The effects of allospecific mitochondrial genome on the fitness of northern redbelly dace (Chrosomus eos)

Abstract

Instantaneous mitochondrial introgression events allow the disentangling of the effects of hybridization from those of allospecific mtDNA. Such process frequently occurred in the fish Chrosomus eos, resulting in cybrid individuals composed of a C. eos nuclear genome but with a C. neogaeus mtDNA. This provides a valuable model to address the fundamental question: How well do introgressed individuals perform in their native environment? We infer where de novo production of cybrids occurred to discriminate native environments from those colonized by cybrids in 25 sites from two regions (West‐Qc and East‐Qc) in Quebec (Canada). We then compared the relative abundance of wild types and cybrids as a measure integrating both fitness and de novo production of cybrids. According to mtDNA variation, 12 introgression events are required to explain the diversity of cybrids. Five cybrid lineages could not be associated with in situ introgression events. This includes one haplotype carried by 93% of the cybrids expected to have colonized West‐Qc. These cybrids also displayed a nearly complete allopatric distribution with wild types. We still inferred de novo production of cybrids at seven sites, that accounted for 70% of the cybrids in East‐Qc. Wild‐type and cybrid individuals coexist in all East‐Qc sites while cybrids were less abundant. Allopatry of cybrids restricted to the postglacial expansion suggests the existence of higher fitness for cybrids in specific conditions, allowing for the colonization of different environments and expanding the species’ range. However, allospecific mtDNA does not provide a higher fitness to cybrids in their native environment compared to wild types, making the success of an introgressed lineage uncertain.

Effects of mitonuclear combination and thermal acclimation on the energetic phenotype

“…higher metabolism and/or excess capacity) is likely mitigated by its instability in high temperature. This aforementioned balance of trade‐offs could explain previously observed allopatry of cybrids restricted to the postglacial expansion (Angers, Leung et al, 2018).…”

“…A total of 129 young‐of‐the‐year C. eos (<2 cm), including both wild types and cybrids, were sampled at AS‐1 site (Angers, Chapdelaine et al, 2018). This is a small lake of 4.87 ha located in the southern part of Quebec, Canada (45° 54′ 58′′N, 74° 04′ 23′′W), where the coexistence of wild types and cybrids has been previously detected (Angers, Leung et al, 2018). The individuals were brought to the laboratory and randomly distributed into six aquariums (two aquariums in three closed water circuits) at 21°C for 3 months.…”

“…The disruption of this coevolution may impair the catalytic capacity of the electron transport system and ATP synthase enzymes, thus affecting the entire ATP production process and finally the organismal fitness (Barreto & Burton, 2013; Blier, Dufresne, & Burton, 2001). Even if mitonuclear disruption is expected to generally result in negative effects on the phenotype, some positive effects have also been described (Angers, Leung, Vetil, Deremiens, & Vergilino, 2018; Deremiens, Schwartz, Angers, Glemet, & Angers, 2015; Dey, Barrientos, & Moraes, 2000; Toews, Mandic, Richards, & Irwin, 2014). For example, in the yellow‐rumped warbler ( Setophaga spp.)…”

Sperm-dependent asexual species matter in ecology and evolution

“…Backcrossing to sexual relatives has been directly reported from several apomictic species, e.g., in Hieracium, Ranunculus and Taraxacum (Hörandl and Paun 2007), which supposedly helps to generate new cytotypes (Sailer et al 2020) and local reversal to sex (Majeský et al 2012), thereby contradicting Darlington's "dead end of evolution" hypothesis (Darlington 1939). The geneflow from asexual to sexual populations has also been demonstrated in various asexual animals ranging from flatworms to vertebrates (Hotz et al 1992;Goddard and Schultz 1993;Vorburger 2001;Sousa-Santos et al 2006;D'Souza and Michiels 2009;Scali 2009;Angers et al 2018).…”

Genome-wide and cuticular hydrocarbon evidence shed light on potential drivers of speciation in a Neotropical ant species complex

“…Mt performance affects every aspect of individual fitness and its correct function relies on mitonuclear compatibility (Angers et al 2018;Zaidi and Makova 2019). This intimate interaction between the mt and nuclear products has led to a strong coevolution between both genomes (Blier et al 2001;Burton et al 2013;Chou and Leu 2015).…”