Tuesday, April 7, 2009

Bio-convergent parallel: Anuroid & Hominoid

Arkive Video: Gorillas vertical wading and wet-sit-eating

left: dryland gelada, long-tailed, vertical-trunk, dry-sit-eat grasses, no air sac
right: lowland gorilla, tail-less, vertical-trunk, wet-sit-eat sedges, air sac

Another Video: Lowland Gorillas eating sedge rhyzomes and high-protein AHV (Aquatic Herbaceous Vegetation) while sitting-floating in forest open wetland Arkive video link

DD: The question is not "do air sacs always cause loss of tail?", but "is the complete loss of tail in hominoids due (in part) to laryngeal air sac?" The answer is clear, yes, float-sit-feeding with inflatable air sac selects for tail loss.

MV: Not so clear IMO: may depend on body size, size of airsacs, terrestrial vs aquatic milieu, salt vs fresh water milieu, time spent in trees & water, arm-hanging vs hopping vs above-branch, etc.

DD: parallel convergence at forest-waterside (swamp, wetland, shore):

left: Axlotl, long-tailed 'tadpole' with external gills and legs, swims but doesn't sit
right: Macaque, long-tailed, with lungs and legs, swims but doesn't feed sit-floating

Tadpoles with long tail swim, they don't sit partially feeding in water, they don't have prehensile tongue; frogs with no tail sit partially in water, and use long prehensile tongue to eat. Some frogs then evolved more arboreal traits (better climbing skills, less swimming), others spend much time on lake bottoms and developed more aquatic traits (skin 'gill' breathing)

left: tree frogs have since further specialized to arborealty, more 'spidery' and colorful
right: aquatic frog with hydrodynamic red external gills re-adapted to full submersion

Monkeys with long tails swim (Nasalis, Long-tailed macaque); while Ndoki swamp gorillas
(~LCA H-oid) with no tail sit partially in water while feeding.

left: tree apes have since further specialized to arborealty, more 'spidery' and colorful
right: aquatic apes (humans) with hydrodynamic hair re-adapted to submersion diving

AFAIK, neither spidery tree frogs nor deep-submersion frogs inflate their throat air sacs as much as forest-waterside frogs.

AFAIK, neither spidery tree apes (gibbon) nor deep submersion apes (humans) inflate their throat air sacs as much as forest-waterside apes.

Parallel pattern. Partial sit-float eating -> air sac -> tail lost; eventually species body size may enlarge at forest-waterside, OR become full-time spidery at arboreal canopy OR adapt deep submersion with active skin glands* or skin gills* as per photos.

DD: Complete loss of tail = vertical-trunk float-sitting while plucking-foraging. Laryngeal air sacs. Compare to long tailed gelada sitting while plucking-foraging grass on dry ground. No air sacs there, of course.

MV: Some baboons have short tails IIRC?

DD: None lost their tail, many highland monkeys (cold nights select for short tails) with non-prehensile tails have short tails. Tail covers peri-anal region, in water, muscle valves and tissue close peri-anal region.

Dry-sit-eating (no air sac, long-tailed) savanna gelada vs wet/float-sit-eating (air sac, tail-less) Ndoki swamp gorilla

* frogs and salamanders may respire via gills, lungs or skin. I conjecture that the eccrine skin glands of humans (inactive in African apes except volar eccrines) function in very limited respiration. link

Evolution Canyon European-African micro-climates in Jordan Rift Valley

Flowering plants & veination 140ma:
The study, by Dr Tim Brodribb and Dr Taylor Field of the University of Tasmania and University of Tennessee, used plant physiology to reveal how flowering plants, including crops, were able to dominate land by evolving more efficient hydraulics, or 'leaf plumbing', to increase rates of photosynthesis.

"Flowering plants are the most abundant and ecologically successful group of plants on earth," said Brodribb. "One reason for this dominance is the relatively high photosynthetic capacity of their leaves, but when and how this increased photosynthetic capacity evolved has been a mystery."

Using measurements of leaf vein density and a linked hydraulic-photosynthesis model, Brodribb and Field reconstructed the evolution of leaf hydraulic capacity in seed plants. Their results revealed that an evolutionary transformation in the plumbing of angiosperm leaves pushed photosynthetic capacity to new heights.

The reason for the success of this evolutionary step is that under relatively low atmospheric C02 conditions, like those existing at present, water transport efficiency and photosynthetic performance are tightly linked. Therefore adaptations that increase water transport will enhance maximum photosynthesis, exerting substantial evolutionary leverage over competing species.

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