Nivells de diversitat genètica en espècies d'amfibis

Abstract

Amphibians are the cordata animal group with the highest threatened species percentage, the 40% according to the IUCN red list. The alterations in their habitats caused by the increase of the agricultural activity, add up to the threats of the climatic change, ozone layer degradation, introduction of investor species and pathogens cause great mortalities in amphibia populations. In a reduced and isolated population there is an increase of consanguinity and a loss in genetic diversity, which makes the population more vulnerable and reduces its adaptability and survival capability. In this work the available papers in the Web of Science (WOS) that presented data of genetic diversity in amphibia populations where reviewed in order to compare the levels of genetic diversity between threatened and non-threatened species according to the IUCN. Diversity index in mitochondrial DNA (mtDNA) where used because the available papers in WOS presented a higher impact in the scientific community that those that used microsatellite loci (H-index 44 in mtDNA and 35 in microsatellite). 324 scientific papers where reviewed, starting from the first published in 1991 to the ones published in 2018. From this works only 62 presented information on population diversity, in forms of haplotype number, haplotype diversity and nucleotide diversity, on amphibian species indexed in the IUCN. Results show a low number of threatened species studied (21) in comparison with nonthreatened (61). The haplotype number was correlated with the sample size and couldn’t be used as a genetic diversity index in the comparisons. The levels of haplotype diversity where similar between threatened and non-threatened species (0.696 ±0.196 in threatened, 0.723 ±0.144 in non-threatened), but nucleotide diversity was significantly lower in the threatened species group (0.0030 ±0.0027 in threatened, 0.0422 ±0.0830 in non-threatened). These results seem independent of the mitochondrial marker used or the territory studied. As a result, nucleotide diversity seems more sensible than haplotype diversity to population declines of threatened species and could be indicator of the threatened state. In this regard, some nonthreatened species show similar values to those of threatened species and tracking could be required