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Genetic structure and demographic history of the endangered tree species Dysoxylum malabaricum (Meliaceae) in Western Ghats, India: implications for conservation in a biodiversity hotspot.

ABSTRACT: The impact of fragmentation by human activities on genetic diversity of forest trees is an important concern in forest conservation, especially in tropical forests. Dysoxylum malabaricum (white cedar) is an economically important tree species, endemic to the Western Ghats, India, one of the world's eight most important biodiversity hotspots. As D. malabaricum is under pressure of disturbance and fragmentation together with overharvesting, conservation efforts are required in this species. In this study, range-wide genetic structure of twelve D. malabaricum populations was evaluated to assess the impact of human activities on genetic diversity and infer the species' evolutionary history, using both nuclear and chloroplast (cp) DNA simple sequence repeats (SSR). As genetic diversity and population structure did not differ among seedling, juvenile and adult age classes, reproductive success among the old-growth trees and long distance seed dispersal by hornbills were suggested to contribute to maintain genetic diversity. The fixation index (F IS) was significantly correlated with latitude, with a higher level of inbreeding in the northern populations, possibly reflecting a more severe ecosystem disturbance in those populations. Both nuclear and cpSSRs revealed northern and southern genetic groups with some discordance of their distributions; however, they did not correlate with any of the two geographic gaps known as genetic barriers to animals. Approximate Bayesian computation-based inference from nuclear SSRs suggested that population divergence occurred before the last glacial maximum. Finally we discussed the implications of these results, in particular the presence of a clear pattern of historical genetic subdivision, on conservation policies.

SUBMITTER: Bodare S

PROVIDER: S-EPMC3797473 | biostudies-literature | 2013 Sep

REPOSITORIES: biostudies-literature

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Genetic structure and demographic history of the endangered tree species Dysoxylum malabaricum (Meliaceae) in Western Ghats, India: implications for conservation in a biodiversity hotspot.

Bodare Sofia S Tsuda Yoshiaki Y Ravikanth Gudasalamani G Uma Shaanker Ramanan R Lascoux Martin M

Ecology and evolution 20130806 10

The impact of fragmentation by human activities on genetic diversity of forest trees is an important concern in forest conservation, especially in tropical forests. Dysoxylum malabaricum (white cedar) is an economically important tree species, endemic to the Western Ghats, India, one of the world's eight most important biodiversity hotspots. As D. malabaricum is under pressure of disturbance and fragmentation together with overharvesting, conservation efforts are required in this species. In thi ...[more]

PMID: 24223264

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Project description:BackgroundHigh taxonomic level endemism in the Western Ghats-Sri Lanka biodiversity hotspot has been typically attributed to the subcontinent's geological history of long-term isolation. Subsequent out of -- and into India dispersal of species after accretion to the Eurasian mainland is therefore often seen as a biogeographic factor that 'diluted' the composition of previously isolated Indian biota. However, few molecular studies have focussed on into-India dispersal as a possible source of endemism on the subcontinent. Using c. 6000 base pairs of mitochondrial and nuclear DNA, we investigated the evolutionary history and biogeography of true toads (Bufonidae), a group that colonized the Indian Subcontinent after the Indo-Asia collision.ResultsContrary to previous studies, Old World toads were recovered as a nested clade within New World Bufonidae, indicating a single colonization event. Species currently classified as Ansonia and Pedostibes were both recovered as being non-monophyletic, providing evidence for the independent origin of torrential and arboreal ecomorphs on the Indian subcontinent and in South-East Asia. Our analyses also revealed a previously unrecognized adaptive radiation of toads containing a variety of larval and adult ecomorphs. Molecular dating estimates and biogeographic analyses indicate that the early diversification of this clade happened in the Western Ghats and Sri Lanka during the Late Oligocene to Early Miocene.ConclusionPaleoclimate reconstructions have shown that the Early Neogene of India was marked by major environmental changes, with the transition from a zonal- to the current monsoon-dominated climate. After arrival in the Western Ghats-Sri Lanka hotspot, toads diversified in situ, with only one lineage able to successfully disperse out of these mountains. Consequently, higher taxonomic level endemism on the Indian Subcontinent is not only the result of Cretaceous isolation, but also of invasion, isolation and radiation of new elements after accretion to the Eurasian mainland.

