© Ralf Schneider
We have news today showing how the biological world we see now only makes sense in the context of the Theory of Evolution, and showing how well the TOE meshes with other strands of scientific evidence, in this case, genetics, plate techtonics and oceanography.
It was produced by an international research collaboration, involving a research team led by evolutionary biologist Professor Axel Meyer of the University of Konstanz, Germany and researchers from China and Singapore, which was able to identify factors that led to the success of the seahorse from a developmental biology perspective: its quickness to adapt by, for example, repeatedly evolving spines in the skin and its fast genetic rates of evolution.
Their results were published, open access, on 17 February 2021 in Nature Communications.
From the Konstanza Universität press release:
Abstract
Seahorses have a circum-global distribution in tropical to temperate coastal waters. Yet, seahorses show many adaptations for a sedentary, cryptic lifestyle: they require specific habitats, such as seagrass, kelp or coral reefs, lack pelvic and caudal fins, and give birth to directly developed offspring without pronounced pelagic larval stage, rendering long-range dispersal by conventional means inefficient. Here we investigate seahorses’ worldwide dispersal and biogeographic patterns based on a de novo genome assembly of Hippocampus erectus as well as 358 re-sequenced genomes from 21 species. Seahorses evolved in the late Oligocene and subsequent circum-global colonization routes are identified and linked to changing dynamics in ocean currents and paleo-temporal seaway openings. Furthermore, the genetic basis of the recurring “bony spines” adaptive phenotype is linked to independent substitutions in a key developmental gene. Analyses thus suggest that rafting via ocean currents compensates for poor dispersal and rapid adaptation facilitates colonizing new habitats.
Click image to enlargea Geographic sampling locations for sampled seahorses with patterns of nucleotide diversity (π) of the 21 seahorse species across 22 chromosomes. Maps from Wessel et al. (2013) under GNU GPL license91.
b Neighbor-joining tree constructed with genome-wide SNPs of 358 seahorses. Location pin symbols in (a) and branch background in (b) correspond to each other. Seahorses illustrations by Geng Qin. Source data are provided as a Source Data file[XLSX].
Copyright: © 2021 The authors. Published by Springer Nature Ltd.Open access
Reprinted under a Creative Commons Attribution 4.0 International License (CC BY 4.0)
Seahorses are extremely poor swimmers. Surprisingly, however, they can be found in all of the world’s oceans. On the basis of almost 360 different seahorse genomes, a group of researchers studied how these special fish were able to spread so successfully worldwide. Based on an evolutionary tree of 21 species it was possible to reconstruct the dispersal routes of seahorses worldwide and to explain where and when new species emerged. The international research collaboration involving the research team led by evolutionary biologist Professor Axel Meyer at the University of Konstanz and researchers from China and Singapore was able to identify factors that led to the success of the seahorse from a developmental biology perspective: its quickness to adapt by, for example, repeatedly evolving spines in the skin and its fast genetic rates of evolution. The results were published on 17 February 2021 in Nature Communications.
Seahorses of the genus Hippocampus emerged about 25 million years ago in the Indo-Pacific region from pipefish, their closest relatives. And while the latter usually swim fairly well, seahorses lack their pelvic and tail fins and evolved a prehensile tail instead that can be used, for example, to hold on to seaweed or corals. Early on, they split into two main groups. “One group stayed mainly in the same place, while the other spread all over the world”, says Dr Ralf Schneider, who is now a postdoctoral researcher at the GEOMAR Helmholtz Centre for Ocean Research Kiel, and participated in the study while working as a doctoral researcher in Axel Meyer’s research team. In their original home waters of the Indo-Pacific, the remaining species diversified in a unique island environment, while the other group made its way into the Pacific Ocean via Africa, Europe and the Americas.
Travelling the world by raft
The particularly large amount of data collected for the study enabled the research team to create an especially reliable seahorse tree showing the relationships between species and the global dispersal routes of the seahorse. Evolutionary biologist, Dr Schneider, says: “If you compare the relationships between the species to the ocean currents, you notice that seahorses were transported across the oceans”. If, for example, they were carried out to sea during storms, they used their grasping tail to hold on to anything they could find, like a piece of algae or a tree trunk. These are places where the animals could survive for a long time. The currents often swept these “rafts” hundreds of kilometres across the ocean before they landed someplace where the seahorses could hop off and find a new home.
