MACROEVOLUTION IN BENTHIC FORAMINIFERA: A REVIEW OF ATTRIBUTES LEADING TO LONGEVITY
Journal Article
Overview
abstract
ABSTRACT; Benthic foraminifera have flourished throughout the Phanerozoic and are abundant today, ranging from barely brackish coastal waters to the deep-sea abyss. With their high densities in sediment, they are important as lower trophic level members and to the carbon cycle. Morphospecies durations can be relatively long, with mean partial ranges of about 20 Myr for both rare and abundant taxa. In marine invertebrates with a fossil record, macroevolution has been effectively studied by looking at genus or species duration compared to factors such as abundance and geographic distribution. Most research finds a positive correlation between duration and geographic range, but in the benthic foraminifera, it has been shown that neither abundance nor geographic range necessarily have a significant positive relationship with duration. This is perplexing. Why do so many benthic foraminiferal species have such great longevity; what makes them so successful through time? This paper reviews past work and provides some new data to address these questions. The overriding attribute promoting survival seems to be dispersal method. Living species disperse mainly through the use of resting propagules, and ensuing populations exhibit a log series distribution in space and time. The fossil record shows that dispersal is very rapid, and characteristic biogeographic and evolutionary patterns can be observed in shallow and deeper water communities. Another attribute of benthic foraminifera that seems to protect against extinction is environmental tolerance, the biotic abilities living species may have to proliferate in a habitat. For example, many living benthic species thrive in low-oxygen settings, and others easily tolerate pollutants, as new data on heavy metals show. Dispersal methods and environmental adaptations help expand geographic range, protecting against extinction.
