[MARMAM] New publication on Spatio-temporal patterns of genetic diversity in the Mediterranean striped dolphin

Stefania Gaspari stefaniagaspari at gmail.com
Sun Feb 3 07:25:05 PST 2019

Dear colleagues,

On behave of my colleagues I am pleased to announce the publication of our new paper: 

Gaspari S, Marsili L, Natali C, et al.
Spatio-temporal patterns of genetic diversity in the Mediterranean striped dolphin (Stenella coeruleoalba). 
J Zool Syst Evol Res. 2019;00:1–14. https://doi.org/10.1111/jzs.12265 <https://doi.org/10.1111/jzs.12265>

Comparing the genetic composition of wild animals between geographic regions with distinct environments is common in evolutionary studies. However, genetic composition can also change through time in response to environmental changes but studies examining this are carried out less often. 
In this study, we characterize striped dolphin genetic composition in the Mediterranean Sea across both geography and time. We provide genotype data for 15 microsatellite loci and 919 bp of mtDNA control region, collected over 21 years across all main Mediterranean Sea basins. We investigated spatial genetic structure using both classical and Bayesian population structure methods, and compared it with temporal patterns of genetic change using time-series statistics. We integrated the temporal datasets with known environmental pressures and data on social structure, to infer potential drivers
of observed changes. Geographic analyses suggest weak differentiation for striped dolphin in the Mediterranean Sea, with evidence for a recent expansion. Temporal analyses show significant cyclical fluctuations in genetic composition over 21 years, which correspond well with recurrent morbillivirus epizootics. Similarly, social group composition shows changes in the relative number of juveniles and adults per group, and an overall increase in the number of adults per group relative to juveniles over the time period. We suggest that the observed changes in genetic and group composition could relate to specific dynamics of morbillivirus resistance. Overall, our study highlights the importance of tracking long-term genetic variation and the potential for this species as a model in studying genetic adaptation to environmental stress.

Concluding remarks
Our study shows that continuous longterm genetic data of wild animal populations can reveal genetic changes in response to cyclical environmental pressures (morbillivirus epizootics in this case). Contrastingly, comparison of different geographic regions with different environmental conditions showed very little evidence of genetic differentiation. Furthermore, such time-series data allowed a more robust interpretation of the relationship between genetic variation and survival to ecological pressures in the striped dolphin. Although rapid population growth and immigration contribute to effective recovery from epizootics, our results suggest the potential for a genetic mechanism of adaptation to the virus. These adaptive processes would have remained very difficult to infer from samples obtained at individual points in time. Further work would aim at understanding whether
this potential adaptation results from constant selective pressures or a series of selective sweeps. This study also carries important conservation and animal welfare implications for the Mediterranean biodiversity hotspot, as striped dolphin could represent a potential morbillivirus reservoir
in the region. Morbillivirus infection has been, in fact, increasingly observed in other marine mammals such as bottlenose dolphins (Di Guardo et al., 2013), fin whales (Mazzariol et al., 2012), and the critically endangered monk seal (van de Bildt et al., 2000), which further emphasize the need to carry out more detailed studies on this biological system. 


Stefania Gaspari

Dr. Stefania Gaspari, Ph.D.
stefaniagaspari at gmail.com
gasparistefania at pec.it
skype: stefaniagaspari
Mob:+39 3337551556

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