Consequences of Hybridization in Mammals: A Systematic Review

Abstract

Hybridization, defined as breeding between two distinct taxonomic units, can have an important effect on the evolutionary patterns in cross-breeding taxa. Although interspecific hybridization has frequently been considered as a maladaptive process, which threatens species genetic integrity and survival via genetic swamping and outbreeding depression, in some cases hybridization can introduce novel adaptive variation and increase fitness. Most studies to date focused on documenting hybridization events and analyzing their causes, while relatively little is known about the consequences of hybridization and its impact on the parental species. To address this knowledge gap, we conducted a systematic review of studies on hybridization in mammals published in 2010–2021, and identified 115 relevant studies. Of 13 categories of hybridization consequences described in these studies, the most common negative consequence (21% of studies) was genetic swamping and the most common positive consequence (8%) was the gain of novel adaptive variation. The total frequency of negative consequences (49%) was higher than positive (13%) and neutral (38%) consequences. These frequencies are biased by the detection possibilities of microsatellite loci, the most common genetic markers used in the papers assessed. As negative outcomes are typically easier to demonstrate than positive ones (e.g., extinction vs hybrid speciation), they may be over-represented in publications. Transition towards genomic studies involving both neutral and adaptive variation will provide a better insight into the real impacts of hybridization.

Positive selection in gamete interaction proteins inCarnivora

“…Consequently, this implies an economy of reproductive efforts (Turner & Hoekstra, 2008). While the latter is the traditional way in which hetero-specific hybridization is frequently considered, here we explore a less treated consequence of hybridization that may play a fundamental role for small population endangered species: the inter-specific hybridization as an enabler for introgression, a mechanism that can introduce novel adaptive variations, and quickly raise diversity and increase fitness (Adavoudi et al, 2021). To do so, we measured and compared amino acid diversity for gamete interaction proteins among different Carnivora taxa and delved into their evolutionary histories assessing selective forces influence and uncovering events of rapid evolution and positive selection.…”

Gene drive in species complexes: defining target organisms

“…Potential control of this pest species using an engineered gene drive might therefore be expected to impact also on its sibling species. Because there are also numerous examples of introgression between a broad range of closely related animal species, including insects [57], chiclid fish [58], salamanders [59], frogs [60], lizards [61], Darwin's finches [62], and mammals [63][64][65], the considerations here may inform, on a case-by-case basis, ERA for the potential use of engineered gene drives in the biocontrol of a wide array of animal pest species.…”

Genotyping-by-sequencing (GBS) as a tool for interspecies hybrid detection

“…Recently, it has been proven that hybridisation and gene flow between species is much more widespread than previously thought (Pfennig, 2021). It is estimated that hybridisation affects as many as 10% of animals (Adavoudi and Pilot, 2022). The causes of hybridisation are usually a sudden reduction of the population, the reduced availability of mating partners, the destruction of species' natural habitats, the introduction of a new species to a given habitat, the migration of species or even deliberate human activity (Yadav et al, 2019).…”