The Effect of Recurrent Floods on Genetic Composition of Marble Trout Populations

A changing global climate can threaten the diversity of species and ecosystems. We explore the consequences of catastrophic disturbances in determining the evolutionary and demographic histories of secluded marble trout populations in Slovenian streams subjected to weather extremes, in particular recurrent flash floods and debris flows causing massive mortalities. Using microsatellite data, a pattern of extreme genetic differentiation was found among populations (global FST of 0.716), which exceeds the highest values reported in freshwater fish. All locations showed low levels of genetic diversity as evidenced by low heterozygosities and a mean of only 2 alleles per locus, with few or no rare alleles. Many loci showed a discontinuous allele distribution, with missing alleles across the allele size range, suggestive of a population contraction. Accordingly, bottleneck episodes were inferred for all samples with a reduction in population size of 3–4 orders of magnitude. The reduced level of genetic diversity observed in all populations implies a strong impact of genetic drift, and suggests that along with limited gene flow, genetic differentiation might have been exacerbated by recurrent mortalities likely caused by flash flood and debris flows. Due to its low evolutionary potential the species might fail to cope with an intensification and altered frequency of flash flood events predicted to occur with climate change

North American montane red foxes: expansion, fragmentation, and the origin of the Sacramento Valley red fox

Most native red foxes (Vulpes vulpes) in the western contiguous United States appear to be climatically restricted to colder regions in the major mountain ranges and, in some areas, have suffered precipitous declines in abundance that may be linked to warming trends. However, another population of unknown origin has occurred in arid habitats in the Sacramento Valley of California well outside this narrow bioclimatic niche since at least 1880. If native, this population would be ecologically distinct among indigenous North American red foxes. We used mitochondrial and microsatellite markers from historical and modern samples (modes: 1910–1930 and 2000–2008, respectively) obtained throughout the western United States to determine the origins of the Sacramento Valley red fox, and assess the historical and modern connectivity and genetic effective population sizes of Sacramento Valley and montane red foxes. We found clear and consistent evidence supporting the indigenous origin of the Sacramento Valley population, including the phylogenetic positioning of the dominant, endemic mtDNA clade and microsatellite clustering of the Sacramento Valley population with the nearest montane population. Based on both mitochondrial and microsatellite AMOVAs, connectivity among Western populations of red foxes declined substantially between historical and modern time periods. Estimates based on temporal losses in gene diversity for both marker types suggest that both the Sierra Nevada (including the Southern Cascades population) and the Sacramento Valley populations have small genetic effective population sizes. Significant heterozygote excesses also indicate the occurrence of recent bottlenecks in these populations. Both substitutions distinguishing the 2 endemic Sacramento Valley haplotypes from the dominant montane haplotype were in the coding region and nonsynonymous, consistent with adaptive differences. These findings along with previously reported body size distinctions between Sacramento Valley and montane red foxes argue for distinct subspecific status for the Sacramento Valley red fox, for which we propose the designation V. v. patwin n. subsp. The small genetic effective population size estimates for the Sierra Nevada red fox and Sacramento Valley red fox are cause for concern, as is the possibility of genetic introgression into the latter population from an adjacent, recently established nonnative population

Geographic influence on genetic structure in the widespread Neotropical tree, Simarouba amara (Simaroubaceae)

This study aimed to assess the population genetic structure of a widespread Neotropical tree species, Simarouba amara, at local, regional and continental spatial scales. We used five microsatellite loci to examine genetic variation in 14 natural populations (N=478 individuals) of this vertebrate dispersed rain forest tree species in Panama, Ecuador, and French Guiana. Estimates of genetic differentiation (Fst and Rst) were significant among all but one population pair and global differentiation was moderate (Fst=0.25, Rst=0.33) with 94% of genetic variation ascribed to differences among three main geographic regions (Central America, Western Ecuador, Amazon basin). There was no evidence of isolation by distance within regions. Allele-size mutations contributed significantly (RST > FST) to the divergences between cis and trans-Andean populations, highlighting the role of the northern Andean cordilleras as an important geographic barrier for this species.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83290/1/Hardesty2010TrPB.pd

Genetic and ecological data reveal species boundaries between viviparous and oviparous lizard lineages

Identification of cryptic species is an essential aim for conservation biologists to avoid premature extinctions of ‘unrecognized’ species. Integrating different types of data can undoubtedly aid in resolving the issue of species delimitation. We studied here two lineages of the common lizard Zootoca vivipara that display different reproductive mode (the viviparous Z. v. vivipara and the oviparous Z. v. carniolica) and that overlap their distributional ranges in the European Alps. With the purpose of delimiting species’ boundaries, we analyzed their ecological, genetic and natural history features. More than 300 samples were collected and analyzed at cytochrome b and 11 microsatellites loci for investigating genetic variation, population structure, individual relatedness and evolutionary histories of the two lineages. Additionally, we compared their ecological niches using eight ecological variables. Genetic data showed contrasting patterns of genetic structure between the two lineages, different demographic dynamics and no hybridization events. Also strong ecological differences (such as temperature) emerged between the two lineages, and niche overlap was limited. Taken together, these results indicate that Z. v. vivipara and Z. v. carniolica should be recognized as two separate species, and particular conservation consideration should be given to the oviparous lineage that tends to live in areas threatened by increasing impact of human activities. However, recent and rapid climate warming might determine an increasing risk for the persistence of the viviparous lineage, being adapted to cold environment

The world's most isolated and distinct whale population? Humpback whales of the Arabian Sea.

A clear understanding of population structure is essential for assessing conservation status and implementing management strategies. A small, non-migratory population of humpback whales in the Arabian Sea is classified as "Endangered" on the IUCN Red List of Threatened Species, an assessment constrained by a lack of data, including limited understanding of its relationship to other populations. We analysed 11 microsatellite markers and mitochondrial DNA sequences extracted from 67 Arabian Sea humpback whale tissue samples and compared them to equivalent datasets from the Southern Hemisphere and North Pacific. Results show that the Arabian Sea population is highly distinct; estimates of gene flow and divergence times suggest a Southern Indian Ocean origin but indicate that it has been isolated for approximately 70,000 years, remarkable for a species that is typically highly migratory. Genetic diversity values are significantly lower than those obtained for Southern Hemisphere populations and signatures of ancient and recent genetic bottlenecks were identified. Our findings suggest this is the world's most isolated humpback whale population, which, when combined with low population abundance estimates and anthropogenic threats, raises concern for its survival. We recommend an amendment of the status of the population to "Critically Endangered" on the IUCN Red List