Naturally occurring hybrids of coral reef butterflyfishes have similar fitness compared to parental species

Abstract

Hybridisation can produce evolutionary novelty by increasing fitness and adaptive capacity. Heterosis, or hybrid vigour, has been documented in many plant and animal taxa, and is a notable consequence of hybridisation that has been exploited for decades in agriculture and aquaculture. On the contrary, loss of fitness in naturally occurring hybrid taxa has been observed in many cases. This can have negative consequences for the parental species involved (wasted reproductive effort), and has raised concerns for species conservation. This study evaluates the relative fitness of previously documented butterflyfish hybrids of the genus Chaetodon from the Indo-Pacific suture zone at Christmas Island. Histological examination confirmed the reproductive viability of Chaetodon hybrids. Examination of liver lipid content showed that hybrid body condition was not significantly different from parent species body condition. Lastly, size at age data revealed no difference in growth rates and asymptotic length between hybrids and parent species. Based on the traits measured in this study, naturally occurring hybrids of Chaetodon butterflyfishes have similar fitness to their parental species, and are unlikely to supplant parental species under current environmental conditions at the suture zone. However, given sufficient fitness and ongoing genetic exchange between the respective parental species, hybrids are likely to persist within the suture zone.

Genomic islands of divergence in the Yellow Tang and the Brushtail Tang Surgeonfishes

“…Indeed, the relative abundance of Z. scopas, Z. flavescens, and their hybrids was estimated at 90.9%, 5.6%, and 3.5%, respectively (authors’ unpublished data recorded from 2013 to 2016, based on 102 visual transects over 32 sites, total number of Zebrasoma individuals = 428). A pattern of directional introgression, as was observed here, that may be predicted by skewed abundances of parental species, is not unusual, as was reported in several other coral reef fish species (Crow et al., ; Harrison et al., ; Montanari, Hobbs, Pratchett, Bay, & Van Herwerden, ; Yaakub, Bellwood, Herwerden, & Walsh, ).…”

“…However, based on outlier loci (where species are distinguishable), we did not find evidence of introgression in Z. flavescens individuals from Hawaii. We also found that Z. scopas from Moorea hardly contain any genetic material assigned to Z. flavescens (Figure 3 observed here, that may be predicted by skewed abundances of parental species, is not unusual, as was reported in several other coral reef fish species (Crow et al, 2007;Harrison et al, 2017;Montanari, Hobbs, Pratchett, Bay, & Van Herwerden, 2017;Yaakub, Bellwood, Herwerden, & Walsh, 2006).…”

Species integrity, introgression, and genetic variation across a coral reef fish hybrid zone

“…Hybridization was once considered rare in the marine environment (Arnold, 1997); however, a surge of recent studies has challenged these traditional perceptions of hybrid scarcity (Gardner, 1997; Harrison et al., 2017; He, Johansen, Hoey, Pappas, & Berumen, 2019; Johansen et al., 2017; Montanari, Hobbs, Pratchett, Bay, & van Herwerden, 2017; Montanari, Hobbs, Pratchett, & van Herwerden, 2016; Pazmiño et al., 2019; Willis, van Oppen, Miller, Vollmer, & Ayre, 2006). Hybridization is particularly common in coral reef fishes, where largely allopatric sister species hybridize at their biogeographic borders.…”

“…This would be an effective evolutionary strategy if hybrid fitness is comparable to purebred fitness. To test this hypothesis, future studies should quantify hybrid and parent species fitness in this system, as was done for butterflyfish hybrids and parent species at the Christmas island suture zone(Montanari et al, 2017) and experimentally test whether queue's function as expected in a hybrid context. Smaller hybrid and A. sandaracinos mate preferences are not evident in the ecological data, as results retain the signature of larger species mate choice throughout the hybrid zone.…”

Comparative Transcriptome Profiling Analysis Uncovers Novel Heterosis-Related Candidate Genes Associated with Muscular Endurance in Mules

“…Unlike these two models, the third model explains interactions between nonallelic genes, which are created due to new combinations in the hybrid. With the development of functional genomics and the improvement of RNA sequencing (RNA-seq) technologies, the molecular basis of heterosis has been investigated at the transcriptional level of gene expression in several plant and animal species such as cattle [ 14 ], mice [ 15 ], pig [ 16 ], chicken [ 17 ], coral reef butterflyfish [ 18 ], and crossed lamb [ 19 ].…”