Evolutionary ecology and life-history patterns in the deep sea

Abstract

It has been proposed that the high diversity found in the deep sea is the product of the stability of the physical environment for long periods of time. The predictability of the environment allows the extensive biological interactions occurring over evolutionary time to be in the direction of reduction in biological stress. The historic results are stable and complex Biologically Accomodated Communities composed of large numbers of stenotopic species. Not all major taxa of the deep sea are so diverse. Species belonging to these taxa tend to have broader depth ranges, are more cosmopolitian and eurytopic, produce larger number of eggs, and have a larval stage that allows wide dispersion. Such features characterize biota of more physically stressed, low-diversity habitats, e.g. shallow boreal seas. Similar contrasting patterns can be demonstrated for biota in marin, freshwater, and terrestrial regimes when comparing historically stable environments with more variable habitats. Two diverging evolutionary pathways thus lead toward low diversity, physically controlled or high diveristy, biologically accommodated communities and r or K modes of existence. What we know of life-history characteristics of the deep-sea fauna suggests that the alternate thesis of intensive predation as the source of high diversity may not be correct.