Since seahorses have been around for more than 25 million years, it was important to factor in that ocean currents have changed over time as tectonic plates have shifted. For example, about 15 million years ago, the Tethys Ocean was almost as large as today’s Mediterranean Sea. On the west side, where the Strait of Gibraltar is located today, it connected to the Atlantic Ocean. On the east side, where the Arabian Peninsula is today, it led to the Indian Ocean.
Tectonic shifts change ocean currents
The researchers were able to underscore, for example, that the seahorses were able to colonize the Tethys Ocean via the Arabian Sea just before the tectonic plates shifted and sealed off the eastern connection. The resulting current flowing westward towards the Atlantic Ocean brought seahorses to North America. A few million years later, this western connection also closed and the entire Tethys Ocean dried out. Ralf Schneider: “Until now it was unclear whether seahorses in the Atlantic all traced their lineage to species from the Arabian Sea that had travelled south along the east coast of Africa, around the Cape of Good Hope and across the southern Atlantic Ocean to reach South America. We found out that a second lineage of seahorses had done just that, albeit later”.
Since the research team gathered 20 animal samples from each habitat, it was also possible to measure the genetic variation between individuals. And this generally revealed: The greater the variation, the larger the population. “We can reconstruct the age of a variation based on its type. This makes it possible to calculate the size of the population at different points in time”, the evolutionary biologist explains. This calculation reveals that the population that crossed the Atlantic Ocean to North America was very small, supporting the hypothesis that it have [sic] come from just a few animals brought there by the ocean’s currents while holding on to a raft. The same data also showed that, even today, seahorses from Africa cross the southern Atlantic Ocean and introduce their genetic material into the South American population.
Fast and flexible adaptation
Seahorses not only spread around the world by travelling with the ocean currents, but they were also surprisingly good at settling in new habitats. Seahorses have greatly modified genomes and, throughout their evolution, they have lost many genes, emerged with new ones or gained duplicates. This means: Seahorses change very quickly in comparison to other fish. This is probably why different types of “bony spines” evolved quickly and independently of each other that protect seahorses from predation in some habitats.
Some of the genes have been identified that exhibit particular modifications for certain species, but they are not the same for all species. Multiple fast and independent selections led to the development of spines, and although the same genes play a role in this development, different mutations were responsible. This shows that the slower, sessile seahorses were particularly able to adapt quickly to their environments. This is one of the main reasons the research team gives for seahorses being so successful in colonizing new habitats. [My highlight]
Image: Ralf Schneider
By comparing the genomes of different populations of seahorse, the team was able to show how closely related they were and where the founder population came from, giving a comprehensive map of the distribution pattern and evolution of each population as well as occasional ingress of genes from other populations.
What Creationists should find disturbing is the fact highlighted above, "Seahorses have greatly modified genomes and, throughout their evolution, they have lost many genes, emerged with new ones or gained duplicates". This of course runs counter to several of their sacred dogmas:
- Evolution by loss of genetic information, which Creationists claim is impossible because loss of information should be fatal.
- Evolution by gaining genetic information, which Creationists wrongly claim is impossible because it contravenes Shannon Information Theory and the Second Law of Thermodynamic, regardless of the fact that gene duplication is commonplace in nature.
- Evolution by mutation, which Creationists claim is invariably detrimental and therefore 'devolutionary' (© Michael J. Behe/Discovery Institute).
Since so much Creationist dogma is counter-factual, this little difficulty should be easily waved aside and ignored, just as they will need to ignore the fact that, as this paper inadvertently demonstrates, not only is the TOE emphatically not a theory in crisis, about to be overthrown and become the fist ever scientific theory to be replaced by a supernatural one without any supporting evidence, but it is the foundation theory of biology and the only one to make sense of the diversification we see in nature, such as that of the different species and local populations of seahorse.
But then people who can be persuaded that magic is a scientific idea can also be persuaded that a magician just arranged all the different seahorse genomes and their world-wide distribution to make it look like it would if the local populations had split off from earlier populations and drifted to their present locations on ocean currents and then evolved in situ. In other words, Creationists need to believe in an intelligent designer who tries to trick us by arranging the world so it just looks like the product of natural forces.
No comments :
Post a Comment
Obscene, threatening or obnoxious messages, preaching, abuse and spam will be removed, as will anything by known Internet trolls and stalkers, by known sock-puppet accounts and anything not connected with the post,
A claim made without evidence can be dismissed without evidence. Remember: your opinion is not an established fact unless corroborated.