Genetic erosion in the snailLittoraria subvittata(Reid, 1986) due to mangrove deforestation

Abstract

In tropical coastal ecosystems mangrove forests are important as feeding, spawning, breeding and nursery grounds for many marine species. High human population pressure in coastal areas has led to the loss and deterioration of mangrove habitats. Solar salt production can affect these habitats along the East African coast. Littorinid snails live on mangrove trees, forming an important component of the mangrove ecosystem and have been used as bioindicators of environmental health and community stress. Littoraria subvittata is the most abundant littorinid species in mangroves along the East African coast. Partial mitochondrial cytochrome oxidase subunit 1 (COI) gene sequences of 298 individuals were used to assess the impact of mangrove deforestation at salt ponds on the genetic diversity and structuring of L. subvittata populations, as well as to infer the demographic history of the species. Nucleotide and haplotype diversities were found to be lower in samples from mangroves at salt ponds than in samples from natural mangroves. The mean nucleotide diversity was 0.049 ± 0.036% and 0.115 ± 0.068% in mangroves at salt ponds and natural mangroves, respectively. The mean haplotype diversity was 0.23 ± 0.14 and 0.50 ± 0.14 in mangroves at salt ponds and natural mangroves, respectively. Analysis of molecular variance (AMOVA) detected a significant population structure (Ф st = 0.049; P < 0.0001) for the combined populations. Hierarchical AMOVA detected a significant population genetic structure only between populations from mangroves at salt ponds and natural mangroves (Φ ct = 0.022; P < 0.05), but not between any other groupings. Populations from natural mangrove sites showed a significant genetic structure (Ф st = 0.054, P < 0.0001), while populations from sites at salt ponds could not be differentiated (Ф st = −0.0026, P = 0.64). Reduced effective population size was observed in most samples from mangrove sites at salt ponds compared with natural mangrove. The direction of migrants was mostly from salt ponds to natural mangroves. These results show that salt ponds have a negative impact on the genetic diversity of L. subvittata populations and modify the population's genetic structure.

Genetic diversity and connectivity in the East African giant mud crab Scylla serrata: Implications for fisheries management

“…serrata in the WIO [ 26 , 27 ] and the Western Pacific [ 33 ]. Similar findings were also reported in other mangrove fauna in the WIO [ 19 , 24 ]. The high haplotype diversity and low nucleotide diversity might indicate genetic bottleneck events, where most haplotypes became extinct, followed by population expansion [ 57 ].…”

“…Although giant mud crabs have very high dispersal capacities [ 4 ], they might, over time, suffer these consequences [ 18 ]. Such consequences were reported in other mangrove fauna in the region [ 19 , 20 ]. Since genetic diversity is the basis for adaptation, management of genetic diversity is crucial for maintaining the sustainability of marine resources.…”

Reduced genetic diversity and alteration of gene flow in a fiddler crab due to mangrove degradation

“…The differences observed in allelic richness and heterozygosity are therefore likely to be explained by environmental stress and unfavourable conditions caused by the salt farming activities. Lower genetic diversity in populations of Littoraria subvittata is observed at salt ponds in comparison to natural mangroves at the Tanzanian coast [ 68 ]. A recent study has also demonstrated the negative correlation between heavy metal concentrations in tissues of prawns and genetic diversity [ 69 ].…”

Genetic evidence for a single stock of giant tiger prawns Penaeus monodon in demarcated prawn fishing zones of Tanzania

“…However, because information on the genetic stock structure of giant tiger prawns in Tanzania is currently limited, there is a chance that the three demarcated fishing zones do not correspond to the genetic stock structure of giant tiger prawns. Available data focuses primarily on the genetic stock structures of the Indian prawns (Fenneropenaeus indicus), crabs, mangrove snails, and other marine fauna from Tanzania (Mwakosya et al, 2018;Nehemia et al, 2017Nehemia et al, , 2019Otwoma & Kochzius, 2016;Rumisha et al, 2018). The only available study on giant tiger prawns was primarily concerned with the impact of trace metal pollution on genetic connectivity, so samples were drawn primarily from pollution hotspots rather than prawn fishing grounds in the three demarcated zones (Rumisha, Leermakers, et al, 2017).…”