Environmental and anthropogenic drivers of connectivity patterns: A basis for prioritizing conservation efforts for threatened populations

Gubili, Chrysoula; Mariani, Stefano; Weckworth, Byron V.; Galpern, Paul; McDevitt, Allan D.; Hebblewhite, Mark; Nickel, Barry; Musiani, Marco

doi:10.1111/eva.12443

Cited by 19 publications

(14 citation statements)

References 96 publications

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“…Such dual origin is a major driver of genetic differentiation among herds (Yannic et al ). Our results support also the findings of previous local and regional studies indicating that caribou populations show remarkable genetic differentiation despite the high dispersal potential of the species (Courtois et al , Boulet et al , Weckworth et al , Mager et al , , Colson et al , Gubili et al ). This suggests the presence of mechanisms behind genetic isolation other than geographical distance, such as physical barriers to dispersal, predation risk avoidance or isolation by environment (Serrouya et al , Weckworth et al , Mager et al , Yannic et al , Gubili et al ).…”

Section: Discussionsupporting

confidence: 92%

Linking genetic and ecological differentiation in an ungulate with a circumpolar distribution

et al. 2017

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Genetic differentiation among populations may arise from the disruption of gene flow due to local adaptation to distinct environments and/or neutral accumulation of mutations and genetic drift resulted from geographical isolation. Quantifying the role of these processes in determining the genetic structure of natural populations remains challenging. Here, we analyze the relative contribution of isolation‐by‐resistance (IBR), isolation‐by‐environment (IBE), genetic drift and historical isolation in allopatry during Pleistocene glacial cycles on shaping patterns of genetic differentiation in caribou/reindeer populations Rangifer tarandus across the entire distribution range of the species. Our study integrates analyses at range‐wide and regional scales to partial out the effects of historical and contemporary isolation mechanisms. At the circumpolar scale, our results indicate that genetic differentiation is predominantly explained by IBR and historical isolation. At a regional scale, we found that IBR, IBE and population size significantly explained the spatial distribution of genetic variation among populations belonging to the Euro‐Beringian lineage within North America. In contrast, genetic differentiation among populations within the North American lineage was predominantly explained by IBR and population size, but not IBE. We also found discrepancies between genetic and ecotype designation across the Holarctic species distribution range. Overall, these results indicate that multiple isolating mechanisms have played roles in shaping the spatial distribution of genetic variation across the distribution range of a large mammal with high potential for gene flow. Considering multiple spatial scales and simultaneously testing a comprehensive suite of potential isolating mechanisms, our study contributes to understand the ecological and evolutionary processes underlying organism–landscape interactions.

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Section: Discussionsupporting

confidence: 92%

Linking genetic and ecological differentiation in an ungulate with a circumpolar distribution

et al. 2017

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“…First, the program assumes that samples are evolutionarily independent (the program is based on the multinomial Dirichlet model), violating this assumption may influence estimates of F ST , alpha and selection type. In addition, even while focusing on a conservative statistical methodology to obtain a limited set of outlier SNPs (as we did), the program is known to provide false positives (especially in species like caribou that are subject to Isolation by Distance) (Gubili et al, ) that indicate balancing selection (Lotterhos & Whitlock, ). Lotterhos and Whitlock () recognize that for most types of landscape genomic data (like ours), significance of outliers should be viewed with caution, because genetic correlations among samples (e.g., units not evolutionarily independent) may result in a violation of model assumptions.…”

Section: Methodsmentioning

confidence: 99%

Genomics, environment and balancing selection in behaviourally bimodal populations: The caribou case

et al. 2019

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Selection forces that favour different phenotypes in different environments can change frequencies of genes between populations along environmental clines. Clines are also compatible with balancing forces, such as negative frequency‐dependent selection (NFDS), which maintains phenotypic polymorphisms within populations. For example, NFDS is hypothesized to maintain partial migration, a dimorphic behavioural trait prominent in species where only a fraction of the population seasonally migrates. Overall, NFDS is believed to be a common phenomenon in nature, yet a scarcity of studies were published linking naturally occurring allelic variation with bimodal or multimodal phenotypes and balancing selection. We applied a Pool‐seq approach and detected selection on alleles associated with environmental variables along a North–South gradient in western North American caribou, a species displaying partially migratory behaviour. On 51 loci, we found a signature of balancing selection, which could be related to NFDS and ultimately the maintenance of the phenotypic polymorphisms known within these populations. Yet, remarkably, we detected directional selection on a locus when our sample was divided into two behaviourally distinctive groups regardless of geographic provenance (a subset of GPS‐collared migratory or sedentary individuals), indicating that, within populations, phenotypically homogeneous groups were genetically distinctive. Loci under selection were linked to functional genes involved in oxidative stress response, body development and taste perception. Overall, results indicated genetic differentiation along an environmental gradient of caribou populations, which we found characterized by genes potentially undergoing balancing selection. We suggest that the underlining balancing force, NFDS, plays a strong role within populations harbouring multiple haplotypes and phenotypes, as it is the norm in animals, plants and humans too.

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“…To achieve a long-term preservation of wild reindeer in Norway, management efforts with focus on increasing population sizes and genetic connectivity among populations should be prioritized-especially for the smaller and more isolated populations, provided that conservation of genetic variation is an objective (as documented for other Rangifer sub-species in North America; e.g. Courtois et al 2003;Gubili et al 2017). This is important considering the fact that several studies have documented negative effects of landscape changes, such as habitat loss and fragmentation, which is expected to co-occur with increasing levels of impacts from other stressors (such as, but not limited to, climate: e.g.…”

Section: Management Implicationsmentioning

confidence: 99%

Recent large-scale landscape changes, genetic drift and reintroductions characterize the genetic structure of Norwegian wild reindeer

et al. 2019

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Landscape changes, such as habitat loss and fragmentation, subdivide wild populations, reduce their size, and limit gene flow. These changes may further lead to depletion of genetic variation within populations as well as accelerating differentiation among populations. As a migratory species requiring large living areas, wild reindeer (Rangifer tarandus) is highly vulnerable to human activity. The number and continued presence of wild reindeer have been significantly reduced due to accelerating anthropogenic habitat modifications, as well as displacement in benefit of domesticated herds of the species. As a basis for future management strategies we assess genetic structure and levels of genetic variation in Norwegian wild reindeer by analysing 12 microsatellite loci and the mitochondrial control region in 21 management units with varying population sizes. Overall, both markers showed highly varying levels of genetic variation, with reduced variation in the smaller and more isolated populations. The microsatellite data indicated a relationship between population size and genetic variation. This relationship was positive and linear until a threshold for population size was reached at approximately 1500 reindeer. We found high levels of differentiation among most populations, indicating low levels of gene flow, but only a weak correlation between geographic and genetic distances. Our results imply that the genetic structure of Norwegian wild reindeer is mainly driven by recent colonization history, population size, as well as human-induced landscape fragmentation, restricting gene flow and leading to high levels of genetic drift. To sustain viable populations, conservation strategies should focus on genetic connectivity between populations.

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Environmental and anthropogenic drivers of connectivity patterns: A basis for prioritizing conservation efforts for threatened populations

Cited by 19 publications

References 96 publications

Linking genetic and ecological differentiation in an ungulate with a circumpolar distribution

Linking genetic and ecological differentiation in an ungulate with a circumpolar distribution

Genomics, environment and balancing selection in behaviourally bimodal populations: The caribou case

Recent large-scale landscape changes, genetic drift and reintroductions characterize the genetic structure of Norwegian wild reindeer

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