"On thing to clarify. I think what the articles are suggesting is that bits of forests/trees/logs are being washed off during hurricanes and eventually made their way to new islands instead of animals being 'blown off by the wind' as mentioned above. This sounds more reasonable."
Longer range "blown off" should be much more likely to be successful when some "rafts" are involved which increase the lift and protect the animal inside. But in shorter range other possibilities become more likely and also consider that typhoon and flooding being a frequent and violent disturbance that would cause mixing of populations. In particular I was thinking if there exist a clear boundary of the range (and genetic distance) of Macropodus hongkongensis and M. concolor, both extends from South China to Hainan Island and (North) Vietnam.
"In fact, phylogenetic evidence suggests that these 'rafts' moved animals around quite frequently in a long enough time span. Even longer distance oceanic dispersal from Madagascar to India has been suggested for chameleons based on mt-DNA phylogeny of the taxa (http://www.nature.com/nature/jou ... full/415784a.html).
An even more bazaar example is the New World monkeys. Fossil evidence and DNA phylogenetic reconstructions have suggested that all monkeys living in South America are derived from an African common ancestor, and the separation between Old World and New World monkeys are long after the separation of the two continents. Hence, there must have existed a 'raft' made from a patch of forest or floating vegetation large enough to carry a population of monkeys across the Atlantic. It is a contentious idea, but till this date it is still the preferred theory explaining how the New World monkeys got to where they are now. (http://www.bbc.com/earth/story/2 ... -to-south-america).
Chameleons are likely originated from Africa and radiated to Europe and Madagascar while later extirpated in Africa. The Atlantic was not that wide in Oligocene and possibly oceanic islands existed between Madagascar and India as suggested by later studies.
Hominids as well as monkeys should have originated both in Africa and migrated to the New World from several possible routes.
"However, I personally still have doubts about using hurricanes, bad weather, and rafts to explain animal dispersal. In particular, I still believe that it is highly unlikely for freshwater fish to be transferred from one place to another by these mechanisms. Snails, lizards, and monkeys hanging on to tree branches in rafts blown across the ocean, I could imagine, but fish seems unlikely to make it through in this manner.............."
How about a gradual "spreading" of some individuals from time to time with ongoing genetic mixing? This should have somehow reduced the diversity index...
In general, there was a "Intermediate Disturbance Hypothesis" which theorized upon related issues of diversity and disturbance.
The intermediate disturbance hypothesis is a completely unrelated concept I think?
To my understanding, the intermediate disturbance hypothesis suggests that biodiversity in a habitat is highest when disturbance is intermediate. This is based on the assumption that habitats will be increasingly be occupied by a few specialist species highly adapted to the environment if the disturbance is low, and that few species are able to cope under the change and environmental pressures brought about by disturbance if the disturbance is high, both leading to low diversity.
Personally, I am a believer of the intermediate disturbance hypothesis, though I think it is extremely difficult to quantify and prove its existence. This will eventually bring us back to the earlier discussion of whether human intervention/disturbance should be applied to the ecosystem in order to prevent the system from reaching its last succession state, which has relatively low biodiversity. (e.g. should we clear forests to maintain grasslands)"
It may hardly be a strict one as a common phenomenon of biologic theories and many of its ingredients may be interpreted differently. Be it typhoon or human disturbance or something else, we should be having a low biodiversity in HK. Going back to the topic of 松鼠, if we take that the present populations ex-Lantau were introduced and that food trees for the species are lacking in Lantau, I incline not to consider bringing them to the island in the meantime.
[ 本帖最後由 jasonpoon 於 2017-5-24 04:46 編輯