Mapping and monitoring genetic diversity of an alpine freshwater top
predator by applying newly proposed indicators
Abstract
Genetic diversity is the basis for population adaptation and long-term
survival, yet rarely considered in biodiversity monitoring. One key
issue is the need for useful and straightforward indicators of genetic
diversity. To test newly proposed indicators, we monitored genetic
diversity over 40 years (1970-2010) in metapopulations of brown trout
inhabiting 27 small mountain lakes representing 10 water systems in
central Sweden. Three of the indicators were previously proposed for
broad, international use for the Convention on Biological Diversity
(CBD) context, while three others were recently elaborated for national
use by a Swedish science-management effort and applied for the first
time here. The Swedish indicators use molecular genetic data to monitor
genetic diversity within and between populations and assess the
effective population size (Ne). We used a panel of 96 SNPs and
identified 29 discrete populations retained over time. Over 40 percent
of the lakes harbored more than one population indicating that brown
trout biodiversity hidden as cryptic, sympatric populations are more
common than recognized. The Ne indicator showed values below the
threshold (Ne≤500) in 20 populations with five showing Ne<100.
Although statistically significant genetic diversity reductions occurred
in several populations, they were mostly within proposed threshold
limits. Metapopulation structure appears to buffer against diversity
loss; when applying the indicators to metapopulations most indicators
suggest an acceptable genetic status in all but one system. The CBD
indicators agreed with the national ones but provided less detail. We
propose that all indicators applied here are appropriate for monitoring
genetic diversity within species.