Final Report Summary - MYANMAR-FISH (Myanmar freshwater biogeography; understanding a zoogeographical transition zone)
The tropical rivers of Asia are hotspots of biodiversity, home to thousands of species of freshwater fishes. Wild-caught freshwater fishes are an important food resource, an important source of income for small scale fishing operations and their beauty has long made some species popular in the aquarium trade. Despite their importance and popularity, there has so far been little scientific attention devoted to understanding their genetic diversity and evolutionary history.
The research undertaken here took a close look at diversity for a few key groups of fishes that occur across Southern Asia; the leaffishes (Badidae), earthworm eels (Chaudhuriidae), and snakeheads (Channidae). These groups were specifically chosen to represent a range of fishes, including groups that are ecologically specialised and relatively unknown, and groups that are economically important and widespread. The project looked at genetic diversity in these groups and also at differences in their appearance (morphology) for closely related species that occur in different areas. Using DNA data, phylogenetic trees were constructed that estimate the evolutionary relationships (“family trees”). These trees are useful for understanding the evolutionary relationship among species, and for helping to classify species into higher-level groups (genera, families etc.). The study looked at many fish specimens, including historical specimens that were collected over 150 years ago and more recent material. Some additional new specimens were also collected, in order to fill gaps in existing collections of Asian fishes. In fact, this work would not have been possible without historical and recent Natural History Collections, demonstrating the ongoing importance of museum collections for understanding biodiversity.
Results of this research revealed new and interesting details. Among the snakeheads, the Channa marulius group that was previously thought to comprise only three species probably actually comprises eight. It turns out that, although the members of this group all look superficially similar, fishes from different areas actually have small morphological differences (in scale and vertebrae counts), and large genetic differences too. The phylogeny constructed for the earthworm eels, using the first genetic data ever generated for the Family Chaudhuriidae, provides the first ever estimate of the evolutionary relationships for species and genera in this group. The results revealed an unexpected position of one species, which upon closer examination proved to be a new species in a new genus.
The results of this study are important because they set a baseline for conservation management. Without precise information about what constitutes a species (what its limits are and where it occurs) it is difficult to evaluate the scale at which conservation should be focused in order to preserve the diversity of species in a changing and developing world. It is also important for wild fishing operations that need accurate knowledge about what they are catching in order to preserve wild fish stocks. In future, it may also be important to fish farmers who want to breed indigenous fish for profit and food security. Knowledge about species and species group relationships is also essential for future studies that might examine in detail how evolution has led to changes in the morphology of different species, a field of study known as comparative anatomy.
The phylogenetic results generated in this research also contain interesting information that sheds light on evolution and the distribution of biological diversity in the natural world. The freshwater fish of Southern Asia exist in a particularly interesting and complicated geographical landscape. For the most part, they occur in large river basins such as the Ganges, Ayeyarwady, and Mekong, falling into two fish biogeographical zones (Indian and Southeast Asian), although the border between zones (somewhere in Myanmar) is not well understood. The major rivers from both zones represent some of the largest and longest in the world, and they all originate very close to each other high in the Himalayan Mountains on the Tibetan plateau. Before the mountains started to rise 40-50 million years ago the rivers didn’t exist in their current form, and neither did many of the fish species that we recognise today. As the Himalayas started to form the rivers started to change, gaining more water from mountain weather systems, changing route and direction, dividing and re-uniting as the mountains thrust up in many stages over millennia, but the exact nature of all these river changes is not known from the geological record. The fact that many closely related fish species live today in all these different rivers is strong evidence that they once had common ancestors in ancient connected river systems, and where geological information is lacking, it is the very relationships among fish species in modern day river basins that gives the best clue as to how the ancient rivers were once connected. Furthermore, it is possible to understand the sequence of river separation through time by looking at the level of difference and similarity between fishes in different rivers.
Just as species have different ecological preferences and habitats, each group of fishes studied here turned out to have different histories of speciation and diversification. The discovery of common patterns of speciation among groups, however, provides good evidence that ancient river changes promoted diversification, contributing to the formation of the fish diversity that can be observed today. These changes include the separation of the Brahmaputra R. (Bangladesh) and Chindwin R. (Myanmar) and the old connection between the Salween R. (Myanmar) and the Mae Khlong R. (Thailand).
This helps answer questions including “how have ancient landscape changes helped shape diversity in Asian fish species?” and “how fish diversity distributed across Myanmar – the transition zone between Indian and Southeast Asian biogeographical zones?” Results bring new information to the fields of Freshwater Biogeography and Evolution, adding to the body of knowledge about how evolution had progressed in some of the most biodiverse and little studied freshwater regions in the world, and helping to tell the story of the evolution of modern day species and ecosystems.
