The Spatial Signature of Introgression After a Biological Invasion With Hybridization

Abstract

The accumulation of genome-wide molecular data has emphasized the important role of hybridization in the evolution of many organisms, which may carry introgressed genomic segments resulting from past admixture events with other taxa. Despite a number of examples of hybridization occurring during biological invasions, the resulting spatial patterns of genomic introgression remain poorly understood. Preliminary simulation studies have suggested a heterogeneous spatial level of introgression for invasive taxa after range expansion. We investigated in detail the robustness of this pattern and its persistence over time for both invasive and local organisms. Using spatially explicit simulations, we explored the spatial distribution of introgression across the area of colonization of an invasive taxon hybridizing with a local taxon. The general pattern for neutral loci supported by our results is an increasing introgression of local genes into the invasive taxon with the increase in the distance from the source of the invasion and a decreasing introgression of invasive genes into the local taxon. However, we also show there is some variation in this general trend depending on the scenario investigated. Spatial heterogeneity of introgression within a given taxon is thus an expected neutral pattern in structured populations after a biological invasion with a low to moderate amount of hybridization. We further show that this pattern is consistent with published empirical observations. Using additional simulations, we argue that the spatial pattern of Neanderthal introgression in modern humans, which has been documented to be higher in Asia than in Europe, can be explained by a model of hybridization with Neanderthals in Eurasia during the range expansion of modern humans from Africa. Our results support the view that weak hybridization during range expansion may explain spatially heterogeneous introgression patterns without the need to invoke selection.

Introgression dynamics from invasive pigs into wild boar following the March 2011 natural and anthropogenic disasters at Fukushima

“…The decrease of introgressed genes in the wild boars' genomes with the increase in the distance from the invasion source ( figure 4 ) and with time is likely to be caused from the wild boar being most abundant in the evacuated zone [ 10 ] and the random mating tendencies of wild boar in this area (electronic supplementary material, figure S6), which in turn, increases the opportunity of backcross generations with wild boar and less chance of direct contact between remaining invasive pigs or other hybrids. Particularly, our result may be an indication of demic diffusion [ 25 ] in the wild, in which the invader gene pool is progressively diluted along the expansion due to recurrent admixture with the native species. This contrasts with reported hybridization in European wild boar populations where, despite new developments of intensive indoor pig farming, older hybridization events are being followed-up by interbreeding among hybrids, or recent escaped pigs, resulting in ongoing introgression on multiple occasions [ 42 ].…”

“…Here, we evaluate the hypotheses that range expansion acts as resistance against hybridization, and that invasion success is dependent on the invaders' response to naturalization; both hypotheses have been often embedded in evolution [ 22 , 24 , 25 ]. Specifically, we determined the extent of the genetic introgression from invasive pigs into wild boar in Fukushima Prefecture after the FDNPP accident, and observed the longevity of introgressed alleles or organelles to evaluate the above hypotheses.…”

Evaluating Causes of Current Genetic Gradients of Modern Humans of the Iberian Peninsula

“…Despite spatially explicit computer simulations are computationally slow compared with other simulation approaches (i.e., the standard coalescent), these simulations are highly realistic by explicitly taking into account evolutionary, geographic, and environmental information ( Dunning et al 1995 ; Epperson et al 2010 ; Benguigui and Arenas 2014 ). We performed spatially explicit computer simulations of genetic data with the framework SPLATCHE3 ( Currat et al 2019 ), a simulator that has been widely used for human evolutionary studies (e.g., Currat and Excoffier 2004 , 2005 ; Ray 2005 ; Francois et al 2010 ; Alves et al 2016; Pimenta et al 2017 ; Branco and Arenas 2018 ; Quilodrán et al 2020 ). Basically, this framework consists of the following three main steps: 1) A forward-in-time simulation (from the past to the present) of the entire population upon a user-specified landscape, demographic and migration model.…”

The Genomic Processes of Biological Invasions: From Invasive Species to Cancer Metastases and Back Again

“…Genetic markers have been used to identify the genetic makeup of invasive populations, and understand how genome level processes contribute to invasion of diverse natural ecosystems (Bock et al, 2015;Colautti and Lau, 2015;Dlugosch et al, 2015;Rius et al, 2015b;Mounger et al, 2021a). Studies in the native and introduced ranges have reported that many invasive populations undergo only modest reductions in genetic variation due to multiple introductions (Stepien et al, 2005;Dlugosch and Parker, 2008a;Snyder and Stepien, 2017;Flucher et al, 2021), hybridization (Fitzpatrick et al, 2009;Scascitelli et al, 2010;van Riemsdijk et al, 2018van Riemsdijk et al, , 2020Quilodrán et al, 2020), or Allee effects that result from reverse density dependence or cooperation (Kramer and Sarnelle, 2008;Aikio et al, 2010;Rius et al, 2015b). For example, sequences of mitochondrial DNA revealed multiple invasion sources for both dreissenid mussels and goby species of fish, and that this diversity was correlated to rapid spread and colonization success in a variety of habitats (Stepien et al, 2005).…”