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by culi 1219 days ago
Interesting, I wouldn't really think the ocean food chain is "more complicated". Soil ecosystems themselves are extremely complex and much more tightly integrated with what's happening above ground than we often realize for example

But I do agree there's some really interesting key differences. For one, speciation on land is often driven by geological barriers that split populations apart. But these types of barriers are much less common in the ocean where this only really happens to organisms that are restricted to shallow waters (and even then "island-hopping" happens much more commonly)
2 comments
gtvwill 1219 days ago
Temperature and depth are your barriers in the ocean. Water can be shallow and swimmable but if it's too cold to live in for a species it may well be a brick wall.
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kuhewa 1218 days ago
But broadly, the distribution of thermal habitat isn't very complex, it varies across a latitudinal cline and at a broad regional scale with ocean currents but your don't have small island-sized patches of warm water for example. Most fine scale anomalies are short lived especially relative to the scales speciation happens over.

Depth is a thing and can separate disparate communuties on seamounts like alpine species on mountain tops. The difference is most Maine species have a pelagic larval stage and can disperse widely, so barriers to gene flow are more limited than on land.

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kuhewa 1218 days ago
Well, you have the same thing happening in marine sediments as well with interstitial organisms, and really in the water itself you have this still fairly poorly understood food web (see: Marine microbial loop) occuring before your reach a size of familiar organisms.

Different terrestrial and marine habitats and assemblages come to mind where one may be more complex than another but overall if the degree of niche partitioning at any given trophic level was a wash between land and sea water, I think marine may take the cake on complexity just due to the webs being longer and thus room for more edges between nodes https://pubmed.ncbi.nlm.nih.gov/27322123/

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