Concern over hybridization risks should not preclude conservation interventions

Abstract

Conservation interventions such as assisted migration and genetic alterations are controversial in part because, through unintended hybridization events, they may imperil native species. Threats could stem from hybrid offspring having altered fitness or from genetic swamping due to extensive introgression of non‐native genes. Over the last 40 years, papers discussing hybridization increasingly use value‐laden terminology (e.g., “genetic contamination”). Such terms presume that any amount of hybridization equates to harm, but this perspective is at odds with modern evolutionary theory's recognition of hybridization as a creative force that can accelerate evolution or spur adaptive breakthroughs. To assess the evidence undergirding perceptions of hybridization threats, we examined the IUCN's Global Invasive Species Database (GISD). Of 870 invasive species, the GISD identified 35 as potentially threatening endemic taxa via hybridization. For each of these 35 species, we assessed the quality of data that the GISD cited pertaining to hybridization. Direct evidence for hybridization was cited for only 16 species, and there was neither direct nor indirect evidence demonstrating reduced fitness of hybrid offspring for 18 species. In our era of rapid environmental change, it is time to examine hybridization case‐by‐case and not to presume that hybridization always presents a threat to biodiversity, but rather, to consider it as a potential pathway to species survival.

Species Delimitation and Conservation in Taxonomically Challenging Lineages: The Case of Two Clades of Capurodendron (Sapotaceae) in Madagascar

“…As assessments of hybrids are not recommended for the IUCN Red list (except plant hybrids treated as species), the morphospecies Capurodendron androyense x mandrarense , C. androyense x microphyllum , C. pervillei x oblongifolium , and C. pervillei x perrieri do not need a conservation status. From a conservation point of view, the role of hybrids in population dynamics is unclear [ 72 , 73 , 74 ]. On the one hand, they could favor species extinction due to the introgression of one taxon in another, leading, for example, to a reduction of the populations of Capurodendron microphyllum , which would be partially replaced by C. androyense x microphyllum .…”

Why intended consequences?

“…Both reintroduction (Smith & Peterson, 2021) and intentional genetic introgression (Newhouse & Powell, 2020) are part of a spectrum of genetic interventions that have historically succeeded and can facilitate ecosystem restoration. Two papers question prominent historical conventions within the field of conservation: the maintenance of ecosystem integrity (Rohwer & Marris, 2021) and an aversion to hybridization in the name of maintaining genetic purity (Hirashiki, Kareiva, & Marvier, 2021). Brister, Holbrook, and Palmer (2021) diagnose the causes and consequences of an "ethos of restraint."…”

Exploring the intersections of governance, constituencies, and risk in genetic interventions

“…The workshop addressed commonalities across these approaches, while recognizing heightened attention and concern around the use of advanced biotechnology. In this article, we focus on this more controversial subset of genetic interventions for conservation benefit, which could include creation of hybrids to increase viability (Hirashiki, Marvier, & Kareiva, 2021), genetic modifications for invasive species control (Teem et al, 2020), and facilitated adaptation (Newhouse & Powell, 2021). These newer practices can complement conventional conservation methods (Novak, Maloney, & Phelan, 2018;Supple & Shapiro, 2018).…”