Reduced genetic diversity and alteration of gene flow in a fiddler crab due to mangrove degradation
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Date
2017
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Publisher
PLOS
Abstract
The fiddler crab Austruca occidentalis is a dominant species in mangrove forests along the
East African coast. It enhances soil aeration and, through its engineering activities, makes oth-
erwise-inaccessible food available for other marine organisms. Despite its importance, the hab-
itat of A. occidentalis is threatened by human activities. Clearing the mangroves for salt farming
and selective logging of mangroves trees continue to jeopardise mangrove ecosystems in the
Western Indian Ocean. This study aims to use partial mitochondrial COI gene sequences and
nuclear microsatellites to determine whether salt farming activities in mangroves have a nega-
tive impact on the genetic diversity and gene flow of A. occidentalis collected along the Tanza-
nia coast. The level of genetic diversity for both mitochondrial DNA and nuclear microsatellites
are relatively lower in samples from salt ponds compared to natural mangrove sites. Analysis
of molecular variance (AMOVA) among all populations showed low but significant differentia-
tion (COI: F st = 0.022, P < 0.05; microsatellites: F st = 0.022, P < 0.001). A hierarchical AMOVA
indicates lower but significant genetic differentiation among populations from salt ponds and
natural mangroves sites (COI: F ct = 0.033, P < 0.05; microsatellites: F ct = 0.018, P = < 0.01).
These results indicate that salt farming has a significant negative impact on the genetic diver-
sity of A. occidentalis. Since higher genetic diversity contributes to a stable population, restoring
the cleared habitats might be the most effective measures for the conservation of genetic diver-
sity and hence adaptive potential to environmental change in this species.
Description
Journal Article
Keywords
Genetic diversity, Gene flow, Fiddler crab, Mangrove degradation