New publications

Isolation by Time during an Arctic Phytoplankton Spring Bloom

ArticleinJournal of Eukaryotic Microbiology · August 2016
DOI: 10.1111/jeu.12356
Anna Tammilehto,  Phillip C Watts, Nina Lundholm
The arctic phytoplankton spring bloom, which is often diatom-dominated, is a key event that provides the high latitude communities with a fundamental flux of organic carbon. During a bloom, phytoplankton may increase its biomass by orders of magnitude within days. Yet, very little is known about phytoplankton bloom dynamics, including for example how blooming affects genetic composition and diversity of a population. Here, we quantified the genetic composition and temporal changes of the diatom Fragilariopsis cylindrus, which is one of the most important primary producers in the Arctic, during the spring bloom in western Greenland, using 13 novel microsatellite markers developed for this study. We found that genetic differentiation (quantified using sample-specific FST) decreased between time points as the bloom progressed, with the most drastic changes in FST occurring at the start of the bloom; thus the genetic structure of the bloom is characterized by isolation by time. There was little temporal variation in genetic diversity throughout the bloom (mean HE=0.57), despite marked fluctuations in F. cylindrus cell concentrations and the temporal change in sample-specific FST. Based on this novel pattern of genetic differentiation, we suggest that blooming behavior may promote genetic diversity of a phytoplankton population.

Geographic Cline in the Shape of the Moose Mandible: Indications of an Adaptive Trend

Article in Journal of Mammalian Evolution  - Online version

DOI: 10.1007/s10914-016-9344-y

Veli-Matti Kangas, Seppo Rytkönen, Laura Kvist, Teemu Käpylä, Tuire Nygrén & Jouni Aspi


Intra-specific geographic variation is probably one of the most common patterns studied in ungulate morphology. However, the shape of the mandible, a crucial feature with regard to feeding, has been greatly understudied in this context. Here, we utilized a museum collection of moose (Alces alces) mandibles to investigate whether we could detect significant variation in this species, and test for the existence of geographic patterns and associations with population genetic structure. We applied a landmark-based geometric morphometrics approach, analyzing shape data with principal component analysis and linear mixed models. A significant geographic shift in the shape of the moose mandible was revealed.
The main pattern was similar in both sexes; however, there was a consistent difference in shape between males and females over the latitudinal scale. The main changes included an enlargement in the attachment surfaces of the muscles controlling biting and mastication, suggesting more effective mastication towards the north, plausibly as an adaptive response to a harder and tougher wintertime diet. Additionally, more subtle, yet statistically significant age-related shape variation was discovered. Interestingly, no or only a weak association between the morphometric variation and the genetic population structure was detected with neutral molecular markers.

Last updated: 29.8.2016