Dr Eleanor Adamson, Marie-Curie International Incoming Fellow (2013-2015) (eas.adamson@gmail.com)
Dr Ralf Britz, Fish Researcher, Natural History Museum London (r.britz@nhm.ac.uk
The research undertaken here took a close look at diversity for a few key groups of fishes that occur across Southern Asia; the leaffishes (Badidae), earthworm eels (Chaudhuriidae), and snakeheads (Channidae). These groups were specifically chosen to represent a range of fishes, including groups that are ecologically specialised and relatively unknown, and groups that are economically important and widespread. The project looked at genetic diversity in these groups and also at differences in their appearance (morphology) for closely related species that occur in different areas. Using DNA data, phylogenetic trees were constructed that estimate the evolutionary relationships (“family trees”). These trees are useful for understanding the evolutionary relationship among species, and for helping to classify species into higher-level groups (genera, families etc.). The study looked at many fish specimens, including historical specimens that were collected over 150 years ago and more recent material. Some additional new specimens were also collected, in order to fill gaps in existing collections of Asian fishes. In fact, this work would not have been possible without historical and recent Natural History Collections, demonstrating the ongoing importance of museum collections for understanding biodiversity.
Results of this research revealed new and interesting details. Among the snakeheads, the Channa marulius group that was previously thought to comprise only three species probably actually comprises eight. It turns out that, although the members of this group all look superficially similar, fishes from different areas actually have small morphological differences (in scale and vertebrae counts), and large genetic differences too. The phylogeny constructed for the earthworm eels, using the first genetic data ever generated for the Family Chaudhuriidae, provides the first ever estimate of the evolutionary relationships for species and genera in this group. The results revealed an unexpected position of one species, which upon closer examination proved to be a new species in a new genus.
The results of this study are important because they set a baseline for conservation management. Without precise information about what constitutes a species (what its limits are and where it occurs) it is difficult to evaluate the scale at which conservation should be focused in order to preserve the diversity of species in a changing and developing world. It is also important for wild fishing operations that need accurate knowledge about what they are catching in order to preserve wild fish stocks. In future, it may also be important to fish farmers who want to breed indigenous fish for profit and food security. Knowledge about species and species group relationships is also essential for future studies that might examine in detail how evolution has led to changes in the morphology of different species, a field of study known as comparative anatomy.
The phylogenetic results generated in this research also contain interesting information that sheds light on evolution and the distribution of biological diversity in the natural world. The freshwater fish of Southern Asia exist in a particularly interesting and complicated geographical landscape. For the most part, they occur in large river basins such as the Ganges, Ayeyarwady, and Mekong, falling into two fish biogeographical zones (Indian and Southeast Asian), although the border between zones (somewhere in Myanmar) is not well understood. The major rivers from both zones represent some of the largest and longest in the world, and they all originate very close to each other high in the Himalayan Mountains on the Tibetan plateau. Before the mountains started to rise 40-50 million years ago the rivers didn’t exist in their current form, and neither did many of the fish species that we recognise today. As the Himalayas started to form the rivers started to change, gaining more water from mountain weather systems, changing route and direction, dividing and re-uniting as the mountains thrust up in many stages over millennia, but the exact nature of all these river changes is not known from the geological record. The fact that many closely related fish species live today in all these different rivers is strong evidence that they once had common ancestors in ancient connected river systems, and where geological information is lacking, it is the very relationships among fish species in modern day river basins that gives the best clue as to how the ancient rivers were once connected. Furthermore, it is possible to understand the sequence of river separation through time by looking at the level of difference and similarity between fishes in different rivers.
Just as species have different ecological preferences and habitats, each group of fishes studied here turned out to have different histories of speciation and diversification. The discovery of common patterns of speciation among groups, however, provides good evidence that ancient river changes promoted diversification, contributing to the formation of the fish diversity that can be observed today. These changes include the separation of the Brahmaputra R. (Bangladesh) and Chindwin R. (Myanmar) and the old connection between the Salween R. (Myanmar) and the Mae Khlong R. (Thailand).
This helps answer questions including “how have ancient landscape changes helped shape diversity in Asian fish species?” and “how fish diversity distributed across Myanmar – the transition zone between Indian and Southeast Asian biogeographical zones?” Results bring new information to the fields of Freshwater Biogeography and Evolution, adding to the body of knowledge about how evolution had progressed in some of the most biodiverse and little studied freshwater regions in the world, and helping to tell the story of the evolution of modern day species and ecosystems.
Dr Eleanor Adamson, Marie-Curie International Incoming Fellow (2013-2015) (eas.adamson@gmail.com)
Dr Ralf Britz, Fish Researcher, Natural History Museum London (r.britz@nhm.ac.uk