Biology subjects

Weinkauf, M. F. G.

Publications and source records attributed to Weinkauf, M. F. G..

2 recordsLinked to original sources

bioRxiv2020

Reproduction of a marine planktonic protist: Individual success versus population survival

Understanding the biology of reproduction is important for retracing key evolutionary processes in organisms, yet gaining detailed insights often poses major challenges. Planktonic Foraminifera are globally distributed marine microbial eukaryotes and important contributors to the global carbon cycle. Their extant biodiversity shows restricted distribution patterns of some species, whereas others are cosmopolitan in the world ocean. Planktonic Foraminifera cannot be bred under laboratory conditions, and thus details of their life cycle remain incomplete. Solely the production of flagellated gametes has been observed and taken as an indication for an exclusively sexual reproduction. Yet, sexual reproduction by spawning of gametes in the open ocean relies on sufficient gamete encounters to maintain viable populations, which represents a problem for organisms that lack the means of active propulsion and are marked by low population densities. To increase knowledge on the reproductive biology of planktonic Foraminifera, we applied a dynamic, individual-based modelling approach with parameters based on laboratory and field observations to test if random gamete encounters under commonly observed population densities are sufficient for maintaining viable populations. We show that temporal synchronization and potentially spatial concentration of gamete release seems inevitable for maintenance of the population. We argue that planktonic Foraminifera optimized their individual reproductive success at the expense of community-wide gene flow, which may explain their high degree of diversity. Our modelling approach helps to illuminate foraminiferal population dynamics and to predict the existence of necessary reproduction strategies, which may be detected in future field experiments. This study therefore contributes to our understanding of plankton ecology and evolution and their reproductive strategies in the open ocean.

ecology↗

bioRxiv2019

Extinctions in marine plankton preceded by stabilizing selection

Unless they adapt, populations facing persistent stress are threatened by extinction. Theoretically, populations facing stress can react by either disruption, increasing trait variation, or stabilisation, decreasing trait variation. In the short term, the more economical response is stabilisation, because it quickly transfers a large part of the population closer to a new ecological optimum. However, canalisation is deleterious in the face of persistently increasing stress because it reduces variability and thus decreases the ability to react to further change in stress. Understanding how natural populations react to intensifying stress reaching terminal levels is key to assessing their resilience to environmental change such as that caused by global warming. Because extinctions are hard to predict, observational data on the adaptive reaction of populations facing extinction are rare. In this study, we make use of the glacial salinity rise in the Red Sea as a natural experiment allowing us to analyse the reaction of planktonic Foraminifera to stress escalation in the geological past. We analyse morphological trait state and variance in two species across a salinity rise leading to their local extinction. One species reacted by stabilisation in shape and size, detectable several thousand years prior to extinction. The second species reacted by trait divergence, but each of the two divergent populations remains stable or reacted by further stabilisation. These observations indicate that the default reaction of the studied Foraminifera is stabilisation and that stress escalation did not lead to the local emergence of adapted forms. Inability to breach the global adaptive threshold would explain why communities of Foraminifera, and many other groups of marine plankton, reacted to Quaternary climate change by faithfully tracking their zonally shifting environments. It also means that populations of marine species adapted to response by migration, when exposed to stress outside of the adaptive range, will be at risk of extinction.

ecology↗