Project description:The population of the globally endangered hog deer (Axis porcinus) has declined severely across its geographic range. Intensive monitoring of its demographic and genetic status is necessary. We examined the demographic and genetic structure of a small hog deer population in Keibul Lamjao National Park (KLNP), located on the western fringe of the Indo-Burma biodiversity hotspot for conservation planning. The distribution pattern of hog deer in the Park was derived based on the presence/absence of faecal pellets in 1 km × 1 km grids. We used double-observer distance sampling method to derive the hog deer abundance and population structure and compared with previous data to derive the population trend. We determined the genetic diversity of the population through microsatellite screening and bottleneck detection. The overall pellet density was 0.34 ± 0.02 pellets km-2 restricted to only 22.34 ± 0.20 km2 area of the park. The estimated density of the deer in the park was 1.82-4.32 individuals km-2. The population showed a declining trend from 2006-08 (p < 0.05, R2 = 0.916) with 8% annum-1 and an increasing trend from 2003-2018 (p < 0.05, R2 = 0.9304) with 10% annum-1. The adult male-to-female ratio and fawn-to-doe ratio were 36.2 ± 1.9 males per 100 females and 16.5 ± 0.4 fawns per 100 females, respectively. The molecular examination suggested that the mean number of alleles at 23 loci was 2.70 ± 0.18, the observed heterozygosity (Ho) ranged from 0.26 to 0.63 (mean 0.42 ± 0.02), the expected heterozygosity (He) ranged from 0.23 to 0.73 (? = 0.51 ± 0.03), and the polymorphic information content (PIC) ranged from 0.2 to 0.67 (? = 0.43 ± 0.03) indicating a moderate level of genetic diversity. Although no bottleneck in the population was observed, the loss of genetic diversity may affect the evolutionary potential of the species at the site by limiting the selection flexibility. Conservation planning coupled with scientific management regime will help in the long term persistence of the population in the region.

Project description:Background and questionThe harvesting of medicinal plants from wild sources is escalating in many parts of the world, compromising the long-term survival of natural populations of medicinally important plants and sustainability of sources of raw material to meet pharmaceutical industry needs. Although protected areas are considered to play a central role in conservation of plant genetic resources, the effectiveness of protected areas for maintaining medicinal plant populations subject to intense harvesting pressure remain largely unknown. We conducted genetic and demographic studies of Nothapodytes nimmoniana Graham, one of the extensively harvested medicinal plant species in the Western Ghats biodiversity hotspot, India to assess the effectiveness of protected areas in long-term maintenance of economically important plant species.Methodology/principal findingsThe analysis of adults and seedlings of N. nimmoniana in four protected and four non-protected areas using 7 nuclear microsatellite loci revealed that populations that are distributed within protected areas are subject to lower levels of harvesting and maintain higher genetic diversity (He = 0.816, Ho = 0.607, A = 18.857) than populations in adjoining non-protected areas (He = 0.781, Ho = 0.511, A = 15.571). Furthermore, seedlings in protected areas had significantly higher observed heterozygosity (Ho = 0.630) and private alleles as compared to seedlings in adjoining non-protected areas (Ho = 0.426). Most populations revealed signatures of recent genetic bottleneck. The prediction of long-term maintenance of genetic diversity using BOTTLESIM indicated that current population sizes of the species are not sufficient to maintain 90% of present genetic diversity for next 100 years.Conclusions/significanceOverall, these results highlight the need for establishing more protected areas encompassing a large number of adult plants in the Western Ghats to conserve genetic diversity of economically and medicinally important plant species.

Dataset Information

Genetic structure and demographic history of the endangered tree species Dysoxylum malabaricum (Meliaceae) in Western Ghats, India: implications for conservation in a biodiversity hotspot.

Publications

Genetic structure and demographic history of the endangered tree species Dysoxylum malabaricum (Meliaceae) in Western Ghats, India: implications for conservation in a biodiversity hotspot.

Similar Datasets

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