the infamous vampire bats.
The team used CT scans and other methods to analyze the shapes and sizes of jaws, premolars and molars in more than 100 noctilionoid species. The bats included both museum specimens and a limited number of wild bats captured for study purposes. The researchers compared the relative sizes of teeth and other cranial features among species with different types of diets, and used mathematical modeling to determine how those differences are generated during development.
The team found that, in noctilionoid bats, certain “developmental rules” caused them to generate the right assortment of teeth to fit in their diet-formed grins. For example, bats with long jaws — like nectar-feeders — or intermediate jaws, like many insect-eaters, tended to have the usual complement of three premolars and three molars on each side of the jaw. But bats with short jaws, including most fruit-eating bats, tended to ditch the middle premolar or the back molar, if not both.
“When you have more space, you can have more teeth,” said Sadier. “But for bats with a shorter space, even though they have a more powerful bite, you simply run out of room for all these teeth.”
Having a shorter jaw may also explain why many short-faced bats also tended to have wider front molars.
“The first teeth to appear tend to grow bigger since there is not enough space for the next ones to emerge,” said Sadier.
“This project is giving us the opportunity to actually test some of the assumptions that have been made about how tooth growth, shape and size are regulated in mammals,” said Santana. “We know surprisingly little about how these very important structures develop!”
Many studies about mammalian tooth development were done in mice, which have only molars and heavily modified incisors. Scientists are not entirely sure if the genes and developmental patterns that control tooth development in mice also operate in mammals with more “ancestral” sets of chompers — like bats and humans.
Sadier, Santana and their colleagues believe their project, which is ongoing, can start to answer these questions in bats — along with many other outstanding questions about how evolution shapes mammalian features. They’re expanding this study to include noctilionoid incisors and canines, and hope to uncover more of the genetic and developmental mechanisms that control tooth development in this diverse group of bats.
“We see such strong selective pressures in these bats: Shapes have to closely match their function,” said Santana. “I think there are many more evolutionary secrets hidden in these species.”
Co-authors are Neal Anthwal, a research associate at King’s College London; Andrew Krause, an assistant professor at the Durham University in the U.K.; Renaud Dessalles, a mathematician with Green Shield Technology; Robert Haase, a researcher at the Dresden University of Technology in Germany; UCLA research scientists Michael Lake, Laurent Bentolila and Natalie Nieves; and Karen Sears, a professor at UCLA. The research is funded by the National Science Foundation.
AbstractTo add to the embarrassment for creationists of the Bible getting the 'bat kind' so hopelessly wrong, there is the little matter of all this evolution taking place in the 99.97% of the history of life on Earth that occurred before 'Creation Week'.
Tooth classes are an innovation that has contributed to the evolutionary success of mammals. However, our understanding of the mechanisms by which tooth classes diversified remain limited. We use the evolutionary radiation of noctilionoid bats to show how the tooth developmental program evolved during the adaptation to new diet types. Combining morphological, developmental and mathematical modeling approaches, we demonstrate that tooth classes develop through independent developmental cascades that deviate from classical models. We show that the diversification of tooth number and size is driven by jaw growth rate modulation, explaining the rapid gain/loss of teeth in this clade. Finally, we mathematically model the successive appearance of tooth buds, supporting the hypothesis that growth acts as a key driver of the evolution of tooth number and size. Our work reveal how growth, by tinkering with reaction/diffusion processes, drives the diversification of tooth classes and other repeated structure during adaptive radiations.
Introduction
From the conical shape of the earliest vertebrate teeth, mammals have evolved a heterodont dentition with four tooth classes (incisors, canines, premolars, and molars), each with distinct morphologies that allow for specific functions during food processing1. This innovation enabled mammals’ evolution of complex teeth with a wide diversity of morphologies and their subsequent utilization of a broad range of dietary sources; it is therefore considered a key innovation in the evolutionary success of the group1,2,3. In the last 30 years, the study of vertebrate tooth development has led to new insights regarding the evolution of teeth in various clades2,4,5,6. However, our understanding of the origin and diversification of mammalian tooth classes remains limited in large part because most developmental studies on mammalian teeth have focused on mice. With their derived, reduced dentition containing only molars and extremely modified ever-growing incisors, mice make a less than ideal model system for studying the origins of mammalian tooth classes. The field of evo-devo therefore needs a mammalian model with a complete dentition with which to study the developmental foundation of the evolution and diversification of tooth classes. The ideal mammalian group to fill this gap would possess a complete dentition (e.g., all four tooth classes), a large morphological variation in this dentition, and accessible development from a morphological and experimental point of view. Noctilionoid bats meet all of these requirements. Emerging 45 million years ago, noctilionoid bats underwent a major evolutionary radiation such that today their more than 200 species utilize nearly all possible mammalian diets (i.e., fruit, nectar and pollen, leaves, seeds, arthropods, small vertebrates, fish, and even blood)7 …Fig. 1: Dentition diversity in noctilionoid bats.
a Tooth formula and jaw length of noctilionoid bats. Jaw length is represented with a color code (yellow to purple, short to long) and premolar and molars losses events by circles or squares respectively. Some losses happened independently in different clades. Diet is indicated with icons. b Morphogroups used in this study: regular jaw (3P3MR), long jaw (3P3ML), intermediate jaw (2P3MR) and short jaw (2P3MS and 2P2MS). Tooth classes are indicated by a letter: i, incisor; c, canine; p, premolar; m, molar. Representative genera and species investigated during development. Scale bar: 2 mm. c Picture of four species representative of the four different morphogroups that exhibit differences in jaw size and tooth composition. Source data are provided as Source Data File 1. Icons: Fig (CC BY 3.0), created by Linseed Studio from Noun Project; Pollen: (CC BY 3.0), created by Lars Meiertoberens; Blood (CC BY 3.0), created by romzicon.Sadier, A., Anthwal, N., Krause, A.L. et al.
Bat teeth illuminate the diversification of mammalian tooth classes.
Nat Commun 14, 4687 (2023). https://doi.org/10.1038/s41467-023-40158-4
Copyright: © 2023 The authors.
Published by Springer Nature Ltd. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)
This gives us yet another example of why the writings of primitive Bronze Age pastoralists can't be taken seriously as a record of the history of Earth and how the life on it came to be the way it is today, and refuting the ridiculous claim that the Bible is the inerrant word of a creator deity, when science shows how it can't possibly be the work of the god described in it.
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